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Old 03-14-2009, 06:36 PM   #31
mark1305 OP
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OK, drank some beer, took my nap, uploaded a few pics...


Set the shafts in place. I used a baby nose syringe loaded with water to check for when the housing reached 100C from the heat gun. A couple of drops every so often as it got close and when they sizzled - voila! I also had the two shafts in the freezer to shrink the bearings. It all slid together quicker than in the video on Joerg's webpage about assembling the parts.

However, putting the gear shafts in the fridge makes them get really wet with frost/condensation. I spent a good while warming them back up with the heat gun to make them dry off. Lesson learned: Best bet is to just chill the bearings by placing them on a Ziplock full of crushed ice rather than chilling the whole shaft(s)




Here's a trick to help you... When diddling the shifter into place and engaging the forks with their respective grooves, stuff a clean rag in to keep everything engaged until you get the bolts in.


Even though it's easy to get everything to mesh with the shifter in neutral, as I pushed and shoved to line up the bolt holes the shifter kicked itself into second gear which made it much easier to line up the bolt holes. That may or may not be just an oddity of how the gears were aligned at that moment.


Now we're talking...



Almost forgot - the detent roller swap....



Sorry for the blurry photo. Marking the bearing height to see how much material to mill out of the bridge-style depth gauge stop I have alluded to in previous posts. More detailed photos to come after I finish the clamping part and actually test it out.



Stay tuned.
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Old 03-14-2009, 08:16 PM   #32
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Old 03-14-2009, 08:38 PM   #33
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Wowzer, this is great. Can you expound a bit on the "detent roller swap"?

T.
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Old 03-14-2009, 09:09 PM   #34
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Quote:
Originally Posted by Infracaninophile
Wowzer, this is great. Can you expound a bit on the "detent roller swap"?

T.
Yep. Tomorrow. I'm getting ready to pass out right now.

And Hey Kevin! I see you're back home and watching this thread. Great to see ya and ride with you again at the Scrub.
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Old 03-15-2009, 07:45 AM   #35
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Is there a specific reason you're not using Mold-a-Gauge to to measure the endplay of the shafts??
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Old 03-15-2009, 08:06 AM   #36
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Good question. I'm not using Plasti Gauge or similar products because of the effort required to get the rear cover back off of the bearings.

I'm guessing that's the reason that normal practice is to use some type of measuring plate and do a little math.
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Old 03-15-2009, 08:15 AM   #37
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Quote:
Originally Posted by Infracaninophile
Wowzer, this is great. Can you expound a bit on the "detent roller swap"?

T.
The roller swap....

The transmission originally in the bike when I bought it had the solid aluminum roller in the shifter mechanism. At some point in time that gearbox had been opened and serviced. So I don't know if the aluminum roller was factory installed or an upgrade performed later.

The '84 transmission I bought on Ebay and overhauled had the plain nylon roller. After working them both by hand while both transmissions were apart, I planned to leave the nylon roller in place as it felt like it was ever so slightly smoother.

Then when I started reassembling everything I took one more close look at the rollers and noticed some wear on the nylon roller. The aluminum roller had no wear marks at all. So I swapped it onto the shifter mechanism.
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Old 03-17-2009, 05:36 PM   #38
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After finding a couple of places of unequal thickness on the Lexan shim plate despite the sides both measure nearly flat, I tried to mill the offending high spots with limited success. I got it closer to parallel sides, but still not perfect and I discovered while tramming the cross slide with the milling vise mounted that i had .001" runout from front to back, but .000" along the ways. So I adjusted my cutting pattern to capitalize on the zero runout axis, but still had problems as the milling setup doesn't have to travel to cut the required area in a single pass.

So I focused on finishing the huge bridge-style depth gauge stop.


It was a cut and try design, but with a lot of thought and trial fits before marking and cutting the relief/rise part.

It does not flex or deflect with normal handling and I'm satisfied that the measurements are accurate AND repeatable.

First off measuring the bearing heights above the flange. Because the bridge was designed (intended) to have a 20.00mm height above the working surface, the math should have been easier. In practice I could only index it securely at 19.93mm. Still easy math.




