Smiths (magmo) speedometer repair.

[GM6VXB]

Re-building a Smiths Magmo type speedometer, basically swapping parts between my original semi functioning one and a very poor condition one.
So far got all except the milometer working but found the small brass gear that is driven from the worm drive (end of drive cable)
has teeth missing and is BER.
Looking back on old threads it appears these gears are now unobtainium.
'Googling' for similar 20 tooth brass gears does not come up with anything similar. Suspect plastic ones will not be up to the job, but
cannot find similar ones of these either !.
Gear is 20 tooth one, about 9MM diameter, 2MM thick, with a splined hole 4MM diameter. All measurements are approximate.

Anyone ever managed to get replacement gears, not counting removing from a U/S speedometer ?.
Well beyond my capabilites to cut a new gear on a lathe.

Yes I know, run it without the milometer, but it is nice to know how many miles I am doing having done what I thought was
a 30 mile trip which my wife told me was actually 50 miles !.

Martin, GM6VXB

[Ivor Hawkins]

Hi Martin, I mess around with vintage clocks and watches, when I’m not fiddling with Austins, so it may be worth trying Cousinsuk.com, there is a chance they’ll have a gear wheel to suit.

[Tony Griffiths]

For tiny gears, it might be worth trying: https://www.hpcgears.com/n/products/12.s..._gears.php
Do you know what the DP is? Might it be something like 32? If so: https://www.hpcgears.com/pdf_c33/23.96-23.101.pdf

[GM6VXB]

Ivor,
Had a look through the site but did not spot any suitable gears. Will have a longer look tonight as I may have missed something.

Tony,
The teeth on the gear are mostly missing, but I suspect a 20 tooth 32 DP gear is going to be pretty close.
Have taken the gear off the shaft and it has a splines so this would cause problems re fitting.
Might just order some 20 tooth gears on spec and try filing splines.

Managed to get one fully working speedometer now. Did suspect the mile counter was the cause of the ruined gear
but left it driven by an old battery drill for several hours and seems to count up without sticking.

So basically just have to get the mile counter drive sorted and I will have a spare unit should the fitted one ever fail.

Also (for fun) found an APP that works on my Iphone and Ipad that does both speed and milage, so if all else fails !.

Martin.