I'm preparing some Big 4 crankcases for blasting and was wondering what the original finish was...Some parts of the cases are 'as cast' with a reasonably fine cast finish. Other parts are smoother than this and look like they have been polished or at least fettled off more thoroughly in the past...
They are reasonably early WD Big 4...Removing the various bumps and knocks won't be a problem (sorry to all you 'patina' boys) and I can restore the 'cast' finish where required...But should they be completely in this finish or are the smoother sreas also part of the original finish?....Ian

email (option): ian@wright52.plus.com

Ian I will be interested to see what Rik and Lex say when they return from a very cold, wet, miserable Kempton. Ron

email (option): ronpier@talk21.com

Hello Ian,

As far as I know they were standard sand casting finish without much special attention except where it was machined (all contact surfaces) which by its nature would then have a more smooth surface.
In the assembly books you do find reference to "polished" as special requirement, so that was not the standard.
I doubt the military would have wanted polished crankcases, and the pictures I have seem to support that.

It does seem that prewar/early war sand was slightly finer structure than lateron in the war. The castings showed a relatively smoother surface.

Cheers,

Rob

email (option): wd16h@telfort.nl

Thanks Rob...Ian

email (option): ian@wright52.plus.com

You are welcome Ian

I may not be a forum tiger but still a source for information

Cheers,

Rob

email (option): wd16h@telfort.nl

As Rob says, the early (read pre-war and 1939) cases were much better finished castings. They went down the same line as the civilian production. The castings were cleaner to start with and I have the impression that they were cleaned up with a linisher on the visible areas.

If the number stampings still have clean sharp edges and the area around is fairly even then I feel that you can take that as a guide to the finish of the larger flat areas.

The timing and tappet covers were cleaned up on civilian models but not highly polished unless, as Rob syas extra was paid. Nortons weren't a glamorous 'Promenade Percy' type of machine.

The factory ledgers contain a note that timing and tappet covers on WD models were to be "sand-blast finish"

email (option): 79x100@gmail.com

Yes, Rik is right, they appear very dull on the wartime pictures, a good way to replicate the finish is, to bead plast the parts, and then "polish"them with coarse stainless steel kitchen utensils cleaning steel wool and wd40, this closes the pores, and gives a nice sand cast finish.



It dulls down after awhile, here it's very shiny!

Cheers,

Lex

email (option): welbike@welbike.net