Small motor needed (toy motor size)

I need a motor about the size of a toy motor, which is able to run 5000 hours or more at 5000 RPM. I would expect that would be easy, since there's so little current and the brush contact area is so small a diameter, wear should be a whole lot less than big motors. Sure such motors have less space for brushes, but that should be more than compensated by the small diameter of the brush contact area.

Anyway, I need one that can run 5000 hours. So far I only found a few which give info on how long they last, and it is around 500 hours.

Anyone know where I'd get such a motor?

The ideal size (other similar sizes considered) is 20.4 mm (.803 inches) in diameter, 25mm (.988 in.) long body, 15.4 mm (.606 in.) across flats.

Brushless would also be an option of course.

I'd like to find one that is fairly cheap, but I'm willing to pay more for a good long life and reliable motor. This is for my 3D printer project, and I want it cheap enough to be affordable to the very poor. Ideally under a dollar in quantity.

And, of course yet another option is to make the thing ourselves. In that case, ideas on easier to produce designs would be nice. 'Course, regular toy motors don't look to difficult, but then if we are going to produce one, brushless might be a good idea.

Tony

I'm afraid I can't help you, but I'm curious at to what the motor is for?

The 3D printer I'm making.

Tony

I got that, I meant what job is it doing in your design? If its for cooling, pc fans are cheap,reliable and come with blades already, otherwise I was just curious as to how you were eking out useful torque from them.

They do everything in my design. The torque comes from gears. Not huge torque, but I think it should do the job.

Tony

Ah fair enough, I hadn't seen suitable gears sold without a motor attached, so I hadn't made the connection. When I've used small motors, regardless of price, the lifespan is hugely variable. It might be cheaper overall to use the absolute cheapest you can get, and make the design so they can be replaced easily. Also, lifespan is dramatically increased by not running at their maximum speed. Just suggestions, but they might help.

Higher price rarely means quality, usually it just means rip off.

Maybe things like burrs on the commutator (the spinning part that the brushes contact) and the gap between the copper with a sharp edge on it, is what causes the inconsistent lifespan.

Tony

If you look at these two pictures you can see the difference between the cheapest type of motors and a slightly more expensive one.

The first has plastic bearings and thin strips for the brushes.
[objects.reprap.org]

The second has bronze bearings and the brushes are solid blocks of metal.

[objects.reprap.org]

Moving up the scale you get spring loaded carbon brushes and a ring of varistors around the commutator. These suppress the sparks giving less RFI and better life.

edit: removed img tags as they don't work for some reason?

Edited 2 time(s). Last edit at 03/23/2010 08:53AM by nophead.

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[www.hydraraptor.blogspot.com]

Thanks. Actually I was just taking apart motors, and oddly enough, I found out the motor I ordered has copper impregnated graphite brushes.

Copper impregnated graphite looks a lot like copper, it is hard to know for sure, but it scratches easily, and looks just a little different than copper. Darker at some angles and lighter at other angles.

Any idea how long this type of motor typically lasts?

Quote

Moving up the scale you get spring loaded carbon brushes and a ring of varistors around the commutator. These suppress the sparks giving less RFI and better life.

Sounds interesting. Do you think anyone does that on motors of this size?

Tony

Tony,

I haven't made a study of it, but here are some brushless motors, just so you can see what is available:
[hobbyking.com]
(Hobby king is in Hong Kong so has cheap shipping)

Maybe also worth searching:
[www.towerhobbies.com]

You can use the hobbyking site to see what you might be able to get in large boxes from a supplier on alibaba.

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What's your machine look like? Will you be putting it up in the wiki?

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-Sebastien, RepRap.org library gnome.

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