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Scraping White Metal - Chris.Dallas - 17-11-2021
Advice required please!
I’ve dismantled our chummy’s engine to install a new crank and found the pistons and white metal look quite fresh! The big ends are too large to fit the crank so the original one must have had a few grinds…. Does anyone know someone capable of scraping these to the new crank within reasonable distance of Didcot?
Thanks
RE: Scraping White Metal - Bob Culver - 17-11-2021
I take it by big you mean small? If the difference in more than just a few thou not really practicable (esp if time considered) Older firms (and some on Forum) will have a jig for resizring. However there is no going back the other way to fit a smaller crank so the crank needs to be uncracked and likely to live long. Any poor fit of the cap halves should be corrected first, hopefully requiring very little corrction.
RE: Scraping White Metal - Ian Williams - 17-11-2021
Have you any spare rods Chris, if so have an experiment on a spare first, with a little practice, although tedious its not too hard to hand fit a rod.
RE: Scraping White Metal - Colin Reed - 17-11-2021
HI CHRIS,
What is wrong with crank that you need to change it .
Colin
NZ
RE: Scraping White Metal - GCD - 17-11-2021
Have a walk to the Great Western Society Depot - I an sure that one of their members in the Locomotive Dept will teach you how to do the job - scraping in W/M bearings is part of their bread & butter.
One thought - have you assembled the bearings and checked that the bores are round? If the bearings have been remettled you may find that the butts have closed in and will need to be spread - they will show you how to do this as well.
RE: Scraping White Metal - Stuart Giles - 17-11-2021
If the existing crank has been ground and the new one is standard size, that is likely to be an awful lot of scraping; typically crank grinds are done in 0.010" (10 thou') increments, your crank could easily be '30 under' or more. Whereas each scraper stroke gives a 'peeling' of about 0.0001" ( one ten thousanth). The big ends can be bored in a milling machine or (by using a simple jig) on a lathe to size, leaving no, or minimal scraping to get a good final fit. An 'old school' machine shop or any decent jobbing engineer should be able to do that boring for you.
RE: Scraping White Metal - Chris.Dallas - 17-11-2021
The 1 5/16 crank has wear on the main bearing surfaces so someone has attacked these areas with what looks like a chisel or Mole grips to roughen the surface abs take up wear! Importantly I use the car for trials and lots on the road so purchased a new crank to install. Having suffered a crank breakage in my teens which wrecked the crankcase I have no desire for a repeat. In my view there is only one use for a 90+ year old Austin crank….. that’s on the shelf!
Thank you all I will do some further checking but buy the sounds will need to have them bored or re metalled.
RE: Scraping White Metal - AustinWood - 17-11-2021
We fitted a phoenix 1-1/8 crank into our engine. The old crank was -0.020" and the white metal was sound. My friendly machine shop bored the existing while metal to suit the new crank. Simplest way of doing it.
RE: Scraping White Metal - Chris.Dallas - 17-11-2021
Thank you all I will do some further checking but buy the sounds will need to have them bored or re metalled.
RE: Scraping White Metal - Steve Jones - 17-11-2021
I think Ruairidh has done (or arranged for this to be done) in the past for people. Also such as Robert Foreman is worth contacting.
If the car you're talking about is DO 6628 then I'm pretty sure the metalling was done by Steve Cotterell so will have been done well.
Steve