best motor for my project.

Im building a arduino robot and ive been looking around for a bit for a good motor and wheel for my project. The wheel im looking for needs to be able to pull about 25 pounds up a 20 degree or so incline. I mainly look on ebay and ive been searching stuff like "arduino wheel" and "wheel and motor" but i mostly end up with little motors that look like they would have a difficult time pulling more then a gram. Or motors with no wheels. Im new to the arduino robot building, and as such im learning along the way.

25 pounds per wheel or total? How many driven wheels? What sort of diameter wheel? How fast do you want to be able to move?

If you're searching for a robot wheel, try "robot wheel", not "arduino wheel".

But first you need some numbers to those questions so we can figure out the torque and power.

25 pounds on total, which will be 2 motorized wheels and 1 caster. It needs to be able to move at about walking speed so 7 miles per hour should be good. However as low as 3 would be acceptable. The diameter needs to be about 3 inches. Ill add suspension if needed. I will continue searching.

Well what ive found seems to be good i found this.

Don’t focus on “Arduino” wheel or anything like that.

You already know the wheel will not be powered by the Arduino. All the Arduino will be doing is providing signals to transistors or relays. There is nothing Arduino specific about what goes on the other side of those ‘switches’.

INTP: Don't focus on "Arduino" wheel or anything like that.

You already know the wheel will not be powered by the Arduino. All the Arduino will be doing is providing signals to transistors or relays. There is nothing Arduino specific about what goes on the other side of those 'switches'.

i know im just looking for motors that come with the wheels. Im new to working with motors and wheels and i dont know the correct speaifications i shouls be looking for. I am considering using 4 wheels instead 2 but doing such would cost more money and also it would dramatically decrease the Turing radius , and im gonna need thos thing to turn on a dime.

brenden_nerd_: 25 pounds on total, which will be 2 motorized wheels and 1 caster. It needs to be able to move at about walking speed so 7 miles per hour should be good. However as low as 3 would be acceptable. The diameter needs to be about 3 inches. Ill add suspension if needed. I will continue searching.

Right, first things first, SI units everywhere.

So that's a mass of 11.4kg, weight of 111N, speed 3.1m/s, wheel radius 0.0375m

sin(20) = 0.34, so component of weight along the slope = 0.34 x 111 = 38N, so 19N per tyre tangential force.

We have radius 0.0375 so torque per wheel = 0.0375 x 19 = 0.7Nm

angular velocity = speed/radius = 3.1 / 0.0375 = 83 rad/s (roughly 800 rpm)

Right in the real world we'll need gears and there will be friction. So lets call our torque requirement 1.2Nm per wheel to be on the safe side. Power per motor is now easy to calculate, angular velocity x torque = 83 x 1.2 = 100W (roughly, per motor)

Lets sanity check that - we are raising a mass of 11kg at about 1.1m/s, which needs 120W not including losses, ie 60W per motor. Allowing for losses 100W motors sound about right.

Most motors of that class will run at 2400 to 4000rpm, so lets say 4:1 reduction gearing 3200rpm and 0.3Nm as our motor specs.

It will probably mean 24V 4A is the sort of winding rating you are looking for.

Well what ive found seems to be good i found this http://www.ebay.com/itm/160857177259

Well no, frankly its completely hopeless for your purposes.

This might be more like it: http://www.ebay.com/itm/Electric-Scooter-24V-100W-100-Watt-Engine-Motor-Power-Generator-Razor-H-ST00-/380854140911?hash=item58acacffef:g:6XUAAOxyGwNTES1u

But lastly lets think a little more about the specs. You probably don't want or expect full speed operation up that 20 degree incline, and most of the time you won't need that full torque. So in reality its probably OK to down-rate that torque specification to 0.4Nm continuous, 1.2Nm peak, which would allow 35W motors or so, and 12V is then a reasonable supply voltage.

This motor doesn't seem to have a current or power rating, but the 800rpm is good and the size suggests it might be OK with 30W: http://www.ebay.com/itm/37mm-12V-DC-800RPM-Replacement-Torque-Gear-Box-Motor-New-/330795268239?hash=item4d04ef388f:g:~GEAAOSwQupXUT9A

And finally we can calculate the acceleration with the ~30W motors driven normally:

mass 11.4kg, wheel torque 0.3Nm x 2, so tangential force = 8N per wheel, 16N in total,
acceleration = force/mass = 16/11.4 = 1.4m/s/s, or top speed in 2.2s

Note that the 20 degree slope will mean overdriving the motors quite hard, so they will risk
burning out if attempted for long time - the only solutions are bigger motors or selectable gear
ratios (ie fancy gear boxes).

Wow thanks markT! Ok now i just need to find a wheel to fit on that motor. This is great!

https://en.wikipedia.org/wiki/Brushed_DC_electric_motor#Torque_and_speed_of_a_DC_motor https://en.wikipedia.org/wiki/Classical_mechanics

Oh thanks. I was able to find info on it already. Thank you everyone!