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The tapered pushrod portion of the article is incorrect!
 

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i'll wait till it comes in the ole mailbox... good looking BBF612 ;)
 

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Can you elaborate, please?
"Heavy wall tapered designs also provide (theoretically) increases strength and decreased harmonics"

Unless I am reading this wrong, the article is implying tapered are better than straight, which is simply not the case. The only advantage they have is increasing diameter in a situation where clearance is a problem at either end.
Otherwise, it is purely diameter vs length. Straight wins every time due to its larger diameter throughout the length of the pushrod.
We have been over this before correct?
Just wanted to point this out, so the internet theory I hear often, doesnt get taken as gospel by others trying to learn.
 

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"Heavy wall tapered designs also provide (theoretically) increases strength and decreased harmonics"

Unless I am reading this wrong, the article is implying tapered are better than straight, which is simply not the case. The only advantage they have is increasing diameter in a situation where clearance is a problem at either end.
Otherwise, it is purely diameter vs length. Straight wins every time due to its larger diameter throughout the length of the pushrod.
We have been over this before correct?
Just wanted to point this out, so the internet theory I hear often, doesnt get taken as gospel by others trying to learn.
I agree
 

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Yes, we have discussed this before. The theory behind tapered pushrods goes back to a basic mechanical engineering axiom that a triangular shape will withstand more load than a square or rectangular shape. The tapered section of the pushrod can be viewed as a triangular shape and will therefore be stronger than a straight pushrod.
This triangular shape theory can also be seen in the structure of steel bridges, flagpoles and early skyscrapers such as the Empire State Building, Chrysler Building, etc. Also most high performance pushrod manufacturers do recommend tapered (and double tapered pushrods) when engine architecture allows their use. I have not read the article yet, as my copy of the magazine hasn't arrived yet. (I think my mailman takes some of my magazine home and reads them before delivering them . . . . . . . LOL)
 

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I would expect straight vs. tapered push rod to be have spintron tested?

Since we are talking building engineering - I have not seen tapered tubular columns used anywhere.
 

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Yes, we have discussed this before. The theory behind tapered pushrods goes back to a basic mechanical engineering axiom that a triangular shape will withstand more load than a square or rectangular shape. The tapered section of the pushrod can be viewed as a triangular shape and will therefore be stronger than a straight pushrod.
This triangular shape theory can also be seen in the structure of steel bridges, flagpoles and early skyscrapers such as the Empire State Building, Chrysler Building, etc. Also most high performance pushrod manufacturers do recommend tapered (and double tapered pushrods) when engine architecture allows their use. I have not read the article yet, as my copy of the magazine hasn't arrived yet. (I think my mailman takes some of my magazine home and reads them before delivering them . . . . . . . LOL)
Mechanical engineering axiom?
A pushrod is not a building, it’s not a pyramid nor does it have an unlimited base. All you’re dealing with is Euler buckling.
Pcrit=4pi^2EI/Le^2

I is the area moment of inertia of the cross section. The lower “I” or longer “Le”, the lower the critical buckling load.

The next important item is what frequency is the first bending mode:
Omega(radians/second)= sqrt(K/m)

K = stiffness = 48EI/L^3
E is Young’s Modulus

m = piD^2/4 L*density

Put it all together:

omega = sqrt(48EI/(L^4*piD^2/4*density))

The longer the pushrod, the lower its first mode frequency, same with more mass from larger diameter. I’ll leave the rest of the simplification to youse guys to figger out how diameter influences stiffness at a greater rate than mass.

Sheesh, I thought everyone knew this simple stuff.

https://www.engineeringtoolbox.com/euler-column-formula-d_1813.html

https://www.quora.com/What-is-the-s...-constant-and-stiffness-for-a-cantilever-beam
 

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Yes, we have discussed this before. The theory behind tapered pushrods goes back to a basic mechanical engineering axiom that a triangular shape will withstand more load than a square or rectangular shape. The tapered section of the pushrod can be viewed as a triangular shape and will therefore be stronger than a straight pushrod.
This triangular shape theory can also be seen in the structure of steel bridges, flagpoles and early skyscrapers such as the Empire State Building, Chrysler Building, etc. Also most high performance pushrod manufacturers do recommend tapered (and double tapered pushrods) when engine architecture allows their use. I have not read the article yet, as my copy of the magazine hasn't arrived yet. (I think my mailman takes some of my magazine home and reads them before delivering them . . . . . . . LOL)
Your architectural examples may be true, but they are fixed ends, not pivoting as in a pushrod.
As I stated before, when talking pushrods, it comes down to diameter vs length. Just the way it is.
I know the tapered theory may seem plausible, but it's definitely not true when talking pushrods!
 

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Mechanical engineering axiom?
A pushrod is not a building, it’s not a pyramid nor does it have an unlimited base. All you’re dealing with is Euler buckling.
Pcrit=4pi^2EI/Le^2

I is the area moment of inertia of the cross section. The lower “I” or longer “Le”, the lower the critical buckling load.

The next important item is what frequency is the first bending mode:
Omega(radians/second)= sqrt(K/m)

K = stiffness = 48EI/L^3
E is Young’s Modulus

m = piD^2/4 L*density

Put it all together:

omega = sqrt(48EI/(L^4*piD^2/4*density))

The longer the pushrod, the lower its first mode frequency, same with more mass from larger diameter. I’ll leave the rest of the simplification to youse guys to figger out how diameter influences stiffness at a greater rate than mass.

Sheesh, I thought everyone knew this simple stuff.

https://www.engineeringtoolbox.com/euler-column-formula-d_1813.html

https://www.quora.com/What-is-the-s...-constant-and-stiffness-for-a-cantilever-beam
What he said! ^^^^^^^^^^ ;)
 
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Discussion Starter #13
The article stated, "Tapered ends are often needed for clearance at lifters or rockers, and heavy-wall tapered designs also provide (theoretically) increase strength and decreased harmonics, especially in high-lift, high-rpm applications.

When taper is incorporated into the pushrod design, this can reduce the deflection of the pushrod by placing the thicker area at the lifter end where the greatest energy is generated and can aid in dampening valve train harmonics. "



It is all very well qualified what the article meant and if a few words are not taken out of context, very well understood. ;)
 

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The article stated, "Tapered ends are often needed for clearance at lifters or rockers, and heavy-wall tapered designs also provide (theoretically) increase strength and decreased harmonics, especially in high-lift, high-rpm applications.

When taper is incorporated into the pushrod design, this can reduce the deflection of the pushrod by placing the thicker area at the lifter end where the greatest energy is generated and can aid in dampening valve train harmonics. "



It is all very well qualified what the article meant and if a few words are not taken out of context, very well understood. ;)
Put back into full context, like you did above, doesn't change the implied meaning, or make either case correct. Other than the tapered end (tips) for clearance.
 

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As Rick! and Warp have so nicely illuminated. Taper on pushrods is not incorporated in the pushrod for strength but for clearance and fitment, not for strength as some tend to think.
 

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Greg @ Smith Brothers always recommends (to me) straight wall for strength, tapered if you need some clearance.
I think I'd take Warp and Rick!'s word over a magazine article. These guys should be the ones writing the articles.
 
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