| Re: [GMCnet] Former GM Employees [message #105318] |
Sun, 07 November 2010 04:00  |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
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Senior Member |
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Yes, indeed, the governor as used in the Hydramatic has been built in almost any
conceivable combination of weights and springs. The heavy weights are separated
from the lighter ones by springs and it is the lighter ones that actually push
on the regulator valve. The idea is that at low speed the springs hold the
weights apart and the pressure regulated by the governor is a function of the
total of the 4 weights, 2 on each side. There is a pair of weights on each side
and each side pushes independently on the governor valve. This creates a very
steep rise in pressure at low speed - up to maybe 30 mph. At what we called the
"break point" the centrifugal force (yeah, I know that's not technically correct
terminology, but bear with me) on the heavy weights overcomes the spring force
and they go out against a stop. As the speed rises from there the pressure is
proportional to the centrifugal force on the lighter weights plus the force of
the springs. The problem for the transmission tuner is that the "corner" at the
break point is very pronounced and it is difficult to get the shift points
spread out the way one might like. Solution: Create a 3-stage governor curve
with 2 break points. You can do that by making one of the heavy weights lighter
than the other. The springs can also be made with different loads. This
doesn't help a lot, as the second curve is still just half of the first (the
third being about 1/5 of the others). Is there a worry about the unbalance this
creates? Apparently not, as I've never seen a problem, and back in the olden
days I spent many an hour at the governor stand creating governor curves. I
previously posted a chart that showed a typical governor curve.
What would I recommend? Take the governor apart and drill a hole in the outside
surface of one of the heavier weights about as big as practical. This will
extend the heavy-throttle 1-2 shift points and make the part throttle 3-2 shifts
slightly easier to get. The full throttle 1-2 shifts won't be affected. But I
would only do this mod if the governor was out of the transmission already.
It's not worth doing much more work than that. The rear wheel drive THM 400 is
another matter entirely - pulling the governor is about a 2-minute job.
I hope my explanation wasn't too obscure.
Gary Casey
I can't tell you why the "flyweight" governor in the transmission has
different weights but I can tell you that just about every hydromechanical
propeller control and jet engine fuel control has a flyweight governor in
it. They work in the same way that the one in the transmission works. The
position of the weights changes the position of a pilot in a sleeve which
controls pressures used to regulate propeller or jet engine rpm. In thirty
years as a Hamilton Standard rep I NEVER saw one that had different weights.
In fact IIRC they were matched sets! The first time I read a message stating
that the flyweights were different in the transmission I said "BS" to
myself. Fortunately I did some research before I opened my mouth and sure
enough they were!
Regards,
Rob M.
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| Re: [GMCnet] Former GM Employees [message #105325 is a reply to message #105318] |
Sun, 07 November 2010 08:33  |
 |
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Gary,
Thanks, great explanation!
I now know why the flyweights in a prop control or JFC are the same, they
are designed to keep the engine and prop running at a constant rpm.
Regards,
Rob M.
USAussie
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Gary Casey
Sent: Sunday, November 07, 2010 4:00 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Former GM Employees
Yes, indeed, the governor as used in the Hydramatic has been built in almost
any
conceivable combination of weights and springs. The heavy weights are
separated
from the lighter ones by springs and it is the lighter ones that actually
push
on the regulator valve. The idea is that at low speed the springs hold the
weights apart and the pressure regulated by the governor is a function of
the
total of the 4 weights, 2 on each side. There is a pair of weights on each
side
and each side pushes independently on the governor valve. This creates a
very
steep rise in pressure at low speed - up to maybe 30 mph. At what we called
the
"break point" the centrifugal force (yeah, I know that's not technically
correct
terminology, but bear with me) on the heavy weights overcomes the spring
force
and they go out against a stop. As the speed rises from there the pressure
is
proportional to the centrifugal force on the lighter weights plus the force
of
the springs. The problem for the transmission tuner is that the "corner" at
the
break point is very pronounced and it is difficult to get the shift points
spread out the way one might like. Solution: Create a 3-stage governor
curve
with 2 break points. You can do that by making one of the heavy weights
lighter
than the other. The springs can also be made with different loads. This
doesn't help a lot, as the second curve is still just half of the first (the
third being about 1/5 of the others). Is there a worry about the unbalance
this
creates? Apparently not, as I've never seen a problem, and back in the
olden
days I spent many an hour at the governor stand creating governor curves. I
previously posted a chart that showed a typical governor curve.
What would I recommend? Take the governor apart and drill a hole in the
outside
surface of one of the heavier weights about as big as practical. This will
extend the heavy-throttle 1-2 shift points and make the part throttle 3-2
shifts
slightly easier to get. The full throttle 1-2 shifts won't be affected.
But I
would only do this mod if the governor was out of the transmission already.
It's not worth doing much more work than that. The rear wheel drive THM
400 is
another matter entirely - pulling the governor is about a 2-minute job.
I hope my explanation wasn't too obscure.
Gary Casey
I can't tell you why the "flyweight" governor in the transmission has
different weights but I can tell you that just about every hydromechanical
propeller control and jet engine fuel control has a flyweight governor in
it. They work in the same way that the one in the transmission works. The
position of the weights changes the position of a pilot in a sleeve which
controls pressures used to regulate propeller or jet engine rpm. In thirty
years as a Hamilton Standard rep I NEVER saw one that had different weights.
In fact IIRC they were matched sets! The first time I read a message stating
that the flyweights were different in the transmission I said "BS" to
myself. Fortunately I did some research before I opened my mouth and sure
enough they were!
Regards,
Rob M.
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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