Hi all, further to my project of replacing the dynamo with a PM-alternator, I need to know at what speed the Lucas dynamo was spinning in idle.
In order to calculate this, I will need to know the diameter of all the gears inside the timing train. Also needed is the idling speed of the motor.
Thank you for any info.

Michael

Instead of calculating the dynamo RPM, why not measure it? There are any number of inexpensive contact and laser (non contact) tachometers available online. see:

https://www.amazon.com/gp/product/B004Q8L894/ref=ask_ql_qh_dp_hza

and

https://www.amazon.com/Vktech-DT6235B-Digital-Contact-Tachometer/dp/B00GRQHW0M/ref=sr_1_3/135-6389394-8709348?ie=UTF8&qid=1509460114&sr=8-3&keywords=contact+tachometer&dpID=41m4C2mF9KL&preST=_SY300_QL70_&dpSrc=srch

as examples. Prices vary widely. The laser models use a small piece of reflective tape on the shaft end. I used similar mechanical devices in my field work with success.

Good luck

Dave W.

email (option): dwdiak4@gmail.com

Well the magneto runs at half engine speed so all you need to know is the step up ratio of the mag to dynamo gears. ie the fibre wheel and the steel gear on the dynamo then times two. As for the idling rpm, well on retard you can probably count them then times by two

Just bought one on Ebay. Eng pound 7,30 free postage made in China.
Although I can count the revs at idle when the engine is warm and the ignition retarded

John

email (option): john.kater@chello.nl

The fiber magdyno gear has 58 teeth and the dynamo 22. Now you can do the maths

Cheers, Michiel

So a ratio of more or less 2.6 to 1 between the fibre gear and the dynamo...

Assuming tick over speed is 800-1000rpm (say 900) the mag is running at 450rpm...and the dynamo at 1170 rpm...At engine speeds of..

2000rpm...2600rpm
3000rpm...3900rpm
4000rpm...5200rpm....Ian

email (option): ian@wright52.plus.com

Yes that's spot on Ian. I got my calculations in a twist in a previous post.