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Discussion Starter #1
Hello,

Building another 25.x chassis, 25.1 this round. I have the 2020 NHRA book and a brand new January 3rd, 2020 25.1 spec book. I have read both front to back and I can't find the maximum lean back angle for the main hoop. I have searched here and all over, but am missing the reference. I have read snippets that say 20 degrees max (I want to lean back 14 degrees). I have called the tech inspector up here in the northeast, but he didn't have the info in his memory bank and won't be home for awhile to reference rulebook (tech is a part time gig for him). Is there any place someone could point out that I am missing? I've read General, all classes, 25.1 current book, and am just missing it.

TIA
Scott
 

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Since SFI 25.1 first came out,
( funny car cage era of late 80s)
there has never been a NHRA tech guy measure the amount of lay back on a main hoop ive ever seen...nor has any of them asked how much...
I started laying bk main hoops in early 90s while most builders installed them vertically perpendicular to the track surface.

They (nhra tech guys) dont even carry a device to measure degrees...ive never seen it done ..
A sonic checker and gauge to measure tube diam. Tape measure 1 time on a dash bar distance in front of the furthest forward loint of the A post door bar [email protected] dash bar ht..
As it (dash bar) cannot extend more than 8" forward of front side of said A post tube @ ht cogruent to dash bar elevation... & that was on a retrofit upgrade to 25.1 on what was basically a bracket car ...

That rule was not easy to find either..
Like your 20° rule u believe u saw ...

But it was later spelled out in sfi SFI spec as i recall.

Ive seen a a few rules that were somewhat hidden over 30+ yrs of building cars prof. In 5 world championship race car programs..
That dash bar rule...cuz that was in like 1999.

All my experience has been in door cars nhra/ihra pro stk and pro mod builds.
So not bk yard crap. Prof programs..

And have yet to see in SFI specs, in writing,
a rule on lay back angle. Doesnt mean there isnt 1... and 20 is a ton .....unless i knew more about the design and why its like that.

That being said.
When i designed the chassis that Bickel used on all his pro stock cars, including Yates , who won 2 world championships with that design , and jerry went on to continue to produced it on all his in house builds from 1993 when i did the block 10 design @7.5°, all the way up to to 2002 w/my design,
( till dischbein went to work there, in like 2002, .. as i left not long after i did that design and went west and did a run at Rells... but that yates car set the GM wind tunnel record w/that chassis & him an Maskins got to W/Chmp'ships out of it.)

and Bickel still sells that exact design on his kit chassis and blueprint chassis drawings...that design is 7.5° lay bk. from vertical. Which was more than anyone was doing then.
I did it primarily for driver comfort and so we had to design a new 4 link bracket just for that design change as the upper and lower 4 link crossmembers are now at to great a disperty for our bracket geometry to be correct as it relates to the rear end housing geometry.

Ive built hundreds of 25-1 & 25-2 chassis over many yrs, but never seen the constraints surrounding the 4 link geometry to warrant 14°..not on a main hoop rear car anyhow.
but its not that much more than 7.5° , which is about an inch and a half (1.5") when u drop a plumb bob off the bk side of main hoop- at top of it- down to jig table ( and measure forward to lower 4 link c/member, on a typical 37.5-40+" ht main hoop like in a firebird/camaro of that era.

So 14° would be about 3" behind the lower
4 link crossmember at the bottom,
by plumb bob.

This is not a main hoop forward design is it?

Is main hoop 100% behind drivers helmet?

Ive built and designed many of the most radical chassis ever done in NHRA , including the 1st pro stock truck that had NO BARS going out the rear top of cab,
& thru the bed into the tail section under the bed cover, bk in '98.

we debuted Trk at Indy & won best eng at Pomona world finals as Indy politics already had someone lined up w/a supergas roadster...lol..
We had invented the 1st billet adj 4 link in 97.
So the trk was tech the 2nd one done that actually had infinitely adjustable~ billet 4 link brkts, a system that moved in .125" increments up or down...( which Ness later copied & patented)

Point is... ive push more boundrys than nhra cared to see at times..
And nobody from NHRA ,
(INCLUDING THAT BASTARD 'JOE TECH', WHO FOUND SOMETHING WRONG ON NEARLY EVERY NEW DESIGNED CHASSIS anyone did...)
Bounced my truck deal, or any other main hoop design ive done... My own car is a Forward deal that is prolly further than any built today even.. ...
Nobody EVER questioned or measured any of our bar angles ..including M/Hoop.

Ive had the rule book memorized for decades, as well as the most door car SFI specs. 25.1, 25.2 ect...

So if u seen 20° in writing...and its not in rule bk or sfi 25.1 specs.
I cant image where it would be.. other than there are some addendums in each tech guys sfi manual on rare occasion that we the general pubilc and builders dont get issued.
My old tech guy would ket me photo copy them while he was doing a car if it came up during a new cert..

Clearly u have a very unique custom 4 link bracket design then to need 14°? If its a rear hoop car..

i usually try to be right before i go and stick my neck out ( physically or verbally) ,

but i guess if u seen it in writing @ 20° then u seen it.
20° would certainly be where i would likely cap it.
Cuz the drivers head is gonna be way forward of it on a standard rear main hoop when driver is 100% in front of it~
type of design ..
if its a "main hoop forward" car design..
then obviously not.. and 4 link brkt design is then irrelevant ...

Joe did catch my excess of 1" stagger in that pro stock truck , or maybe it was kiwi.. but many guys who saw the trk at 1st thought it looked really clean and slick, with no bars out the cab ..
But since they didnt fully know rules wondered if it was legal without tubes thru rear of cab into bed area. It was not..
Oct 7th 1998 Rag issue ( i believe was date) had a full 1 pg article on trk showing the billet 4 link which ness filed for patent on my idea 3 yrs later. My own car i have now was the 1st...pro stk car i built in '97 using the 4 link setup.. it did not get ink in the rag cuz it was never raced in pro stk... lost sponsor.

By SFI standards the no tubes out rear of cab was not illegal..not then anyways.

As they ( sfi) only spec's the tube diam.'s departing the main hoop rearward in # and min size for a given # of tubes..
Its based on number of of tubes connecting main hoop to rear tail section.. more tubes = smaller diam s can be used.. whether its 4 or 6..
Those are the kind of rules guys miss...but there called out in sfi 25.1x
Let us know if u find it in writing...
Thx
 

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Discussion Starter #5
Since SFI 25.1 first came out,
( funny car cage era of late 80s)
there has never been a NHRA tech guy measure the amount of lay back on a main hoop ive ever seen...nor has any of them asked how much...
I started laying bk main hoops in early 90s while most builders installed them vertically perpendicular to the track surface.

They (nhra tech guys) dont even carry a device to measure degrees...ive never seen it done ..
A sonic checker and gauge to measure tube diam. Tape measure 1 time on a dash bar distance in front of the furthest forward loint of the A post door bar [email protected] dash bar ht..
As it (dash bar) cannot extend more than 8" forward of front side of said A post tube @ ht cogruent to dash bar elevation... & that was on a retrofit upgrade to 25.1 on what was basically a bracket car ...

That rule was not easy to find either..
Like your 20° rule u believe u saw ...

But it was later spelled out in sfi SFI spec as i recall.

Ive seen a a few rules that were somewhat hidden over 30+ yrs of building cars prof. In 5 world championship race car programs..
That dash bar rule...cuz that was in like 1999.

All my experience has been in door cars nhra/ihra pro stk and pro mod builds.
So not bk yard crap. Prof programs..

And have yet to see in SFI specs, in writing,
a rule on lay back angle. Doesnt mean there isnt 1... and 20 is a ton .....unless i knew more about the design and why its like that.

That being said.
When i designed the chassis that Bickel used on all his pro stock cars, including Yates , who won 2 world championships with that design , and jerry went on to continue to produced it on all his in house builds from 1993 when i did the block 10 design @7.5°, all the way up to to 2002 w/my design,
( till dischbein went to work there, in like 2002, .. as i left not long after i did that design and went west and did a run at Rells... but that yates car set the GM wind tunnel record w/that chassis & him an Maskins got to W/Chmp'ships out of it.)

and Bickel still sells that exact design on his kit chassis and blueprint chassis drawings...that design is 7.5° lay bk. from vertical. Which was more than anyone was doing then.
I did it primarily for driver comfort and so we had to design a new 4 link bracket just for that design change as the upper and lower 4 link crossmembers are now at to great a disperty for our bracket geometry to be correct as it relates to the rear end housing geometry.

Ive built hundreds of 25-1 & 25-2 chassis over many yrs, but never seen the constraints surrounding the 4 link geometry to warrant 14°..not on a main hoop rear car anyhow.
but its not that much more than 7.5° , which is about an inch and a half (1.5") when u drop a plumb bob off the bk side of main hoop- at top of it- down to jig table ( and measure forward to lower 4 link c/member, on a typical 37.5-40+" ht main hoop like in a firebird/camaro of that era.

So 14° would be about 3" behind the lower
4 link crossmember at the bottom,
by plumb bob.

This is not a main hoop forward design is it?

Is main hoop 100% behind drivers helmet?

