I'm busy learning a bit of electronics, and trying to create an analog gauge replica of a Cessna 172 aircraft altimeter.
I'm using an Arduino Mega 2560 to fiddle with, and thinking of using a stepper motor to drive the two hands on the gauge.
The tricky part of this is, driving two hands, sitting on the same axle on the gauge using one stepper motor. So I'm trying to figure out a way how I can achieve this.
I have an idea to have two shafts inside of each other, an inner shaft driving the one hand, and another shaft around the inner shaft for the other hand. The inner shaft is driven directly by the servo motor, and a few gears attached to it, should transfer the rotation at a ratio of 1:10 (I think), to the outer shaft.
So with each revolution of the long hand, the shorter hand needs to revolve 1/10th of a full rotation.
The question is, where can I buy these kind of shafts that fit snuggly into each other, that will allow me to fit gears to them? Are there kits I can buy for this sort of implementation?