Pushrod shape

General engine tech -- Drag Racing to Circle Track

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BOOT
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Re: Pushrod shape

Post by BOOT » Fri Dec 15, 2017 1:07 am

The goal of the post is to see if another shape pushrod will not bend/deflect/buckle better than round. Round will defiantly do those and recover if not pushed beyond it's elastic point.


Last post.
I know as much as I can learn and try to keep an open mind to anything!

If I didn't overthink stuff I wouldn't be on speedtalk!

Sparksalot
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Re: Pushrod shape

Post by Sparksalot » Fri Dec 15, 2017 3:16 am

My last post on the subject as well. I hope you, BOOT have done your due diligence and determined what you're hearing here is correct.

I sense you are young and seeking knowledge and I commend you greatly for your quest for knowledge. My apologies if I'm wrong.

Buckling failure of a column under lateral dynamic loading is one of the most vexing problems looking for a strong analytical solution out there. If you are not busy for the next forty years or so and interested enough there is a life's work ahead of you.

Geoff2
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Re: Pushrod shape

Post by Geoff2 » Fri Dec 15, 2017 3:33 am

Boot,
I think it is safe to say that a round PR is gives the best strength/weight ratio for what we use PRs for.

People over several decades have had the time & money to experiment with different shapes & cross sections...& are still using round tube. Got to be a message there...

lefty o
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Re: Pushrod shape

Post by lefty o » Fri Dec 15, 2017 11:37 am

Geoff2 wrote:
Fri Dec 15, 2017 3:33 am
Boot,
I think it is safe to say that a round PR is gives the best strength/weight ratio for what we use PRs for.

People over several decades have had the time & money to experiment with different shapes & cross sections...& are still using round tube. Got to be a message there...
i speculate there are 2 main reasons why we use a round tube pushrod. 1 is it works fairly well, 2 it is cost effective.

digger
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Re: Pushrod shape

Post by digger » Fri Dec 15, 2017 6:10 pm

with effectively a ball joint at either end it makes sense for it to be symmetric about every axis i.e. round

Nefario
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Re: Pushrod shape

Post by Nefario » Fri Dec 15, 2017 9:44 pm

BOOT wrote:
Fri Dec 15, 2017 1:07 am
......if another shape pushrod will not bend/deflect/buckle better than round.
Think about what you mean by "better". A round pushrod is a column that has the same loading characteristics in any direction AND it's a simple solution. If you constrained a pushrod in one direction it could be non-symetrical and stiffer in another direction. A 2-piece pushrod with the joint sliding in a fixed guide could be MUCH stronger because the column is half as long.

Tubular pushrods have developed because they're simple, predictable, manufacturable, and good enough.

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