Author Topic: Rear suspension wear on Mark Series  (Read 2345 times)

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Offline jeffen

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Rear suspension wear on Mark Series
« on: 24 Aug 2011 at 14:54 »
Is there a known repair procedure for that part of the frame that is worn by lack of lub. in the bushes (27374) of the torsion bar operating lever (29546/7)? In my case it looks a though water has got in and badly corroded the bearing area of the frame.

Offline eddie

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Re: Rear suspension wear on Mark Series
« Reply #1 on: 24 Aug 2011 at 16:14 »
Jeffen,
            The tube that bush 27374 turns on is not, as some people think, the tail end of the bottom frame tube, but is a case hardened tube that is pressed in. Therefore, they can be replaced should the need arise. Having said that, they can be very stubborn - having been in place for over fifty years! Some frames have bronze rear lugs - heating these makes removal of the tubes somewhat easier. Unfortunately, these tubes were never offered as a separate part, so new manufacture will be the only option unless you can salvage some from an otherwise scrap frame.
               
                Regards,
                               Eddie.

Offline jeffen

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Re: Rear suspension wear on Mark Series
« Reply #2 on: 25 Aug 2011 at 08:39 »
Thanks Eddie,

Do you think that they could be knocked out from the front end of the frame, given a lot of heat and a big hammer?  As an

alternative I did think of shrinking a thin wall sleeves over the corroded shafts and boring the bushes to suit.

Jeff

Offline eddie

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Re: Rear suspension wear on Mark Series
« Reply #3 on: 25 Aug 2011 at 09:08 »
Jeff,   
       When Mr Douglas produced the first postwar models they suffered from breakages of the bottom frame tube, so later frames had thicker tubes (about 1/8" wall), making it almost impossible get anything against the ends of the pivot sleeves to drive them out.
       You could try making up a special puller to remove the sleeves. Start off with a couple of blocks of steel about 2" x 3"x 5/8" with 1" holes bored in the centre. Then, in one block, drill and tap 2 holes in the sides for pinch bolts, then drill and tap another 2 holes in the face, either side of the 1" bore (for the jacking bolts). With an angle grinder, grind 2 flats on the sleeve (as seats for the pinch bolts). Slide the plain block over the sleeve until it rests against the back of the frame lug, then clamp the second block to the sleeve using the pinch bolts. Using the 2 jacking bolts, you should then be able to draw the sleeve out of the lug. If your luck is in, you may be able to clean up the sleeves and then replace them back to front so that you have new bearing surfaces. If doing this, I would reccommend that everything is cleaned before reassembly and that the sleeves are retained with a good grade of Loctite. The 2 flats that you ground on the sleeves should not present any problems as they will then be hidden well inside the frame lug.
         Good luck with the repairs,
                Regards,
                              Eddie.

Offline jeffen

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Re: Rear suspension wear on Mark Series
« Reply #4 on: 25 Aug 2011 at 17:01 »
Thanks again Eddie, I was thinging along the same lines.
In time I'll let you know the outcome.

Jeff

 

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