Then take direct measurements of the bearing pockets in the rear cover.
This is actually a staged photo after I had calculated and put two shim stack into the housing with tape to avoid accidentally spilling tthem back out. I have to run over to the dealer tomorrow to pick up the one odd size shim I need (0.200mm)




The math is simplified with this bridge - measure the bearings above the housing fange and subtract from the baseline setting (in this case 19.93mm). Measure the depth of bearing pockets in the cover and subtract the baseline 19.93mm from those numbers. Calculate for gasket thickness and desired clearance of .05mm and you easily determine the shim stack needed.

So far so good.
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Old 03-17-2009, 06:05 PM   #39
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Quote:
Originally Posted by mark1305
Good question. I'm not using Plasti Gauge or similar products because of the effort required to get the rear cover back off of the bearings.

I'm guessing that's the reason that normal practice is to use some type of measuring plate and do a little math.
Actually, I think the reason for using a measuring plate is the time involved, not necessarily the effort.

The reason I ask is, whilst your measurements and setup--which is VERY NICE--will work for your rear cover, what about a rear cover from a different tranny??

Given the extremely tight tolerances spec'd for the shafts, I am thinking that there might be significantly more variance 'tiwxt covers and measuring devices, which might be why a lot of the learned will tell you that BMW never sent out a properly shimmed tranny from the factory. Factor in some measurement uncertaintity, and you will go well beyond the allowable tolerance.

My thinking is that by using the Mold-a-Gauge you tailor the shims to each sceanrio--including any gasket squish--independent of any extraneous variables, which, while more time consuming, might just be closer to spec in the end.

Thoughts??

kix
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Old 03-17-2009, 06:09 PM   #40
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Quote:
Originally Posted by mark1305
After finding a couple of places of unequal thickness on the Lexan shim plate despite the sides both measure nearly flat, I tried to mill the offending high spots with limited success. I got it closer to parallel sides, but still not perfect and I discovered while tramming the cross slide with the milling vise mounted that i had .001" runout from front to back, but .000" along the ways. So I adjusted my cutting pattern to capitalize on the zero runout axis, but still had problems as the milling setup doesn't have to travel to cut the required area in a single pass.

So I focused on finishing the huge bridge-style depth gauge stop.


It was a cut and try design, but with a lot of thought and trial fits before marking and cutting the relief/rise part.

It does not flex or deflect with normal handling and I'm satisfied that the measurements are accurate AND repeatable.

First off measuring the bearing heights above the flange. Because the bridge was designed (intended) to have a 20.00mm height above the working surface, the math should have been easier. In practice I could only index it securely at 19.93mm. Still easy math.




Then take direct measurements of the bearing pockets in the rear cover.
This is actually a staged photo after I had calculated and put two shim stack into the housing with tape to avoid accidentally spilling tthem back out. I have to run over to the dealer tomorrow to pick up the one odd size shim I need (0.200mm)




The math is simplified with this bridge - measure the bearings above the housing fange and subtract from the baseline setting (in this case 19.93mm). Measure the depth of bearing pockets in the cover and subtract the baseline 19.93mm from those numbers. Calculate for gasket thickness and desired clearance of .05mm and you easily determine the shim stack needed.

So far so good.
I just wanted to explicitly say that you have really done an excellent job w/ your setup.
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Old 03-17-2009, 06:31 PM   #41
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Quote:
Originally Posted by kixtand
Actually, I think the reason for using a measuring plate is the time involved, not necessarily the effort.

The reason I ask is, whilst your measurements and setup--which is VERY NICE--will work for your rear cover, what about a rear cover from a different tranny??

Given the extremely tight tolerances spec'd for the shafts, I am thinking that there might be significantly more variance 'tiwxt covers and measuring devices, which might be why a lot of the learned will tell you that BMW never sent out a properly shimmed tranny from the factory. Factor in some measurement uncertaintity, and you will go well beyond the allowable tolerance.

My thinking is that by using the Mold-a-Gauge you tailor the shims to each sceanrio--including any gasket squish--independent of any extraneous variables, which, while more time consuming, might just be closer to spec in the end.