Ive built and designed many of the most radical chassis ever done in NHRA , including the 1st pro stock truck that had NO BARS going out the rear top of cab,
& thru the bed into the tail section under the bed cover, bk in '98.

we debuted Trk at Indy & won best eng at Pomona world finals as Indy politics already had someone lined up w/a supergas roadster...lol..
We had invented the 1st billet adj 4 link in 97.
So the trk was tech the 2nd one done that actually had infinitely adjustable~ billet 4 link brkts, a system that moved in .125" increments up or down...( which Ness later copied & patented)

Point is... ive push more boundrys than nhra cared to see at times..
And nobody from NHRA ,
(INCLUDING THAT BASTARD 'JOE TECH', WHO FOUND SOMETHING WRONG ON NEARLY EVERY NEW DESIGNED CHASSIS anyone did...)
Bounced my truck deal, or any other main hoop design ive done... My own car is a Forward deal that is prolly further than any built today even.. ...
Nobody EVER questioned or measured any of our bar angles ..including M/Hoop.

Ive had the rule book memorized for decades, as well as the most door car SFI specs. 25.1, 25.2 ect...

So if u seen 20° in writing...and its not in rule bk or sfi 25.1 specs.
I cant image where it would be.. other than there are some addendums in each tech guys sfi manual on rare occasion that we the general pubilc and builders dont get issued.
My old tech guy would ket me photo copy them while he was doing a car if it came up during a new cert..

Clearly u have a very unique custom 4 link bracket design then to need 14°? If its a rear hoop car..

i usually try to be right before i go and stick my neck out ( physically or verbally) ,

but i guess if u seen it in writing @ 20° then u seen it.
20° would certainly be where i would likely cap it.
Cuz the drivers head is gonna be way forward of it on a standard rear main hoop when driver is 100% in front of it~
type of design ..
if its a "main hoop forward" car design..
then obviously not.. and 4 link brkt design is then irrelevant ...

Joe did catch my excess of 1" stagger in that pro stock truck , or maybe it was kiwi.. but many guys who saw the trk at 1st thought it looked really clean and slick, with no bars out the cab ..
But since they didnt fully know rules wondered if it was legal without tubes thru rear of cab into bed area. It was not..
Oct 7th 1998 Rag issue ( i believe was date) had a full 1 pg article on trk showing the billet 4 link which ness filed for patent on my idea 3 yrs later. My own car i have now was the 1st...pro stk car i built in '97 using the 4 link setup.. it did not get ink in the rag cuz it was never raced in pro stk... lost sponsor.

By SFI standards the no tubes out rear of cab was not illegal..not then anyways.

As they ( sfi) only spec's the tube diam.'s departing the main hoop rearward in # and min size for a given # of tubes..
Its based on number of of tubes connecting main hoop to rear tail section.. more tubes = smaller diam s can be used.. whether its 4 or 6..
Those are the kind of rules guys miss...but there called out in sfi 25.1x
Let us know if u find it in writing...
Thx

660sherpa,

Wow! Thanks for all of that information, you are obviously a wealth of great information for all of us.

I am sure what I did see about 20 degrees was part of another spec, I absolutely haven't seen it in the book.

I appreciate you taking the time to spell everything out in detail. My new build does have the helmet completely in front of the main hoop. I did this for two reasons. By the spec, having the main hoop aft is the lightest configuration. Also, it happens to line up with the angle of the rear angle of the front window of the "stock" 70 Camaro body.

I say "stock" because the body is carbon, made at the house, completely factory dimension except for stretched wheel wells for the rear. I made a mold of the factory Camaro body and then laid a carbon body into that mold.

This is the second chassis I will build for the factory 70 Camaro body, my first is in the operational race car that I have been running since 2012. It's a 521 Hemi C Screw that has been as heavy as 2600 with factory steel body and 2358 with home made carbon. The main hoop on that car is is just a couple of degrees back with the helmet at the midpoint of the bar. I love the look of the "mid helmet" cage, but wanted to look at every posssible ounce as this will end up competing in the ADRL or other outlaw stuff and other than it's giant dimensions, light weight is the goal.

Thanks again for your input, off to weld...... and weld..... and weld

ScottRod
 

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Yes. That design your using is the litest due to all the 1.5" x .065 wall along the main hoop plane as well as inner F/C bar.
Bout .37 lbs per running ft vs 1.625"x.083 wall. So at the 30,000ft elevation level looking down at your race car, it would seem like it only makes sense to use that design.

I felt the exact same way up until about 1996. But thats another topic to be addressed later or further down in this post if i dont get tired of punching on this tiny ph keypad 1st.

That design your using is an early 80s configuration that should be credited to Don Ness, as he was 1 of the 1st to produce that design in a somewhat mass production configuration. And Willie Rells also in his early days did this orig design as well.
( now willie told me he gives credit toRon Butler for influencing his early design wrk as Ron was a great car builder in his day. He worked on the infamous carrol shelby program we all know about from Ford v Ferrari...thats yet another tangent we need to stay off of tonite..

Then Willie (Rells) went on to later pioneer the 1st main hoop forward chassis's
(Circa 1984 or so) which in '88 when i was working for jerry haas, he copied willies design after having jerry yeomans berretta willie had built in the shop as we were re-tinning it after the total cluster F#%K of the Demsey Hardy fire where the mag tinwork burned Demsey's arm and half the car down, followed by nhra outlawing mag..
So yeoman, from kansas, figured having us in StL re tin the thing was more geographically feasable. So it was easy to see the willie design in all its naked glory when stripped of its beautiful mag work done by jim Moore, Ed Weidamann jr. & of coarse the excellent craftsman , willie himself... so thats how the haas cars went to a main hoop forward design.
Know how the previous haas design came about? Copy'd by picture and hand written notes taken from Don ness's shop by "DD" and so now you could buy a ness car and get it on time w/guratanteed completion date.
Then after 88 u could get a willie car using the main hoop forward and "dash bar" design on a haas car once again in mass production and on time.
We buolt like 36 complete cars that season btw... a real henry ford assembly line for sure.
Ok..bk to topic...

So the willie haas car, or jerry rells, take ur puc, was born and was more of a mid center helmet under hoop design.
That willie chassis design was a main hoop forward of 8" in front of lower 4 link crossmember. ( i built them while working for willie..not cuz i copied them like the others...

Then Don went onto build the 1st hoop fully forward interaction (of helmet behind) design in late 80s/early 90s.
That was closer to 12" forward of lower
4L C/Member, as i recall.

Ive built all 3 styles many times for many reasons, and have specific reasons for each, based on the cars specific
( or rarely~ lack of specificity) purpose and class intention.

No doubt the rear hoop by wt# is litest.
By ~.37 lb per running ft.

But from the engineering aspect,
not nearly as structurally rigid, nor as functional from a
drive bar force distribution aspect,
(due to the 2 dimensional flat plane ) from the force vectors generated by such combinations as a C rotor Hemi..
I own a C rotor myself. Raced um. Tuned on chassis's w/them.

If your willing too do your calculations on how much wt# you will save,
I never needed to do the math cuz i needed the strength in the versions using more 83 wall... so i developed ways to safely and cost effectively remove the necessary wt to offset the chassis's unruly attentions to psychological counseling by Jenny Craig.

If you care too put in the time and do the math... plus or minus a lb or 2 is within reason, as i dont expect u to 'gonkulate' things like the filler rod aspect/differential & such,
into this measuring of diff designs....

then if you relay to us, that disparity of said wt#,
In private if u wish, since doing all that wrk is valuable time for you, and not something that you might be ready to share for free
w / the world,

as im prepared to share my portion of responding input of highly prized wt# savings to the same world.. just yet..
in my life
( saving it for 1 of my podcast topics)
Thinkin of starting a really good indepth technology podcast for us guys to share our craft together as im getting old and dont wanna die without passing some of the 60,000 + hrs i hav in this trade along to others before i take a dirt nap.

This calculation you need to do is the comparisons that abundance of 1.5"x.065" tubing design vs the increased 83 wall design in the 25.1 spec by wt#.

<I believe you might reconsider your purpose of using the lightest of the 3 designs to carry the massive force vector loads of what I assume is on a big tire car???
on that note;
2D lite wt main hoop vertical plain
vs the 3d plain of the other 2 versions...
Aka, the .083 wall forward versions,
( either 1 of the 2 sfi types using added 83 wall)..

and i then, in return,
I show u how not only to save as much wt#,
or possibly more wt#
( & no... NO TITANIUM WILL BE REQUIRED to do this..waiste of money and poor marriageof materials for screw car power,

as its a bad choice (Ti) for nearly all applications of and into chassis integration, not to mention expensive)
< the formula we used to use wrks out to a cost of about $780 per every lb# saved using 6AL4v as laterals, diagonals, as well as horizontals/ verticals into the true load bearing structure of the 25-1 chassis itself.

I will then show you where to make up the wt# by what your leaving on the table,
that your not aware of.... unless you once worked for me or studied my car designs..

( yes, this is a very bold and arrogant statement to make,... perhaps border line comparable to the~"pre-maddona pompous ass" statement) that Roy Hill once called ALL OF US "chassis builders" in a blanket statement, but spoken verbally to me directly, at an IHRA race 1 wkend in Bristol...

If your not down for the task...I dont blame you and no worries... as you need to build what YOU WANT IN A CAR. NOT WHAT I WANT.. but Im offering if you wznt to learn something you may not already know.
And if you were to know what I already know.
Then yes..u wasted some time... So im ok either way.. but is your chassis rigidity not as important as your wt# savings.
I hold stock in both...
So did Willie and Don.. and thats why the master of lite wt, willie rells, switched to main hoop forward cars...
Nuff said...
Thx for the reply and kind words..
Regards,


Btw..on another note.....

