On Wed, 18 Oct 2017 07:08:30 -0700, Cemetery Polka wrote:
On Wed, 18 Oct 2017 08:00:23 -0400, Ed Huntress
wrote:
On Tue, 17 Oct 2017 13:12:35 -0700, Cemetery Polka wrote:
On Tue, 17 Oct 2017 15:45:14 -0400, Ed Huntress
wrote:
On Tue, 17 Oct 2017 11:31:55 -0700, Cemetery Polka wrote:
Sounds like mine is the same arrangement.
https://www.colemanequip.com/parts/m...E-SYSTEM-0WCr/
It's not a shoe though, but a band around a drum. I cleaned
everything, lightly greased the balls, and adjusted. It works Ok on
the level, but is really crap when I'm pointed up a steep hill and
stopped trying to shift gears. I figured it surely must have worked
better when new, but a friend who knows these tractors from the old
days told me the brakes were never any good. Based on your experience
though, I'll give everything a more critical look next time it's
apart.
Ed, if you're reading this, please give your opinion on the
arrangement. The plate 35 presses against the inside of the housing.
It seems to me that the cam/ball/disc thing can only be effective IF
the band is effective, which makes it a dubious idea. Ever known
anything else that uses such a system?
Wphew, you're really asking the wrong guy. It looks to me like the
balls ride on ramps, and the drum would have to be clutched to a stop
(by the band), or nearly so, for the balls to ride up the ramps and
put pressure on the discs, right?
Exactly. I suppose it's supposed to multiply the effect of the band.
Except that the band is wimpy, and unless it's gripping sufficiently,
there isn't much pressure on the balls and the plate.
It looks like the balls are part of
a freewheeling clutch.
It's a very primitive manual brake system. One housing outboard on
each side of the transmission. Here are some pics
guts http://www.hagantractorparts.com/CaseBrakeAssembly.jpg
In this one, you can see the left brake housing just ahead of the rear
axle housing. The disc pushes against the outboard face of the
housing.
http://www.tractorbynet.com/forums/f...mg_1620_rs-jpg
Here's one that's a little more true to life. 
http://img.photobucket.com/albums/v1...ractor0002.jpg
Brake housing is just below the guy's hand. Comes off easily, bands
stay with the housing. Then the drum with the disc and balls slides
off the output shaft. Points given for being easy to work on but it's
quite a bit of iron considering the anemic performance.
It's strange, for a brake. There must have been some considerations
that aren't obvious, in order to engineer something like that.
After all, leading-shoe drum brakes will give you all the mechanical
"amplification" you want.
Appears to be a holdover from earlier farm tractor models.
The bare tractor is only about 3200 lbs. With a loader and hoe it's
nearly triple that. Did some searching yesterday and found several
comments about the inadequacies of these brakes, and one mention of
improving them by using oversize balls. Perhaps with disc friction
material wear, the balls must move so far on the ramps that the drum
rotates too much before the disc makes contact. I'll check it out next
time the brake housings are off. Maybe the drum assembly can be
shimmed a bit outboard.
I can see the attraction of using the vehicle's momentum to provide
leverage, which works well on electric trailer brakes for example. But
if the compound balls/ramp/disc thing was a good idea it should have
been more popular.
My first thought was that it's very compact, which may have been the
main idea. My second thought was that it's something from an era when
we expected to make adjustments and replacements to mechanical parts
for all kinds of things -- including cars.
Still, I'd like to know what the engineers were thinking. Overrunning
clutches in most applications are either on or off, like a Bendix
drive; the balls are either fully released, or locked on. There
doubtless are exceptions, but, as I said, the mechanism is known to
give trouble when parts wear.
At least you can see what's going on. A digital version would be a
real headache. d8-)
--
Ed Huntress