Missed my point kinda, if it's stiffer why not use a smaller square that has comparable stiffness to the round, long as it's stiff enough to not break.Geoff2 wrote: ↑Tue Dec 12, 2017 4:07 am 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.
Pushrod shape
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Re: Pushrod shape
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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!
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Re: Pushrod shape
I make no claims to be an expert in anything but if it makes you happy I have a degree in mechanical engineering. If you have details that explain what your saying plz share, I'm never afraid to change my mind or admit my idea was incorrect if the end result is better and I learn something.Sparksalot wrote: ↑Tue Dec 12, 2017 4:06 am 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.
Channel About My diy Projects & Reviews https://www.youtube.com/c/BOOTdiy
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!
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!
Re: Pushrod shape
read two posts upBOOT wrote: ↑Tue Dec 12, 2017 5:08 amI make no claims to be an expert in anything but if it makes you happy I have a degree in mechanical engineering. If you have details that explain what your saying plz share, I'm never afraid to change my mind or admit my idea was incorrect if the end result is better and I learn something.Sparksalot wrote: ↑Tue Dec 12, 2017 4:06 am 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.
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Re: Pushrod shape
Sparksalot wrote: ↑Tue Dec 12, 2017 4:06 am 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.
[/quote
OK, I'll bite. WHAT is the correct answer??
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Re: Pushrod shape
Wrong on the tapered vs straight pushrod. But let's not go there AGAIN! LOLengineguyBill wrote: ↑Mon Dec 11, 2017 10:07 pm 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 . . . . . . . ?
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Re: Pushrod shape
Last time I checked, round tube has strength in all directions, square or rectangles maximum strength is directional.
Its all length vs cross section is it not?!?
Its all length vs cross section is it not?!?
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Re: Pushrod shape
Yeah, that is why I added the qualifier "in my opinion . . . . ." It seems to also be the opinion of the major high performance pushrod manufacturers, though.
Carry on . . . . . .
Carry on . . . . . .
Bill
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Re: Pushrod shape
The ONLY time a taper should be used, is for clearance purposes where a straight will not fit. Any manufacture that has the tapered is stronger opinion should be avoided!!!engineguyBill wrote: ↑Tue Dec 12, 2017 12:33 pm Yeah, that is why I added the qualifier "in my opinion . . . . ." It seems to also be the opinion of the major high performance pushrod manufacturers, though.
Carry on . . . . . .
Stiffness is all about length vs cross section..........period!
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Re: Pushrod shape
square tube is not stronger than round as stated.
the idea of a fluted push rod is interesting, basically having external bracing makes it act like a much larger cross section, It may stiffen the push rod with minimal weight gain.
the idea of a fluted push rod is interesting, basically having external bracing makes it act like a much larger cross section, It may stiffen the push rod with minimal weight gain.
Re: Pushrod shape
I do too. For a given cross-sectional area (ie mass) a round member is stiffer in unconstrained buckling than a square member because it has a greater moment of inertia (for that given area). Also you might look up "double butted" bicycle frame tubing which has thicker walls at the ends, sort of the same principle as a double tapered pushrod.
But - I've had some ideas for low-mass constrained pushrods I'd like to experiment with....square might be easier to deal with...
Dave
Re: Pushrod shape
I can tell you from experience with gun barrels, I know it is not the same as a pushrod...Some people claim that the fluting makes the barrel stiffer. It is not the same as a bead rolled into sheet metal. Any time you remove material from a barrel it gets weaker...I would have to say the same with pushrods. Only thing fluting would accomplish is to save weight.
Re: Pushrod shape
Constrained pushrods has interested me also...If it was guided most of the way it wouldn't take much for a pushrod to work with high spring loads. Here's a thought...Have you ever seen the inside of a digital read out scale? A tube with a whole bunch of ball bearings inside. What if that same principle was used with pushrods. I know the whole part couldn't be ball bearings, the ends would need to be solid pieces capable of moving the duration of the valve lift without coming out of the tube or constraint. You could possibly make bent pushrods that would move out of the way of intake ports or whatever obstacle...Probably won't work, would be failure prone and put hundreds of ball bearings in the oil pan, but Its cool to think about stuff like that anyway...lol
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Re: Pushrod shape
cgarb wrote: ↑Tue Dec 12, 2017 6:42 pm Constrained pushrods has interested me also...If it was guided most of the way it wouldn't take much for a pushrod to work with high spring loads. Here's a thought...Have you ever seen the inside of a digital read out scale? A tube with a whole bunch of ball bearings inside. What if that same principle was used with pushrods. I know the whole part couldn't be ball bearings, the ends would need to be solid pieces capable of moving the duration of the valve lift without coming out of the tube or constraint. You could possibly make bent pushrods that would move out of the way of intake ports or whatever obstacle...Probably won't work, would be failure prone and put hundreds of ball bearings in the oil pan, but Its cool to think about stuff like that anyway...lol
I think it's been done.
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Re: Pushrod shape
Regarding the fluting, for it to work you would have to go larger on the od then flute to get the weight back down for it to end up stiffercgarb wrote: ↑Tue Dec 12, 2017 6:34 pm I can tell you from experience with gun barrels, I know it is not the same as a pushrod...Some people claim that the fluting makes the barrel stiffer. It is not the same as a bead rolled into sheet metal. Any time you remove material from a barrel it gets weaker...I would have to say the same with pushrods. Only thing fluting would accomplish is to save weight.
Re: Pushrod shape
I’ve wondered how much column strength do you really need if the forces aren’t too great and it can’t go sideways? Piano wire? With a ball brazed on each end?
How about a really skinny pushrod with a short “twiddler rod” to follow the rocker arm? Valvetrain weight might be reduced considerably
Dave