Carrier Rear Brake Drums

kevin powles · #1 27-08-12, 20:02

Hi folks.

I am in need of brake drums for the carrier, I have a set which someone has over machined in the past, I would rather put on some drums which fitted the original brake shoes.

Have carrier parts to trade.

kev.

rob love · #2 27-08-12, 22:28

You can always get shims put behind your new linings, or re-arc the shoes (grind the linings so the fit is right) to fit the drums. Likelihood is you will never wear out a set of shoes, but there is no replacement for nice smooth drums on a carrier.

RichardT10829 · #3 27-08-12, 23:07

Can you not have the drums re lined, my thoughts were along the lines of machining the hub out then heat it up, drop a pre machined ring in so when the hub cools it grabs the ring and you have in essence new hubs

rob love · #4 27-08-12, 23:54

I have never heard of such a thing as sleeving the drums.

A brake reliner can usually supply thicker shoe linings however to match up to oversize drums. Likely a lot cheaper (and a lot more accepted) than Richard's suggestion.

My apologies to Richard: there are no bad ideas when brainstorming.

Lynn Eades · #5 28-08-12, 08:18

What happens when your drum gets hot? Does the sleeve spin?

Not saying it cant be done, just have some safety concerns.
What is a brake? a device that converts kinetic energy into heat (which is then disapated into the air)

RichardT10829 · #6 28-08-12, 09:57

I know but I would imagine that the hub would need to be glowing to get the sleeve to fit, is he going to be driving the carrier hard enough and long enough to generate that kind of heat ?...... I suppose a key way could be machined between drum and sleeve

twas just a thought, I am sure an engineering firm would be able to give the in's and out's

Phil Waterman · #7 28-08-12, 18:22

Hi All

I vaguely remember hearing that brake drums were at one time were sleeved as an alternative to new ones.

Temperature differential need not be that great. Putting new starter rings on flywheels only requires heating the ring to 350F with the flywheel at room temperature. The trick is to put the ring gear on in one smooth movement as once contact is made the ring cools and shrinks.

Cheers Phil

Lynn Eades · #8 28-08-12, 22:37

That may well be the case, however the production of a cast iron ring, followed by the machining, fitting, and finish machining, to end up up with a somewhat weak result just wouldn't be worth it. Especially in this day and age, where questions would be asked, if a failure happened.
To go to the trouble of casting the repair ring, you may as well cast a complete drum.
Another avenue could be to turn the outside of the drum, and shrink on a steel "support" ring, which would be safer. This would allow a greater bore size to the drum. I dont think you'll want to do this either.

Kevin, turning out the drums and fitting thicker than std. linings is common. Modern drum brake vehicles have a maximum oversize. Back when the carriers were in wartime service, you replaced with a standard part. Your drum has a strengthening rib on the outside.
What you need to do is ascertain the original diameter, and compare that with what O.S.your drums will clean up at. From there is the hard part. Is that O.S. acceptable from a safety point of veiw? (I dont know who you ask)
Once that's decided, then the rest is easy. An O.S. brake will work better than a std. one. (bigger effective dia., and bigger surface area)
You will need to fit the o.s. linings, and have them ground to fit exactly, the drum radius.
In theory both sides should be done the same size to ballance the brakes, however, I dont think you could tell the difference. It is probably better to take the minimum out of each one, as it might still give you room for doing it all again later.
I wouldn't put shims behind the linings. Every separate piece (including sleeves in, and rings on the drum) is a barrier, or potential barrier to heat transfer.(the faster this can happen, the more efficient is your brake)
Some of the heat from your linings is disapated out through the shoes. A thicker lining of one piece is as good as it gets. Bonding is good as it does away with the rivets, which would be the biggest single reason for having to turn out the drums.

kevin powles · #9 28-08-12, 23:34

Hi, Thanks for the advice guys, I think I will go with oversize shoes, the drums themselves have a perfect finish and run true, I will get some shoes made and then run them in with the track off and brake on, I done this on the tank hunter and it bedded the brakes in well. I think the drums have been turned out so just that inner chamfer had been lost. Some previous log puller had modified the expanders to get more travel, I think i mentioned this before in another thread.

cheers kev.