That 25.5 spec mentioned earlier that was wrote out by SFI & consultants for them..
or should i say the designed spec of 25-5...
Has to be the most incompetently done dose of the clap ive ever seen people do.. SFI could not have ever hired more backward thinking people to do that deal..

I took 1 look at that back half spec when it came out, and said

""if i gotta build this bent up pcs of chit for a client, i will just pass on the job.""
And i have...passed...
What an exercise in engineering abomination.
 

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660, If and when you do a podcast please post to let us know. Information with explanation is rare in the chassis world. The history with it is a real bonus. Always liked the rells cars. Enjoyed the history lesson. va nova
 

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Discussion Starter #8
The short answer, around 4 pounds saved.
I like the detailed discussion and hope to continue the dialog.
The longer answer, is a comparison between the "A" and "C" diagrams in the 25.1 spec and the bars involved. Doing a fair comparison, we need to add for 12A and B being a little longer as the main hoop is further back up top, then subtract for the 62 inch 15 bar (all of these are at the .37 pounds you correctly noted as 1.625 .83 is 1.367 per foot and 1.5 .65 is .9962), and 44 and 46 bar (about another 60 inches).

Going a little deeper into the discussion, here is how I look at the 25.1 (or 2 like my current Camaro) spec. With the high horsepower cars we are all goofing around with nowadays, I see the modern Pro Mod as two chassis put together because we want to be safe, but also want a car like we grew up hot rodding in whatever era we grew up.

In my mind, the four link forward, the center of the car, is now built similar to a funny car chassis to the front of the motor. This area deals with the bulk of the torque generated and is the basis for everything to get the car down the track. The surrounding cage that protects the driver and the passenger side, and in my weird reality, is along for the ride. It provides an even further perimeter structure that none of the funny cars or dragsters enjoy giving the benefit of further combating twisting moment up to the rear motor plate, and obviously driver protection in the event of a mishap.

I don't have an opinion on anything other than the 25.1 and 2, that's all I have built. My current 25.2 is a bunch heavier than what I am building, some of it is from the differences in spec, other parts were just huge support bars put in from advice from others that in the end are just serious dead weight or could have been much smaller and done the job well.

As far as the Jenny Craig part of the equation, I fully agree and have done my homework there. I keep my fat percentages down with strict diet and exercise, my only flaw is being tall and carrying extra muscle mass.

I look forward to your lightweight thoughts, I am always up for learning new stuff!!

Scott
 

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Ive only got a few minutes, so I cannot touch on all the valid points you made right now.

What stands out at the moment is the harnessing of torque distribution. Willie started the 1st torque boxes and after i left Rells I went onto expand on it considerably.
(Now thats in production fashion.)

Widmer actually developed the 1st real torque box car in '84.
( a 1 off deal. Not in production..he didnt build cars for a living..just 1 for himself..so many never saw it at Pomona)
He and I have been colleagues since circa 1989. He is 1 sharp cat who like mysrlf, keeps a low profile...and both of us hav escaped being burnt at the stake on many occasions for both doing things people hated, and then on rare occasions sharing them w public, which chapped the azz's of the competition. We both hav our reasons..but i think its just fun to
" poke the bear" of competitors ehos only defense is tocall it heresy and burn u in public to discredit u so there own clients dont leave them and flock to u...or us in this case. Larry in eng development..myself in chassis development. Ok..moving on..


If you look at , or get answers from guys who have done chassis repairs to pro mods over the last few decades.
Where is the majority of those repairs being done?
( 1st clue)
Its not the front half the car, forewall forward.
2nd) its not the tail section rearward of the upper shock mnts
3rd) its not any of the tubing about about 15" ABOVE the FLOOR STRUCTURE, center cockpit or otherwise. Notice i said above 15"....!!!????

So that leaves the rear and mid cockpit floor area... which inside the cockpit,
Has been/is mainly the center X bars in floor. Seen tons of thos crack n break..

And then going reaward of said X members, its now the most common area of rear, which lies directly AROUND the 4 link brackets themselves. AGAIN..Around...
I wont be more specific than that at the moment. But u guys know what i mean if u are in the game.

So if the most repaired areas,
over many 100s of cars that have cracked, crushed, or damaged these tubes , and brackets,
is also, THE SAME AREA as the A drawing 2d, flat plane design, using all that 1.5x .065 wall tubing....???!!!!

Do we really want to put the most destructive engine combination known to man....
( the billet hemmmroid C screwed pwr plant) in FRONT if the WEAKEST ( also lightest)
of the 3 generally accepted construction practices of A, B & C? ( by SFI standards)

For less than say, 10 TOTAL lbs of additional wt. savings??? Things that make u go "hhmmmm?" Right?

What most guys Ive had the opportunity to educate on this subject...
many which did not initially grasp the increased integrity design of ( B/C)
the hoop forward by looking at it from well below the normal 30k ft elevation level.
"Cuz SFI ssid its all good any of the 3 ways?"

A carpenter's acronym;
Build a 2x4 framed up wall..wide as a main hoop..
<similating the 2d A drawing single plain main hoop design.>

This wall is just 1 wall. Attached at the floor only for the moment..
<yes , u will then have other walls 90° on the outsides later to support it...but stay with me.
for illustration purposes...

U then build a main hoop forward wall where you have a 3 dimensional presents compared to the 2d spec A ..
Braces going rearward of an otherwise 2d wall now..
(simulating tubes that go towards the rearward upper/lower 4 link cross member)
U can push that 2d (A) wall secure only to the floor right, over easily.
But build a reverse "Bay window" style wall the has angularity of additional short walls on each outside of the 2d wall.. going backwards to the 4 link bracket area..

and u know have a 3d wall which u cannot just push over effortlessly.

Of coarse all 3 designs eventually get 3d support from cockpit cage structure.
Yes... but when breaking down the structure, u must look at pcs..
not just the entire design. Why? Cuz the entire design never breaks or cracks on the pro mod chassis, does it?
Only areas are suffering damage from high acceleration rates and of coarse the much more contrlled, but still on occasion, shake rattle and body roll..

But rather than make anyone following this thread in a "drinking from the firehose right now sorta way",

Just think about this 1subject 1st,
And that single flat wall 2d (A)
( main hoop rear design,
and the entire force vectors applied to it, via 4 link system pushing ( & pulling) on that flat stand alone,
Like framed up 2x4 carpenters wall..
For again. Less than 10 lbs.
I can get u 10 lbs in places i guarantee u havnt thought of. Why..cuz i did um 25 yrs ago and havnt see but maybe 2 guys copy it oflr figure it out on there own...
So like i said...even without jenny craig..
There is wt# to be saved without expenses.
2 of them actually mske significant improvements to the cars driveability and overall strength to wt ratio beyond the wt# itself even...so same wts but using these techiques which save wt, are still better regardless of the wt loss.
No thats a tonuge twister i thk.

All that above, Vs the wall that has a 3rd dimension B& C) because they both have additional angular support walls on the outsides going rearwardtowards the what???..
""Area that gets damged 1st the majority of the time, excluding the floor X of coarse""

Look at the lower 4 link cross member of each design. A is straight.
B is straight only in middle ( 4 link) and then on each side of brkts, it kicks FORWARD angularly, to the point about 8" in (B) front of the center area where ur 4 link brackets are attached.

Then the main hoop sits at that (8")
forward location, giving that area reward,
which is the most repaired area of these cars , ( broken record) ...
more depth to structure. Hence structure integrity increased.

And since the A design is using the smaller diam (by about an additional 10%) of .065 wall ( thinner as well). Oh, and lets not foget the 1.5" vs 1.625" % increase...
Wait for it...wait for it.....Bang!!!
27++++% more wall thickness in .083 vs 065.
So almost 10% in diam increase..
As well as 'nearly' 28% wall incease.

As Yoda might say..
"Leavin 27+% wall thickness on the table,
we are?"

So.... We must beg the question.
Is using the thinnest, & smalleat diam. spec'd SFI drawing material, really a good idea?? for less than 10 lbs of savings?
You said 4.. i trust u but never bothered w/the math...why..cuz some things the minds eye see's..but i wanted u to quantify it in real #'s so its more tangible for the mind.
And others..very fee others who might be following this unobtrusively odd and boring thread to all the world but us ..what?? 4 huys now??
How bout u 2 lurkers out tgere just raise ur hand so i know ive manged to get an entire audience of 6 peeps on this worn out, jackazz's rant on a topic only Scott cares about...which hey...if just 1 guy cares.
Is it not our duty to at least be supportive.
Sidebar:
Widmer told me 30 yrs ago. Look... its ok to "take" from the industry. Taking means learning from others and absorbing info that folks besides yourself worked really hard to collect, and in aflash, enlightened you with it. Maybe saving u yrs or maybe u never got it otherwise...BUT.. HE SAID...BUT..
THERE WILL COME A DAY...A day when u should, and must...by an unwritten code of ethics...give bk to your community something's that only may you and a few others have learned.... and just as i have hopefully taught u a few things i hold close to my development heart, so should you give bk 1 say when u can provide some help or at least spur on another guys mind to think about something he nay not have other wise considered. So we can all take.
But at some point we must give bk.
Most of my giving bk has been by consulting.
Mostly 1 on 1. This social media, forum thing is really new to me. Do i dont know proper etiquette or any of this online stuff.

