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Intermediate Gear Shaft End Float in Casing

  • 21 Apr 2021 8:38 AM
    Message # 10334990

    Hello all,

    Hope someone can help.

    On my '28 101 I have the clutch casing parts ready to assemble.

    If I fit the intermediate gear shaft into the "Driver Case" S2433 (the end of the shaft with the "woodruff" key), then fit the outer cover S2437, the shaft has quite a lot of end float between the cases.

    Measuring all the parts with a digital caliper I got end float of around 2.65mm (0.104").

    I attach a PDF drawing which I have created showing the section through the cases, with the shaft moved sideways to illustrate the problem, and also a picture of the actual cases, where the gap between the thrust washer and end of the shaft can be seen.

    The thrust washer that is fitted to the inner (driver) case S2433 is missing as I found it to be cracked and needs replacing - however I assume it is similar to the outer thrust washer with a central hole large enough to allow the shaft to pass through. (Outer thrust washer has bore diameter 20.75mm (0.817") while the shaft is diameter 20.6mm (0.811")

    The shaft carries 2 sets of caged rollers, which if left like this will allow the rollers to run off the end of the shaft.

    The selection of thrust washers available are to set the intermediate pinion end float, but I'm wondering about centralising the inner shaft.

    The solution that comes to mind is to machine a disc to be fitted behind the ends of the shaft to centralise it.

    Has anyone else noticed this? Or am I missing something?

    Help appreciated.

    2 files
  • 22 Apr 2021 9:21 PM
    Reply # 10340659 on 10334990

    Mick, you've got me confused, sorry!  The main shaft runs all the way through the case and carries the clutch on one end and the drive sprocket and kicker gear on the other end, and it's supported by ball bearings.  The end float of the main shaft is set with thrust washers inside the gearbox.  The counter shaft is fully contained in the gearbox and doesn't go through the inner primary S2433.  Thrust is taken up on the main shaft inside the gear box and the bearings are ball bearings.  What am I missing?

  • 22 Apr 2021 10:02 PM
    Reply # 10340719 on 10334990

    it is called the idle gear and idle gear shaft. The idle gear connects between the driver gear on the crankshaft, and the gear on the clutch basket.

    You have something wrong there, the sideplay should not be that large. Making thicker thrust washers for that large gap, or shim the shaft in the center bore is not a good idea for several reasons.

    Both thrust washers needs to be properly installed, they are and should be same thickness. If you do have both washers installed and still have that sideplay, then I think the thrust washer have spun and the seats are worn deep, modified or wrong thrust washers installed.

    Or shaft is wrong, worn or modified or perhaps the shaft have been installed without the woodruff key and spun grooves in the thrust washers. I don't have the shafts that I have, at hand, so I can't measure it for you right now today. 

    Last modified: 22 Apr 2021 10:24 PM | Carl-Erik Renquist
  • 23 Apr 2021 3:44 AM
    Reply # 10341708 on 10334990

    Hi all, thanks for your input.

    Yes it is the idler gear shaft between the engine gear and clutch - I just used the Indian parts book descriptions which are sometimes not what we would use in todays language.

    I have checked the shaft and there's no evidence of spinning due to missing key.

    I have measured the shaft central portion upon which the rollers run, this measures 33.16mm (1.306") and also the distance between the bushes in the casings as 35.94mm (1.415"), I attach pictures showing the expanding gauge inside the casings and the resultant measurement - so the actual gap left is actually 2.78mm (0.109") slightly different than my calculated measurement earlier, but still a large difference.

    One thing I did notice was that the woodruff key had rotated in its groove when fitted causing the end of the key to get really badly damaged - see picture of key removed.

    By this I mean that as the shaft is inserted into the keyed bush, the woodruff key has been caught and pushed back (rotated) causing the rear end of the key to rise and catch on the grove in the bush - if you fit things to woodruff keyed shafts you will be familiar with this problem! Sometimes it is necessary to "fit" the key by filing the top of the key to make a proper fit. 

    Do you think it is possible that forcing the shaft into the bush with a mis-aligned key could have pushed the inner casing bush into the casing too far - see attached pictures of damaged key and the relative position of the bush to the recess for the thrust washer (note washer not fitted).

    Should the face of the bush be almost level with the face for the thrust washer on the inner casing?

    Hopefully someone has an engine in pieces (like mine) who can check and advise.

    Regards Mick 

    5 files
  • 23 Apr 2021 1:25 PM
    Reply # 10342983 on 10334990

    Mick, sorry I misunderstood!  Here's a couple of pictures to start, let me know if you'd like more or have me take some measurements!

    2 files
  • 23 Apr 2021 3:56 PM
    Reply # 10343342 on 10334990

    one more picture after assembly, I've got an effective .036" end float.  That may increase or decrease once the cases are bolted up tight with a gasket.

    (I cannot get the shaft out of the keyed bushing, tried a little heat gun action but it won't budge.)

    1 file
  • 25 Apr 2021 5:27 AM
    Reply # 10347638 on 10334990


    Thanks for the input.

    I'm coming to the conclusion that the keyed bush on the inner casing has been pushed in when the shaft plus woodruff key was fitted with misaligned key. If you refer back to my earlier posting with 5 images, one clearly shows the keyed bush way down below the surface for the thrust washer.

    Looking at the damage to the key, some considerable force must have been used to press the shaft into the bush.

    I don't have any idea what the original machining of the bare casting is like in terms of bore depth to take the bush (as bush is still in there), so it is possible that factory assembly was to press the bush in flush to the face of the casting with room spare behind the bush to allow for tolerances - or course this is my conjecture - Feel free to correct me!

    The only problem with verifying where the top of the bush should be - is that without removing the keyed end of the shaft from the casing, it's not easy to check dimensions.

    Now I have 2 options:

    Option 1 is to try to make or  modify a blind bush puller that can grip the tiny amount of gap behind the bush, heat the whole case up in the oven, and try to pull the bush back to the desired position.

    Option 2 is to machine up a disc (thick washer), with a cut-out to clear the woodruff key to take out the end float. The disc would be trapped behind the new thrust washer when everything is assembled. Downside is that woodruff key engagement will be reduced.

    Unfortunately due to the keyway, I cannot use the sized bar/grease and hydraulic force method to push the bush out.

    I'm going to put that part to one side for now and ponder, while I do something else on the list!

    I'm sure someone else must have found this problem??

    Regards Mick

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