Brake Back Plate

specifications, colours, contract nos, variations etc
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Michael.Brown
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Brake Back Plate

Post by Michael.Brown »

Hi all,

Ok Gents, question time. Long shot, any idea what the dia should be for the centre hole in the W/NG brake back plate 4360-42 which sits on the shoulder of the brake plate lock nut 4380-30. The new part from Draganfly is 0.120" undersize so not useable. However it could be that the hole has been opened up in the back plate although it doesn't appear at first sight to be the case.
20211215_191822.jpg
Mike
1942 Ariel W/NG 350cc
1960 Ariel Leader 250cc
1963 LE Velocette 192cc
Michael.Brown
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Re: Brake Back Plate

Post by Michael.Brown »

Hi all,

Update on the back plate hole size. I have it on good authority that it should be 0.75" dia, so the Draganfly back plate nut is correct. As I suggested as a possibility it looks like someone has opened the hole out to 0.870" dia which is why I had a discrepancy. Plan B will be to use the non std nut to centre and clamp the back plate instead, which fits with a 0.002" clearance 🙂

Mike
1942 Ariel W/NG 350cc
1960 Ariel Leader 250cc
1963 LE Velocette 192cc
will_curry
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Re: Brake Back Plate

Post by will_curry »

I've just had the chance to measure my brake plate and the rigid plate
hole is as you say 0.75".

I also measured a plunger frame brake plate and the hole in that is
0.87"
nevhunter
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Re: Brake Back Plate

Post by nevhunter »

.002" won't do any harm. A larger Hex will stabilise it better. True up the backing plate also. Many of them are quite distorted. The one for the plunger cam works the other way and the return spring is different. You may need to drill another hole for the spring if you have a plunger plate. Nev
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Roger Gwynn
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Re: Brake Back Plate

Post by Roger Gwynn »

The early plunger brake arms operated in the same direction as the rigid ones, which is what causes the rear wheel to lock up. The rear brake arm return spring is one of the few parts that Ariel modified several times. There 7 that I know of.
Roger Gwynn, Membership Secretary, curator of the Machine Register and the works drawings. Director of Draganfly Motorcycles, Craven Equipment and Supreme Motorcycles mostly retired.
Michael.Brown
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Re: Brake Back Plate

Post by Michael.Brown »

Hi Guys,

All very interesting, so perhaps I have the wrong back plate (i.e. for a plunger) but if I bush the centre hole down to 0.750" that should allow me to use the Draganfly back plate nut in the correct position for a rigid back plate. Also explains why it looks factory and not machined out.

Thanks for all your help

Mike
1942 Ariel W/NG 350cc
1960 Ariel Leader 250cc
1963 LE Velocette 192cc
will_curry
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Re: Brake Back Plate

Post by will_curry »

I might have confused things here. I'm sure your back plate is from a rigid frame and
someone for some reason has opened the hole out. Plunger brake plates have a
slot into which the brake anchor engages which your plate doesn't have. The only
other candidate is a brake plate from an early swinging arm frame. While they use the
same sort of anchor as the rigid frame the anchor point is much further away from
the operating cam. I can't see any problem with bushing your plate back to its original
size.
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