Bout 4 yrs ago i posted 1 time on how willie was the master of lite wt# and why.
I hot roasted by some long timers, got told to go to the newbie section... i was pissed.
So i dropped out. Like a month later i went bk...saw like a few guys beggin for me to come bk cuz they weee genuinely interested in learning and seen that maybe i knew something that the guys who verbally ran me off may never know. Its a world of jealousy out there.....ok...gotta really wrap this up...

although i really didn't want to divulge "all this much" about this next point, or at all maybe...,
much less before we get into the world of podcasting ... if we infact do...

( which by the way ive only considered recently do to my semi retirement, after more than 3 decades of car building, but thats yet another subject for later).

But the big question when examining damaged chassis's might be this.

Im about to use an eng metaphor i thk we all an relate too..

( not unlike camshafts that have gotten literally 2Xs as large in diam. from yrs ago,
withliterally double+ the amt of bearing journal support to said camshaft,

( &certainly not mandated by any spec,
( like sfi 25-1, ect)
but by the greater need for [email protected] the cost of added wt#)
The chassis specs we are building too now on 25-1/25-2 may very well be the same conundrum.
Just cuz the spec calls out a MIN TUBE SIZE and WALL, does NOT MEAN ITS SUFFICIENT IN ITS ABILITY TO HANDLE THE increased forces that we know are CLEARLY present in todays typical screw blown hemi or any big pwradder car, as those NOS cars can tear some chit up too..

just by looking at the 60fts we have evolved into, over the past 20+yrs, while
SFI A~B~C havntchg'd much..??

Also SFI, while not evolving the materials, or sizes, or diams much at all, other than 25-2, and the strengths of the stuff we are directly pushing on ( & pulling) & against...
for over 2 decades now. NOTHINGS CHG'D.
Construction wise..spec wise...but pwr has.
60fts have...These are directly related to what we need to be building to absorb these increased loads.

So where were we 2 decades ago in 60ft?
And where were we 2 decades ago on that 4 link tubing spec area of the car?
1 area has changed...60s and pwr..
1 has not. What are min build specs are.
And do we wanna chose the lightest and lowest strength materials spec.
From a safety standpoint, which we havnt even touched on yet.... the specs are doing ok i suppose. But how bout from the increased pwr standpoint??? Thats chg'd.

So a chassis design and material spec that was good in 1997... is still good in 2020?
( plus a few tubes and a interior ceiling and some outer leg protection.
None of these additional items are in chassis tubing, which means these are safety related but not load beari g under pwr related updates.

Say what you want. Think what you want.
But I know what im seeing and thinking.
Nobody made the prostock guys go to telephone pole sized cam shafts (for safety) or installing enuff bearing journals to support the Golden Gate bridge..

But its funny how, without us ( as racers) being "Forced Too update/upgrade" to
increase the cam core strengths, we still did.. adding more wt#..
a lot of it when u think about the chg's in block design, as well as cam core itself, even if it is gun drilled..

Im trying to spell out the answer here without literally spelling it out. So the average lazy reader will have moved on long before he got to this point in my
""supposed to be qwik note""
That was to be , continued later...

Digest these somewhat simple points before we go down the road of the entire chassis design front to bk.

We can get there. Sure.
But making the rest of the guys who really want to learn ( all 6 of them following this) by drinking " from the firehose "
just turns them off, and they walk away forever.. Cuz what takes 10s of thousands of hrs to learn, just cannot always be conveyed in a few forum posts.

I can count on 1 hand how many times ive posted on forums in my entire career.

Im only now "coming out of the closet," to begin with, since I no longer have to directly rely on feeding myself from all my past decades of 16+hrs a day x 7days a week,
for more yrs than many on here hav been alive.. im semi retired now..

All those yrs of wrk, we used, to get to know how VERY LITTLE, WE DO KNOW... TRUST ME..its not much..

for anyone still awake after this rant,
thats 10+ mins u never get bk in ur life..
for those who bailed early...

thx..cuz i may hav to come out of retirement 1 day, if the family doesnt stop spending money like its methanol during pwr tour...
and i dont want to compete with myself if i dont have too..(J/k)...well..sort of ( eye roll)

To be continued...possibly...if u lurkers will raise ur hands. Dont hav to speak..just a smile will do..
u perpin/peepin Tom~ bastards, ?
Nuff Said,
Regards,
 

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Discussion Starter #10
I will then show you where to make up the wt# by what your leaving on the table,
that your not aware of.... unless you once worked for me or studied my car designs..

I look forward to your lightweight thoughts, I am always up for learning new stuff!!
Ok, you said a lot of stuff, I am listening and reading carefully.......... I understand and agree with the area of damage (the lower X and that area), looking forward to understanding how the number 15 bar gets heavily into play in relation to the bars below (X).

Looking forward to further thoughts from you.

Scott
 

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I'm guessing 25.1 rules are alot more in depth than 25.2. That's said my few hours reading and looking over and over those diagrams. This post seems to.confuse me more. I follow the weight vs strength. Got it. I understand theres better places to save. I got lost with the wall analogy. Is it the more forward bar has the cage bars behind it better supporting or did I take it completely wrong
 

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Love this discussion. I can understand why the B and C designs are better for handling the forces applied to the 4 link brackets. Keep us updated on the podcast.
 

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In the 25.5C spec...it's in Note VI.5.A, and states "...and the Main Hoop (10) can lean back a maximum of 20d from vertical." Page 7 in that spec for reference
 

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Scott, and to u few others.
I can more easily address the new guys who jumped in 1st, who hav a simpler question or 2, at u others guys expense.. cuz we hav confusion..

Any 1 who openly admits to not understanding my explanation/explanations. Deserves something better from us.

Yes, My grammar and punctuation on a small ph key board is much worse than a laptop.
(So maybe i need to get on a real keyboard..)

Which btw, U all who just say
"please explain"
I get the.....
"Hey dude, ur just confusing me"!

This really Started as an explanation to Scott,
wanting to build the litest chassis SFI allows for a screw blown hemi..and was there any pitfalls to it. And nobody spoke up.
So we did..

The drinkin from the "firehose" thing doesnt always hav a
trickle to drink from setting in My brain..

It see's alot of this crap, since ive spent 30+ yrs , um...closer to 35, doing this for a living now..

and its me, trying to do my best,
to convey & still condense,
but it has these pcs of history,
which tie things together...in my own mind, im saying...

1st~
25-1 vs 25-2 -- in My minds eye version of 25-2, it is an upgraded version of
25-1, for heavier cars, runnin 6.00s. No real secret there...i get that. Hope uguys see it that way too.
Now a few of us were puttin X's in roof as well as floors before 25-2 came along.
Willie, Jim, and myself.. but hey, lets not lie to ourselves. Jim & I both learned that from Willie.. bk then..nobody used an X in the roof if u weren't forced to by SFI.
Except Willie...then jim and myself...
Cuz just like the floor, the roof needs an X.
Spec'd or NOT!!..
only 25-2 calls for it vs 25-1..
Ok..gettin off the rails way to early here..
Bk on topic...sorta...

Cars were getting Heavier than what were being built @ 25-1 inceptions for the cars around 2350lbs. Hence 25-2.. more tubing & heavier wall for more wt... but really more power. Cuz u had to hav big pwr to move big wt# to 6.00.. so u could argue it was a hp spec, not a wt# spec.. Both i suppose..

We were not even trying to built 2850+lb cars (on purpose), not really..
till Mel Roth created PSCA,
& its early 2000's rules structure.

Not on purpose anyway. ( heavy cars)

Why build a ridiculously hvy car??
Cuz he created classes like Heavy Street & others, and called um street cars.
Pacific Street Car Association
Heavy on the word street..too set himself apart from typical boring NHRA STUFF & steelcars that had no chance anywhere else out west...excluding Orlando for the moment..

They were not..street cars..
maybe steel body'd tube chassis cars/trucks..but not street cars..just heavy tube cars w/big pwr for the era..

So when NHRA SFI pro stock 25-1specs were looked at...... for thesecars..it didnt seem plausible. To much "F"=MA
( google it.. f= ma.)
and our early version of pro mod came around in 1989-90, born from IHRA Top Sportsman.....which followed a thing called "Advanced ET" in NHRA's WORLD .


We were building mostly 2350lb cars or liter when possible for ( top sportsman)
TS ,
or aka, the early days of pro mod,
that were built to a prostock chassis spec, if at all..( laughing)
and "Bills" ( kuhlmans)
1st w/double frame rails car, was done by a guy most of u dont know...but should hav..
Cuz he was F#$king awesome..
( sidebar)
His name, Gary Hajek, & he built among many other things ,
the 1st truely recognized Dbl frame rail Door Car chassis in 4130, for Bill Kuhlmann.

when Gary was contracted by Bill Kuhlmann to construct Bills 1st Berretta chassis.
At about age 25/26 tops...
<Previously~his ( bills) white 3rd gen Camaro , that Bill built himself,
& mig'd together> than ran that 1st 200mph door car hit, at an ihra event..

The Berretta, Not to be confused w/Bill's own diy Camaro, that ran this 1st 200mph in TS IHRA, was 1st to run 200 in door car history.

And soon after that, the chassis/4link area nearly crushed inward, the 4 link area itself, not just too awful long after that 1st 200mph pass. So Bill decided to contract a guy who knew chassis's nearly as good as Willie or Don Ness, but was within 40 miles and had already built more world championships cars than most diy guys hav built cars, period..

"Hmm. Does that lilsidebar tie into this topic at all?" The crushed 4 link think of the 200mph king of the hill @ the time??

Yes, most of us know Bill's own DIY built car was mild steel /mig welded. THICK mild.
But mild sterl mig welded non the less..

