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E: Engine Twin Dynamo Pinion Retaining Nut


paw99

Website User
VOC Member
Dynamo drive lock washer should be PD23/1 NOT 508 and E50/4 pinion shim ET173/1 should be deleted.(too large a hole)
Can I ask another related question, please? My dynamo drive pinion nut has only about two threads to hold on to at end of armature, even before I add the locking washer, this worries me; Can someone please advise dimensions of PD16 dynamo sprocket boss, as that's the most likely component to take up the space.
The one I have measures 0.315" across the main part, and 0.473" overall (there is a shallow protruding ring on the dynamo side and a deeper protruding ring on the sprocket side).
Regards
Peter Killow
 

b'knighted

Well Known and Active Website User
VOC Member
Now moved to new thread - many thanks

Hi Peter,
The old thread was about the gear drive in the Comet timing chest. Have you got a Comet now or are you asking about the chain driven dynamo drive on your twin?
 
Last edited:

paw99

Website User
VOC Member
Hi Peter,
This thread is about the gear drive in the Comet timing chest. Have you got a Comet now or are you asking about the chain driven drive on your twin?
Sorry Ian, my inexperienced mistake - yes the twin dynamo drive, not timing at all; where should I post it?
I was going to ring you to ask, but can't find your number!
Do you have my email address for a chat?
Cheers
 

timetraveller

Well Known and Active Website User
VOC Member
Peter, something is wrong and I suggest you do not use the bike until it is sorted out. If that nut comes off the dynamo drive and goes through the primary chain it can break the chain and/or break a piece out of the front of the crank case and more. Two threads is not enough. Also your description of the dynamo drive sprocket does not sound right. There should not be a raised portion on either side of the central hole. The sprocket teeth themselves should run in the central line of the chain. Does yours do that? There are different drive shafts on different dynamos. Some are tapered and some are parallel. Do you have all the correct parts to mesh together?
 

paw99

Website User
VOC Member
Peter, something is wrong and I suggest you do not use the bike until it is sorted out. If that nut comes off the dynamo drive and goes through the primary chain it can break the chain and/or break a piece out of the front of the crank case and more. Two threads is not enough. Also your description of the dynamo drive sprocket does not sound right. There should not be a raised portion on either side of the central hole. The sprocket teeth themselves should run in the central line of the chain. Does yours do that? There are different drive shafts on different dynamos. Some are tapered and some are parallel. Do you have all the correct parts to mesh together?
Hi Timetraveller,and thanks for reply.
I apologise to all for being on wrong thread - I searched for Dynamo Drive, and this one came up.
Should Twin Dynamo be somewhere else?
My situation is: I fully appreciate the damage that loose metal in primary chaincase would cause, hence my concern.
I have "C" Rapide, and the dynamo drive is as per handbook, tapered drive from armature, through dynamo drive boss, oil thrower ring, drive sprocket, drive plate.
There is only about 1/8 " of thread showing when these are in position.
My question is why, and I wonder if the PD16 drive boss (with tapered hole) may be too thick.
So I measured it, and need dimensions of a known correct PD16 to compare.
I believe the armature thread is correct length, as I have two the same.
Dynamo is Miller, the long 3" one.
The raised portions i referred to are not on the sprocket, but are on the drive boss.
In hope of a safe solution
Peter
 

timetraveller

Well Known and Active Website User
VOC Member
Peter, I do not have a PD16 so cannot help with the thickness of that but two questions might help. Is the dynamo right up against the back of the crank case casting and is the sprocket in the centre of the chain. If the latter is correct but there is a gap between the casting and the dynamo body then perhaps there is something wrong with the PD16. You also refer to the dynamo as the 'long 3" one'. All the Miller dynamos for Vincents which I have seen are about an inch shorter than the later Lucas dynamos. 5" as opposed to 6" from memory but someone will correct me if that is wrong.
 

