needles ?

[jethro]

I am working on a rd-17 crank which had journal pitting- which I have mostly cleaned up but at the cost of reducing the diammeter a thousanth or two.
I was thinking how it would be possible to off set that change. The first – most obvious thought was to replace the needles with new needles which
are a few thousanths fatter than the stock ones. I noticed that 4mm is .002 bigger than the rollers. Found 4 mm rollers about the right length.
Unfortunately— what the bearing people call 4 mm is actualy same size as the stock needle (more or less anyway). never that simple is it……

None the less I am wondering what could be done to needles to fatten them up a bit. if there was a way- it would have to preserve the
surface finnish and roundness of the needle. Maybe hard chrome- but I believe that normally comes out rough and had to be ground.
Wondering about titaneium nitride maybe ? dont know how that is done….. Need between 1 to 2 thousanths increase. Can reduce crank to fit the result. Some kind of tumble electroplating with a hard element like cobalt ? (if cobalt plating exists…. 🙂 )

Anyone else had this idea and had any creative thoughts of how to do it and what to use ?

something like this could save a lot of cranks…

Tim

PS…..
My main bearing needles are .158 inches thick and .733 inches long.

I see the sizes of drill bits and hence drill rod are—–
#21= .159
#20= .161
#19= .166
4.2 mm = .1654

Might be possible if I can find proper hardness and surface finish

PPS. Found a product made by "PM steel" – product called "Firechrome44" – it is hardened, ground and polished drill rod.
just have to see if they make it in #20 size.

will get a new crank if I can find one. might try this also as an experiment. All that woud have to be done is cut them to the correct
length and polish the corners. ( i think-)

[wedgie]

If it were a hard to find part your idea might be worth a shot. In this case, it makes more sense to just get a replacement crank.

[jethro]

I am widely known for doing things the hard way — 🙂

[foot_doctor]

No need to worry about the additional clearance. We have regularly increased the connecting rod big end size by .002" for several of our racing engines. No adverse effects have been observed. The engine may "rattle" a bit more at idle, but it should not fail if the journals are round. Most formerly stock engines that were repourposed for racing, have been loosened up in that fashion. Looser, sloppy main bearings also add to the performance levels without adding to premature failure. Tight motors are simply quieter. R.T.

[Author]

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