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Mechanical rev counter drive

trev.birkbeck

Website User
Non-VOC Member
My Shadow has a mechanical rev counter and this was driven from the end of the mag, this being a manual A/R so the rev counter did not affect the timing.
Converted to an automatic A/R now and am wondering how to drive the rev counter. Paul Richardson says it can't be done without using a manual mag! Does anyone have any experience of driving the RC from an automatic A/R.
I have a feeling it has to be driven from the outside to avoid affecting the timing.
Trevor Birkbeck :confused:
 
F

Flatout

Guest
Mechanical Rev Counter for sale on ebay.

My Shadow has a mechanical rev counter and this was driven from the end of the mag, this being a manual A/R so the rev counter did not affect the timing.
Converted to an automatic A/R now and am wondering how to drive the rev counter. Paul Richardson says it can't be done without using a manual mag! Does anyone have any experience of driving the RC from an automatic A/R.
I have a feeling it has to be driven from the outside to avoid affecting the timing.
Trevor Birkbeck :confused:

Item # 190196120898
 

Paul Ennis

Well Known and Active Website User
VOC Member
Rev-counter drive

Hi Trev,
I'm glad to hear that you're still playing with Vins.
Your question sparked the memory of an article in MPH from about the time I joined the Club. It was written by the late Paul Morgan and described his method of driving his rev-counter. Somehow it didn't make FYO, but a trawl through my MPHs found it in MPH 232 May 1968.
He made a 'cup' which covered the ATD with a hole in the bottom for access to the centre nut. A peg on the base of the 'cup' drove a slotted plate (to allow for any mis-alignment) mounted on the Smiths gearbox.
If you don't have MPH 232, send me an e-mail or PM and I'll send you a photo-copy of the original article.
Cheers, Paul.
 

trev.birkbeck

Website User
Non-VOC Member
Hi Paul
Great to hear from you. Well, you know how it is - once you've got Vincentitis in your blood, that's it for life till you croak. Last tax disc on the Shadow was 1992!!! Been busy, mind. Modern bikes, off road bikes, hang gliding (still number 1), gliding, paragliding, snowboarding, etc, etc.
Anyway, I'm well on with the Shadow now, Egli next (remember, the one that you persuaded me to have a go at racing on), 2nd Egli after that then the Comets. I'm going to have to speed up or croaksville will catch up on me.
Paul Morgan's method was how I expected it to be - I don't have MPH 232 and it would be great if you could let me have a copy of that article.
Email address...trev.birkbeck@virgin.net
Tel 07836 342312....home 01765 658486
Hope to see you soon...on my Vin, of course.
Trev :)
 

Norvin1000

Website User
Non-VOC Member
Trev counter

Hiya Trevor! Phil B here!

Have you considered an electronic tacho, driven off one of the ignition leads? See http://www.elliotdesign.co.uk/products/classic.html
I have one of their Classic Clubman series tachos (model LC 80C) for my Norvin project.

The Norvin is currently in a molecular state (lots of bits in boxes in my loft follwing a house move), with the original Shadow crank having gone to gentleman Bob Dunn for an eternity of re-threading the shafts and installing a dry belt drive pinion / alternator rotor.

How's life in the DHPC? When did you last fly?
Phil Blakeney, Ashton under Lyne 07900 361903
 

manxnortonman

Well Known and Active Website User
VOC Member
Rev counter drive

My Shadow has a mechanical rev counter and this was driven from the end of the mag, this being a manual A/R so the rev counter did not affect the timing.
Converted to an automatic A/R now and am wondering how to drive the rev counter. Paul Richardson says it can't be done without using a manual mag! Does anyone have any experience of driving the RC from an automatic A/R.
I have a feeling it has to be driven from the outside to avoid affecting the timing.
Trevor Birkbeck :confused:
Trevor,
It can be done as I have fitted a 5" rev counter to my rapide which has an auto adv/retard mechanism. I assume you have the normal angle drive on your timining case. Heres how you do it. The drive is taken off the locating bolt in the centre of the auto unit ie the one you tighten the unit to the mag. Obtain a good quality 5/16 socket a one with multi positions internally that look like serations (Brittol etc). Measure the distance between the base of the nut on the auto adv unit to the tag base of the angle drive. Turn the socket down on a lathe until you have 5th clearance (end float)the square end. Now you have a socket with serations one end and nothing the other. Cut two half moon shapes to fit into the end so the tag on the angle drive slots between the half moons. Braze into position and turn off any excess material. This now sits on the mag nut and drives your rev counter. Simple.Any problems give me a call 07952-866193. I was going to have a batch made but could`nt see the demand. It does not effect the running of the engine and the socket if machined/brazed correctly just sits there and must drive the rev counter.
Regards Garry
 

manxnortonman

Well Known and Active Website User
VOC Member
Rev counter drive

My Shadow has a mechanical rev counter and this was driven from the end of the mag, this being a manual A/R so the rev counter did not affect the timing.
Converted to an automatic A/R now and am wondering how to drive the rev counter. Paul Richardson says it can't be done without using a manual mag! Does anyone have any experience of driving the RC from an automatic A/R.
I have a feeling it has to be driven from the outside to avoid affecting the timing.
Trevor Birkbeck :confused:
Trevor,
It can be done as I have fitted a 5" rev counter to my rapide which has an auto adv/retard mechanism. I assume you have the normal angle drive on your timining case. Heres how you do it. The drive is taken off the locating bolt in the centre of the auto unit ie the one you tighten the unit to the mag. Obtain a good quality 5/16 socket a one with multi positions internally that look like serations (Brittol etc). Measure the distance between the base of the nut on the auto adv unit to the tag base of the angle drive. Turn the socket down on a lathe until you have 5th clearance (end float)the square end. Now you have a socket with serations one end and nothing the other. Cut two half moon shapes to fit into the end so the tag on the angle drive slots between the half moons. Braze into position and turn off any excess material. This now sits on the mag nut and drives your rev counter. Simple.Any problems give me a call 07952-866193. I was going to have a batch made but could`nt see the demand. It does not effect the running of the engine and the socket if machined/brazed correctly just sits there and must drive the rev counter.
Regards Garry
 

Vic Youel

Well Known and Active Website User
Non-VOC Member
Rev Counter drive

Better still, buy a replacement for the ATD holding bolt with the right magneto taper/thread and left hand thread holding it in. All you need to do is cut the end to the correct lenght to suit your drive and add a suitable drive slot.

£8 will buy this from Price Productions (see MPH advert); call roy Price on 01 480 473225.

I am getting Maughan's to addapt one for me to suit an old end cover I bought years ago from Ted Davis and a drive I bought from a guy at Kempton who made them for rev counters used on Manx Norton's.

Vic
 

Vic Youel

Well Known and Active Website User
Non-VOC Member
ATD Rev Counter Drive

Graham Maughan has just given me an update. An overseas customer had expressed an interest but expressed concern that the drive taken from the ATD fixing nut could force the nut to come loose in trying to drive the Rev counter gear box and drive cable load.

Graham is developing a locking system to prevent potential damage.

Vic
 
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