Yellow Bullet Forums banner

1 - 20 of 47 Posts

·
Misanthropist
Joined
·
3,142 Posts
Discussion Starter #1
For the record.......who's aluminum rods are actually FORGED, as opposed to just cut-out aluminum "plate"??
 

·
Registered
Joined
·
49,436 Posts
BME is the only company I know of.
 

·
Misanthropist
Joined
·
3,142 Posts
Discussion Starter #4
BME is one.....

Yes. I'm aware that BME is one. And as far as I'm aware, they are the ONLY forged aluminum rod. I do strongly believe that all the others are merely cut (CNC'd) out of aluminum plate stock.
 

·
RED ROCKET
Joined
·
8,630 Posts
if i ever go to an alum rod it will be bme rods.
 

·
Registered
Joined
·
224 Posts
I wouldn't get too caught up in the "forged vs. billet" argument. I worked as a manufacturing engineer in the aircraft industry for years, and most all aircraft prints specify grain direction of wrought plate or "forged billets". When I began designing my own products, I started to question how important this was. I called every aircraft design engineer I knew and asked them to QUANTIFY the benifits of grain direction. They all said the same thing: "Oh, it's VERY important!". But none of them could tell me specifically HOW important (it's all imbedded in the stress analysis software these days). I finally called a materials testing lab. I got the old guy who runs the physical tests on material every day, and asked him what the difference is between testing an aluminum sample transverse to the grain and along the grain. His reply was "What thickness are we talking about?" When I asked him to elaborate, he explained his findings. Thin sheet will behave differently, since the majority of the material is worked during the rolling process. And then, the only major difference is the amount of elongation before rupture (but this is WAY past the elastic range of the material anyway). I asked him about 1" plate. He said the amount of "skin" that is subjected to the affects of roll forging a plate are so negligable that he can't tell the difference between the two orientations when testing a sample. A forging has this compressed "skin" as well, but again, the affected skin is very thin when compared to the entire section thickness of a connecting rod. Now when you consider the fact that alloys used for forging applications are usually modified from their rolled or extruded counterparts (i.e. 6063 for forgings vs. 6061 for plate and extrusions), there are usually compromises in the material makeup of "forging" alloys to make them eject from the forging die with less chance of galling or sticking.

Do not confuse this with comparing FORGINGS and CASTINGS. Castings are poured MOLTEN metal, and are never "sqeezed" at all (unless it is a "Hipped" casting, Google "Hot Isotropic Press" ). This is why cast metals have porosity in them. But WROUGHT metals (rolled plate, extruded bar, and forgings) are ALL squeezed in the hot, solid state.
 

·
Registered
Joined
·
19,969 Posts
^^^I will second that...Paul, thanks for taking the time to bring your "expertise" to the table.
 

·
Registered
Joined
·
985 Posts
I wouldn't get too caught up in the "forged vs. billet" argument. I worked as a manufacturing engineer in the aircraft industry for years, and most all aircraft prints specify grain direction of wrought plate or "forged billets". When I began designing my own products, I started to question how important this was. I called every aircraft design engineer I knew and asked them to QUANTIFY the benifits of grain direction. They all said the same thing: "Oh, it's VERY important!". But none of them could tell me specifically HOW important (it's all imbedded in the stress analysis software these days). I finally called a materials testing lab. I got the old guy who runs the physical tests on material every day, and asked him what the difference is between testing an aluminum sample transverse to the grain and along the grain. His reply was "What thickness are we talking about?" When I asked him to elaborate, he explained his findings. Thin sheet will behave differently, since the majority of the material is worked during the rolling process. And then, the only major difference is the amount of elongation before rupture (but this is WAY past the elastic range of the material anyway). I asked him about 1" plate. He said the amount of "skin" that is subjected to the affects of roll forging a plate are so negligable that he can't tell the difference between the two orientations when testing a sample. A forging has this compressed "skin" as well, but again, the affected skin is very thin when compared to the entire section thickness of a connecting rod. Now when you consider the fact that alloys used for forging applications are usually modified from their rolled or extruded counterparts (i.e. 6063 for forgings vs. 6061 for plate and extrusions), there are usually compromises in the material makeup of "forging" alloys to make them eject from the forging die with less chance of galling or sticking.

Do not confuse this with comparing FORGINGS and CASTINGS. Castings are poured MOLTEN metal, and are never "sqeezed" at all (unless it is a "Hipped" casting, Google "Hot Isotropic Press" ). This is why cast metals have porosity in them. But WROUGHT metals (rolled plate, extruded bar, and forgings) are ALL squeezed in the hot, solid state.
ALL I CAN SAY IS WOW.GOOD STUFF
 

·
Registered
Joined
·
224 Posts
well ...what is better?....:confused:...forged or plate?...
Good question. Let me share some experience with aluminum rods specifically...

