Dc motor

I'm very new to this and I'm only on my second bot however I need some questions answering. Thank you in advance.

1. Can I mod a dc motor (6v - 15v) so it will will respond like a servo e.g if I want it to go faster or slower? Or do I need a speed controller? Also if I can mod it how would I connect it to my transmitter?

As far as I know, if you were to 'mod' a motor to control its speed, you'd basically be making a speed controller, which work by (as far as I know) sending pulses of current to the motor with varying widths (Pulse Width Modulator) in order to change the 'average' DC voltage. I guess you could use some kind of transistor/amplifier circuit if you just wanted to control the voltage over the motor (which is proportional to the force given with a constant magnetic field), but I have no idea how well that would work. I'm new to roboteering too, but I do study this sort of thing at Uni.

So TL;DR: no? I don't think so, at least not conveniently.

I'd go with a speed controller, they are cheap these days and a far simpler solution than making your own. You'd connect the ESC to a receiver which talks to the transmitter so it's all nice and simple and no custom stuff needed.

Most modern motor controllers work by rapidly switching the motor on and off. If you have a 12v supply and you turn it on for 1 second then off for 2 and repeat it'll give the same speed as running it at 4V. Now replace seconds with a much much faster time scale. It's a nice and efficient system with minimal losses and can handle high current inexpensively.

Many thanks for your replys. Its been a much needed help. I've decided to use a speed controller just for its simplicity. Thanks again!