STILL...
how much hp did he really have to run 200 THEN, vs an NHRA pro stk car like it 10/15/20+ yrs ago...??

That Camaro of Bills was a NOS 3 kit
" more money sonny mtr" as i recall,
& the Car, Bill built @his hm shop...

Bill did, none the less, run the 1st 200mph pass in his DIY mild steel white Camaro..

which nearly tore the 4 link out of itself..
not just too long after. Hence..contracting a guy who was young & very well educated in race car construction.
Last yr Hajek ran IHRA pro stk w his father, while workin for Haas, he finished hirer in the world, in points, than the boss.
That ull give someone u wrk for the redazz, especially when ur like 25 yrs ole and u built ur car and ur dad tunes it...lmao..
Gary was just bad azz.. an im dam lucky to hav worked for him.. he was a really great guy who could not only weld w/the best of um, but build or drive as good as anyone else in the top 5..

Now Bill had some isdues causing the Camaro chassis to tear up the 4 link area.
Partly......noOOO....
LARGELY....
cuz Bill believed sliding the clutch was waisting all the power, ( & A bad idea)
And if they had worked that hard to build hp..by gosh.... he was gonna use it..not slip it away....
the philosophy then was, in Bills Bills mind as well as some others,
WHY make BIG PWR and then SLIP the clutch , and waiste it ALL away.... heehee....

A huge historical learning curve lesson, YES..
in AND ALONE thats another interesting topic..but for nother time...perhaps..

So Bill , post 3 gen Camaro 4 link crush..
contracted Gary Hajek of
* Hi-Tek race cars*,
(Gary, was former shop foreman,
top guy/ early employee in Haas program..

who also helped build & did most of welding of the chassis the "Mad dog's" barreled Tbird, that rolled like 7.5 times or so,
at Atlanta, against Butch, ~utube it~ ...
( Maddog & BG = bob glidden for u young'ns)

then after the BG crash, whats Bob do??
BG jumps out of car, as it rolled
( barrel mind u)
to a stopped..
and covered his Boss 429 intake manifold..
w/its carbs & top torn off, using his fire jacket . It was a bad bad crash.
( dbl sidebar.. monday morning post crash..ph rings at haas's.. billy.. says to Gary.
"Dad crashed the car yest.."
( long before internet & livecasts)
He's ok.. said a start new car TODAY!!
28days later, Gary & Dishbein not only build complete new car, but itcame bk from Hookers ( hooker painted 98% of haas's cars then) on the 28th day.. & Hooker had it close to but shy of a wk.. so Gary & Steve built bobs new car in bout 21 days.
Bobs stops in on day 2...post race...tells Gary.
""Every main tube in new car , I want in .083 1.625"""
""But Bob""..Gary replies... " the car will be quite a bit heavier than what u like.."
Mad dog turns around, says to Gary..w/smile.. " dont worry... I just make more pwr " & turns away, and off to Whiteland.. ( Indiana) to mk more pwr we all presumed...lmao.. that 083 car was later known as ole Betsy..she went on to win more races than u could count.. but thats yet another story...
Moving on..


BTW, why Do u think BG coveredup the intake after the crash before camera crew and safety Safari could get to him???....
not what u think...
Not cuz he had nitrous plumbing being hidden...or other illegal means..
Nope.
Still, many accused bob of that,
cuz he was runnin fast..

But rather, the real reason 35 yrs later, can now be revealed i suppose..
It was to hide what VERY few PEEPS knew, and that was that the Aries/Root built, magnesium, cast, ( none the less ),
2x4 dominator intake manifold atop bobs boss 429, w/ bolt on alum sides and top plates, was a freakin cast intake anyone could buy...
Actually it was Roots " bolt on top"
blower version, of the Root boss 9 cast mag intake, as the plenum and runners were identical in both the NA and blower intakes.

Blowerversion had on top a removable cast plate, w/bolt on top, for blower apps,
( mostly boat guys used um),
vs the same mag cast tunnel ram version which was not friendly to the bolt on plenum design, which made entry of runner radius mods much easier,

but it still used the same floor and port runner design that was brilliant,
even if on accident in design.

I suspect it was also easier to pattern make/ & cast that way.
But it was ignorant bliss of design,
& what we later learned to be excellent technology...a nice advantage over the GM guys for sure w/the deep V plenum floors on fab'd intakes..

That intake manifold was a design Tom Robert's had came up with during the pattern making process for Nick & Allan.. <Aries/Root> Roberts said BG made fun of it at 1st an said something like, "did u use a mailbox for a pattern?"..
But man did it make pwr ov a V flr intake.

Its was jokingly known as the boss 429 'mailbox' intake, ( BG used the blower version w/bolt on top, as its easier to mod. Add volume w/diff alum sides, and a custom alum top to make it look like an all fab intake due to cardboard covering the runners an rails...)...
and it was actually quite special, unbeknownst to 99% of the eng development industry,
at the time,
(but a sweet lil HP advantage when used right)

cuz it had the 1st EVER RUNNER DESIGN
Used ... <in pro stk>....
which imparted the concept of bottom runner floor length equaling, or nearly equivalent to top runner ceiling length,..

( does a airplane not fall out of sky w/o diff lengths above and below wing skin length diff. Or lack of i should say...

unless u got huge aerobat plane w big hp to pull a symmetric wing design , it (aircraft)
will drop like a rock..

W/no pressure differential, & without varied wing length surfaces. Same principles apply to an intake runner but inversely.
Sounds a bit confusing.. icircle bk 1 day for those who dont get it...

Yes, i know a bit about combustion eng development..& aero work..

well, the end result of a nearly = top/bottom runner length , was/is a net result of a more balanced out "air speed" at the valve seat perimeter, and wrks quite nicely, when applied right.

( vs a V floor intake w/ 2 diff airspeeds arriving at valve seat at same time, from floor to roof of port...a diff in length acts more like a plane wing creates lift..
U dont want a huge delta P at the seat of valve).
this topic can be covered later, in an Aero 101 thing, if any interestisthere..
if not, no worries..this is a chassis post..yes.
But some things do tie in at times.
Like the all 083 car BG went on to win severa3yrs of championships with..even thou it was heavy... so yes..it does pertain to topic... if ur willing to do the historical research, in order to see into the future of the sport. Its all matters.. Just depends on whether ur willing to use the info & results.

1more thing on the intake deal that contributed to carrying the extra wt both at crash and after..
since top and bottom air speed reaches the valve seat closer to same time, w/ a runner thats more = at roof & floor,

UNLIKE a plane wing which does not use = air velocity, but the opposite to create lift..
Causing Delta P differential.
for said wing lift....
Good for plane.. yes
Bad for homogeneous fuel mixture inside an intake manifold...as air/fuel mixture crosses over valve seat/valve head, and enters the cyl shortly before the single most important event in an eng.. Combustion...which infact rotates a crankshaft..not airflow..
But again... no sense in arguements over airflow vs quality combustion now...thats another topic entirely...

But that idea/design, of Tom Roberts, that Maddog was hiding, post crash...
took Eon's for others to figure out...
Some STILL hav NOT figured it OUT yet,
35 yrs later.... LMFAO...
Was it an accident of engineering marvel?? Umm.. likely.. YES..
but just like an airplane wing does it very well, Delta P differential.
so does a "V bottomed", typical fab'd up 2x4 plenum intake, of many decades used,
that creates varied velocities at the valve seat vs a ~~intake runner whos top & bottom are nearly = in distance from top or mouth, to valve seat.. kerping ur air fuel mixture more homogeneous ( ho ma jon us).

Which the ( valve seat) is likely 1 of,
if not, the most critically important area at which the air/fuel mixture must make a huge transition, and run ""the gauntlet"" as we say,
of Delta P change,..
It must be done w/o separating the homogeneous air/fuel mixture, going into the cyl, or ur quality of combustion is $hit,
which if it then separates,
& turns to wet out.... it then leads up to the most important event in the eng responsiblity, COMBUSTION!!) Or lack of..
w/a poor mixture quality...& BG didnt need any of u guys,
and tv cameras, an peeps at hm watchin a later cbs broadcast, seeingthis stuff, & every eng builder asking themselves why is he running a ""cast production intake"" on 1 of the qwikest cars in the country ??WTF???
A CAST intake on an NHRA pro stk car??
Why??? Cuz when we adk why? We follow up w / investigation...right,,??

U gotta hide ur secrets. No 2 ways about it.

Everyone thought BG was hiding something like nitrous or something else...nope...

He was hiding what was a cast Ford part # design feature, that had in it, a design feature that could be used on all the other 50 GM pro stk cars in country. Nothing more... nothin less. But that .083 wall chassis ( everywhere it was normally 1.5" x .065" car, really hauled azz..it won several championships...ole Betsy did.. nobody would believed u if u said that car had 083 almost everywhere it should have 1.5 x 065..

Cant argue w/success.. Heavier than spec car wins tons of races an championships.

Everyone thought maybe BGs intakes were these fantastic works of Alum metal art w/ crazy dams/diverters/ect.. Nope....alum tops, cast mag runners from 1984..lol..

Damb it.
Was not supposed to turn into Combustion 101... thats like season 2 of the podcast along w/Aero.. j/k


Ok, so Gary build the 4130 chassis for Berretta, previous he had built the chassis BG crashed that was bad..& its predecessor of 083 which flew like a dart as well.

Gary built that Berretta double rail chassis that Bill K. finished out himself, hung bdy, tinwrk, ect..
( as he wanted to save $$$..)
Vs his own skills of mild steel & mig'd... but a still true statement..