I built some rods when I was maintaining a fleet of blown alky BBC's. We were consuming a lot of rods and had a CNC with extra capacity. I chose Alcoa 7150 plate for my rods. It is a material developed for Airbus, specifically for upper milled wing skins. It is similar to 7050 (actually the same thing, but the alloying elements are more tightly controlled to hit one end or the other of the accepatable range for 7050). Alcoa claims it has better properties in compression that 7050. I thought this would be desireable for connecting rods. I made 50 rods, and never broke one, but I did see signs of impending failure at the small end when a few sets were pushed on the number of cycles. It was a major pain making them, and for what GRP charges I couldn't justify making them again. I now use GRP's made of the "Pro" material (which I suspected was 7150), but have never seen the same cracking on the small ends.

While crewing for Hirata's A/Fuel team, I got some exposure to R&R's rods. He claims to have a proprietary extruded alloy bar. Prior to that, he used plate and we did experience failures but not after he changed to the extrusion. He claimed the same rod weighed more from the extruded bar than the plate, which could be an indication of greater compression than rolled plate. But it could have been a change in alloying elemets also. Unfortunately, none of the rod manufacturers tell you what alloy they're using. I have a hard time believing a company like Alcoa cares much about the aftermarket connecting rod market, so I doubt it is little more than marketing hype.

The bottom line is this...no matter what, FATIGUE LIFE is by far the most important aspect of using aluminum rods. Always start with NEW rods, and track the time you have on them. If the rod geometry is correct for the application, the manufacturer can probably tell you with great predicatability how long they'll last. Aluminum will ALWAYS fail eventually when loaded and unloaded repeatidly. The higher the load, the less cycles until failure. But even the lightest loads will break aluminum eventually (unlike steel and titanium which will achieve infinite fatigue life if the loads are small enough). This is why airplanes are ALWAYS taken out of service (in the U.S.) when they get a certain amount of hours on them.
 

·
Misanthropist
Joined
·
3,142 Posts
Discussion Starter #14
I wouldn't get too caught up in the "forged vs. billet" argument. I worked as a manufacturing engineer in the aircraft industry for years, and most all aircraft prints specify grain direction of wrought plate or "forged billets". When I began designing my own products, I started to question how important this was. I called every aircraft design engineer I knew and asked them to QUANTIFY the benifits of grain direction. They all said the same thing: "Oh, it's VERY important!". But none of them could tell me specifically HOW important (it's all imbedded in the stress analysis software these days). I finally called a materials testing lab. I got the old guy who runs the physical tests on material every day, and asked him what the difference is between testing an aluminum sample transverse to the grain and along the grain. His reply was "What thickness are we talking about?" When I asked him to elaborate, he explained his findings. Thin sheet will behave differently, since the majority of the material is worked during the rolling process. And then, the only major difference is the amount of elongation before rupture (but this is WAY past the elastic range of the material anyway). I asked him about 1" plate. He said the amount of "skin" that is subjected to the affects of roll forging a plate are so negligable that he can't tell the difference between the two orientations when testing a sample. A forging has this compressed "skin" as well, but again, the affected skin is very thin when compared to the entire section thickness of a connecting rod. Now when you consider the fact that alloys used for forging applications are usually modified from their rolled or extruded counterparts (i.e. 6063 for forgings vs. 6061 for plate and extrusions), there are usually compromises in the material makeup of "forging" alloys to make them eject from the forging die with less chance of galling or sticking.

Do not confuse this with comparing FORGINGS and CASTINGS. Castings are poured MOLTEN metal, and are never "sqeezed" at all (unless it is a "Hipped" casting, Google "Hot Isotropic Press" ). This is why cast metals have porosity in them. But WROUGHT metals (rolled plate, extruded bar, and forgings) are ALL squeezed in the hot, solid state.
That being said...I believe the preferred rod would be BME.
 

·
Registered
Joined
·
1,183 Posts
Chris how many passes do you tell your customers to put on one of your 420 nmca builds before its time for a new set, I know you use MGP. I talked to Michael there and he told me 60 1/8 mile passes then check them I thought that was kinda low but maybe its because of the stroke and the 9000 to 9500 rpm, but I know you turn more rpm and have less stroke just wondering.
 

·
Registered
Joined
·
1,059 Posts
That being said...I believe the preferred rod would be BME.
:confused:

Care to explain your basis for this? The material argument made above would indicate to me there is no significant difference in our world between the forging and billet style rods. The limited education on materials(college level materials course) that I have would generally agree...if you have another point of view lets here it.
 
1 - 20 of 47 Posts
Top