I have a brake drum that I was going to use in my transmission but I noticed that the internal splines are chewed up . I'm wondering if this will hang up the clutch discs and cause trouble ?
brake drum small (114.4 k)
Yes, it's a potential problem. If the lugs isn't as damaged you may use a small square file to smoothen the lugs before use, but in this case it looks like you may get a little too close to the threaded holes for the driving plate screws when it's straight?
Another issue is that you'll want all the lugs filed the same amount since otherwise only two tabs on the large clutch discs will take all the load if the spacing between lugs isn't the same as the discs, and then the load on these two lugs will be high and they'll wear soon again.
You may be lucky finding a better narrow brake drum - or you may swap it to the much better wide 26/27 drum design with lug shoes. Then you'll need the 26/27 driving plate and large clutch discs too. It will fit in an earlier transmission without shortening if you use the narrow brake band and the old hogshead.
There are also good repro narrow brake drums made - with lug shoes.
Thanks for the reply . that makes sense . I do have a 26/27 transmision and had thought about using the wider brake drum , but I've been told it won't fit in a 15 engine ---I was also wondering if the pedal shafts from the 15 hogshead would line up ?
You can cut the wide drum down to fit the 15. Need a 26/27 driven plate. Dan
I think the 27 drum will fit in the 3-dip pan when you use the 15 hogshead and a narrow brake band. The band will only use the front part of the drum, but it wouldn't matter much. You must use the driving plate from the 27 drum, the large clutch discs and the three steel washers under the clutch drum from the later trans.
See this recent thread about a similar issue :
So no need to cut the late drum to make it fit, it's the wide brake band that wouldn't fit with a three dip pan.
You can also change your drum by a new one.
I did so and was pleased to have it done. Change the slow speed and brake drum on the 1926 Touring and I found an other car when I start driving it with the new Drums.
Remember to check the reverse drum really carefully while into the transmission - they seem to be the weakest and are often cracked in the spokes. Only crack that eventually may be ok would be from a rivet into one of the lightening holes - then it can't grow anywhere.
That's why we made new ones.
Good point by Roger is that the reverse drum also cracks in the spokes. I would be diligent while you have it apart and magnaflux them to be certain.
Just a heads up if you narrow a 26-27 drum, you don't use a 26-26 driven plate- use the early driven plate and remachine the 6 bolt holes in the early driven plate for the different bolt circle diameter of the later brake drum.
Just curious why you suggest not using the 26/27 drive plate.
You will use a 26/27 drive plate. You are cutting the drum down to the width of the band. That leaves a lip for the drive plate to sit down into. This give you a full flat surface for the band to work on. Simple matter then to use the '25 and earlier bolts and wire as usual.
Dan, When I used the 26-7 drum, I machined it down in width but left a full band width and used the 26-7 driven plate. That way there is no mis-matching of the drum surface and the outer diameter of the driven plate to chew up the band. It worked well for me.
Allan from down under.