some advise for me shaft
Turbo Mini Forums

Crank shaft that is...

This is for an NA engine.


I'm looking in to having it lightened, wedged, cross drilled, nitrided. All of that lark.


I've sort of said to my self, bollocks to being able to drive it round town. I'll just beef up my left leg a bit. Things changed a little since I started building this motor. I now have a 750g pressure plate, and a light weight flywheel from minispares (what ever weight that is), so want a shiney crank to go with it all.

And possibly some H-beam con rods from A&R precision, rather than polishing up the standards, but I don't know how likely that is.

I've been talking to MED today and aparently they must regrind the journals as a matter of course, because they clamp on them. hmmm....


The journals are already 10thou under size. So will end up 20thou. Would this be okay for 90-110 horses? this seems a relatively good guess for the specs I have decided to go for now.

20thou doesn't seem all that much material, but still...


I know it's mostly down to how you drive it, rather than the power put through it. So what sort of power/ driving style would be suggested for undersized bearing journals?



Many thanks,


Matt

MED?!

I bought a crank from MED. Don't think I'll buy another though.

like you said, 20 thou off 2" mains and 1.75" big end journals is nothing. It'll be fine

If anything the reduced bearing circumference will yield a helpful reduction in parasitic losses

Edited by adcyork on 11th Jun, 2013.

oh really??

What was up with it?

if you like a baggy fit it'll be fine. I suppose they need to make it a baggy fit so that it won't bind with the 0.003" run out

But then this might just have been the one I had.

Other than that it looked pretty and did actually work until i hade a center main bearing failure. Now initially that could be put down to other certain misshaps, but that baggy fit was frowned upon by more than one engine builder, and what I have been told by a certain other first class engine builder, was the baggy fit likely had been a contributing factor. That said I still cannot discount the fact I left out a certain important O ring so that can only be speculation.

No problem with the mains being reground, mine were resized to s size which requires a lot more to come off.

I'm not sure about the clamping on the mains though, I can't see why you'd need to?

Have you tried rob walker engineering?

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi

Andy, they also do them as a batch sort of job, rather than one by one as they get them in, so send yours off and get cracking with your motor.

The bloke that I spoke to umm'ed and errr'ed when I said that it was already 10thou undersize, and sort of put the wind up me but 20 or 30thou is actually bugger all any way.



Hmm, that is a little bit sloppy, Sprocket.

Bummer that it happened, but I hope yours was a one off. Meaning that nicely like.

Alternatively, click the Force Racing banner at the top and get in touch with Carl.

His cranks are top notch and much better value than other places. Really happy with mine. Carl took over 1KG of it.

Too many engine builders seem to have a that'll do attitude. Regarding sizing have a look in the yellow bible too. You may get away with just regrinding to bottom tolerance if the journals just need cleaning up a bit.

I would go force racing without question. Well I will be when getting my crank done.