Ball bearings it is indeed. At least in the ones I have worked on.
There is, or was, a company that made and sold these out there and it
is their product I worked on and had plenty of fun with.
Whatever they made THEIR “ball” portion of the bearings out of did
not withstand pickling at all. Thus I gained experience in rebuilding
them! How fun!
The bearing is almost exactly like a roller bearing or bicycle wheel
bearing and worked wonderfully. I would suggest using one as an
example. The ball bearings are what I had to replicate. The ball
bearing housing was fortunately made of gold and did not disappear in
the repair process.
I used the same process one would use for granulation to make new
ball bearings. Nip some pieces of gold wire all a similar length,
scrape your charcoal block to make powdered charcoal, place the
powder on your block, embed the pieces of wire in the powder and then
use a soft flame, heat the powder until the pieces of wire melt into
Use a sieve to sort them into a supply all the same size.
The bearing housing is two tubes of different diameters with the
ball bearings between. As I suggested above, I would suggest getting
a bearing from a bike shop and use it for a model.