Author Topic: mk v. Frame.  (Read 1091 times)

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Offline phil1

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mk v. Frame.
« on: 27 Apr 2019 at 12:36 »
Hi friends I have a query regarding my lower near side frame tube, it has some extra strengthening gusset around the foot rest boss adjoining the tube, which is quite different to the other side, the down side of this to me is the exhaust hanger cannot slide back as far as would like, perhaps there is a simple answer? Many thanks Phil.

Offline Jonathan Hewitt

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Re: mk v. Frame.
« Reply #1 on: 27 Apr 2019 at 16:49 »
Hi have you a picture to post ?
jonathan

Offline Neville Heath

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Re: mk v. Frame.
« Reply #2 on: 27 Apr 2019 at 19:36 »
Frames are known to have broken at this point. Sounds as if yours has and has been sleeved over.
Neville

Offline phil1

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Re: mk v. Frame.
« Reply #3 on: 28 Apr 2019 at 09:18 »
Hi friends thanks for your help, as you say Neville it may have had some repair in the past. I am enclosing pictures for reference. Phil.

Offline eddie

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Re: mk v. Frame.
« Reply #4 on: 28 Apr 2019 at 18:21 »
A suggestion!! Make an exhaust pipe 'P' clip with the leg long enough to go on the gearbox/footrest bolt - then shorten the gearbox spacer by the thickness of the 'P' clip so that the new clip can be fitted out of sight behind the frame tube.

  Regards,
                 Eddie.

Offline phil1

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Re: mk v. Frame.
« Reply #5 on: 29 Apr 2019 at 15:39 »
Hi Eddie, Thanks for your good suggestion. I am a great fan of P clips, however as you can see from the picture I would like to try cutting back the gusset so I can at least slide the exhaust hanger to the other side of the centre stand peg. Hoping there is enough weld in the repaired area of the boss. I would welcome any further thoughts. Many thanks Phil.

Offline eddie

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Re: mk v. Frame.
« Reply #6 on: 29 Apr 2019 at 16:42 »
Phil,
        The big problem with Mark frames is that when they fracture it is immediately adjacent to the lug. To effect a strong repair to the tube, the lug has to be cut back and the tube ends cleaned up so that they are completely devoid of any of the original braze before any attempt is made to weld the frame tube - any contamination from the brass will render the weld fillet extremely brittle!. In the past, I have cut the lug back by about 5/16" by carefully hacksawing down to the braze between the lug and the tube (without marking the actual tube), then file a flat on the separated end of the lug, then with a sharp cold chisel, peel off the separated end of the lug.  The final bit of preparation is to file off any remaining braze and chamfer the broken ends of tube. A piece of angle iron used as a crude v block can be clamped to the side of the tubes to keep them in line whilst tacking the tubes together again. When the tube is fully welded, it can be cleaned up and the end of the lug built up with silicon bronze rod to restore it's original shape.
   When the repair is complete, check out the swinging arm pivot pins - the original Douglas pins were drilled right through, so greasing the pin usually forced the grease past the blanking plates in the swinging arm, with very little getting into the bearing - hence causing even more stress on a frame lug that is already subjected to more than it's fair share of complicated stresses. The repro pins that Club spares had made were modified to be blank ended, to make sure the grease went where intended! If you have the original pins, it would pay to knock the blanking discs out of the swinging arm pivots, so that plugs can be pressed into the bore of the pins - then the blanking discs can be replaced - even if a slacker fit (they will now only have to keep the dirt out rather than resist the hydraulic force of the grease gun!)

Regards,
              Eddie.

Offline phil1

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Re: mk v. Frame.
« Reply #7 on: 30 Apr 2019 at 18:01 »
Hi Eddie, many thanks for the technical advice. I believe my problem was as you say to do with the poor maintenance of those many joints and bushes which were in really bad shape. However the bronze welded repair looks very well done so my plan is to reduce the length of that long gusset to within 1/2" of the foot rest boss therefore allowing me to shift that exhaust hanger much nearer to where it should be, hopefully all will be well. Regards Phil. 

Offline Neville Heath

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Re: mk v. Frame.
« Reply #8 on: 01 May 2019 at 20:13 »
Phil
It's up to you but my advice is to leave that gusset as it is. I like Eddies idea of a P clip best.
Neville

Offline phil1

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Re: mk v. Frame.
« Reply #9 on: 05 May 2019 at 09:38 »
Hi Neville thanks for all your input, I must say there's been a lot to learn re the Douglas and I dare say I've not finished yet, I'm on about nine hundred miles now with my new pistons and cylinders and await to see what she might do with her  best foot forward. Regards. Phil.

Offline ccmman

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Re: mk v. Frame.
« Reply #10 on: 15 May 2019 at 08:49 »
Hi Phil, it is an interesting design issue. I was thinking about the rather scary possibility of a frame tube cracking at a critical point, and, lets face it with my luck, when I'm pinning it with chin on tank!

Headstock lugs etc usually have good long sleeves, with heavily v'eed out slots in the sides, which reduces the stress raiser at the joint. Having a plain butt end on the lug is not good engineering practice, and a definite black mark on the designers paper. Cant imagine it saves much in the manufacturing process either?

 

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