[AT] Now Ralph Video -- disc brakes

[Dean Vinson]

Thanks, John--I do have a parts book and even a disc brake repair pamphlet
from IH, but I've never had the brakes on my SM apart to really study them.

My gut feel, however, is still that even in top condition they could hardly
represent enough of an improvement over the old band-and-drum brakes on the
straight Ms to be worth the dramatic increase in complexity.  On the old
brakes, a friction band surrounded a rotating drum; pushing the brake pedal
tightened the band.  100% of the contact area was at the extreme outer edge
of the rotating drum, and the mechanism was dead simple, easy to adjust,
easy to replace, and always seemed plenty effective to me.  On the disc
brakes, some of the contact area is close in toward the center of the discs
where the torque rules work against effective braking, and as you noted the
assemblies are expensive and difficult to properly adjust and repair.  I've
tinkered with mine a little bit to get the left and right sides to grab at
the same time, and to resolve a tendency of the right brake to stick, and
they work okay but not great.  I love the tractor but would be tempted to
swap on some M drum brakes if I had to do much work with it.

Dean Vinson
Dayton, Ohio


-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of jtchall at nc.rr.com
Sent: Thursday, December 27, 2012 8:41 PM
To: Antique tractor email discussion group
Subject: Re: [AT] Now Ralph Video -- disc brakes

Dean, here is how the disc brakes work on the 2 JD combines I have worked on

and on a DC Case. Your Super M may have the same setup, I'm sure you could 
access the parts book online to verify. For each brake there are 2 discs 
with linings on both faces for a total of 4 areas of contact. The first area

of contact is against the transmission housing (it may be a renewable 
plate). The second and third areas are 2 cast iron plates held together by 2

big springs and separated by 3 or 4 ball bearings (about 3/4 dia.). The 
fourth area of contact is the housing that covers all of this and bolts to 
the transmission.  The 2 brake discs, and the 2 cast iron plates all float 
on the shaft coming out of the transmission. Actually this shaft is probably

pressed into the bearing in the end of the housing. There should be a couple

links that resemble huge roller chain links between the 2 cast iron plates. 
This is where the brake linkage hooks. When the pedal is depressed, one of 
the plates will rotate on the bearings. The bearings are sitting in 
spherical pockets. As the plate rotates the gap between the 2 widens, thus 
applying pressure to all 4 disc surfaces.

I have no idea if this is an improvement over band brakes---probably yes 
assuming every thing is in good working order. They cost a small fortune to 
rebuild.  I have heard a lot of folks complain about these brakes over the 
years. It has been my opinion that they were not properly rebuilt. If you 
get a grease leak from the transmission, you most likely need to replace the

disc that got greasy. Also, the discs tend to wear circular pockets into the

steel surfaces they rub against. If the new discs are slightly larger, then 
they will be riding on a high spot. That needs to be addressed when 
rebuilding just like facing a flywheel when doing a clutch job.

Probably far more than you wanted to know, certainly more than I intended to

type to begin with!

John Hall