E: Engine rev counter

[davidd]

The Grey Flash and Lightnings had steel ET48 gears (the ATD gear).

I think P.J. Morgan wrote an article in MPH about the tach drive. He used a large bell-like adapter to run the tach and avoid the weights. I like the small aluminum adapter that grips the pins and has clearance for the posts:

The holes marked in orange fit on the small pins. The additional holes are just for lightness. Mill straight across to clear the posts.

It is best if you use the Smith BG1507 right angle drive, which was OEM. I think the BG1508, which is the replacement, is not as robust.

David

 

[chankly bore]

Just remember that the armature bearings are in a paper cup in a 65 year old housing. Personally I wouldn't hang any more stress off the end of them!Go manual slack wire. The A.T.D. is also a poor design. Look at a (real) B.T.H. one if you want to see how it should have been done. Years ago Ted Davis used to sell them for Vincents. Has anyone still got one?

 

[bmetcalf]

Is a photo of a BTH ATD available to see how it is different from the Lucas item?

 

[chankly bore]

There is a photo. on the internet. Look under BTH A.T.D. Main advantage is robust clock-type return spring. Velocette ones are wrong direction, Triumph early side-valve TRW's are clockwise, which is correct for Vincents but require some grafting on to our ET48 pinions. The ones Ted Davis supplied were on brand-new pinions-probably ex-Factory.

 

[greg brillus]

Both designs are good and bad, The BTH probably a bit more robust in it's design, though they do wear as the rollers are quite heavy, and the clock springs are quite weak. I had one recently on a 69 Venom that was very weak allowing the engine to advance too quickly and detonate. I disassembled it and shimmed up the spring adding more tension which did help. At least they are constantly lubricated, but they were probably never designed to last this long. They would both be expensive to make, remembering the chaps that use to make them in their retirement are no longer with us. This is one of the reasons some of these parts have become expensive as a machine shop has bigger overheads, and finding those with enough interest to make these parts is getting thin.

 

[erik]

qdavidd:this construction has an influence on the weights.the weights have to turn fast to go on full advance.and they Retard easier.

 

[Simon Dinsdale]

qdavidd:this construction has an influence on the weights.the weights have to turn fast to go on full advance.and they Retard easier.

I was also thinking that. The rev counter drive needs to connect to the gear or metalwork directly bolted to the gear and not the central bolt or arm.
Simon

 

[Martyn Goodwin]

Is a photo of a BTH ATD available to see how it is different from the Lucas item?

What about it Charlie?? - I know you have the BTH ATD - AND a camera

 

[bmetcalf]

I googled "bth atd", then clicked images and got this:

https://www.google.com/search?q=bth...AUICygC&biw=1920&bih=950#imgrc=gfaHjkYA25aa7M:

lots of good pix, etc. there.

 

[erik]

there are two angled Irons fitted to the wheel.These are really strong enough to drive a rev Counter.my idea is to make a fork over atd which runs in two bearings in an intermediat housing between the cover and the angled gearbox?