Does anybody have the original dimensions of the early rear brake drums. Say 1911
Interested in the original inside diameter and the width of the complete drum. What would be a maximum gap between the drum and the axle housing generally seen? I have about 8 mm which is exposing part of the brake shoe. Have just fully rebuilt the diff and axle end float etc is spot on. My drums maybe worn from earlier wearing / contact with the diff outer backing plates
Cheers & Happy New Year
Alan in Western Australia
1906-1925 brake drum interchanges. [Hubs do not as straight vs tapered hub.] The 1909-1921 was part number 2818 and factory number (drawing number) 3. In 1922 catalog the part number remained the same but the factory number was given a B indicating some changes were made -- but the part still would fit and function the same. The larger 1926-27 brake drum was part number 2818B and factory number 3C.
I would guess, but it is only a guess -- did you use the new rear axles that are 1/16 inch longer? Ref: http://www.modeltford.com/item/2505HS.aspx see the comment about the extra length. That could contribute to some of the extra clearance but that should only move it out an additional 1.5875 mm.
A simple test would be to remove the axle key an see how they fit without the key installed. If they fit fine without the key -- then work with installing them again and test it. If necessary -- modify the key length etc.
Page 590 of Bruce McCalley's (RIP) book has a photo of a new 1915 (has 1914 style axle) that I think shows the proper fit.
Hap l9l5 cut off
Thank you Hap.
Yes, i do have new (slightly longer) axles fitted to my differential. These would certainly add a small amount to the problem. Have tried it without the keys and the clearance is the same. It must be an issue with the width of the drum which may have been worn away a bit by rubbing on the axle housing at one stage as there are signs of damage on both the drum and housing.
Does anyone have a drawing of these drums? Pointless ordering replacements until it's known what the "new" width is.
I have seen several Ts where the small gap between the backing plate and the drum is enough to allow you to see the edge of the brake shoes inside. And they all had original axles although maybe with a shim to prevent the drum from rubbing against either the backing plate or brake shoes. Wear on both axle and hub tapers cause the hub and drum to move slightly inboard. The new axles that are made that slight amount longer are made that way to correct the problem without the use of shims. The effect is the same. The hub and drum move out enough to clear the brake shoes and backing plate, but sometimes that movement is enough to be able to see the edge of the shoes.
Jack up the rear end, then rotate the wheel while watching the drum closely to make sure the drum and hub are straight. I have seen hubs that were not straight and allowed viewing of the brake shoes about half way around the drum. Also try to look at the end of the hub to be sure the axle is straight.
Provided everything checks out straight and solid. If the gap isn't much over 1/16 inch or more than about 3mm for those in the more enlightened parts of the world, I wouldn't worry about it much.
If the aesthetics are important, you may need to "dish" the drum slightly. This can be done easily with a small press. The drum should be bolted to a hub or stack of outer flanges to keep the center area square and only the outer part of the drum dished. Trial and error checking for fit to make certain the drum runs true is about the only way to go (unless you are doing a bunch of them).
As far as the drum being messed up or worn causing the problem? It is possible. I have seen many strange things done to T parts over the years. However, I would consider that unlikely. Of all the Ts and wheels and drums I have worked with over the years, only a few were messed up much, and they were quite obvious visually at little more than a glance.
For dimensions, the only resource I have is to measure used drums that I have. The outer diameter is about 8 1/4 inches (21cm), width 1 3/16 inch (3cm), metal thickness 1/8 inch (3.5mm). I hope I got those measurements right. Remember, I live in a less enlightened country.
I hope some of this could help.
Drive carefully, and enjoy, W2