AlanG Posted July 1, 2018 Report Share Posted July 1, 2018 Just taken a bit of a punt on a cheap crankshaft. Mains will have to be reground to - .040". I see that these are available from Revingtons. Just wondered how detrimental - .040" might be? Is this common practice going this much undersize these days? I will of course have it NDT'd before doing anything. Alan. Quote Link to post Share on other sites
Motorsport Mickey Posted July 1, 2018 Report Share Posted July 1, 2018 (edited) If you are on a 4 cylinder crankshaft it wouldnt bother me at all. I won my last TR Register championship using a crankshaft offset ground on the big ends by nearly 1 mm which meant using -60 thou big ends (Massey Ferguespn) . Completed 12 races and 12 practices and 93 laps of Snetterton ( high revs circuit)) without problem. Engine carried on another 2 years racing before rebuild, just renew bearings at end of every season, no problem. Given you specify the mains I consider them not so problematical and because of the likely easier life of road use It would not bother me. Mick Richards Edited July 1, 2018 by Motorsport Mickey Quote Link to post Share on other sites
AlanG Posted July 2, 2018 Author Report Share Posted July 2, 2018 Thanks for that Mick. Just hope it's crack free now. Alan. Quote Link to post Share on other sites
RogerH Posted July 2, 2018 Report Share Posted July 2, 2018 Hi Alan, one significant area on the 4 pot crank for cracking is the Big-end journal to web radius. ALL other area should be inspected but the above has the majority of disasters. Magnetic Particle Inspection is the preferred method (often referred to as Magnaflux - wrongly). If you find a BE/crank web crack I would suggest the crank is scrap - don;t try to machine it away as you will be in dodgy territory. Roger Quote Link to post Share on other sites
AlanG Posted July 2, 2018 Author Report Share Posted July 2, 2018 Thanks for that Roger. I will make sure that area is specifically looked at. I think we have similar pasts. I was in Airworthiness at BAE. Flight incident investigations on Hawks world wide. ( we never mentioned the word crash). Fatique cracking and other defects were frequently found. Alan. Quote Link to post Share on other sites
RogerH Posted July 2, 2018 Report Share Posted July 2, 2018 Hi Alan, same here in NDT. We didn't refer to cracks but discontinuities. Roger But they were still cracked Quote Link to post Share on other sites
Waldi Posted July 2, 2018 Report Share Posted July 2, 2018 Funny, We call them linear indications:) Waldi Quote Link to post Share on other sites
RogerH Posted July 2, 2018 Report Share Posted July 2, 2018 ....but they are still cracks....... Roger Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.