That Berretta then ran 200mph, like 14 or 17 times before anyone else had hit 200.
It was an "A chassis Design,"
W/ 083" where A calls for 065"in and arpund the 4 link area..

So the point is Bills car still used 1.625" x .083 wall where the later , SFI spec calls for 1.500" x .065"wall in those 4 link areas..

So there is a point to this sidebar guys.???
& i hope ur getting it..??

U can built above sfi spec. ~ Yes.
Just not below it.. ~obviously..
We all know that...

but can we bring ourselves to ACTUALLY do it??? put .083 in place of .065 and 1/8" larger at the expense of say, the 4 lbs Scott calculated???
(assuming u dont build a Main hoop forward chassis, but build an SFI "A" style,
replacing the 065 around the 4 link w/ 083?)
Worked for Mad dog and 200mph bill..
W/ a lot less hp/ tor than a screw hemorrhoid.


(& yes, Mad dog ""bobby g"" did almost do it that race....200mph.. when bill went 200..
Mad dog ran 199.xx, in Darlington as i recall, in an nhra pro stk car that was only 600".. lmao.. no juice..just good air and 100" more tgan NHRA trim. What a feat!!
And w/ 083 wall Betsy too boot.,!!

< oh...& BGs cars were built by whom again??
Non other than... Gary Hajek
( & Dishbein as well) ( @haas's shop)
While the boss is still wrkin a day job...

& he ( gary) built Bill's car, ..
Same guy who built the chassis that ran 200 like 17 times before anyone else did...
( SHOCKING!!! ~~~~~~NOT)
Gary was a fantastic racecar builder and I was blessed to study under him until his untimely death.
If he had not died so young, @ 28.
U guys would be praising this guy vs all the others who are now considered the top hitter car builders of fast door cars.

This guy was building world champion cars at 25 yrs old, or younger actually...
History is important guys... its ur crystal ball into the future of technology...
& that BG 083 wall car was built by steve dieschbien as well as Gary Hajek @ haas's>

While Haas was still workin a day job.
and these 2 guys were getting it done day in an day out...
2 bad azzcar builders w/awesome skills an talent..circa 1985/86..

"""An Ametuer learns from his mistakes,
A professional learns from the successes of others"""
Thats why i spent 17 yrs workin for/with sharp cats , before I struck out on my own.

Mad dog used his 500" heads on a 600" block combo, to simulate, for testing purposes, for the BIG SHOW @nhra ...
Practically Free testing on good tracks...
Smart guy...id say...he wasnt tryin to win the ihra championship..just use there sandbox to go qwiker on the Big Show...still ended up winning lots of purses,
and finishing in top 2-3 most yrs he did it..

(600" was a small eng combo in comparison to other ihra racers @ time,
But it was the Most cu in BG could get into the 10.2/.300 ford Root eng blks,
A decent rod ratio like the 500" stuff had,
that simulate/create a comparable combo, to test for the NHRA 500" races..
for testing, data collection.

while others in IHRA like ricky were using 706s or bigger... BG was like #2 qual @ 600"..

Bk to Dbl frame rail deal now.
Joe Lepone had prolly the 2nd Dbl frame rail car, that Ness built in '88,...for nhra pro stk..

built shortly, not long after gary did Bills beretta chassis..the concept was getting traction..
( joes car had the dope smokin rollpapers sponsor, on that Berretta, as i recall).

when Joe had the clutch JUST RIGHT, on occasion, before we understood sliding very well..., it 60'd pretty darn qwik,
but was unrepeatable, w/clutch tech of that era being a 3 finger rag, single disk then,
and a 500" eng torque of less than 800ft lbs at 8000+ rpms.. not enuff torq for dual rail car to be advantageous.

Not enuff spunk for the stiffer chassis and poor shock tech of the era , to get a dbl frame rail car to really work w/such low torque vs a pro mod pwr adder deal..
Our shk technology was crap then.
( thats why ibuilt a shk dyno before ALL THE BIG CHASSIS BUILDERS went out an bought 1. Again..wasnt hard to see the future...just lk at the past... flimsy cars were easier toget down bad tracks?? Wtf?? Why i asked myself?
The answer.. cuz we are behind on the shk technology and need the car chassis to flex to mk the shk work w/ tire compounds we had then..

Bill & Don actually did some cross collaborating on big wing & dbl frame rail topic, 1 helpin the other in trade out of tech.
( u tell me what u know, i tell u what i know, sorta thing...)

F#*k... this deal has got all sorts of off topic...!!!! My bad...
To much info, pent up, stored up info, useless info i will take to my grave.
Stored up for too long...i guess...
nobody really cares about it.
Its Just lost in history....ok..i care...but who the F%&k am I? Im nobody..

Its like havn blue ballz for racing technology & history i suppose..

Why is history & historical knowledge so important?? IMO..

Cuz its the closest thing ANY OF US HAV TO A CRYSTAL BALL, or as close as u will ever possess to knowing what lies ahead.
Its knowing the past..1st...when trying to move forward..into the future.. what worked..? what didnt..? why..??

And yes.
"Those who do not know history are doomed to repeat it"
...very old saying...we all know it..
or hav benefited from it. Or not...lol

Some know the ""doomed part"" of it,....
not the "knowing part"- of drag racing door car history, in most cases.

Trust me, U will benefit from an understanding of history in your area of ANY interest,
much more than being doomed by it,
as long as u use it (the knowledge) as
wisely as possible.

This has gotten way out of hand...

Ok.
The main hoop strenght "CONFUSION" COMMENTS topic.

Build and weld up a A drawing main hoop in your mind. JUST THE MAIN HOOP AREA AND ITS ONNER TUBE SUPPORTS IN 2D.

Tack weld it , OR SECURE IT, to the jig table. In ur mind....

So we are not wasting ALOT of time/materials..

Stand on jig ( in ur mind) & try to push on it.
This flat 2d main hoop w 4 link brackets welded to it. No bars going forward or rearward yet..
Try to Push it over.. its just a 2d flat Plane,
of A drawing main hoop, w/065 wall diag's and upper 4 link crossmember,
and its inner tubes within the 2D plane..
Like building ur main hoop and inner tubing on a table thats flat..then stand it up like ur putting it in the jig to start going forward/backwards..
But before u do.. push on it w ur mind like its under load..

Does the flat plane 2D A drawing design stand up to u pushing on it in ur mind??
W/1000 ft lbs of torque X's a 2.50 low gear x 5.00 ring/ pinion,
which then = 1000 x 2.5 x 5.0 of torque divided by 2 rear wheels..???
Now my screw C made over 2000 ft lbs of torq.. So u can use that if u want to push on ur main hoop u built in your mind using my math equation as to what kind of torque u are dealing with at the tires thats pushing on the 4 link area, and pulling of coarse..
So just use instead
2000+ ft lbs. X's <even a> 1.80 <low>
X a 4.30 <ring gear>... do that math???

So in ur mind, does the flat 2d A main hoop design w/ 065 wall tubing fold over, flat, from the forces, on ur jig table,??
W the forces & the leverage u hav when trying to push over the 2D flat plain A drawing main hoop...
All that vs the B & C designs which put a 3rd dimention to the integrity of the forces applied upon.

Remember, besides the 083 main hoop in A diagram.
The rst of those tubes within are all .065 x 1.5" outside diam.
With all that force going into the main hoop thats in a flat plane..?? In your minds eye of coarse..

Im saying to do this in ur mind.
Vs in material..
Will it fold over to the floor or jig surface more easily since it has no support in a 3d or 3rd dimension...???
( thats what i was trying to spell out in the last post, so maybe this clarifys it some?
I hope anyway..?)

Now then,
build the B & C Versions in your mind.
2000 ft lbs of Tor, X's ur choice of low gear,
X's ur choice if ring/pinion.
Divided by 2
[ 2 rear wheels applying these force vector multiples]
Not the entire cage...Not Yet.

Why?
Cuz we dont tear up entire cages on these chassis building them to sfi SFI specs.
But we do tear up that 4 link area and floor X.. so just play along for now..
Vs trying to problve me wrong.
I wont argue u all are more likely smarter than i am.
But hav u seen what ive seen?
Done what ive done?
That.. can be more powerful than a high I Q.
Which i do not hav...

..just usethe main hoop bk to 4 link on B/C B/C drawings,
But go thru all 3 designs in ur mind..
then apply forces to each..
Thats what im askin from u.

And push on each of them, in ur mind, and see if they, B/C sfi specs,
fall over ( in ur mind).
as easily as the flat plane, 2D ,
"A" drawing design did?
At least in ur mind anyhow.

Does that explanation help anyone who is confused to somewhat understand what Im trying to convey?
Hopefully.. but maybe im doing a poor job explaining..again..im not very smart..
And im not a teacher...just a dumb azz racecar builder...heavy on the "dumbazz".

So.
Compare all 3..without the rest of the cage tubes going forward or bkward...in ur mind.

Which designs take more force,
before collapsing,

assuming u hav not yet built the rest of the cockpit structure yet, fore & aft...of coarse.

Just a A,B, & C comparison of strength in main hoop to 4 link integrity/ integration ~
designs ~
as they relate to absorbing the forces and force vectors generated by the lower bar pushing and upper 4 link bar pulling on the chassis under acceleration.

Is the firehose dribbling at allyet?
Or still full blast? Or in between I hope @ the very least.

Now Scott, i gotta apologize to u for not answering ur question yet,
about the X vs #15 bar. And I will attempt to still get to it..

