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Wallaby crank bearings

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Daggers:
Hi,
As a newcomer to internal combustion modelling I have been trying to learn as much as possible whilst putting together a cam grinder as a bit of covid light relief.
When reading the build series for E.T.W’s Wallaby(ME 1962) I was especially interested in the crank and cam build notes as this will be a new experience for me.
In his notes for the steel crank running in bronze bearings he states that finishing the 7/16”(11.1mm)split bearing bores should not be finished by reaming but by scraping.
Is this still the preferred practice ?
I would like to have anyone’s views, practical experience, tools used, all comments gratefully received.

crueby:
I use lapping compound on mine, rather than scraping. Mainly since I dont know how to do it with scraping!

ChuckKey:
I have scraped 3/8" split bearing halves. It was time consuming but worked very well.

Roger B:
Scraping was considered to hold the lubricant film well but as the Wallaby had force fed lubrication I am not sure that it would make much difference. Reaming is quite difficult to do well, especially in bronze which can be quite 'grabby'. Having said that I have reamed all my bearings, which run on steel shafts. Boring is another option but this requires a suitable set of plug gauges. Drill and bore or drill, bore then ream is an open question  :thinking:

Daggers:
Thanks for the comments chaps.

Crueby - I have used laps on larger shafts & bores etc, did you use conventional fine grit or some of the finer diamond pastes?

Chuckkey - I can imagine that you need a lot of patience to scrape that small a diameter. Can I ask what sort of scraper you used, small ground hss bit ?

Roger B - I have used scraping on a number of 1930’s and 40’s vehicle’s that used white metal bearings usually  where the oil pressure was quite low. It just seemed quite a tricky operation on a bearing surface that is so small. You are quite correct that some bronzes are grabby. I was going to use sae660, I think I will need to do a couple of experiments a see what works.

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