paw99

Website User
VOC Member
Peter, I do not have a PD16 so cannot help with the thickness of that but two questions might help. Is the dynamo right up against the back of the crank case casting and is the sprocket in the centre of the chain. If the latter is correct but there is a gap between the casting and the dynamo body then perhaps there is something wrong with the PD16. You also refer to the dynamo as the 'long 3" one'. All the Miller dynamos for Vincents which I have seen are about an inch shorter than the later Lucas dynamos. 5" as opposed to 6" from memory but someone will correct me if that is wrong.
Yes, I take your point about alignment with chain; but before that, I need to have the sprocket securely attached to the dynamo. The alignment may be affected by the presence or absence of a felt washer between the dynamo and chaincase - do you know if there should be one?
I think my next step is to ask Bill Parr (Technical Officer) or VOC spares company .
Thanks for your help
 

robin

Well Known and Active Website User
VOC Member
Peter,
The correct nut to use is ET154. This screws up inside the drive pinion.
Robin.
 

paw99

Website User
VOC Member
Peter,
The correct nut to use is ET154. This screws up inside the drive pinion.
Robin.
Many thanks Robin, that seems to answer my question well.
But very different to what the various Vincent literature would have me believe!
(Or I am reading the spares list wrongly).
Thanks
Peter
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
For a twin the parts are shown on MO14. The nut is plain 3/8" BSF, #198. This is what I have on my Rapide.
26912
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I use the PD17AS on my Prince with a half depth nylock nut without any problems.
A nylock nut will be a lot easier than bending the PD 23 lock washer shown on the MO14. The PD15/1 has a small tapped hole. I don't know what that hole was intended for but I have put in a small drilled bolt and lock wired it to my drilled 198 nut.
 

paw99

Website User
VOC Member
A nylock nut will be a lot easier than bending the PD 23 lock washer shown on the MO14. The PD15/1 has a small tapped hole. I don't know what that hole was intended for but I have put in a small drilled bolt and lock wired it to my drilled 198 nut.
Hi - yes, nyloc would be good, I shall look out for one.
The hole in the drive plate I think is probably for the tab of the tab washer.
Cheers
Peter
 

vin998

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I use the treaded hole in the PD15 sprocket to put a tempory long 1/4 BSF bolt in. Then you can hold the bolt to easily manouver the sprocket through primary cover and into place. Once positioned then remove the long bolt and put a short one in which is drilled across the head to allow you to wirelock it to the 198 nut. I have never used PD23 tab washer as without that it allows 198 nut a bit more thread to engage. Also use a small amount of Loctite nutlock (weak version) on nut 198.
Simon
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I use the treaded hole in the PD15 sprocket to put a tempory long 1/4 BSF bolt in. Then you can hold the bolt to easily manouver the sprocket through primary cover and into place. Once positioned then remove the long bolt and put a short one in which is drilled across the head to allow you to wirelock it to the 198 nut. I have never used PD23 tab washer as without that it allows 198 nut a bit more thread to engage. Also use a small amount of Loctite nutlock (weak version) on nut 198.
Simon
Good idea about the long bolt to help when manoeuvring the sprocket. It is a bit of a juggling act in an awkward space. I also don't bother with the lock washer.
 

stu spalding

Well Known and Active Website User
VOC Member
The hole in my PD15 is threaded 1/4 BSW to take a cover screw. Just thought I'd mention it in case someone jams the wrong bolt in. Cheers, Stu.
 

paw99

Website User
VOC Member
Well done all, now I have quite a range of solutions...and for all of them, I believe that the direction of dynamo rotation will tighten the nut rather than loosen it.

I do like the ET158 method, as this will fill the gap between drive plate PD17 and armature shaft, give plenty of thread and also still be lockable by the excellent 1/4 BSF idea.
But that depends on it going in, and how long it is.
Cheers
Peter
 

kettlrj

Well Known and Active Website User
VOC Member
The tapped hole in the sprocket is definitely 1/4" Whit so that you can use one of the screws that you took out of the cover plate for access to the drive.
 

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