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3T Crankshaft rebuild

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  • 3T Crankshaft rebuild

    I have just rebuilt the crankshaft for a Greeves Essex and thought that I would share the experience with you.

    When I purchased a 32DD Essex some 3 years ago I thought about restoring it, but ended up just replacing tyres, brakes and cables with a view to sorting out the bugs then pulling it apart reconditioning the motor and then painting it, well that didn’t happen, I just kept riding.
    In the end the rattles from down below just got louder and the bike got slower, time for action.
    I was determined to collect all the bits before I dismantled the motor, some +0.010” pistons from JP, didn’t really like those (very heavy) so I sourced some +0.015”’ Villiers pistons from VS along with some seals.
    VS would only supply reconditioned rods and not just crankpins, so I made a batch of crankpins and centre shafts from EN36A (case hardening nickel chrome steel) and dispatched them to be heat treated and the ground to 0.001” oversize.
    While I was waiting my thoughts turned to improving my horrible Chinese 20 ton press, I dismantled the bottle jack, remachined the base and ram, then converted it to work upside down, much better!
    I down loaded an Alpha bearing PDF file about crankshaft reconditioning and machined up all the press plates and a large tube to accommodate the crankshaft.
    Rebored the cylinders on the lathe, they didn’t clean up at +10 so I ended up using the genuine Villiers pistons, a friend returned a favour and honed them to size.
    When I had all the parts ready I dismantled the motor and the first job was to check the crank between centres for run out, turned out it had 0.004” thou woof in the right hand shaft, this was quickly corrected with a large dead blow hammer. (to be continued).
    Pete from the Antipodes
    Attached Files

  • #2
    3T Crankshaft rebuild cont

    Alpha recommended marking the crank to aid realignment on reassembly, this was done in the lathe, I also made a realignment tool to fit around the centre plate.
    Dis-assembly was straight forward with the outer crank halves being removed, followed by inner wheels, then the centre shaft and then the crank pins.
    The outer bearings were then removed from their shafts, an inspection revealed all was well except from some minor fretting in the right hand outer shaft crank pin hole, possibly due to the misalignment. (to be continued).
    Pete from the Antipodes
    Attached Files

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    • #3
      3T Crankshaft re-build cont

      Both rods were lapped out to take standard ¼ x5/16 rollers, the little ends re-bushed and reamed to size, the centre shaft was fitted with a labyrinth seal, I measured it and the interference fit in the wheels was 0.0023” which was fine so I refitted it. (to be continued).
      Pete from the Antipodes
      Attached Files

      Comment


      • #4
        3T Crankshaft re-build cont.

        With the con-rods finished it was time for pressing everything back together, first the crank-pins were fitted to the outer shafts the rod, cage and rollers fitted and then partially assembled with the inner wheels in a small arbour press, before shim steel was inserted between the rod and webs before final assembly in the big press, this regulate the big end side clearance.
        Both crank halves were roughly trued in the 3 jaw chuck in the lathe to +/- 0.003” Total Indicator Reading (TIR), the bearing was then fitted to the inner plate, the inner shaft and labyrinth seal fitted and then pressed into one crank half. (to be continued).
        Pete from the Antipodes
        Attached Files

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        • #5
          3T Crankshaft re-build cont.

          The centre shaft with plate bearing and seal was then pressed into the right side assembly, then the left hand side was offered up and correctly positioned using the aligning tool, and before final assembly, 3 spacers were placed between the crank webs to allow the whole assembly to be pressed home without upseting the outer crank, with this completed it was now time to get things trued up. (to be continued).
          Pete from the Antipodes
          Attached Files

          Comment


          • #6
            3T Crankshaft re-build the end

            I did try to true it up between centres but soon realized that there were too many things happening at once so I made a set of v blocks and an angle plate to support the centre plate.
            I needed some bearings to temporarily fit to the shafts to true it up, but both are normally an interference fit, so I attacked the bores of some old smooth running ones with a flap wheel until they were a neat sliding fit.
            This enabled me to treat the entire assembly as two single cylinder cranks, and in no time at all I had the whole assembly running true, one side 0.0005 TIR and the other 0.001 TIR past experience told me to leave it at that.
            The motor went back together easily, the crank assembly ran super smoothly in the cases, so it looks like I will be riding fairly gently for the next 6 or700 miles, I do hope you enjoyed my journey.
            Pete from the Antipodes
            Attached Files

            Comment


            • #7
              Very interesting Pete, not many people attempt to rebuild these cranks, Mike Palmer here in UK used to do them some years ago.
              Interesting that you fitted a labyrinth seal, the 4T crank had this type, effectively a piston type ring running in a groove. Did you use one of these or made one yourself. Have you any pics of that?

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              • #8
                Labyrinth seal

                Hi John, Sorry no photo's, sometimes you build up a bit of momentum and forget to get the camera out.
                The labyrinth seals would be very easy to make, Brian Wooley in some of his Silverstone tuning articles describes how to make them using Honda 50 piston rings.
                The motor looks to be very original and came fitted with a labyrinth seal the date on the flywheel is 10/63 and the bike is a 32DD.
                Another interesting thing is the way that the cylinders wear because there are virtually no fins between the cylinders, when I was boring it, I stopped several times to check that the cylinder was still running true.
                Surprisingly the whole crank refurbish was very cheap, the most expensive items were FAG brass caged roller bearings.
                Cheers Pete from the Antipodes

                Comment


                • #9
                  Looks like Villiers may have fitted a labyrinth seal to the later 325's. I was only aware they were fitted to the 4T which came out in 1964. When I had a 4T crank done by Mike Palmer he modifed it with two back to back rubber seals. He said he could not see a way of re fitting the labyrinth seal as he had to break the original to get it apart. Odd as Villiers obviously assembled it ok.

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                  • #10
                    3T crank

                    Err, I don't think I will try this at home folks! Blimey Hawkie well done that took a lot of figuring out and very interesting post.
                    Last edited by John Pattinson; 11/04/2017, 01:18 PM. Reason: grammar correction

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                    • #11
                      Object lesson in making a simple engine complex!

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                      • #12
                        With regards to labyrinth seals, Steve Gollings tells me they have both these available (presumably NOS Villiers original spares) but they usually fit the standard 2T type double lipped rubber seal with corresponding crank pin as these aid easier starting. As there is always some slight leakage on the metal labyrinth seal this can cause poor starting unless the engine is fitted with a siba dynastart. Personally I am happy with the labyrinth seal as it is not subject deterioration of rubber seals particularly in the middle of the engine and the extreme heat there. The engine in my bike has done in excess of 60000 still with original seal in place.
                        Attached are pics of 4T centre labyrinth centre seal and bearing
                        Attached Files
                        Last edited by John Wakefield; 27/03/2019, 11:01 AM. Reason: pics added

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