PD: Primary Drive Dynamo sprocket engagement

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highbury731

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I am working on fitting my Alton to my Rapide engine. The cases and clamp ET176/1 were made to suit the 3 1/2" Miller. It came to me with the 3" Miller and the eccentric dynamo adaptor sleeve ET202. This gives a measure of adjustment, tho' limited by the steel ring ET164.
With the eccentric sleeve set to give lowest possible alternator position, the alternator drive binds inside ET164. Raise it a little by rotating the eccentric sleeve a little bit, the alternator is on its lowest possible position. The drive sprocket teeth barely engage with the primary drive chain. The tooth tips look level with the rivets in the drive chain, and I can push a 2.5mm drill bit (but not a 3mm bit) between the chain and the root of the dynamo/alternator sprocket. This is too little tooth engagement.
So, what do I do to fix this?
Paul Standeven
 
H

highbury731

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VOC Member
Now that is an interesting idea.

28T x 3/8" = 10.5" circumference

Diameter = circumference/Pi = 3.34"

Diameter for 30 T sprocket, 3.34" x 30/28 = 3.58"

3.58" - 3.34" = 0.24" increase in diameter, and 0.12" reduction in clearance, or 3.05mm.
If I went for a 29T sprocket, it would reduce the clearance to about 1mm at lowest possible adjustment, as now. A 30T would mean raising it a small amount and allow me to set the cleance to say .010" or .015"

As you say, 1 or 2 extra teeth on the sprocket would do it.

I have emaile Hervé Hamon to ask if he can supply such a sprocket. He has probably encountered this issue before.
Paul
 
Vincent Brake

Vincent Brake

Well Known and Active Forum User
VOC Member
Just mill some under the dynamo saddle.
And grind out the hole jn casing.
Take out the silly iron ring.
Close up with silicon gasket.
Premark first, and than silicon just slightly slack, after curing nip up.

Cheers folks!!
 
Vincent Brake

Vincent Brake

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Than its as easy. Bruce, machine a excentic ring. Bit more excentric.
Nice evening on a Lathe.
Only Schaublin of course.
Cheerio.
 
H

highbury731

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Vincent
A more-eccentric adaptor ring is exactly the idea that came to me after your post #4. I will have to look into making one. It would also mean faffing with that steel ring.

What is Schaublin?

I suspect that there is insufficient clearance for an oversize sprocket - it's hard enough to get the 28t one in place.
 
john998

john998

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VOC Member
Hello, is it possible that you can assemble the eccentric ring in another position, hard to describe but if you imagine turning it past maximum up or down adjustment. The dynamo spindle will go in two positions one forward and one back. John.
 
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