The wheel is the 48mm diameter one of these.

Calculating with 17.500 rpm gives:

π*0.048*17500 = 2638.9 m/min

What I have measured is:

6.90*60 = 414.0 m/min

So what to do with above motor specification?

Well I'd first calculate the velocity and force at the wheel rim, getting

v = 42 m/s, F =0.03N

Hmm, 0.03N is not enough force for anything really (3gf)! Clearly some gearing

is needed (which of course it always is with a small motor as torque is limited

by motor volume)

So,

How to proceed?

1) Work out the worst case torque (at the wheel) needed for inclines, acceleration that you need.

2) Work out the max speed (at the wheel).

3) the product of those two gives the power you need for the motor, but you'll

need to add 50 to 100% to allow for transmission losses if you use gears/belts.

4) with the gearing and wheel radius you can then map that to motor specifications,

and thereby select an appropriate motor.

Lets say I have 200g load I want to drive up a 1-in-10 incline worst case - thats

0.2N at the wheel (weight force x 0.1). With two motors you share that, so

0.1N per wheel. Want max speed of 5m/s, then power needed is 0.5W per motor

(double for good measure as will use gears, 1W motors).

Say a 20mm radius wheel, so torque = 2mNm, angular velocity 250 rad/s (2500rpm).

You motor can only do 0.7mNm, so lets assume 5:1 reduction gearing, gives it

3.5mNm and a angular velocity of 350rad/s.

Its rare that you can avoid reduction gearing of some form in a small motor - your

system is overloading your motor completely I think, so the motor can't get

close to its max speed - you are likely overloading the windings as it struggles to

supply enough torque.