Ruckstell ring/pinion clearance.

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noelchico
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Ruckstell ring/pinion clearance.

Post by noelchico » Fri Aug 19, 2022 3:47 pm

I admit I'm a shade tree mechanic (with no air conditioning in my garage). I'm replacing the standard ring gear with no relief on the back with a 39 tooth gear with a relief and a 12 tooth pinion to get a 3.25:1 gear ratio. The previous owner had neglected to replace the right side inner Hiatt bearing resulting in a warped P139 bronze plate and broken shifter housing. I acquired an older Hall-Scott P139 with 10 oil passages that, with a new thrust bearing, shows acceptable 0.002 inch runout. However, on trial fit, I have 0.073 inch movement measured with a dial indicator on a ring gear tooth with the pinion stationary. I don't want to shim that much under the ring gear but figure I would need a .060 -.065 washer under the P147 notch plate to get my .008-12 clearance. I'm open to suggestions.
Noel


speedytinc
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Re: Ruckstell ring/pinion clearance.

Post by speedytinc » Fri Aug 19, 2022 4:17 pm

When I did mine, I machined a ring gear shim from T6 aluminum. No problems so far, but I am concerned for a shift & shear of the bolts.

If you shim the lock plate that much, check the lock collar position in both positions. You may have to bend the shifter fork a similar amount to maintain proper lock ups.


Jerry VanOoteghem
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Re: Ruckstell ring/pinion clearance.

Post by Jerry VanOoteghem » Fri Aug 19, 2022 4:38 pm

I would shim the ring gear. Modifying the location of any of the Ruckstell components may have unintended consequences, as John mentions above. Also, pay no attention to what your actual clearance/backlash is. Adjust the ring & pinion for proper mesh and gear tooth contact and your backlash will take care if itself. I never even measure what my backlash ends up being. It's only important how the gear teeth roll with one another and that they have proper contact. Yes, the books say different... :roll:


Topic author
noelchico
Posts: 191
Joined: Tue Jan 08, 2019 10:42 pm
First Name: Noel
Last Name: Chicoine
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MTFCA Number: 25420
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Re: Ruckstell ring/pinion clearance.

Post by noelchico » Fri Aug 19, 2022 6:13 pm

I very much appreciate the above comments. The ring gear and pinion align well, and the system turns easily. I just trial fitted both a .015 and a .010 shim (0.025 total) and now have .048 so it appears the lateral movement relates directly to the shim thickness. I am hesitant to stack four 0.015 shims and increase the risk of shearing the 10 ring gear bolts. Or do I ignore that much clearance since the gears line up well?
Noel


speedytinc
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Re: Ruckstell ring/pinion clearance.

Post by speedytinc » Fri Aug 19, 2022 6:31 pm

A stack of ring gear shims makes me nervous, any shim there does. .048 is way too far apart for my taste.
I want the gears to line up/mesh AND have a tight enough clearance to evenly fold a strip of paper.

This is the conundrum of using a 12 tooth pinion.

I have thought about narrowing the ledge on the rux bell & using a stock ford 40 tooth ring gear. I have not done all the home work, but there appears to be enough material on the bell to safely remove & keep a ring gear press fit.

Anybody try this? What do you think?


Jerry VanOoteghem
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Re: Ruckstell ring/pinion clearance.

Post by Jerry VanOoteghem » Fri Aug 19, 2022 8:32 pm

Noel,

I wouldn't use a stack of shims. I'd figure out how much shim thickness is needed, then make one thick shim. You're correct in that .048 is still too much backlash. I say it doesn't matter what the backlash is, but as in all things, there are limits. I have never tried to align this "special" set of gears, but it's hard for me to imagine a good contact pattern is occurring with .048 lash.


Allan
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Re: Ruckstell ring/pinion clearance.

Post by Allan » Fri Aug 19, 2022 8:55 pm

I'd come at it another way. You can add a shim in the housing behind bearing to the same amount. A shim in this location is a safer application of shims, it involves modification of nothing, and leaves you free to play with the correct rolling fit of the gear teeth. That fit is not necessarily a given backlash figure. The correct rolling fit will determine what the backlash will be.

Allan from down under.


Allan
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Re: Ruckstell ring/pinion clearance.

Post by Allan » Fri Aug 19, 2022 9:24 pm

Just a clarification. I mentioned placing a shim behind the bearing. The shim goes behind the thrust plate washer. It has the effect of shifting the whole diff centre to the right, but the amount of shift is inconsequential except to alter the gear mesh.

Allan from down under.


Topic author
noelchico
Posts: 191
Joined: Tue Jan 08, 2019 10:42 pm
First Name: Noel
Last Name: Chicoine
* REQUIRED* Type and Year of Model Ts owned: 1920 roadster, 1923 Touring, 1926 Coupe
Location: Pierre, South Dakota
MTFCA Number: 25420
MTFCI Number: 22686
Board Member Since: 2005

Re: Ruckstell ring/pinion clearance.

Post by noelchico » Sat Aug 20, 2022 4:05 pm

The only place I believe I could place a .065 shim is to make one to fit between the notch plate and inner differential housing, but then my shifter fork MAY not move the sliding clutch gear enough for a positive shift. Other spots appear to affect the sliding gear mesh with the notch plate and thrust plate. I've got to think on this some more. :)

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