Analogue Speedo for 7 1/4" loco

[martyn1936]

I am trying to make an analogue speedo for my class 1500 tank engine with the indicator built into a 1" pressure gauge housing. The electronics is all sorted but I cannot find a small meter to fit into the gauge housing. I am not fussed whether the meter is a volt meter or an ammeter as the outputs from the controller can support either.
At the moment I am having to look into the idea of using a servo motor driving via a miniature bowden cable into the back of the meter with the pointer attached to that. This way I could hide the servo motor elsewhere but it is not really the right solution.
I expect that someone has been done this before but I cannot find a small meter anywhere.
Any suggestions gratefully received.
Martyn

[mbrown]

Roy Amsbury described a very small speedometer for his 3.5"g Britannia. It was in the ME - if I remember correctly about 1965-1967 but I may be wrong about that. If I can find the reference I will let you know.

He used a rotating magnet and a pointer on a hairspring from a watch, as I recall.

Malcolm

[martyn1936]

Thank you Malcolm for the info. I think that I have exhausted the search for volt meters or ammeters, but the miniature stepper motor solution looks promising so I am going down that route at the moment, these are as cheap as chips (or cheaper these days) and are very small.
Martyn

[chris vine]

It looks as though you can get mini stepper motors down to 3.5 mm diameter by 5 mm long. Astounding!!
product.minebeamitsumi.com/en/product/category/rotary/steppingmotor/pm/Smalldiametertype.html

Chris.

[Deleted]

Jun 29, 2022 10:34:34 GMT chris vine said:

It looks as though you can get mini stepper motors down to 3.5 mm diameter by 5 mm long. Astounding!!
product.minebeamitsumi.com/en/product/category/rotary/steppingmotor/pm/Smalldiametertype.html

Chris.

wow... now that is impressive...

Pete