But i am trying to bring the other few up to speed 1st, somewhat at ur expense i suppose , ..
( but not on purpose)
since it was ur post to begin with.
Im tryin to get there...i really am..

I guess ur gonna hav to chalk it up to a time where "u are giving up" some of ur own posts/space & time,
in order to give an explanation to the guys who are lost or say they are confused..
Its like the
"giving back" thing, sorta...
at ur expense now, scott, (im afraid...)
& too the guys who are saying they are not yet on board, or are confused.

Cuz going on w/ others still confused isnt helping the greater majority.
Not yet i dont think.

But I will do my best to get bk to ur X vs #15 question.... if u can please bear w/me.

tryin to get the very small but interested group to a specific point,
before we leap ahead... I guess.
Hey.. nobody ever said i was a good teacher..

& im trying to 1st reach the 1s who are intrigued or curious to learn,
the 1s who already are perhaps already sorta primed up the conversation, but not yet gwtting my poor exampke of how to view this topic, i supppose...

So..besides the distractions & the irrelevant history lesson to 99.9% of those who might soneday ready this..

Im tryin to do my part,
and the info side bars, ive thrown in...are an unfortunate penalty all must pay to read my bullchit. It is these historical facts which document much of our understanding of what works or worked for us in the past. And so we try to build on that understanding, hoping its a solid foudation on which to improve, both technologically for applying our Tor/Hp,
As well as from a safety aspect of kerping ourselves & our clients as safe possible, even if it means going beyond the SFI spec for a given A, B , Or C drawing/design..
To achieve the necessary results.

cuz althou sfi SFI specs are somewhat relevant, they are only minimums in reality.
Not maximums...

U teally do want to be a student of history, not just a student of today going forward into the future.
U gotta understand the past in order to invest in, & invent the future.

In order for each of your own crystal ball's to work in the future,
Its my jackazz opinion, that u really do need to hav some understanding of the past.
I promise u that..it will help.
What u dont know can hurt u in this business/sport.
its very important to know how we got to where we are, and more importantly
I believe......WHY....???

At least thats what I believe is imperative.
Maybe im just full of $hit... u can decide for yourselves. Not costing me much either way.

So if A drawing is in a flat plane ( singular) main hoop design
B & C in there 3 D main hoop planes (plural)
..as it relates to the coordination of the 4 link system tied directly too it. Which designs do what differently?? If at all.. its a question..not an answer.. im askin for anyone reading this to ponder it for a bit.

Which designs, ( A,B,C) FOR ur application,
Seem to hav more strutural integrity, or the differential's of such, vs the added wt#, while including the power of a C rotor Hemi.
Vs how each design has or does, stand alone, on there own, unsupported by the rest of the chassis, so far??

Its my opinion weneed to do this examination BEFORE the rest of the STRUCTURE of the CAGE, going FORWARD, OR REARWARD, is put into place??

Does this compute, or just more confusion?? If not somewhat clear...
speak up now!!..NO WAIT.. tead it a few times..
Give it a few days..then yell at me obscene things.. but think on it and the above examples of cars from the past I related too in order to try to shed some light on this topic.

& Dont be afraid, or ashamed to ask.
Anyone of the whole 3-4 people reading this obscene bullchit..
Id rather peeps really feel they understand it,
Rather than just say u do.. for fear of feeling of lesser intellect. Cuz tgey dont come no stupider than me.. Ive had to learn the hard way...30+ yrs of living, eating, and breathing this chit 25/8...not 24/7..
& i still dont know chit..

Cuz if everyone is up to speed yet, im just a poor teacher and need to stop posting this stuff..
Cuz all this time of writing and reading is for nothing...
IMO anyhow.. no fault of the readers..
Fault of the writer..myself...

So are we even close yet on an
A v B v C- thing of the SFI design spec's,
and how the area between the 4 link brackets and how they tie into the main hoop, are in each design,
diff in how they absorb and disperse the force vectors generated via the 4 link bars..?

As they push and pull on the chassis at both the upper and lower 4 link bracket crossmembers as well as how going even further forward into and thru these crossmembers, that are then supported or tied together in the "main hoop forward" designs .. vs the 2d A design..
so vs the A, flat plane...
Which is the lite-est and most simple to build spec. We can all agree on that 1 anyhow.
So maybe we just build on that if my writing doesnt bear fruit..

Of the 3 options SFI gives us...???
Are we content w/ SFIs diams and wall thickness specs on A drawing for 4000+hp?
Im not.. just me thou.

U guys dont hav to subscribe to my thinking..
Better to not follow...but lead.

Thats begs the question.
How much do we need to know to really go from following to leading, vs The all knowing SFI specs.. (laughing)
Same guys who wrote 25.5..omg...

Just gonna ask? Are we there yet?
If not.. speak up now, please...

Wait.. take a day or two 1st and dwell on it all this some... then rain down on this.

& speak up, but only after u hav tortured ur brain w/these ideas..at least a lil.
Ive been doing this torture thing to myself for longer than a lot of people hav been alive.
Regards,

& Apologies for the poor grammar / spelling.
Im to lazy to proofread this stuff. Makes me sound like a pompous azz.. i know...
which i prolly am.
No.. i definitely am..
I like working w / metal, not words..
Id starve if i had to write for a living..
thats for dam sure.

Ok, Bring on the hate.. :+) im kidding. Sorta.

No. . wait.. go head..bash me..wtf...why not..
:+)
 

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I kill parts
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9,907 Posts
Side bars and all, thank you for sharing.


You're one of the seemingly very few who wouldn't disagree with the bundle of .120 wall 1.625 I have laying here for the main rails and 4-link/main hoop/a-pillar/main door bar in my upcoming 25.1 build. - I will have to be 2525-2800# within the classes we run anyway, so I see no reason to run "minimum spec" tubing. I'll gladly take a little added weight in exchange for more safety and a longer fatigue life at the key load points; especially when we'll likely have some ballast to make minimums even with the thicker tubing.


Now I need to sit down with my spec book and think about all this
 

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JP, Yup. I know.
& U know.
Like i said before, 25.1 was implemented in 90s. Bk then a Haas car ( i use haas since he built more cars per yr than anyone in 25-1

A haas car used a .065 wall top~ 4 link bar tubes and a .095" wall bottom tubes for yrs.
Why, cuz thats what Ness orig did 1st..

Since the geometry of overall car was a carbon copy of the '80s Ness 4 link,
( deep into the 90s)
& Don's upper & lower bars were the same length. Where if diff u could easily tell how to install the thinner upper bar in its proper place. Im sure over the yrs some cars got them things mixed up, top vs botyom.
Had to..customers were not told that.
There was no "manual" w any if our cars we built. Not at any "known" program.
These were considered trade secrets for a long time. Wt saving secrets..

So after the 4 link bars came bk from being plated, ( chrome, cad, ect,) and u were the guy assembling the car.
U had to take 2 bars, 1 in each hand.
& do The u "weighted them out thing" like a balance scale...
1 in each hand. Moving each up an down in hand to feel if they wt# same or lil diff..

Cuz 1 pair was (1.25"x 065"
&
1 pair was ~1.25" x 095")
Then u still , set 1 down, & had to pic up a 3rd bar still,
to see if it was yet any lighter or heavier,..
if in case the 1st 2 u felt were to be the same wt. But which wt#??
Heavier 1s or the liter pair??

My Real Point here. ????

In the 90s, a lot of builders were using 1.25" x 065" tops & .095" wall bottoms on 4 link bars.

Now my own, personal NHRA PRO STK legal car, templates & all...
(which that car sits in my shop today, )
& man what a beauty she still is.
Shit on that car nobody has done or seen 20+ yrs later...
lmao...

<basking in a moment of egomania here>
Ok.. done..

that car i built in bk in1997...
totally finished out by 1999..
(delay of funding)

Back then, on my own personal car,
my top bar was 1.25" x 095"
& my bottom was 1.375" x 095".
Not my clients cars. Cuz they didnt see the logic in the wt# increase.. So im not gonna argue... F~it...
If they'd asked..id told um what they need.
But racers are akways smarter than the guys building the cars every day, (oh, and repairing them)
They see there car... as builders, we see many cars a yr built by many builders as well.. I know i did.
My 1st yr of building prof i worked on willie cars, ness cars. Fred smith cars, ( smith brithers out of new england)
And other respected shop. And some not very respected then..but got better w time..
Anyone ever see a carl foltz intake from the 80s...wow.!! Not the same wrk of art they are today. Lemme tell u...

So.. In 1997. Same time we had our already had 25.1 specs to follow, and were using 1.25" bars in .065 & .095, @least in the big programs ,
for most/all the professional clients.
That chg'd , since today. Bar size & wall...
25-1 thou... Not much has chg'd at all, not since 90s...besides 25-2 coming along.

So Today.. if ur not running AT LEAST A
1.5" X .120" wall bottom bar on a 25.1 competition car, or a 25-2 car....
ur not up to date..?? Right?

So if we needed to go from the smallers bar sizes/walls,
i quoted above, from early 25-1days,
to the bigger sizes i spoke of now...???wtf??

Does it not stand to reason, we/u are putting more forces into the
"driving of the chassis",
pushing & pulling @ greater forces now,
if u, or any of the "known builders " ,
or "known prof. racers",
are expecting to have larger 4 bars integrated into there present 4 links...???

Look.. I hate heavy race cars as much as anyone.
But when u gotta weight 2500+ lbs..& many do. Not all.
But heck.. i got guys who gotta go 3k#....
Not just the fly wt# clients.

