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Chain Sprocket Alignment

Submitted by chris_howard on Thu, 07/05/2020
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Submitted by chris_howard on Thu, 07/05/2020

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Hi there having just bolted the engine and gearbox into the frame of my 47 Big 4 I spotted a worrying alignment issue. The problem is the alignment of the rear wheel sprocket and gearbox output sprocket. Taking a piece of wire off of the face of the wheel sprocket and running to the gearbox sprocket shows a misalignment of around 1/2", the wheel sprocket being proud of the gearbox sprocket. The wheel has a new brake drum / sprocket and is fitted with the correct spacer, all new. The gearbox sprocket came with the gearbox and appears to be almost new. Are there any spacers that should go between the gearbox sprocket and bearing as there are none at present. 

Any suggestions as to what may be causing this issue would be gratefully received

 

Chris

Submitted by richard_cornish on Thu, 07/05/2020

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Hi Chris,

   It sounds like you might have the later "lay-down" gearbox sprocket which is fairly flat with a narrow boss, whereas the "upright" gearbox sprocket has a deep dished sprocket with a much wider boss. Are you able to post a photo as this will identify which sprocket you have.

Submitted by philip_ham on Thu, 07/05/2020

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Chris,

When I bought a new gearbox sprocket for my laydown box it was different from the original as it didn't have the wider boss, so was too close to the gearbox shell.  RGM can supply a spacer to correct this alignment.  I was told that this gives a much larger selection of sprockets than can be used to vary the gearing.

Submitted by richard_cornish on Fri, 08/05/2020

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Hi again Chris,

   Definitely a later sprocket, the one you need was used from 1935 to 1949 and fits all upright/dolls head gearboxes from this period. For £24 you would be best to get the right one which is much more dished and the boss is about 3 times wider than yours, then you can sell the later one on. These are available in the NOC shop.

Submitted by philip_ham on Fri, 08/05/2020

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Chris,

The hardened steel spacer sold by RGM is part number 040131E.  See their site for a full description of this part and its uses.

Hi thanks for the info but it looks like a need a different sleeve gear as the new 'correct sprocket' covers all of the threads. A previous middle eastern owner had welded a sprocket to the sleeve gear and now it looks like somewhere in this poor beast history somebody has used whatever they could get to mend something and then bodged it to make it work. The joys of vintage projects.

 

Chris

 


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