sludge tube removal

[Greybeard]

When did sludge traps get introduced into BSA engines?

[JulianS]

On the large journal cranks with radial flywheel bolts only from around May 1957.

[Greybeard]

On the large journal cranks with radial flywheel bolts only from around May 1957.

I wasn't referring to the removable tube but the concept of a centrifugal filter. I guess it was noticed that crud would collect in the crankshaft oil way so enlarging the diameter seemed a good idea.

[JulianS]

Dont know about BSA but certainly Ariel used a centrifugal filter in their singles from the 1930s. An extended oilway in the timing side flywheel capped with a cupped plug, the cup gathering the impurities. They called it an oil purifier. In theory it was removable via the sump for cleaning.

B25/B44 used a similar setup.

[Rex]

My '51 has the trap, though there's no removable tube used.
It is possible (and even recommended by the Ariel cognoscenti) that the sludge trap be removed and cleaned via the sump plate.