unusual MGTC alloy brake drums

[rileyman]

2 years ago I bought a 1949 TC that was originally raced in California prior to 1952. I thought it had Alfin drums but inspection proved them to be a heavy, ferrite, magnetic, stainless steel. I've attached some pics of one drum. To me, it seems the bolting surface, drum back, and inner cooling rib are an alloy sand casting. The inner drum and braking surface shoulder are a more "precise" alloy casting. The other 3 ribs seem to be "plate" circles that were sweated on. I solicited Bob Grunau's opinion as the current "Alfin" guru, but he too was puzzled.
Does anyone know anything about these parts? MY ORIGINAL ATTACHMENTS DID NOT LOAD SO A NEW SET WAS ADDED ON 12/21, SORRY.
Mike in TN

[Duncan M]

Mike, any chance it could be a normal TC drum, that was chilled and then tapped into the outer finned part when the outer part had been heated up in something like a 500* oven? If you go though old car magazines from the late 40's through 50's there are advert's for what I describe above. Also other ones, where two of the outer finned half pieces are bolted together to fit solidly onto the drum. Generally were do at home kits for specific make drums, but also outfits where you send off your drums to them. Usually aluminum outer/fins. Was the car raced in Central or Northern CA? What was his name?

[Steve Simmons]

They look similar to the Alfin-style drums that the local guys here ni So Cal were making some years ago, but not enough fins. Hmmm...

[rileyman]

I don't believe they are based upon MG bits as even the drum's interior is rust-free after 25 years in an Ohio barn. A friend has a TA with exactly the alteration to aluminum "fins" on MG drums as you mentioned. I don't know anything about the actual race history that was alleged. Much evidence exists with ported/shortened head, hot cam, old sleeves bored to just under 120 thou to fit odd pistons, holes in rear fenders for gravel shields. Mike

[Kameron M]

They look like original TC drums on the inside to me, and it would be very difficult to have the casting set up like in the picture, with two different materials.

My suspicion goes with the previous suggestion that the finned area was cast and then shrunk-fit around the original brake drum.

As for your question about rust - my TC drums are original and are almost that clean. Cast metals have pretty decent natural rust resistance, and the metallurgy on the TC seems to be quite quite good... well, in some areas at least.