Speedo in reverse!

[4129R]

and presumably as your car was I believe the spare race car, the speedo may never have been used on that car, and you may have a specially built "blueprinted" race gearbox.

[jbcollier]

Is the speedo cable a know quantity?  No junctions or boxes inserted for a cruise-control or other gawd-help-us?

[pboedker]

Here's a photo into my 365-box. I was planning to change the o-ring and shaft seal, so now I might as well get it done! (Thanks for pushing me).

It shows that my worm drive 'goes the other way' than your's does and hence will try to turn the speedo drive gear clockwise when viewed from the outside.

The second photo shows the speedo drive gear, it has 19 teeth like the one from RD. The one from SJ (it looks similar to yours) is for a 352-box.

I can't remember how the 352 worm gear and speedo drive looks, but it looks like you have such a pair. I also can't remember if the 352-drive meets the top or the bottom of the worm gear like the 365-box. Maybe there's convenient space there without the 5th gear. If the gears meet at the the top that would explain why the 352 worm gear 'pushes inwards'.

[buzzer]

Peter,
I think you’ve nailed it!!!
By some fluke I’ve ended up with a 352 speedo drive gear and a 352 pinion gear.  The gearbox when I got it was missing the speedo drive pinion and sleeve so I guess at some point as it was raced the box was rebuilt with some 352 bits including a 352 speedo drive gear when it didn’t matter. The 352 takes its drive off the top of the box. Problem solved, I just knew it had to be some wierd coincidence.
Now have to sort what the answer is. I’ll talk to Richard in the morning.

[4129R]

Does this mean the 352 box rotates in a different direction to the 365 box?

Does the Renault engine rotate in a different direction to the Lotus Twin Cam engine?

[buzzer]

The pick up on a 352 looks like it’s on top of the worm gear instead of beneath as on the 365. So the boxes rotate the same way just the speedo pick up is a different configuration

[Roger]

I told you the worm was wrong several posts back!!

[4129R]

The worm that turned................. the wrong way.

[buzzer]

Roger,
Yep, but it was the only answer, but Banks supplied a 352 pinion instead of a 365 pinion  and I happened to have a 352 worm installed.

now have to sort out the best/easiest solution that won't cost a fortune.

[jbcollier]

Smiths make speedos that work from a hall effect generator.  I'd have to dig for the numbers but there is a sensor from a Ford that just drops in.  It doesn't care which direction it turns.

[buzzer]

Yes I've seem them, in fact looked them up this morning. I have a VDO hall effect speedo in my Westfield that works well.

[buzzer]

Update. Couldn’t source the right drives. But sourced a reversing 90 drive from a uk company called speedy cable. Fits on the rear of the speedo and is a nice nest bit of kit. A side effect is the speedo cable had a better run and loops nicely to the back of the speedo.