Pdf models 3-6V motors

[Phil.P]

Can anybody comment on what batteries they use with these, please?

I am wondering if a 7.2V NiMH pack, would be too much 'over voltage', and ridiculously fast?

Thanks,
Phil.P

[Peter Butler]

Phil, my only helpful comment would be to dump the 6v motor and replace with a 12v, which is what I do to all PDF and Boot Lane kits.

[Phil.P]

Unfortunately it is not my model, so I have to supply a solution to what the customer has.

Phil.P

[GTB]

I am wondering if a 7.2V NiMH pack, would be too much 'over voltage', and ridiculously fast?

Motor speed is more or less a linear function of voltage in the dc motors we use. So the speed of the model at 7.2V will be about 1.2 times the speed at 6V.

The voltage rating of a small dc motor is fairly nominal, but the cheaper they are, the shorter the design life. The effect of higher voltage on motor life isn't linear and the life reduces much faster once the design voltage is exceeded. Either the brush gear wears out or if the voltage is high enough the armature windings burn out.

That's why you fit a speed control of some sort to electrically powered models, so a loco motor doesn't have to run flat strap all the time.

The main reason to fit a lower voltage battery to a model with an ESC is to limit the absolute top speed, especially if it will be operated regularly by small children.......... ( and some adults... )

The other advantage of a lower voltage battery is that it takes up less room.

Graeme

[ge_rik]

My instinct would be to go for a 4.8v or possibly a 6v pack - as the motor is rated at 3 - 6v.
Most of my locos use LGB motor blocks which are rated as 24v, but I power them with 11.1v li-ion packs - less than half their maximum rating. They run quite happily (as evidenced by my videos), so I'd be inclined to go for a 4.8v (or even a 3.6v) pack.

You could always experiment by making up your own nimh packs.

Rik

[Phil.P]

All valid points..

The problem with lower voltages, but a bigger loco, is that the smaller motors are not so good for starting current, and noise (electrical, rather than mechanical).

A higher voltage supply, means I can supply a RCT-MR603, which is rated to 3 amps.
The RCT-MR601, is only rated to 1.2 amps, and is a little more susceptible to motor-noise, as well.

Phil.P