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[on:]

Hi guys,
I bought one of these: http://www.pololu.com/catalog/product/1107
but, it doesn't have enough power/torque for by project.
I need a motor that can turn about 100 lbs. at around 4-6 rpms under load.
Does anyone have any suggestions on where I can buy a motor that can do this without breaking the bank?

[Reply #1 on:]

Perhaps this site might have what you are looking for.  They are a surplus store that specializes in various sized motors, pumps, pneumatics, etc...

[Reply #2 on:]

Might look here too to see if anything meets your torque/budget needs
http://www.mpja.com/DC-Motors/products/100/

[Reply #3 on:]

thx for the suggestions guys.

[Reply #4 on:]

While looking at the site of another surplus store I often patronize, I found this 12 V_DC car seat motor on sale for $12.50.  They don't mention a torque rating, but given it's intended use and the fact that you'll have to down gear anyway (the shaft goes 190 RPM), it should be able to move over 100 lbs easily.

[Reply #5 on:]

I need a motor that can turn about 100 lbs. at around 4-6 rpms under load.

100lbs is meaningless in this context - for a motor you need torque (turning force) measured in Nm (or sometimes ft-lbs).
Torque requirement is easy to assess for a winch since you multiply the pull-force by the radius of the cable-drum to get the torque on the shaft.

For a vehicle its harder to know the torque without knowing more about transmission, terrain, slope, tyres...

For simply turning a heavy wheel on a bearing you need to know friction losses, but you may need a lot of torque to accelerate the wheel to speed fast enough (and then braking torque to stop it).  Torque here is angular-acceleration times moment-of-inertia (plus any friction losses).  Moment of inertia is proportional to mass and proportional to radius _squared_.

[ You meant RPM - its already plural "revolutions per minute" ]