On Tue, 14 Jul 1998, Lee Jones wrote:

> > Yes, but they are not intended to be continuously rolling. They
> > go to a certain angular position depending on the PPM that they
> > receive on the signal line.
>
> With the standard control circuit board installed, that's true.
> (Actually, the position depends on pulse width, nominally 1.0
> to 2.0 milliseconds for end to end travel; repetition is 20-50
> pulses per second.  I assume PPM was a typo for PWM.)
>

As I recall, it is actually the gap between pulses that determines
position, and the pulses have constant width, hence Pulse Position
Modulation. I could be wrong. I thought that PPM was used instead of PWM
because it was easier to multiplex PPM to get the multiple channels
needed for RC.

> But there's no reason why you can't take a servo, ditch the
> factory control board, bring out the motor leads (using the
> existing wires), and run it as a geared motor.  Think of it
> as a kit of motor, gears, bearings, output shaft, and case.
> Even if you have the gears, getting all the shafts with just
> the right spacing so that the gears mesh with the right
> clearance is time consuming.
>

I see your point. However, you would still need some type of hardware to
connect the servo to the wheels. This could end up being just as
difficult as just connecting some other type of motor to the wheels. It
really depends on what one finds. The gear on the end of the servo (to
which the control horn attaches) is very small.

> You'd have to create your own feadback mechanism though.
>
>
> Tamiya also makes a couple kits of motor, gears, and frame.
> You assemble them with various pieces to get different ratios.
> They have both a spur gear set and a planetary gear set (with
> higher reduction ratio).

This, would of course, be the easiest to use, I think. But, then again,
cost is a big issue here.

>                                                 Lee Jones
>