Thoughts??

kix
Kix

FWIW, I use one of these:



It's made by Teclock (Japan) and is much easier to use than a thimble depth micrometer. It's arguably more accurate than a digital vernier caliper IMHO.

I use a precision ground length of 3/4" keysteel as a bridge, and find that it works well.

I have a measuring plate, but it's shonky and I won't use it. I also have an end cover with several milimeters milled off and the bearing recesses relieved so that I can benchtest the assembled 'box before fitting the end-cover. I can see though the holes created by the milling to check the operation of the 'box.

The 'box in my R90S is a complete hybrid, with a smoothcase '76 housing, '87 internals, and a post '82 end cover. (I also fitted a kickstart mechanism, although I've never used it and have since removed the kickstart lever.) I had no trouble shimming the 'box. I don't use a gasket.

YMMV etc
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Old 03-17-2009, 06:51 PM   #42
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Quote:
Originally Posted by kixtand
I just wanted to explicitly say that you have really done an excellent job w/ your setup.
Very nice job Mark, Thanks for taking the time to lay it out and show us.



Mike
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Old 03-17-2009, 07:00 PM   #43
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Several very good discussion points in thes last few posts. And I've thought about several of them, believe me.

Kixtand, the idea of time versus effort for a plasti-gauge type product does agree very well with a production environment. The home hobbyist has more time to get a more accurate measurement at the expense of spending more time doing it.

Also with regard to a different rear cover, the measuring bridge should work just as well on any cover.... PROVIDED.... it isn't warped. That thought bugged me a little. Those covers are thin enough to carry a little warpage from either original machining or from forces endured in service. I ran an accurate straightedge all around mine, but that is only a modest substitute for a good machinist's flat - which is getting higher on my list of tooling to acquire. I agree that variations in cover machining accuracy may well account for some of the discovered errors in factory shimming.

Max, I've wrestled with the idea many times about milling down my "extra" rear cover from the first gearbox. Only two things have held me back: My mill doesn't have the table travel to do it all in one setup; and I want to keep a whole good case for future needs if they should arise.

Thanks for all the inputs and support. Keeping these 5-speeds alive and well remains an art and there are still new tidbits to discover and share. Once again I have to credit Joerg's excellent Motorcycle Page and the gearbox rebuild section for giving me the info to dive into this project. Anything I can add or anyone else can add by generating discussion just builds the collective wisdom.

Tomorrow I ride over to my local dealer and get the one 0.200mm shim I need and finish the assembly. Hopefully everything will turn smoothly and be ready to go into service on the bike.


Oh yeah, a late thought.... I don't think I mentioned it before, but put that little bastard of a seal in the rear end of the input shaft while you still have it out of the gear box. I tried putting it in the freezer to shrink it - don't waste your time. It has so little mass it will warm up by the time you have the freezer door closed. My recommended method for driving it is use a small (13 oz) hammer as the driver and strike that with another relatively small machinists hammer and drive it as straight as possible. I did warm just the end of the shaft with the heat gun, which may have helped, but was hard to tell for sure.
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Old 03-17-2009, 07:12 PM   #44
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Quote:
Originally Posted by Max Headroom
Kix

FWIW, I use one of these:



It's made by Teclock (Japan) and is much easier to use than a thimble depth micrometer. It's arguably more accurate than a digital vernier caliper IMHO.

I use a precision ground length of 3/4" keysteel as a bridge, and find that it works well.
...snip....
I had to reread that for it to soak in. Good idea. I need to check and see if my set of parallels are long enough and have a pair tall enough to serve as a bridge. I can see the need for a more accurate depth guage like that in the future. You can never have too much precision measuring tools or machine tooling.
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Old 03-17-2009, 09:03 PM   #45
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Mark:

Great thread. I learned a lot. Having the ability to machine stuff is very cool and many people are envious. Thanks.

Is there any way to determine if a trannie has had the circlip installed? Would it hurt anything if I just opened mine up to take a peek and then put the cover back on? I.e: No circlip found means send it off for upgrade. Circlip found means sleeping better. But in either case don't do anything other than open it up, look, and close it back up. Would I still need to do anything more than just replace the gasket?

Hmmm..

Tom
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