# Quick (And stupid) gear motor question

So here is my situation, i plan on building (https://www.instructables.com/id/Beginners-guide-to-building-Arduino-robots-with-Bl/) and i was about to order all the parts and i wondered, why there are so many types of gear motors! my current understanding is the higher "1st" digit (ex 1000:1)means the motor is more accurate and precise and slow. So does that mean one with a low number first (ex 10:1) would be faster? please tell me if i am wrong. So i would like a FAST gear motor for my robot, could anyone post me a link to a good fast gear motor.

Much appreciated!!!

5 years ago
If you are building
https://www.instructables.com/id/Beginners-guide-to-building-Arduino-robots-with-Bl/
and following the recipe closely, you actually have few choices for the gear motor.  That 'ible is based on a particular whatchacallit... chasis kit, linked here:
http://www.zagrosrobotics.com/shop/item.aspx?itemid=884
and only so many motors can fit on so specific thingy. I think that page gives you a choice of two gearmotors that can be added on.

Also that design in that 'ible looks to me like it is powering everything: the Arduino(r), the motor controller, the motors, all from the same 4xAA = 6V battery supply.

What I am saying here is that if you are following the recipe closely, then you actually have fewer choices than you think you have.

To answer the more general question of what do those gear ratio numbers, like for example 100:1, what do those mean?  That simply means the motor turns 100 revolutions for every 1 revolution of the output shaft, and that the torque at the output shaft is approximately 100 times greater than the torque at the motor shaft.  This is the old story of mechanical advantage;
http://en.wikipedia.org/wiki/Mechanical_advantage
i.e trading distance for force, or equivalently, trading speed for torque
http://en.wikipedia.org/wiki/Gear_ratio

I don't know if that makes much sense.  Basically the reason mechanical transmissions in gearmotors exist, is because electrical motors turn very fast, but with little torque, and what the mechanical load, the cart to be moved, or the weight to be lifted, or whatever, it wants large torque and low speed.

Anyway, I am going to humbly recommend you follow the recipe on this one.  I.e. use one of the two motors sold with, recommended for, that chassis. The bigger one had a stall current (1.6 A) that was a little outside the recommended limit (1.2 A) for that motor controller (the DRV8833), but it will probably won't melt it instantly, if you don't stall the motors too much.

broskiz (author)  Jack A Lopez5 years ago
Thank you VERY much for your help this was very infornitive and helped me make my purchase! I am going to buy the 100:1 gear motors that where recomended with the chassis. should i purchase the DRV8833 or is there a better dual motordriver for HP gear motors?
rickharris5 years ago
Your right the gear ratio shows how many turns the motor must do to make the output shaft turn once.

1000:1 means the motor has to turn 1000 times to get the output to turn once. As many small motors may turn 30,000 times a minute this isn't as slow as you might think.

Slowing the motor down also has the effect of increasing the torque(power) available at the output shaft - this can be useful.

I would go for a slowish motor myself at first because fast robots are hard to control. Then if i wanted it to go faster I would put larger wheels on it.