Pushrod shape

[BOOT]

I was thinking bout bracing a part and I've always wondered why some use round tube where I'd use square, if you don't know what I'm talking bout Google round vs square tube. Anyways some say round is stronger and in my n other opinions square is stiffer but round is more durable because it flexes so it's perceived as stronger(cue the round inside the square or vise versa comment).

So while thinking I should use square tube for my purpose because I want no flex/give, I then wondered since many use shaft rockers these days why isn't there any square/diamond or even triangular pushrods(with common style tips of course)? Seems to me you could use a stiffer shape than round and even use a smaller/lighter size(I know that is not the side that matters as much because of ratio, but some would kill for any weight loss and sometimes you just need a smaller pushrod for clearance). I'm sure failure/replacement would be more common at 1st instead of flex but then you'd know you need a larger pushrod. I'm not sure how it would effect harmonics really but I'd think it'd help a lot.

Of course I wouldn't try it with a guideplate because of increased surface contact, so only SA rockers or shaft.

[BOOT]

Of course more shapes than I mentioned would be plausible and maybe even stiffer but the cost.

[cgarb]

I've seen a few pushrods in a U shape...but they didn't work so good.

[BOOT]

Prob the most cost effective method would be use the thickest wall round then CNC machine the shape and heat treat, if enough peaks(star) you could still use a guide plate.

[cjperformance]

This could start a whole new H beam V I beam debate!

[lefty o]

round but fluted down the sides to reduce weight!

[Roundybout]

"I don't remember seeing any square trees"

I'd like triangle shaped pushrods myself.

[BOOT]

round but fluted down the sides to reduce weight!

Yah I'm not sure of the best shape, peaks, rounds, cogs.

Might even be possible to laser a thin wall pushrod, well any round tubular part IE rollcage.

edit: laser so it can be more micro enhanced

[engineguyBill]

Round, double tapered pushrod is the strongest design - in my opinion. When was the last time you saw a square mast on a sailing ship? Or a square flagpole . . . . . . . ?

[swampbuggy]

Gets back to the age old question----what is the application ?

[Zmechanic]

People "say" square is stronger, but do they know? Obviously not. Cylinders are well known to be stronger than square shapes in compression. Of course, double taper and other tapered cylinders came about to help reduce deflection where it is most likely: in the middle.

There is some research that a double taper equlilateral triangle shape is the absolute strongest but I'm not sure if you'd accomplish that since it must come to a cylinder at the ends.

[BOOT]

Anyways some say round is stronger and in my n other opinions square is stiffer but round is more durable because it flexes so it's perceived as stronger.

[Sparksalot]

Try going through engineering school if the original poster is serious about an accurate answer to the question. Yes, we know and there is absolutely no question about the right answer. His or her's were way off base.

[Geoff2]

Very interesting topic.
I believe a square section 3/8", 0.060" wall thickness pushrod, would be stiffer than a round 3/8", 0.060" pushrod. But the square one will be noticeably heavier.....
Where the round section excels is it's ability to resist twisting compared to square or rect section. But this not an issue with pushrods so maybe the round shape is a good compromise between weight & strength, hence it's use.

[digger]

Very interesting topic.
I believe a square section 3/8", 0.060" wall thickness pushrod, would be stiffer than a round 3/8", 0.060" pushrod. But the square one will be noticeably heavier.....
Where the round section excels is it's ability to resist twisting compared to square or rect section. But this not an issue with pushrods so maybe the round shape is a good compromise between weight & strength, hence it's use.

for the same mass (i.e. cross sectional area) the round tube has 20% more resistance to buckling than the square (i.e. the 2nd moment of area is 20% higher) it also needs less space as the diagonal on the square tube is larger