Author Topic: Rear Sprocket for a Dragonfly repair.  (Read 372 times)

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Offline Sgtbiro

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Rear Sprocket for a Dragonfly repair.
« on: 15 Jun 2020 at 18:31 »
Hi all hope someone can help i have been trying to find a local company to ether repair or replace the rear sprocket on my Dragonfly but without any luck they all seem to be unable or unwilling to do the job.
I have noticed from previous conversations on here that some members of the forum have had this done so i was wondering if anyone could recommend someone to do this work for me, any help would be greatly appreciated.

Regards Kevin..   
 

Offline Sgtbiro

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Re: Rear Sprocket for a Dragonfly repair.
« Reply #1 on: 19 Jun 2020 at 17:34 »
PS.
Could anyone please tell me the pitch of the teeth on the rear sprocket.
Cheers Kevin..

Offline eddie

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Re: Rear Sprocket for a Dragonfly repair.
« Reply #2 on: 19 Jun 2020 at 18:26 »
Kevin,
         The rear sprocket is 51 tooth for a 5/8" x 1/4" chain.

   Do you know which wheels you have in your 'Fly?  Are they Douglas (with the sprocket welded on to the brake drum) or British Hub (separate bolt on sprocket)?

   Eddie.

Offline Sgtbiro

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Re: Rear Sprocket for a Dragonfly repair.
« Reply #3 on: 19 Jun 2020 at 18:30 »
Hi Eddie thank you for the reply, my fly has the Douglas welded to the drum type sprocket.

Cheers Kevin..

Offline eddie

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Re: Rear Sprocket for a Dragonfly repair.
« Reply #4 on: 19 Jun 2020 at 20:12 »
Kevin,
          Your local bearing stockist should be able to supply a new mild steel sprocket - they know them as 'plate wheels'. Then you need to find a local 'friendly' engineering firm to machine back the old sprocket to leave the 'legs' attached to the brakedrum. Then get them to machine the centre out of the plate wheel to fit over the legs and weld it into place. Leaving the legs attached to the drum reduces the chance of the welding distorting the drum.

    Regards,
                  Eddie.

Offline Sgtbiro

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Re: Rear Sprocket for a Dragonfly repair.
« Reply #5 on: 20 Jun 2020 at 15:41 »
Hi Eddie i have just spoken to a guy from a local plate wheel manufacture who says that a 51 tooth wheel is non standard and would cost a small fortune to manufacture but has 50t and 52t x 5/8" plates as standard, so would i be able to fit one of these if so how much difference would it make if i did.

Regards Kevin.. 

Offline eddie

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Re: Rear Sprocket for a Dragonfly repair.
« Reply #6 on: 20 Jun 2020 at 17:26 »
Hi Kevin,
               Go for the 52 tooth - it will drop the gearing slightly, but it won't be noticeable. For years I have been running my Dragonfly with a 16 tooth on the gearbox instead of a 17 - that's equivalent to 3 more teeth on the rear wheel - it gives the engine an easier time without any loss of top speed. (Most British bikes were overgeared as supplied by the factories!).

  Regards,
                Eddie.

Offline Sgtbiro

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Re: Rear Sprocket for a Dragonfly repair.
« Reply #7 on: 22 Jun 2020 at 21:32 »
Hi Eddie thank you for the info I have managed to find someone who will supply me with a 51t 5/8 pitch wheel but just a bit on the thick side but I can get this ground down to 1/4 and then welded back onto the drum once again many thanks for all your help.
Regards Kevin...

 

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