'36 Plymouth brake question

[TodFitch]

The May/June 2003 Plymouth Bulletin says CENTRIFUSE brake drums were used on the 1933 PC/PD. I have not found any older application?

Centrifuse brake drums were new for Plymouth in 1933 along with the "silent U" spring shackles and thin shell crankshaft bearings.

[FourDoor]

The May/June 2003 Plymouth Bulletin says CENTRIFUSE brake drums were used on the 1933 PC/PD. I have not found any older application?

[Lew]

Forgot to add that some car makes had problems with seals leaking (usually they were leather) and differential fluid would get past the seals in to the brakes. Hence, a grease fitting or a grease cup was utilized with a huge caution to owners and servicers to not over- grease the rear bearings which would cause the same problem.

[Lew]

Interesting discussion. Model A & later Fords had the steel drums with fading/ warping issues. The dealers offered brake drum bands which were heated and applied to the outside of the drums. Vendors today offer cast iron replacements for the Fords due to the abundance of Fords still on the road. Too bad the're none for Plymouths though we haven't had any issues with our '36. Was told by an old time factory worker friend (now deceased) that the riveting was for production purposes and to limit the expansion from heat, but that was his take on it.

[Carla]

Tod,

Whilst, obviously, I can't certainly know the reasons for developing the 'Centrifuse' brake drum technology, I'd strongly suspect that it was a cost saving measure, rather than one of component quality.

In the high volume production which the Chrysler works did, it would have been significantly cheaper to stamp out the drum centres, then cast the iron outer drum to the steel centre.

Actual cast iron drums, when cast of best quality iron, are significantly superior to the Centrifuse drums. A good example might be the drums used on the Jaguar 'XK 120/140' and 'Mk7/MK8 cars, the last version of drum brakes before the disc types were offered. These were claimed to be a nickel-chrome-iron material, close-grained and very hard (enough so that reboring them to clean up after a careless owner let the lining go down to rivets is 'not easy')

These cars were famous.....or infamous, take your pick.....for the 'one good stop' from speed, after which the drums had to be allowed to cool. (that 'one good stop' saved me from being involved in a nasty bad wreck, some years ago) These brakes were the 'Lockheed two-leading-shoe' system, on front, and far superior in braking to any Centrifuse drum equipped car, particularly in being able to stop in a straight line on pavement.

I would imagine that the price difference between Centrifuse drums, and best quality cast iron drums, is rather dramatic, in high volume production. That said, even the makers of the humble Land Rover used cast drums, before the disc brake options became available.

I don't know when the Centrifuse drums were first in production, but they would have been quite a significant improvement over the common 'rolled steel' drums used on early cars. I don't have factual info, but I'd tend to suspect that the rolled steel drums would have been made from a medium carbon steel, and probably through-hardened. As a generality, the rolled steel drums were 'infamous' for expansion under braking heat, leading to dramatic brake 'fade' conditions.

There is, by now, an entire new generation of drivers who have, most likely, taken disc brake systems 'for granted' and may not be aware of the 'fade' potential of any drum brake..........should some young person decide to run a drum brake car, they really should take the time to experiment with it a bit, to learn when a 'fade' condition may set in.

cheers

Carla

[36 Ply]

Thanks, Plymouths and Tod for the additional information.

Regards,
Pat O'Connor

[TodFitch]

I believe the name used by the Chrysler Corp. was 'CENTRIFUSE" brake drums. I think they found out cast iron surfaces worked better than steel for friction but they couldn't bring themselves to make the complete hub from cast. Not strong enough. So the melding of a cast iron brake 'lining' to a hardened steel hub. (I believe the cast iron also dissipated heat quicker and didn't expand as much. It's the expanding of the brake drum from heat ,during multiple stops, and then moving outward and away from the brake shoes that causes 'brake fading'.)...snip...

They still make brake drums for big trucks that way: http://www.precisionpartnersinc.com/corporate/breaking-news/announces-its-new-long-life-severe-service-brake-drums-centrifuse-plus/

[TodFitch]

...snip...Originally brake fluid was made from linseed oil. The original Chrysler owner's manuals actually give the car owner a method of making their own brake fluid from linseed oil and alcohol if they couldn't  get to a dealer for the good stuff.     

Close but not quite right on the fluids used to cobble together a solution. From the 1933 DeLuxe Plymouth Six Instruction Book:

The master cylinder reservoir on the top of the master cylinder should never be less than half full of genuine Plymouth Hydraulic Brake Liquid, which is obtainable at any authorized Plymouth Service Station. This should be used to the exclusion of all other liquids, but if for some reason the genuine liquid is not available for an immediate requirement, a suitable substitute liquid may be made by thoroughly mixing equal parts of medicinal caster oil and No. 5 denatured alcohol free from acid (wood alcohol should never be used). This formula should only be used when the genuine Plymouth Hydraulic Brake Liquid is not available, and it is important that the improvised liquid be entirely drained from the system as soon as possible and replaced with Plymouth Hydraulic Brake Liquid. Plymouth Brake Liquid is make in very much the same manner, but certain chemicals are added by a very lengthy, as well as difficult, process which neutralizes acids found in the formula prescribed above.

[FourDoor]

I believe the name used by the Chrysler Corp. was 'CENTRIFUSE" brake drums. I think they found out cast iron surfaces worked better than steel for friction but they couldn't bring themselves to make the complete hub from cast. Not strong enough. So the melding of a cast iron brake 'lining' to a hardened steel hub. (I believe the cast iron also dissipated heat quicker and didn't expand as much. It's the expanding of the brake drum from heat ,during multiple stops, and then moving outward and away from the brake shoes that causes 'brake fading'.)
Originally brake fluid was made from linseed oil. The original Chrysler owner's manuals actually give the car owner a method of making their own brake fluid from linseed oil and alcohol if they couldn't  get to a dealer for the good stuff.     

[36 Ply]

John,

Thanks for all the info and the heads-up on the Chrysler book. I will order it.

Regards,
Pat O'Connor

[John Hendricks]

I just checked-- the book is available from Amazon -$25 new, $12 used.  A bargain at twice the price. U need one.

[John Hendricks]

There is a fascinating book - The Birth of Chrysler Corp. and Its Engineering Legacy by Carl Breer.  I am not sure but i bet it is on Amazon.  At any rate brakes were a problem in the early years.  Chrysler engineering worked with another company to develop a special cast brake drum that was mounted to a steel wheel.  It stayed rounder and it lasted longer.  There is also an interesting section of the development of brake fluid and Lockheed brakes.  As far as the outer bearings, I am just guessing, but it may have been that seals were not reliable enuff to have oil sloshing around close to the brake shoes.  It may also be that the semi floating axle as a variation of the full floating, just used the same lub system.
Find that book- u will really appreciate the unique engineering features that Walter P developed.

[36 Ply]

Thanks, John; I'm still wondering WHY they did it that way, what the Plymouth engineers perceived was the advantage of riveting the two together.

Another oddity is that the rear wheel bearings have grease zerks, rather than being lubricated from the differential.

Regards,
Pat O'Connor

[John Hendricks]

They did that for many years - a puller is just part of the tool kit for brake work.  The fun really begins when u look for the tool to adjust the shoes if u have to move the eccentric bottom pivot.

[36 Ply]

Does anyone know why Plymouth riveted the brake drums to the hub on the '36 (and possibly other years)?

I had to buy a puller in order to pull the rear drums/hubs on my '36; was there supposed to be an advantage to riveting the two together?

Thanks,
Pat O'Connor