B.T.H PBM1 Mag-Dyno (Early Series ‘A’ Singles)
- Thread starter Rob H
- Start date
Why, it's bent!
Is this the right one for a Vincent?
Rob
This type of BTH unit was used on early series A singles from 1935 & early 36 but then the factory must have found a few in stores as they were used on a batch of bikes in early 1937 of which mine is one. They were also used on some of the pre A bikes ie, Pythons and maybe Model J.
It looks correct in the photos as in the advance cable takeoff on the points area is the correct side for slackwire advance for Vincent rotation direction. I note that there is only one pickup which is on the correct side for a Vincent, but the other side should have a blanking plate over the redundant pickup hole. So one thing you can check is remove the points cover and check is the cam a single lobe or does it have two lobes? If two then it is most probably off a Scott as the early 1930's Scotts used these as well. If it is off a Scott then because the Scott was 2 stroke then the internal bevel gears for the dynamo drive will be the wrong gearing and if fitted to a Vincent the dynamo will rotate at 1/2 speed which means more revs required to generate the massive 24 watts of 6V electricity.
Has the unit been restored by a reputable person as if not then it could cost a LOT of money to restore / repair due to difficult to source spares. So the value all depends on if it needs a rewind / rebuild.
Simon
This type of BTH unit was used on early series A singles from 1935 & early 36 but then the factory must have found a few in stores as they were used on a batch of bikes in early 1937 of which mine is one. They were also used on some of the pre A bikes ie, Pythons and maybe Model J.
It looks correct in the photos as in the advance cable takeoff on the points area is the correct side for slackwire advance for Vincent rotation direction. I note that there is only one pickup which is on the correct side for a Vincent, but the other side should have a blanking plate over the redundant pickup hole. So one thing you can check is remove the points cover and check is the cam a single lobe or does it have two lobes? If two then it is most probably off a Scott as the early 1930's Scotts used these as well. If it is off a Scott then because the Scott was 2 stroke then the internal bevel gears for the dynamo drive will be the wrong gearing and if fitted to a Vincent the dynamo will rotate at 1/2 speed which means more revs required to generate the massive 24 watts of 6V electricity.
Has the unit been restored by a reputable person as if not then it could cost a LOT of money to restore / repair due to difficult to source spares. So the value all depends on if it needs a rewind / rebuild.
Simon
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Are there any options of something else that can be used on an "A" Single, That is available,
For a Member. Cheers Bill.
Bill
Your fairly limited due to the 35mm to centre of armature height. Miller made a mag dyno for the later series A's to the same height and those are just as hard to find. Years ago owners used to cut the platform to fit a Lucas unit which I believe is approx 10mm larger centre height but today that is a no-no.
I don't know of any other unit out there but there maybe something. Problem is if you want lights & charging then you need a mag/dyno as its the only place to fit a generator on series A singles.
Simon
Your fairly limited due to the 35mm to centre of armature height. Miller made a mag dyno for the later series A's to the same height and those are just as hard to find. Years ago owners used to cut the platform to fit a Lucas unit which I believe is approx 10mm larger centre height but today that is a no-no.
I don't know of any other unit out there but there maybe something. Problem is if you want lights & charging then you need a mag/dyno as its the only place to fit a generator on series A singles.
Simon
Just thought that there is so many Bikes turning up now , There might be a Modern option.
Cheers Bill.
Cheers Bill.
Er, powerdynamo from Germany?
We need more please, Cheers Bill.