Author Topic: Ball ended pushrods  (Read 1134 times)

Offline petertha

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Ball ended pushrods
« on: July 12, 2015, 12:49:38 AM »
This radial I'm building calls for 2mm dia 'spring steel' pushrods. The ends show a rounded over profile. I'm not quite clear if this steel designation means hard steel like drill blank & the round-over profile is ground. Or if its tool steel & ends hardened after profiling. In situ, one pushrod end mates a matching dome cup socket in a threaded rocker arm fitting. The other end mates a similar cup profile in a ring cam follower. Both of these mating parts are specified hardened steel from O1.

Now my question: It seems to me I could make some nice 'ends' to the 2mm pushrod blank by a slight countersink to the end & then attaching a commercial hardened steel ball. I found some balls in +/- range around 2mm, they are inexpensive. What do you think? Could the balls be reliably & permanently attached using high strength locktite or carefully silver soldering?

Offline petertha

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Re: Ball ended pushrods
« Reply #1 on: July 12, 2015, 01:04:01 AM »
some pics

Online Jo

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Re: Ball ended pushrods
« Reply #2 on: July 12, 2015, 07:39:33 AM »
I wouldn't have thought that the rounding of the ends need to be that accurate it is only to allow a little side movement as the engine runs.

Kitti's push rods are 2.4mm thick silver steel with rounded ends and I am planning on doing those by hand with a file.

Jo
Usus est optimum magister

Offline Jasonb

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Re: Ball ended pushrods
« Reply #3 on: July 12, 2015, 07:45:52 AM »
Piano (music) wire cut to length and then held in a cordless drill can then be run against a linisher or bench grinder to put a perfectly functional round end onto it, polish with fine abrasive paper.

The Nemett & Hoglet have like Jo suggests filed silversteel

J

Offline tangler

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Re: Ball ended pushrods
« Reply #4 on: July 12, 2015, 09:15:59 AM »
My Matador, which is a10cc single, uses piano wire pushrods.  This can just about be filed while rotating in the lathe.  As the guys have said, the rounding only needed to be approximate to cope with the slight change of angle as the rocker moves.  In the UK straight piano wire is most easily obtained from aero modelling suppliers.

 Silver soldering a ball on the end will soften the wire and you really need to retain the stiffness.  Whether Loctite can deal with percussive loading is up for debate.

HTH

Rod
« Last Edit: July 12, 2015, 09:34:41 AM by tangler »