Smiths Speedo types

[Mark McKibbin]

Does anyone have a listing of Smiths Speedo Types showing the Turns per Mile as there are plenty for sale but I do not know what for instance a TN is.  A list would make it easier.

I know the 3 speed boxes needed 2240 TPM and the 4 Speeds needed a 1020 TPM Speedo and as I have a 4 speed I'm hoping to find the older style speedo but with about 1000 TPM to match.

[Parazine]

Ha! A very good question. I have seen some information but if there is a specific list of all Smiths types (some specialists claim to have one), it doesn't appear on the web.

A PA is 2240, an A type is variable but usually 3360.

On this topic, does anyone know which speedo was fitted in mid 1927, between the introduction of the gearbox speedo drive and the speedo moving to the centre of the dashboard? It would have been a 2240, could have been a special A type or could be something else (but what?).

[Austin Carr]

From the Triple M Register  ( http://www.triple-mregister.org/forums/t...IC_ID=8857 )

PCN is the lettering which is usual on an M-type face.

I understand the 'D' speedometer operates at 1610 turns per mile but I believe the 'PCN' operates at 2100 turns per mile .

[Parazine]

Yes, PN Speedos from an Austin 10 are 2240 as well. I built a hybrid A type with a PN governor for my chummy (October 1927) to try and get the speedo reading correctly.

I haven't tested it yet.   The speedo drive in the gearbox self destructed last summer and I don't want to disturb the engine at this time......