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Hi all,

I need some advice on making new brake drums for my 1914 Overland Model 79 speedster project. The originals appear to be made from some sort of high tensile pressed steel. My father and I are thinking about fabricating them from carbon steel hollow bar, but heard the thermal and braking properties of ordinary steel are not that good. Another option we have come across is having them cast in mehanite, but have concerns for long term durability due to the thin wall of Overland brake drums, however the wall thickness could be increased marginally.

Any comments or if anyone knows of manufacturer would be greatly appreciated.

Regards

Ben (Australia)

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Ben... You should get Harold Sharon's Book Understanding Your Brass Car. He has a section on restoring brakes just as you want to do including the options of forming and welding on new steel rim, casting in iron, etc. I quote from the HCCA website:

This book would be a welcome gift for any car enthusiast, tinkerer, and scholar of how things work (or sometimes don't!). 175 pages, 8" x 11". Each chapter discusses a major component, such as brakes, steering, combustion theory, how a spark is formed, ignition and cam timing, bearings and lubrication, wheels and tires, etc. Written by a retired engineer, in clear, plain language. Line drawings to illustrate text.

$24.95 + $4.95 for US priority mail delivery to the Continental US

or + $10.95 for shipping to Canada.

For shipping to all other countries, email me for a quote (go here for Jo's email address. It's about 3/4 down the page).

Send Check to:

Jo Sharon

93 Curtis Rd.,

Glastonbury, CT, 06033

Edited by MochetVelo (see edit history)
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Hello,

I would opt for a couple of solid round slugs of C4340 pre heat treated steel

from your local steel supply house (available in solid bar form).

It is just soft enough for easy machining plus having high tensile strength;

probably superior to the drawn steel originals.

Thanks,

Joe

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I have described the remedy forthis problem before on this forum more than once before, and at least once also on HCCA club forum. You need to check the posts in my name, but you find more posts camouflaged with an "underscore" malevalently inserted in my name by something in the system when the forum was "upgraded"a while back. Essentially, you get the pressed steel drums built up with sprayed coating of Metco Spraysteel LS, which is a machinable work-hardening carbon steel. This has such structure that it has similar braking efficiency to cast iron, but on your original drums. I have always build such drums up so they can be finished oversize where there is room. I am not familiar with this make and model, butif the footbrake is external contracting, you can cut a series of grooves at 45 degree angle in the linings about 2 inches apart to get rid of the water in wet conditions. You can also use modern lining composition. There is no other way to fix the problem of worn pressed steel drums which will substantially improve their efficiently, invisibly.

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Ivan... I couldn't find your AACA post on brake drum repair, but here is the HCCA Forum post you wrote in 2006:

I have repaired many such old worn brakedrums. You use a metal spray coating called Metco Spraysteel LS. This is a work-hardening machineable carbon steel with, from memory, about 7% Molybdenum content. It has similar braking characteristics to sg cast iron, and is compatible with modern linings, so you are actually using invisible modern technology to significantly improve the efficiency of early brakes.

It is important with metal spray coatings to rigorously follow proper prceedure. It is best if the rebuild and maching is done on the hub on a mandrel, or otherwise using accurate mounting plates on the mandrel between centres.

First clean and degrease. Take a light cut to make the worn surface true and uniform within reason. Then ideally, take a rough threading cut across, to give extra grip to the coating. If the material remaining is very thin, you may choose to compromise of this, because you need something reasonable to build onto. Then grit-blast with a fairly coarse aluminium oxide grit to further etch and clean the surface. Do not touch the cleaned surface. Avoid

leaving the job exposed to humidity, lest oxide start to form.

First spray coating is Metco 405. The job is heated to above 100C to ensure there is no moisture. The nickel alumimide alloys with a lot of exotherm, ideally just as it hits the surface of the drum revolving in the lathe. The steel coating can be built up as much as 3/16" thickness if necessary (LS stands for "low shrink")

The coating should be sealed when cool enough. Coatings may typically have 5% porosity, and it is best to fill thes voids so moisture cannot enter. On this application you should use a liquid air hardening phenolic.

I use the slowest speed on the lathe (10rpm) to machine with a sharp tungsten carbide tool. If you think the tip is blunt, pull out and resharpen with a diamond wheel. if the coating work-hardens you may have to grind it, which is slower. If the brakes are external contracting, remember to follow Harold Sharon's advice about diagonal grooves in the lining every couple of inches to expell the water in wet conditions. (Napier used this trick too, about 1911 if not before).

If you have an original part that is badly worn, sprayed metal coatings often allow you to salvage it so itwill give better service and last longer than the original material. If you dont trust the thought of coatings that is fine; but for heavens sake never fly in a jet aircraft. The coatings in critical areas are what enable them to function reliably.

_________________

Ivan Saxton

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Thanks for your replys so far everyone all very interesting. Unfortunately the orignal drums that I have are very heavily pitted from rust so may be beyond repair. I forward all this onto my father to see what he thinks. Putting the groves in the external band lining is a good tip thanks I'll keep that in mind.

Ben

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The coating will fill rust pits: You can put on enough to give an unblemished machined finish. A friend once talked me into rebuilding the drems, which were cast as patr of the rear hubs of a little pre-WW12 cylinder English Perry. I was most reluctant because you could see daylight through the drums, but they had no alternative. They never had a problem with the repair in probably over 25 years so far, even though they still use cast iron brake linings on the Spraysteel LS.

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