[singleminded]

The spare drum that i have seems to have had the metal spun over the bearing edge by about a 1/16",it's like a razor.

[phutton]

Interestingly, the 1927 spares list indicates that the M80/90 rear drum uses a 2 1/4" bearing, rather than 2 5/8", but lists a housing (sleeve) to bring it up to 2 5/8! I suspect it is something to do with the spline requiring clearance to enable it to be cut, and the factory's desire to use a standard off-the-shelf bearing. There must then have been a problem, since in 1928 they introduced the special 2 5/8" bearing. No Loctite in those days!

P.

[wessex_man]

Yes I know the bearing is a difficult one. I have looked at it also and can't really find a standard bearing that can be modified by grinding to size and there is never going to be the demand to get them made really economically. I've seen one drum with a bronze bearing in replace of the ball race but I don't know how that long that would really last in practice.

[phutton]

I have looked at this in some depth but, unfortunately, we are quite limited in what we can do. We must maintain the inner 1 1/4" inner diameter, and the 3/8" width, otherwise we run into interchangeability problems. We cannot reduce the bearing housing diameter as that would make machining of the splines impossible. We could use a standard 2 5/8"bearing  and sleeve up the stub axle, but the thinnest available is 7/16" thick, and I don't want to reduce the spline length.

The usual fix is to use a standard 2 1/4" x 1 1/4" x 3/8" KLNJ1-1/4 bearing and sleeve it up to 2 5/8". Any other suggestions would be gratefully received!

[wessex_man]

Would it be worth looking at the narrow custom bearing at the same time?

[phutton]

Depending on prices that we get back, we may well go ahead with this, particularly if the only difference is the thread.

[wessex_man]

Certainly had no problems with the projects done over the years re-rear drum interchangability. Think thats the only difference we can see from what we have Paul. The 1928, first year of design, the brake plate was different but the drum the same. The wheel hub part number (4588) certainly didn't change throughout your period of interest. The part number for for the drum was 4587 upto 1930 to 4587A in1931 to 6782 in 1932. I suspect the major change in part number due to the thread change. So we think you could make one drum to suit for the period just thread changes if you want to be right for years. Most could adapt I think.

Are the club going to make any?

[singleminded]

I have a spare wheel inn the garage paul..just need the diagram to compare to..John Hood

[phutton]

Does anyone know the difference between the 1928-31 rear drum/sprocket and the 1932-35 version, other than the change in thread from BSCY to BSF? If anyone has the later one to hand, could they compare it with the drawings I have done to identify the difference(s)?

If the difference is only the thread, then the batch size makes re-manufacture much more interesting!

Thanks all

Paul H