Gearbox with a 30:1 reduction for my stepper

[satanicoo]

Hello guys,
First i really don't know if this is the correct forum, but this one sounds more fitted to my question, compared to linear/rotary motion.

The problem is quite simple, i need a 30:1 somewhat gear for my small step motor, it has a 3mm shaft.

For now, i would like a cheap one for tests, and on the future a good anti-backslash version for my small cnc creation.
Do you know any store that sells cheap gears/gearboxes for small motors?

I searched on ebay:
http://cgi.ebay.co.uk/12V-DC-300-RPM...d=p3911.c0.m14

And found several of those, i would just have to remove the motor.
The seller doesn't know what is the motor shaft diameter or the gear ratio of it, and doesn't comply in opening one to confirm them.

Do you guys have any idea that could help?

[Matt Adams]

I can ensure you that the ratio is simply too high to use with steppers and get any sort of reasonable performance from steppers unless you're planning on getting something less than 50 RPM out of of the motor and less than 2 RPM out of the gearbox.

The reason I say this is relatively straightforward - the loss in torque at speeds greater than 300 RPM begins to really tapper off. Anything above single digit ratios with stepper motors typically means you'll have more torque at a lower ratio because of the fall off.

What sort of torque and speed outputs are looking for? Many of us on the forum can help.

Matt

[satanicoo]

Hey there,

Searched a bit, and:
PLANETARY GEARBOX
this link gave a good help, i just have to keep digging on ebay.

The use i would give it is to use as a very slow rotating table. Hard to give more details, it's a "special" project.