mechanical tach

[Timothy Keith-Lucas]

Is there a port for a mechanical tachometer, or a way of rigging one, on the Austin etc. 948cc engine? I've got a digital run off a spark plug lead, and the original electrical tach which I've modernized, but the plain reliability of a mechanical tach is appealing.  Any ideas appreciated.

[7Westfield]

The 948 Sprites used a gearbox from the back end of the generator. 

You'll know if yours is right if it has a male thread sticking out the back end. A gearbox goes on there, and then the cable

 

https://mossmotors.com/spm-088a-generator

part #18, same drive cable as speedo

Edited May 11, 2024 by 7Westfield

[Timothy Keith-Lucas]

Wonderful! So it's under the projection out the back end labelled "OIL". I will pursue said, and thank you.

[Timothy Keith-Lucas]

Ooops. No joy. No threads under the cover.  Sounds like a new generator is in my future if I want a mechanical tach.

[7Westfield]

I think Spridgets were the only use of that generator

the shaft and rear plate are different

if you have an oil port, I think you have the regular one

after all, you don't need a tach in an A40..............

 

and then, you need the tach for a spridget

[sagamore]

I have a Smiths mechanical tachometer running off the camshaft. It required modification to the front cover and to the camshaft retaining nut. This in turn requires modifying the rocker cover because the original crankcase vent is lost. It's pretty cool in a luddite sort of way, but a Stack chronometric would have done the same thing tapping off the coil signal.

[Timothy Keith-Lucas]

Thanks. Interesting approach.  At the moment I'm trying to resurrect my positive ground original. I would prefer a mechanical unit, for simplicity and accuracy. The electrical unit has lots of problems, but re-wiring may solve them. I have not found a generator with the mechanical take-off, complicated by my 7 being positive ground.

[7Westfield]

if you want to shell out bucks, moss sells the generators

 it's easy to swap polarity on a gen        you might even have to set it on a new one

what do you have on the car that would be polarity sensitive? I think I just swapped the wires on the  ignition coil when I converted my bugeye, back in the 70's    and maybe the fuel gauge, but being resistance based, it might not care

light bulbs and starters don't care.....

Edited May 14, 2024 by 7Westfield

[jbcollier]

Mechanical tachs are not more accurate than electric/electronic ones.  Had a Climax powered Turner come in with the owner saying there was no power.  The problem?  His mechanical tach read 3k low.

 

Get a tach repair module for the tach you have.  It will be fine.

[IamScotticus]

On 5/11/2024 at 9:04 AM, Timothy Keith-Lucas said:

Ooops. No joy. No threads under the cover.  Sounds like a new generator is in my future if I want a mechanical tach.

Or a voltage regulator?