shaggy48

Is there a simple way to measure the torque from a servo? I'm curious about the servos that came with my radio. The owners manual says the servos will provide 72 oz of torque at 4.8 volts and 88 oz of torque a 6 volt. But I have no way of knowing what the actual torque really is. One of my models requires 80 oz of torque so I'm going to change to a 6 volt battery and "hope" that it works. But is there anyway to measure it? I"d like to load up the system and measure the torque of each servo. Anyone?

Shaggy

Lnewqban

The specified torque is measured in ounces of force, applied in a perpendicular direction to an arm of one inch from the shaft of the servo.

This relation remains constant for any combination of force and arm.

For example, the specs for a Futaba S3004 Standard Ball Bearing Servo read:

Speed: 0.23 sec/60° @ 4.8V
0.19 sec/60° @ 6.0V
Torque: 44 oz-in (3.2 kg-cm) at 4.8V
57 oz-in (4.1 kg-cm) at 6.0V

With 4.8 volts, the servo should be able to lift a max of 44 ounces of weight hanging from an arm of one inch, and 4.4 ounces from an arm of 10 inches.
Beyond that weight, the arm will move, but not at the claimed rotational speed, an dthe motor will be overloaded.

Rafael23cc

My Feedback: (6)

You will notice that the specified torque in most servos is the stall torque. Your 88oz servos at 6v might be too weak on your application. Since the specs are in-oz of torque, the best way to measure it, would be to attach a one-inch arm to the servo and then measure the torque with a fish scale or smiliar device.

Rafael

Rodney

Torque is not in ounces, it is in inch/ounces. For instance, a 30 inch/ounce torque could lift 1 ounce weight at the end of a 30 inch long arm or lift a 30 ounce weight on a 1 inch long arm (this is assuming the weight of the arm is zero of course). And, as mentioned above, that is the point where the servo would stall out which would cause a corresponding large jump in the current draw at that point.

dirtybird

My Feedback: (5)

I tested about 150 servos. Not many came anywhere near what their specifications claimed. One that did burned out quickly when it reached the specified torque. All of them heated up quickly and lost about 50% of their capability.
The tests were conducted in 2006 and I don't have any data after that time but if you are interested send a pm with a servo test request and I will send a copy of the servos curve if I tested it.

Red B.

Nope! Torque is force time lever, i.e., the unit should be inch*ounces, NOT inch/ounces. Outside the U.S the unit is N*m (Newton*meter).

Hibrass

My Feedback: (1)

Spoken like a mechanical engineer...

Ed

shaggy48

Thanks for all the responses. The servos I'm curious about is the
DS821.

Shaggy