Motor Torque (Starting vs Rated)
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Posted by: bikeboy85 ® 10/21/2007, 01:27:49 Author Profile eMail author Edit

I am looking for a DC motor (cheap option, not sure where to look) for a lifting application. Motor is connected to a pulley which will lift a platform via steel cables. The max load to be lifted is 300 lbs Average Power = .11 HP so .25HP will suffice Average Torque = 70 lb-in Desired RPM is 100. So a DC gear motor will do? While looking for motors, I'm getting confused between the terms Starting vs Rated Torque. Whats the difference? Also, any suggestions where to look for cheap motors that can suit my need, and RPM? This is for a student design project. Thanks. Bike Boy Removed - Modified by Administrator at Sun, Oct 21, 2007, 08:35:14

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Re: Motor Torque (Starting vs Rated)
Re: Motor Torque (Starting vs Rated) -- bikeboy85	Post Reply	Top of thread	Forum

Posted by: zekeman ® 10/22/2007, 14:24:11 Author Profile eMail author Edit

Rated torque is the maximum continuous torque available at the design speed that allows the motor to do the work without overheating. Starting torque is the torque the motor delivers at zero speed. i.e. startup. It is also called the stall torque. For a DC motor it is usually at least twice the rated torque, but since the coerresponding armature current is much higher than the rated current, the motor cannot sustain this torque without overheating.Frequent startups may cause overheating as well.

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Re: Motor Torque (Starting vs Rated)
Re: Motor Torque (Starting vs Rated) -- bikeboy85	Post Reply	Top of thread	Forum

Posted by: randykimball ® 10/22/2007, 12:35:14 Author Profile eMail author Edit

Most areas large enough to have an engineering school also have a motor rewind or rebuild shop in the area. I would look-up and contact such a shop and STOP BY (not on the phone) to voice your situation. You may come away with a great bargin or a free motor. At the very least, if you are polite and warm about it, you should come away with good advice and a good knowledge resource. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

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Re: Motor Torque (Starting vs Rated)
Re: Motor Torque (Starting vs Rated) -- bikeboy85	Post Reply	Top of thread	Forum

Posted by: jboggs ® 10/22/2007, 12:08:57 Author Profile eMail author Edit

The torque required to accelerate a mass from rest to operational speed is generally more than that required to maintain that speed and do the work required. Motors generate heat in relation to the torque they are producing, and that heat can be damaging. Thus motors are often designed to withstand the higher torque loads of accleration (starting torque) for limited periods of time. The "rated torque" is the torque the motor can produce at the rated speed on a continuous basis without overheating or damaging itself.

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