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Lining for brass brake drum


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My 1902 White steamer has a single band brake on the chain-drive differential and uses a cast bronze drum. I need advice on what type of lining to use.

When I bought the car it had a woven lining of unknown material (asbestos?) but this had hardly any stopping power. I replaced it with a Scan-Pac 242-OR molded lining (same as McMaster's "high friction" lining). This material ate-up the soft bronze drum badly in just a couple hundred miles and the car still didn't stop well.

There is conjecture that the original lining was leather, but the expert in such things, Bob Knaak, says leather won't withstand the heat generated in brakes...great for clutches but not for brakes.

One person suggested using a woven Kevlar lining like that used with some success in Model-T transmission bands. Chopped Kevlar is, I believe, the replacement for asbestos in modern molded linings but woven Kevlar does not appear to be used, at least as far as I can tell.

Any suggestions along with a discussion of what works for you would be much appreciated!

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I'll give you my opinion on using Kevlar. I manufacture band linings used by many Model T Ford owners and use 100% duPont kevlar. Kevlar has unusually poor abrasion properties and will fray and tear when used in any dry application. The only thing that allows it to be used in a Ford transmission is the fact that it is bathed in oil. I know many claim to use kevlar successfully in cone clutches, but my cone clutch is leather lined and will be lined again in leather when the need arises. I have given away kevlar linings to guys with Model N Fords, Queens, and others who have open planetary drives and all, repeat ALL, have told me the linings were destroyed in less than 500 miles. Based on my experience with Ford transmission linings (over 25 years), I would never recommend the use of kevlar (aramid) fibers in any dry application. My 2 cents...

Frank

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Thanks, Frank and Roger, for your good advice. I have some other very recent input that indicates modern woven material would give good stopping power because its coeffecient of friction is higher, but that it is abrasive and would cause wear on the bronze drum. This material is Kevlar-based. This fellow thinks that the original lining would have been a "treated cotton belting". Sounds to me like Scandanavian band linings for a Model-T. Anybody have thoughts on that? I wonder if it would run dry without shredding. Or if the tarred Scandanavian would work...

Re Roger's suggestion of a steel sleeve. There is a lot of difference in the thermal expansion rates between steel and bronze so I think a press fit between the two would not survive hard braking. But maybe a mechanical attachment could be contrived. I'll think on that. The other option is, of course, to cast an entire new drum in iron. I have been avoiding that because the bronze one has complex cores and would be expensive to reproduce.

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A braking from 60 MPH would be difficult! What is the max. speed of such a vehicle? I'm totally ignorant of those very antique vehicles...

About thermal expansion: which metal expands more? steel or bronze? The fact is that the steel will get first hot, less than the bronze partly due to the limited thermal conductivity between both.

A sleeve into a drum has not such problems but an external sleeve may effectively be a difficult task. The positive aspect of it: you could choose a better lining material.

If I can correctly interpret an old technical book, bronze expansion is more important than steel: the expansion value for bronze is 17.5 and the one for plain steel 11.5. Something to study...

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Roger,

You are right that the steel will get hotter and probably will expand faster eventhough its coefficient of expansion is less than bronze. So maybe a press-fit sleeve would work. And it certainly would allow a better lining material.

Stopping from 60MPH is not a concern...on a good day I can get up to 25 or 30. The concern is a long downhill grade. Steamers (as this car is) have no compression braking. White in one of its publications says to drag a log behind on a long grade.

Tom

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