| Transmission Question: [message #234979] |
Fri, 03 January 2014 19:58  |
noi
Messages: 293
Registered: October 2010
Location: South of Fremont
Karma: 0
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Senior Member |
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Greetings:
Looking for a bit of “schooling” here!
Have read all the discussions about disk brakes/transmission braking and, for the most part, I can understand the points being made - But…. One thing I am not clear on is the following:
“Manny finally said the cut of the gears is the ultimate culprit”
I am curious…. What “gears” are being referenced and what difference does it make on how the gears are cut?
The only experience I have with “gears” is on lathes and manual transmissions – Neither of which seem to care which direction the “power” is being applied from - Not arguing or disagreeing, just looking for some insight.
Thanks for what thoughts you care to share,
Carl P.
76 Birchaven
South of Fremont
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| Re: [GMCnet] Transmission Question: [message #234985 is a reply to message #234979] |
Fri, 03 January 2014 20:26  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Carl,
Most transmission gears are "helical cut", meaning there's a sliding action
as the teeth engage and disengage. Because of the sliding action, there is
a thrust along the axle, the direction dependent upon the direction of
rotation. That's as opposed to "spur" or straight cut gears commonly used
on lathes. Since their engagement and disengagement is purely radial,
there is no axial thrust.l
Even though the TH-425's gears are planetary, they're still helical cut,
yielding axial thrust. What I haven't yet figured out is how that affects
the clutches.
This will give a much better explanation than mine:
http://en.wikipedia.org/wiki/Gear
Ken H.
On Fri, Jan 3, 2014 at 8:58 PM, noi wrote:
>
>
> Greetings:
>
> Looking for a bit of “schooling” here!
>
> Have read all the discussions about disk brakes/transmission braking and,
> for the most part, I can understand the points being made - But…. One thing
> I am not clear on is the following:
>
> “Manny finally said the cut of the gears is the ultimate culprit”
>
> I am curious…. What “gears” are being referenced and what difference does
> it make on how the gears are cut?
>
> The only experience I have with “gears” is on lathes and manual
> transmissions – Neither of which seem to care which direction the “power”
> is being applied from - Not arguing or disagreeing, just looking for some
> insight.
>
> Thanks for what thoughts you care to share,
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Transmission Question: [message #234996 is a reply to message #234985] |
Fri, 03 January 2014 21:40 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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"Even though the TH-425's gears are planetary, they're still helical cut,yielding axial thrust. What I haven't yet figured out is how that affects the clutches."
That's easy: If the gears are cut and mated so the axial thrust presses the clutch together when torque is applied from one side(the input), then applying torque from the opposite side(the output)in the same rotational direction will result in axial thrust of the opposite direction. If the thrust is not held in check by thrust bearings with no play whatsoever, it will act to pull the clutch apart, which will increase the chance for slippage.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] Transmission Question: [message #235003 is a reply to message #234985] |
Fri, 03 January 2014 22:32 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""Carl,
Most transmission gears are "helical cut", meaning there's a sliding action
as the teeth engage and disengage. Because of the sliding action, there is
a thrust along the axle, the direction dependent upon the direction of
rotation. That's as opposed to "spur" or straight cut gears commonly used
on lathes. Since their engagement and disengagement is purely radial,
there is no axial thrust.l
Even though the TH-425's gears are planetary, they're still helical cut,
yielding axial thrust. What I haven't yet figured out is how that affects
the clutches.""
Absolutely none! There is no sliding of gears in a planetary transmission and there is no axial force exerted on any of the clutches.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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