[AT] Now Ralph Video -- disc brakes

jtchall at nc.rr.com jtchall at nc.rr.com
Thu Dec 27 17:41:21 PST 2012


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



-----Original Message----- 
From: Dean Vinson
Sent: Thursday, December 27, 2012 5:21 PM
To: 'Antique tractor email discussion group'
Subject: Re: [AT] Now Ralph Video -- disc brakes

Ralph, thanks for yet another interesting video.

How do those disc brakes on your 40 actually work?  Is there a caliper and
brake pads that press against the disc?  Or does the disc get pressed
against the outer housing?  And how did the old brake shoe type work, before
you put the disc brakes on?

My Famll Super M has disc brakes (that press against the housing), and the
housings look about like those on your tractor.  But I've never been clear
on how they're an improvement over the friction band/brake drum types that
were used on straight Ms for all those years.  Seems less effective and more
complicated.

Thanks--

Dean Vinson
Dayton, Ohio






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