Stepper motor torque ratings (mNm)

[Legion]

How come all the stepper motor datasheets have an "extra" meter unit in their torque ratings? Shouldn't it just be Nm, not mNm?
example: http://www.digikey.ca/product-detail/en/34KM-K206-99W/P14332-ND/2417056

Second if a motor has a holding torque of 6700mNm does that mean it could hold ~1500lbs on a 1 meter long arm?

[Simon]

maybe they mean milliNm, how big are the motors ?

[Legion]

It's that one in the digikey link in the original post. I hope it's not milliNm. That makes what would have been an impressive 1500lbs a lame 1.5lbs. For $300...

[liquibyte]

6700 millinewtons meter = 4.9416664 foot pound or 948.7999462626001 ounce inch.

I've always thought the datasheets on these things were lacking in real world information.

Edit: I don't think they make a stepper that can do 1500 ft/lb, for that you'd probably have to use servos and gears. (2033726.9224978322 mNm  ).  OMHT34-490 NEMA 34 @ 1845 oz/in $545 http://www.omega.com/pptst/OMHT_SERIES.html

[Simon]

It's that one in the digikey link in the original post. I hope it's not milliNm. That makes what would have been an impressive 1500lbs a lame 1.5lbs. For $300...

what do you want from a mere 2 amps or less ?

[Legion]

what do you want from a mere 2 amps or less ?

I don't mind if it needs more current. I'm disappointed because it's the highest torque stepper digikey sells and 1.5lbs isn't that much, and also because to get even that much torque is prohibitively expensive (~$300). I guess it's just a matter of a stepper not being the right tool for the job.

[Simon]

might be the case of the wrong supplier. Find someone that actually specializes in stepper motors. Gee i have something like that on my desk I pulled from an old printer that cost a few 10's of pounds. Unless there is something special about that one that is not being appreciated.

[Legion]

I'm toying with the idea of adding a motor to a misting system so that it lifts the lights out of the way before it starts spraying. The motor would turn a pulley which lifts an arm connected to the lights to move them out of the way. There are two lights and I'd guesstimate that they weigh about 3lbs each.

[Simon]

I'm toying with the idea of adding a motor to a misting system so that it lifts the lights out of the way before it starts spraying. The motor would turn a pulley which lifts an arm connected to the lights to move them out of the way. There are two lights and I'd guesstimate that they weigh about 3lbs each.

surely there is a way to do that with a brushed motor ? and stop switches ?

[Legion]

I'm toying with the idea of adding a motor to a misting system so that it lifts the lights out of the way before it starts spraying. The motor would turn a pulley which lifts an arm connected to the lights to move them out of the way. There are two lights and I'd guesstimate that they weigh about 3lbs each.

surely there is a way to do that with a brushed motor ? and stop switches ?

This is my first foray into motors so I'm not sure. The lights are arranged as in the image below. They hang from their power wires which is why I thought if I had a swing arm attached to a motor it could intersect the hanging wires where they meet the light fixture and rotate 90 degrees towards the ceiling, lifting the lights by their wires as they go.

[Simon]

put a pulley on the pivot point of the arm and connect the motor to it gearing is down. Use a brushed motor that is cheap and powerful or even a brush-less (not saepper) and the arm can hit a switch to cut the motor out when it gets to the end.

Otherwise a servo mechanism can do this, it's a motor geared down driving an arm that also turns a potentiometer so that you have position feedback.