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Selecting iron for brake drums

kelfy

Plastic
Joined
Sep 21, 2023
I'd like to get iron brake drums made for an antique car, 14" ID (2-wheel brakes). It has been suggested I start with material from Dura-Bar and get the drums machined out. I see that they supply 5 grades of ductile iron and 3 grades of cast. How would I choose what would give the best combination of lining friction and heat dissipation? Thanks...
 
If you try to get them cast, be sure to tell them that it's for a museum restoration and you're not going to drive it. I'll bet lots of places won't touch anything to do with brakes or suspension. It may even be that their insurance forbids them from doing so.
 
Definitely try the route that dalmatiangirl61 suggests. Making a brake drum out of a solid hunk of cast iron or durabar will result in 90% of the material ending up in your chip pan. It will be a LOT of material. IF they are smallish you can try trailer drums (inexpensive.) Or take what is left of one of your old drums to a wrecking yard and match it up as close as you can.
 
Definitely convert existing brake drums. After you know which drums can be modified to fit, you could make up 4-5 sets and sell them. It's likely an extremely rare application, but if you're the only guy in the world that has them; someone won't be likely to scoff at $500 for a set.
 
Definitely convert existing brake drums. After you know which drums can be modified to fit, you could make up 4-5 sets and sell them. It's likely an extremely rare application, but if you're the only guy in the world that has them; someone won't be likely to scoff at $500 for a set.

I know a guy who was doing that with a very specific brake pedal setup for a somewhat commonly built collector's car. Did decent selling them, usually came in little batches of sales. He wanted a setup for his own car, so he made some extras and ended up selling quite a few over the years.
 
These have a 14" ID - way bigger that Model T's or Amish carriages. There's no offset to the bolt plate, it's just a big flat dish, similar to photo. I know it's a lot of waste, but for brakes, I would feel better starting with material with the integrity of Dura-Bar's fabrication, vs. pouring a thin shell.
 

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From over 40 years of experience using Durabar products, go find you some one like Windy Hill Foundry to cast you a pair of brake drums. He can cast them using a old drum for a temporary pattern. Durabar is good for many things but don't use it for brake drums or rotors. Such a large bar you're talking about using, it will only have a yield strength of around 20K psi if you're lucky. Most brake drums and rotors are much closer to a class 40 or even 50 gray iron. Which has at least double the yield strength you will ever get out of Durabar. Others may say differently.
 
I would make it out of steel. Roll the O.D. out of flat bar. Make it a little under size for final machining. Cut the center disc out of sheet and weld to the O.D. I would do the final machining on a brake lathe for drum brakes. Probably need to aneal it after all welding is done and before final machining.
 
It has to do with section thickness when the iron is poured. Thicker the section, the slower it cools and lessor yield strength. The thinner the section, faster it cools with a higher yield strength.
 
I'd agree with durabar not being ideal ... if you want castings we can ask around. No one here gives a damn about liability in the US for an antique car. But it'd have to be serious, don't have enough energy for perpetual tire-kickers.

If you wanted to go crazy, we've done an interesting iron-drum-in-aluminum-body set of brakes for a vintage race car. Worked great. If you have a mill and lathe, could do that yourself for a lot less $$.
 
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Not only parking brakes.........many trucks had steel pressed drums for 16x8 brakes .........however ,no truck Im aware of had steel drums after the 1960s.............We used to get truck drums cast locally ,a lot cheaper than import ones ,but they didnt last a fraction of the milage of the good ones .........Good English OEM drums would get a sort of a shiny glaze on them ,and seeming last forever.
 
The car is a 1913 Paige. It has stamped steel drums now. Hand brake and foot brake linings are internal-expanding and external-contracting, respectively - both surfaces need to be machined.

Braking requires looking far ahead. I don't expect to reach modern braking performance, but switching to iron for drums has improved drivability for a lot of cars of this era. There just isn't anybody doing drum castings of this size regularly that I know of. I'll check into Windy Hill. Hopefully they will have a way to build out my drums for a casting pattern.

I'm not a liability kind of a person, but I do want drums that won't crack.

Thanks 4GSR for the numeric data - this is the kind of thing that will really help me understand how to specify the project.
 
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Braking requires looking far ahead. I don't expect to reach modern braking performance, but switching to iron for drums has improved drivability for a lot of cars of this era.
If you are doing the work yourself, I can recommend the iron lining in aluminum body method. It works better than completely iron, but is more labor-intensive. But if you are doing it for yourself, who cares ? It's a hobby :)
 
Would the aluminum body design include friction surfaces on both the inside and outside of the drum? There are two sets of linings, inside and outside, for the hand and the foot brake.
 
Band brakes will never be very effective ....the outer band inhibits cooling.....Id be making a fabricated steel drum .........the catch with ally is heat ....if the drum gets very hot ,then the ally will fail.
 








 
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