Faulty odometer

[ericbushby]

Hi,
The odometer in my speedo went intermittent two months ago. I stripped it, cleaned, lubricated and reassembled it.
It then seemed to work OK, but I remember being puzzled as to how the drive pawl engages with the ratchet.
( I know the action is nearly the opposite of a ratchet and pawl, but that is what it looks like.)
It has now become intermittent again exactly as before.
I think I have now discovered that a very light helical spring is missing from the mechanism. This pushes the pawl into engagement with the toothed wheel on the trip odometer.

So, my request is:- Has anyone got one of these springs, or a dead 1960`s smiths speedo, or the internal gubbins of one in any condition, which has this light spring still on it.
Any suggestions are welcome and I hope someone can help.
Eric in Burnley
1967 S3SE DHC

[john.p.clegg]

Eric
I'll have a look in the shed in the morning...

John

[ericbushby]

Thanks John,
Here`s hoping; even if I looked at one I might be able to make something.
Eric

[Craven]

Hi Eric.
Not sure which spring you think is missing! There is the same arrangement on both total miles and day trip odometer for keeping the pawl on the ratchet wheel, they run from a hook on the frame to a hole in the pawl. One is longer than the other but off the top of my head can?t remember which, so if it?s this spring then you should have a pattern.
There are two small springs inside the barrel assembly, is it one of these you think is missing? Like John I have a look in the morning.
Ron.

[john.p.clegg]

Eric
In my box of speedo bits I've found two springs ( well three actually ),two attached either side of the odometer white plastic things and one on its own...

John

[ericbushby]

Hi Ron,
I have not got the device to hand at the moment, as I do not want to strip it out just yet because I have an M.O.T. test coming up soon. After that I can run without speedo for a while.
I seem to remember that the trip wheels were pushed with the pawl, but the total wheels are directly geared off the trip wheels. So no spring needed there. I believe that there are different versions of this, according to youtube videos.
I could be wrong about that.
I have nothing to work on at the moment.

John, good morning
That sounds very encouraging.
If I could negotiate, scrounge or borrow the bits you have found, then I could offer them up to the mechanism and see if anything makes sense.
As it happens I have to be in Walkden on Thursday afternoon and evening. Would it be possible to meet or call on you.
Regards
Eric

[john.p.clegg]

Thursday is free in my Dairy,get in touch nearer the time...

John

[ericbushby]

John,
Will do, thanks
Eric

[Craven]

Hi Eric,
Spring laid out in John?s photo is the spring you are after. Clearly then you have a different total miles to mine, see pics.
Good luck with the repair.
Ron.

[john.p.clegg]

Looking at that photo,it could still be there but dangling down behind the wheels ( just come off the pawl..)...

John

[Craven]

Hi Eric, John.
From Eric?s description of direct drive between the mileometer and trip it seems the speedo is of a later design.
Maybe these pics are relevant, the closed length of the spring is 10mm or so, between fixing loops.
Ron.

[john.p.clegg]

Thanks Ron

O.K. Eric,plastic pawl or metal pawl?

John

[ericbushby]

Ron, John, yes that`s the one.
Due to your encouragement I have removed the speedo and extracted the gubbins.
The plastic pawl has a hook on the side, which, it is obvious now is where a spring should go.
However I cannot find anywhere to hook the other end.
So, I have made a bracket fixed under the nearby screw; wound a spring from an alarm clock hair spring and reassembled.
It looks like it will work although it is not as pretty as Ron`s example.
I have taken some photos and lost them down the big hole in the computer. I will try harder.
So for now, thanks for your help and leave me with it.
It has been raining today and it wasn`t suitable to be out in the garden.
Cheers,
Eric

[ericbushby]

Hi John and Ron

This is the hook on the pawl.
Scruffy but working new arrangement. The bracket is made from 10 thou. phosphor bronze shim. The spring was wound from an alarm clock hairspring.
Speedo is going back in tonight, with every confidence. Well it worked a bit with no spring.
Thanks again
Eric in Burnley
S3SE DHC
PS some of these captions and pictures are out of sequence. please re-arrange them to make sense. I am going to the garage.

[Chancer]

I remember those internals Eric, it does not need a spring, if you look at the spring steel part on the pivot of the pawl its the spring pressure of that which will hold the pawl against the ratchet Wheel.

There is some play in the plastic arm and the pawl can be disengaged which is probably what has happened in your case and i might even be able to surmise why!

I had the same internals on the speedo of my Caterham, once I had worked out how it functioned I drilled a hole in the back of the speedo casing to line up with the pawl, then when I reached the limit of my limited mileage insurance I could work blind behind the Dashboard with a small screwdriver to disengage the pawl and Voila! The odometer would not register any more miles until the pawl was re-engaged in the same manner.

I dont think that your spring will hurt though.