Can someone tell me how I choose an electric motor, please?

 Hi Everybody,

I've been away for a while, partly because my pc would not let me post to Instructables, and partly through illness. I will get to my projects very shortly and complete them.

I need to buy an electric motor for a friends current project, but I don't know how to choose one wisely.

Essentially it is a Ferris Wheel for Teddies, yes, really! We indulge our kids!

We have worked out the frame weighs about 6 kilos and the contents will weigh about 30 kilos.

The wheel will not spin at the centre, but at the edge, like a real Ferris wheel.

So I think I will need a slow motor with high torque. Each revoloution should take about one hour
(some of the kids are disabled and physically slow, plus if it goes slow enough they'll fall asleep through boredom! Only kidding! I really do need this slow)

Additionally it would be great if the motor could be low voltage.

So any tips on how I would achieve this, please?

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You could choose a high torque motor that has gears that slow the motion of the axl. I have such a device, but in small size.

Alternatively, you can use a high torque fast motor, and then using a PIC, or an Arduino's chip, you could use PWM through a high power transistor to controll the working period of the motor to slow it down.

mattyw217 years ago
That link doesn't work, and I'm looking for a ferris wheel motor too. In my case, it's a replacement for a 7" outdoor Christmas display. Could you resend?
A spit roaster motor would be ideal I should think. Fair amount of torque, already geared too. The ones I've looked at just now are 3..5RPM. WIth a 60:1

What diameter is your wheel ? 
kevinhannan (author)  steveastrouk8 years ago
 Sorry I've been away for a while - family demands and all that kind of thing - really sorry guys.

My wheel is 4 feet inside diameter and 4' 3" OD - cheers steveastrouk ;-)
kevinhannan (author) 8 years ago
 Thank you everybody, lemonie, steveastrouk, zengineer, and Re-design,

I'd choose you all as best answer - I'm going to get the motor in a few days and see what I can do.

I now have a small matter of getting/making two 4 foot hoops..!

I'm hoping to publish a few 'ibles after the New Year. There's just too much going on right now getting ready for winter.

Kind regards
Re-design8 years ago
Spinning at one rpm...  you could use a stepper motor and controller.  They run on 5, 12, 18, 24 or other voltages depending on what you get.  If the load is balanced well then it won't take much of a motor to move the wheel.  A good sized motor out of a good sized printer ought to do it. 

If you're good with gearing or pulleys and belts, just about any motor geared down to 1 rpm should do it.  The mechanical advantage thru the gearing is going to be huge unless you end up introducing too much friction in the gear train. 
kevinhannan (author)  Re-design8 years ago
 I can get any number of printer motors: but I would be surprised if they were so over-engineered to provide torque to shift that weight - however good the bearings are.

How would I provide the pulse to step the motor, and no, I have not done gears before, so I'm really quite eager to learn.

Thanks for the reply, really appreciated. You've given me a few hints as to my next search via the 'net! Cheers, Re-Design!
You'll be surprised at how much torque stepper motors do have.
lemonie8 years ago
You wouldn't need a lot of torque to drive the wheel on it's circumference, because you'd have a lot of gearing there. What about a car-window motor (scrap-yard) 12V and not that weedy?

kevinhannan (author)  lemonie8 years ago
 That's an excellent idea, Lemonie.

Thank you! 

I'll be off to the local scrap yard on pay day...I need to look at gearing though.

Windows don't move that fast, see what it's got on it? And as I said before, if you're driving on the outer rim of the wheel there's a gearing down in that.

Sounds like a job for some kind of rotisserie motor.
Check out this
They even have a battery operated model!
Use at your own risk....

Word of caution:definitely have adult supervision when you have the thing working.
Remember that machines are merciless, especially high torque ones.