Richard Farrant · #10 28-08-12, 23:46

Quote:

Originally Posted by kevin powles

Hi, Thanks for the advice guys, I think I will go with oversize shoes, the drums themselves have a perfect finish and run true, I will get some shoes made and then run them in with the track off and brake on, I done this on the tank hunter and it bedded the brakes in well. I think the drums have been turned out so just that inner chamfer had been lost. Some previous log puller had modified the expanders to get more travel, I think i mentioned this before in another thread.

cheers kev.

Kevin,
Get your local motor factor to do the job, let them measure the drums and get the shoes relined thicker then profiled to fit. Remember the modern lining material is unlike the old asbestos, and will not bed in half as quick. In fact it does the opposite my hardening if you try to do it too quick.

rob love · #11 29-08-12, 00:52

I will second Richard's advice, and add to it that why would you have nice clean drums, nice clean shoes, and then subject them to the excess heat trying to set them in. Bring the hub and drum in with your shoes and let them either shim the linings if they are going with rivets, or else install thicker lining material and grind it to match the radius.

As a mechanic, I use to spend a lot of time removing the glaze from brake shoes. Why would you want to restore a vehicle and start off with the problem before you even get it out of the shop?

cletrac (RIP) · #12 29-08-12, 02:59

The brake drum by itself is likely the same as a civilian 3 ton or such used with the sprocket holder welded on to it. It might be worth finding out for sure. That sprocket holder would be easy to transfer to another drum.

Bob Estabrooks · #13 29-08-12, 03:12

I am glad that CLETRAC mentioned going to the modified civi side. Mr. Ford reused and reused. There has got to be a compliment out there somewhere.

Bob

cletrac (RIP) · #14 29-08-12, 04:58

The part that the sprocket bolts onto is welded to the drum. This makes it different to any truck setup but the basic drum is likely off a three ton. I'd guess three ton because they used the heavier brakes.

Lynn Eades · #15 29-08-12, 08:18

The drum is carrier specific, and the mounting surface for the sprocket is part of the drum casting. Michael, I think that is correct. BTW, I am not sure of this, but I think the "BB" part numbers are of British origin.

rob love · #16 29-08-12, 14:13

BB refers to parts introduced for the 32-34 trucks.

Jack Innes · #17 29-08-12, 16:48

I do not think you would ever normally machine the carrier drums thin enough to be of concern. Bear in mind we are dealing with mechanical brakes that apply much less pressure than modern hydraulic, power systems and very sturdy drums. Many cars in the 20s had stamped steel drums about 1/8" thick. Another point to be made concerns grooves sometimes worn by rivets protruding from worn linings; a bit of a radial groove will have virtually no effect on braking & is sometimes more desirable than turning a great deal of metal off to remove the groove.
Most reliners can apply thicker lining & machine the newly lined shoes to the exact diameter of your finished drum. Each side does not need to be the same diameter but be sure not to mix the shoes up!

From personal experience I have found that bonded linings often come loose on vehicles that are used infrequently. I always prefer to have riveted linings if at all possible.

cletrac (RIP) · #18 30-08-12, 02:21

I took a closer look and what I thought was a weld is something to do with how they made their casting mould.

Bob Carriere · #19 30-08-12, 03:40

When I had my shoes relined in Ottawa the shop insisted on having rivets on the leading edge and trailing edge of the bonded linings. Once they knew that it was for a restoration with only limited expected annual driving they explained that it was a safer and much recommended practice. They also recommended arcing the drums to match the lining's arc and vice versa.... in fact the new linings showed how the lining surface had been adjusted/surfaced ground to match perfectly on the center of the lining. Makes it a lot easier to adjust with the cams and gives very good braking/stopping action.

One must remember to regularly adjust them as per service manual... remember this is old technology..... no self ajusting system.

Bob