strong motor low voltage

[nate4548]

Hi there everyone,

anyone know of a compact low voltage(6-12 volt) electronic motor running at about 25-40 rpm that has power I'd say about 2-3 pounds of torque?

ps. when I say compact I mean kinda small, max. 3 in long and 2-2.5 in wide, of course smaller than that would be better.

I want to drill a hole in the shaft so... the shaft should be at least a quarter of an inch in diameter.

Nate,

edit: it's gotta be reversable.

 

[dknguyen]

2-3 lbs is not a proper torque specification. I'd have to say to take a look at hobby RC outrunners and gearboxes that fit on them. But I don't think it will fall into your size specifications as the gearbox needs too high a reduction to be small (or easy to find).

At those torques and speeds...you might as well just use a hand drill and your trusty old arm. Or get a small drill press for $50, but it will be spinning faster. What is this for?

BTW, it's an electric motor. Not electronic- that's all the circuit board stuff.

 

[nate4548]

sorry if I'm unclear but I need this motor to wind up something that weighs 2-3 pounds.
hope that helps.

Nate,

 

[dknguyen]

Oh, I misread it as you wanted to use the motor as a drill when you said you wanted a motor with a large shaft to drill a hole into...

Well...an RC hobby outrunner with a gearbox is probably your best bet. It may be a bit larger than you want though.

If you use a wheel on the shaft to wind something with, you need more torque (due to the lever effect). Torque is normally a specification of force-length (like Newton-cm/meters or pounds-inches/foot). For a given torque, as the length of the lever arm (or wheel radius) gets longer the applied force at the end (or edge) decreases. But larger wheels also move (or wind) more for a particular RPM since the edge travels farther in one rotation.

So your specifications of RPM and force required isn't really enough information. YOu need to know the linear speed of you want for winding and the weight of the object. From there you can figure out the wheel diameter, motor torque, and motor RPM that you need to achieve. And there is more than one combination of these 3 factors that will achieve the same linear speed and force. If you don't have enough torque, make the wheel smaller (which will slow down the winding speed but increase force), so you can compensate by making the motor spin faster. If you don't have enough speed you can make the wheel larger (but this reduces force, but you don't want to make the wheel so large that the motor does not have enough torque to produce the force at the edge of the wheel to actually spin as fast as you wanted it to). It's a fine balance...increasing speed decreases torque, but after a certain point the motor does not have enough torque to actually go that fast anymore and it actually starts slowing down again.

It is very difficult for motors to spin slowly and produce a lot of torque without a large (and expensive hard to find) gearbox. I suggest that instead, you reduce your wheel size a LOT (like almost bare shaft diameter if possible) to minimize the lever effect, allowing your motor to produce maximimum force on the edge of the shaft with it's torque. THe motor will be spinning fast without the gearbox, but the linear travel per rotation is small because the leverl length/winch diameter is small so the high rotational speed should help compensate for the smaller linear travel per rotation.

But good motor specs are hard to come by unless you're a giant company making a mass order from a company that specifically builds motors...so trial and error with the RC outrunners + gearbox (if you can find one to fit) is probably best.

 

[nate4548]

I checked out the rc outrunners, they are nice but not what I was looking for.
I'm looking for a motor that needs no gearbox it just has to turn at 25-40 rounds a minute.

I'm building an automatic window-shade(I have all the electronic specs figured out) but now I need to find the right motor.
(you ever see the conveyor belts at the supermarket? thats the speed I need It to run,
there isn't going to be a lot of added resistance as the motor roles up the window shade, it's mainly the pole on the top that weighs.

you know of any other motor that you can recommend?

Nate,

 

[dknguyen]

No motor spins that slowly while producing the required torque without a gearbox. Even things as massive as power plant generators spin much faster.

The conveyor motors at super markets are using gearboxes (or some kind of reduction) and are much larger than your size requirements.

Maybe try looking a stepper motor then that produces the most torque when spinning slowly. But I still suspect it won't produce the torque you need.

 

[nate4548]

thanks dknguyen for your help so far,

have a look at this one,

Gear Motor 3: Right Angle Shaft

it is compact, and offers 50 ounce-in of torque and turns 38rpm. Now Maybe it has a gearbox inside.
but that's kind of what I'm looking for. except this one's shaft is too small for me.
I am looking for something with a shaft thats a little bit longer and wider.

Nate,

 

[dknguyen]

THe whole white part on that is the gearbox. THe tiny little silver metallic part is the actual motor.

I was looking back to one of the places I used to buy motors from, and they seem to have increased the number of smaller motors that they provide. Here is a big list of motors that might help:
**broken link removed**

From the list, I recommend one of these:
**broken link removed**
**broken link removed**

You can reduce the voltage to reduce the speed of the motor to what you require (within limits...obviously running at something like 5% of rated voltage isn't going to produce much speed or torque to do anything.