Poor quality castings...

[Parazine]

I think this was mentioned earlier, might have been on the Top Hat thread but the aluminium castings from the Austin Foundry are often of poor quality. The Top Hat crankcase has this near the oil relief valve:

   

The lower inclusion is steel; I tested it with a magnet. The upper one is aluminium, probably denoting a partial melt of the scrap that these crankcases were made from.

The factory workers clearly knew about this as each suspect mark has a bevy of punch marks around it.

The crankcase in the Chummy is a Birmal casting and is 100 times better. I assume that, as production ramped up during 1927, Birmal were subcontracted to produce a certain number of cases. These seem to have the "Austin" script cast on the web whereas the Austin cases have the script on the side.

The Austin cast cases are coded "AF" plus a serial number at the font, by the sump joint, whereas the Birmal cases seem to be coded "BA" plus a serial.

It seems that Birmal finally landed the full contract as I've not seen an Austin cast case from the post vintage period. Perhaps Birmal came up with superior quality at a better price??

[Mike Costigan]

The AF number indicates from which Austin Foundry the casting originated.

[Parazine]

Don't think so Mike, not unless there were over 8 thousand of 'em!

   

[Tony Griffiths]

Could the be a "code"? e.g. foundry No.1 casting 838. Though would the foundry not have cast the number in, rather than stamping it?

[Mike Costigan]

Ah! That's an individually stamped number rather than the cast number that I was visualising.

[Parazine]

Yes, I'd assumed it was a foundry serial number but there are various other, larger "cast in" numbers and letters all over the case. The gearbox cases have a similar foundry number stamped in them....

Sand casting fine detail (like small numbers) is difficult though, I think it would have been easier to have a man with a set of number punches at the end of the 1st inspection process, just after they broke open the moulds....

[Colin Morgan]

Is that just a mark in the casting that comes round in a circle, through where the lower inclusion marks are and then goes up and through that that other mark higher up, or has there been some sort of repair at sometime?

[Parazine]

No repairs, that's the general c**p quality of the sand casting on this early case!

[Hedd_Jones]

Ive always thought that whilst the sand cast cases have poorer surface finish, they are far stronger and easier to repair. Generally there is more metal allowing helicoil or a stepped.stud or whatever.

The die cast cases are simple production engineering. Uses less metal, therefore cheaper. Lighter and harder to repair threads.

And at the end of the day, those inclusions are irrelevancies. They havnt hurt it, and its probalbly 90+ years old

[Mark McKibbin]

Speaking of which, is this a later repair or do you think it's as it left the foundry? There seems to be several repairs, Engine No. 80487.