Rejuvenating a Chronometric Speedo - PHASE 5

[Group Leader Profile]

The rear wheel drive stay the same.

On further thought, that seems extremely sensible from a motorcycle manufacturer's perspective! Build all bikes the same and just bolt an "Imperial" or "Metric" speedo on during assembly depending on where it's going to end up.

Presumably both the input drive worm and odemeter pinion are replaced in order to get the desired ratio? Just thinking out loud really ......

Alan

[Group Leader Profile]

Well, flushed with the success of Phase 2 a friend asked me to take a look at his Chrono from an early 350 Velo as the tripmeter had stopped working.

As you might have gathered I think they are marvellous instruments and so I was only too glad to get the chance for another fiddle around. Turned out that the end of the actuating arm had worn away. No spares are available at the moment (at least to me) so a new one was fashioned out of sheet brass and fitted with a new turned steel pin. You can see (well technically you can't see) the missing bit in the old and new photograph.

Old and New Small.JPG

Replacement Trip Arm Small.JPG

As I didn't have a drawing for it I had to make it up a bit using the corresponding lever from the odemeter to get the rough geometry. Having made it, assembled it and got it working I cleaned and lubricated the clock mech and re-assembled the whole thing only to find the trip reset didn't work winding it backwards to 0. The reason was that the new pawl was a mm or so too long and didn't clear the ratchet teeth properly. There was nothing for it but to completely disassemble it, reduce the length of the pawl by a couple of mm and put it all back together!

Anyway, as you can see in the video, it seems to work and Velo friend is a happy chapy 😀

https://www.youtube.com/watch?v=_U2Hb9GrtdU

[clive Profile]

An excellent piece of work constructing the arm from new Alan. Pity you did not contact me again though as I have a large supply of them..............

Edit by Adverts Editor I must behave. I must behave etc

[Group Leader Profile]

An excellent piece of work constructing the arm from new Alan. Pity you did not contact me again though as I have a large supply of them..............

Edit by Adverts Editor I must behave. I must behave etc

Ha ha! Thanks Clive, I didn't want to be a pain but, now I know, next time stand-by ......

Shame the weather's not better so my mate can go out and test it, although as it's already done ~30 miles on the bench, it would just be an excuse to go for a ride

Alan

[ajscomboman Profile]

Now I know I'm surrounded by such experts with plenty of spares who's gonna be the first one to help out the President who has a trip that won't work either, odo is fine though.

[Group Leader Profile]

I'd give it a go if you like, particularly if there's anyone round here who could provide the replacement parts to save a lot of filing and fiddly turning!
If only there was an advert somewhere ....

Of course, no liabilities and guarantees expressed or implied and all that old disclaimer stuff ......

Alan

[Group Leader Profile]

Recently I have been resuscitating another wonderful Smiths Chronometric Instrument, this time a Tacho.

It was completely Dead on Arrival With a particularly bad attack of rigour mortis having set in at the speedo drive cable entry. Having disembowled it I found the input shaft completely seized and the mechanism thick with grease. Lots of cleaning, unseizing (with the aid of suitable punches and hammers ), re-assembling and lubricating (sparingly) it’s working as good as new and has been running on the bench for over an hour. Hopefully it’s owner(a friend) will be well chuffed!
Fascinating devices (I may have mentioned that before )

Base Plate.jpg

Yuk 1.jpg

Yuk 2.jpg

[Group Leader Profile]

Here it is after the removal of the gunk which revealed some rust.

Clean but Rusty.jpg

I cleaned as much of the rust off as possible (whilst it remained fully assembled) and lightly oiled the surfaces and wiped clean and then lubricated the bearings/rubbing surfaces.

Here it is running on the bench sans dial

https://youtu.be/Fci7h55Hwpg

And then with the dial

https://youtu.be/pTKnee6vX58

I do enjoy tinkering with these wonderful devices!

Alan

[Expat Profile]

Thanks Alan and congrats, fascinating instruments. Totally understand your interest and seeing the Smiths name displayed brings back memory’s of my time with them.

Keep ‘em running.

Steve

[39speedtwin Profile]

I have had a number of NOS Chronometric’s, the majority were turned down by the ‘specialists’, most were seized due to hard grease on the input shaft, I used a hot air gun on the imput once the grease melted, most ran as they should running for at least 15 minutes. I never had one returned.