And ur (aka, john Q racer) already is now convinced he needs a larger/ thicker 4 link bar than what was used in the 90s.
Thats pretty obvious, right?

Then u better damb well expect that the tubes ur applying forces, on ur chasdis @ 4 link and surrounding area,
too , w/said larger 4 link bars,
are seeing greater forces applied to them as well. Regardless of A, B or C spec.

What i do like about an A chassis spec is its simplicity. Very easy to build. By far the easiest.
Just all around way easier to build.

But will I just take SFIs word for it that
1.5" x .065" is stout enuff for that 'A spec' 4000 hp billet screw, ( personal fav)
or twin hair dryer/ or a
960" NOS CAR design??

Umm... no... well, not exactly..
let me say this.

I can..and hav, built A cars w .065. In A spec.
But they didnt look ""just like""
any other A car drawing or SFI spec A drawing that anyone has ever seen w/ there eyes.
Thats for sure.

So if we dont need a better design than Min spec A. Then We shouldnt/dont need a larger or thicker 4 link bar in that chassis than what we were using when 25-1 was setup by SFI. In [email protected] 1.25" diam x 095.

Now im not saying to make old 25-1s cars illegal. Or put of spec.. not at all.

Or that they are not safe in a crash scenario.
They hav held up well overall.
Bill Staley did get over the wall @ the MurderPlex and hit the scoreboard pole broadside...bad deal..fluke deal..
If u stay inside the walls. 25.1 A will keep u safe. Its when u get outside the concrete that all bets are off, imo.. its now unforeseen situations once u get over the concrete.. every track being diff in obstacles u can collide w/ outside da walls.

Ok..bk to topic..
Im gonna try to always do whats on best interest of my cluents or drivers.

I know what works on a build today, for the most part, & on a car thats being done today.. For todays pwr.

But u gotta plan for beyond today unless ur just Super wealthy & can burn thru cash..

Both for todays needs and future needs of these cars pwr inputs. Stuff chgs, and classes chg.

What never chgs. "Less pwr being made"

I suspect most guys who take the time to either read, YB, here at these forums,
or post at these forum,
"Most".. cant afford a new car build every yr.

Cuz if u can. God Bless U & Ur a lucky dog.. Then by all means. Build for today only.
Lite as hell. Toss it after 100/200 runs or so. & Build it lite, but to spec... if ucan do that..
And toss that $200k puppy aside after the end of 1 season...
Now, how bout for the rest of us workin smucks..?? What do we need to do?

Sidebar...
Id love to race anyone w/ a car,
built in 1997, in its orig firm,
against my '97 car..
(My arrogant pre-maddona F#&k attitude)
comin out here... ok.. bk to reality..

If u cant build new every seadon or 2....
U might wanna build for not only today..
But for what ur crystal ball tells u the future of ur class, or ur type of racing, MAY BRING.

Sure..thats easier said than doneat times.

But in '97 when i was putting 1.375" lowers in my own car build, most who saw it just shook there heads, and likely thought i was an idiot..
Well. At least 4 bars can easily be easily replaced on any build. But i knew what i needed for possible IHRA big mtr torque..
Maybe not nhra at that time.. but IH stuff was quite qwiker then...& we might hav wznted to go play in that sandbox.

4 Bars can be chgd easily. Updated..
4 link brackets & chassis tubing area..
not so easy..

Might as well build a new chassis at that point and sell the old 1 to a supergas racer.

Just a lil advice.. on that .120 wall build btw.

U might want to document , "well",
the fact that u used 4130 in .120" wall for future tech purposes.

Since literally most mild steel cars are made of DOM are .120" usually
& yes, some are. .134" wall/resistance seam weld tubing.
cuz .120" seamed wont measure thk enuff do to poor quality control standards..hence why everyoneuses .134" if using seam welded mild steel...man i hate that stuff.

(Like working w/really hard butter on soft bread..)

If an NHRA tech guy see's .120" reading on his sonic checker. It may not look so good on a car thats supposed to be 4130.

As i personally own the same brand/ model sonic chkr as NHRA uses...
He , tech guy, might just not fully 100% believe u did use 4130 in .120" ..
& may think its mild steel car ur passing off.
(Its been tried..) most hav failed.
Sonics can, butvery difficult to differentiate between DOM & 4130 or Docol w/ the speed setting of metallurgy type on a somic chk'r.
Ive yet to see a nhra tech guy who could even use the feature.. and diff brand of 4130 still hav diff circumference speeds as well.

& mild steel in any wall and thickeness,
last time i looked, long ago..
did not allow a cert to 6.00 on any SFI specs using mild steel of any alloy.

Id wanna hav a bit of proof in my pocket,
in case the tech guy has a bug in his azz. Trust me...ive seen it.
Ive bent the rules literally into a pretzel over 30+ yrs. Legal?? Most times 100%.
a few times..F~no..cheated. straight up.
But this was on builds. Not nitrous on engs or nitro in eng oil. Just on car /chassis rules.

Yes, they did catch me @ indy,
in pro stock truck,
w/more than 1" of stagger on my front end..
& did let us run @ that 1 race..
& said fix it by next race.
( sometimes who u know does help)

So i put a full dress pro stk trk, eng an all,
bk up on the jig..
and moved the 1 wheel forward to compliance.

That.. is much easier than a critically integrated "tube/ tubes" in a welded chassis, that the tech guy wants U to replaced.

If im gonna pretzel the rules anywhere.
( twist um around)
Its gonna be something i can
"get them bk happy w/by next race"

We ran a door car once in ihra that was 2".
Not legal.
Someone in the shop..not mentioning any names...
talked to much bout it @ track.

We got wind of a upcoming, singled out, surprise tech check coming on at next event..
So...threw car onto jig.. cut it up, & made it 1"..now legal again..

Went to race.. They chk'd it...it was legal.
No harm..no foul.. but that was in the early 90s.

So be careful on that .120 wall.

Willie's powdercoat guys, RW little, out of San Diego.. were so good they could put an easy .008" on top of a tube that NHRAs sonic checker ( @the time) could not differentiate from the steel tube.

So a pc of .049 looked like 058".
.058" looked like .065".
U get the point.

Now.. Doesnt that sound opposite of what ive conveyed.. Yep. Well, some of thosecars were built before the sfi spec was even born.

Now what u do?? Cut 20 tubes out??

Bk then.. we had bout 775+ft lbs of torque, & about 1100 hp if we were lucky.
Nothin like today pwr wise.

So those "before sfi" chassis were more that strong enuff for the hp range.

Gordy did nearly get his legs tore off in that Ness car that had no rocker bars pre sfi specs. Don used the steel rocker as / in place of, the support tube for the chassis.

We had no specs then.
The Wild west for us builders..

Those who used to scratch there heads after seeing a Rells car carry 250lbs of ballast w/200lb driver @ 2350lbs w/iron blks and 4 spd lencos, used to wonder how a Willie's car were so lite, some times.

Now. Not all willie cars got the same lite wt# treatment.
Only a very very very select few racers of his super lite stuff.
These Guys old timers who were responsible adults, tk responsibility for there ownactions, ( lost art)
and knew how NOT TO tire shake there way into the weeds..

But even w/o that powder coating tid bit. Willies cars were still really lite.
& well designed..

And if u look. Even in 80s 90s. Willie always used larger diam tubes on a the small stuff.

Those 1" x 049 floor laterals ( not diagonals..laterals) in a willie car..they were 1.25" on a 1" min spec.
Those floor laterals were also used to absorb the energy from the lower 4 link crossmember above and beyond what the 2 center 1.5" x065 center frame rails were called on to do. Willies roof X conicided w/his 2 upper tail section bars that went to the main hoop and all the way to rear in 1 pcs tubing.
Those 2 upper tail section bars were in common joint w the X in the roof.

Vs a typical OVER THE TUB BAR that breaks the intersection of that tube running from main hoop to rear of car.
Another story for another time perhaps.

(Broken record here)
Try to document that .120" material usage, for proof to a tech guy if u need a chassis cert.
These chassis must recert every yr as Pro car, & Every 3 as Advanced ET/Sportsman 6.00 ET.

The guy who might believe u this yr
( that ur car is .120" 4130, not mild stl)
might be retired, or gone or move to diff division, by next time , 3 yrs later,
Ur tech inspection needs renewed, & the new guy has a chip on shoulder, and wants to show he's doin his job by bouncing (failing) the guy's car rather than passing it for.120" wall ... thinks its Dom--NOT 4130.

Just a bit of advice.. take for what its worth.. (not much)
Gotta run.
Regards,
Scott. Im gonna get bk to u..
 

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I kill parts
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Thank you, and yes I planned for just that. I've kept my materials receipts to show as necessary and also thankfully am friends with the IHRA tech guy who does our Advanced ET certs. I told him I was going to before even ordering the tubing, also told him I'd leave one small section of tubing behind the seat in the funny car cage bare metal for any future needs of someone to do any sort of testing, etc.


I try not to donate any more money to Glendora than I absolutely have to these days, so we cert IHRA and I'm licensed PDRA. - If we happen to go somewhere that will only accept NHRA credentials, I simply won't race there.


I'm sure you likely know who Richard Earle is, it will be one of his bodies and have had some guidance from him on the chassis as well. - As with any one with much smarts these days, I try to learn something from every different chassis I see. While the root designs may all be very similar, little things make a big difference in the finished product for sure.
 
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