E: Engine Alternative Pushrods

oexing

Well Known and Active Forum User
VOC Member
Arrow rods, no alu tubes ? And without steel end caps ? Aluminium has only one third of stiffness compared to steel, so I would never use same dimensions for copies like steel originals when stiffness is important. The tube types in my picture above work since more than half a century, no problems with more than double length.

Vic
 

oexing

Well Known and Active Forum User
VOC Member
Thanks for the idea about arrows-for-pushrods, I will get some for inspection. You cannot get alu tube material in high tensile basically so am interested what arrows are. 9 mm o.d. look good to me but I suspect the wall thickness to be minimal so guess I will keep the 10mm type with 2mm wall thickness tubing , available easily. Does someone actually run rods made out of arrows, what sizes ?

Vic
 

Robert Watson

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VOC Member
These work well. I have run a set for maybe 50,000 miles. You have to grind a small relief for the adjuster end as they will contact the very bottom of the adjuster at full lift (and break a little bit off). They are fine in the follower cup.
20180716_070048_HDR.jpg
20180716_070059_HDR.jpg
 

Flo

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VOC Member
I can`t believe Aluminium arrows being a suitable start - after some recent consideration I tend towards fairly thin walled steel. Figures for coefficient of linear expansion are for any construction steel 12 to 13 * 10-6 mm/mm K to 16 * 10-6 mm/mm K for 18 8 (1.4301) while Aluminum alloys are typically in excess üf 23 * 10-6 mm/mm K.

The task of the pushrod is to withstand a buckling load corresponding to Euler case #2. Critical load (a force) is dependent on Young`s modulus and geometry. Buckling is a stablity problem, i.e. Since I have no robust data base i have assumed the original to be solid and max diameter being so that it can just be fed through the rocker.

see attached "0" approximation spreadsheet
 

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