03-06-2020, 11:45 AM
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??
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??