Heres one for the maths people QUESTION..............?

Question

This is a pure maths question:

I want to find out the gear reduction value for an electric motor motor which runs at 3500 r.p.m.( motor shaft diameter is .75mm)
I want to to power a vehicle that has 200mm wheels diameter and I want the vehicle to travel at no more than 6km per hour .

Please what is the math to work this one out.

Thats a motor speed of 3500rpm (.75mm motorshaft) gearbox reduction should be ??? This is the question what reduction should it be???to drive a 200mm diameter wheel on a vehicle so the vehicle travels at a maximum of 4km per hour

Any smart ones out there please can give me the answer or how do I work it out Iwas hopeless at maths at school

Thank you.

Answer 1

You mention maximum speeds of both 6 and 4 Kmph but I have worked figures for 4mph only.

4Kmph equals 4/60 Km per minute.

The wheel diameter is 200mm so the circumference is 200*pi mm.

In one revolution the vehicle will cover 200*pi /1000000 Km per min

So at 4 Km ph the wheels are turning at a rate of

(4/60) / (0.0002 * pi) = 106.1 rpm

So the reduction needs to bring 3500 revs down to 106

or 1 to 33 approx.

(Better check my figures as I'm prone to lose the odd decimal place at times.)

Answer 2

This is not a pure maths question - this is an applied maths question. In particular, this is an engineering question.

Answer 3

Probably better to ask it in the engineering section.

Answer 4

Even just reading the question boggled me!!