I’m trying to use either the 994 or 995 gearmotor to move a gear which requires a torque of 53 oz in. Both motors are spec’d above that: 70 and 60 oz in respectively. After testing both motors, the most torque they seem to be able to generate is about 25 - 32 oz in. I’m using 6V and the stall current is about 1.8 A, which is what is specified. The motors won’t be running continuously, so I can crank up the voltage a little, but I don’t want them to burn out, and even at 8V they’re not reaching 40 oz in. I’d expect a +/-15% variation in torque, but 50% seems a bit too much. Is there any reason the generated torque is only about half of the spec?
If you run your motors without a load, what RPM do you get? How are you measuring the torque of the motors, and what are you using for your power supply? Do you have any intermediate electronics between your motor and your power supply?
I’m getting around 96 rpm without a load. To measure torque, I’ve put the motor on the side so the shaft is horizontal, parallel to the ground. I’ve got a printed shaft that is .361" away from the motor shaft that I can grab onto. I’ve tried both adding a weight to the printed shaft and running it, or running it first then putting the weight on as it’s running and seeing at what weight it will stall. I’ve also got a torque gauge, and have used it to hold onto the printed shaft as it’s running and seeing what torque it will stall at. I don’t have any electronics between the motor and my power supply. It’s just two leads that are soldered onto the motor. The power supply has variable voltage and current, and as I mentioned, the stall current is about 1.8 A.
Thanks for your help.
I was initially wondering if we might have shipped you the wrong gear ratio by mistake, but your description of the speed and stall current makes it sound like you have the right motor. We just tested a 298:1 micro metal gearmotor HP here using a torque meter to stall the motor at 6 V and measured between 68 and 83 oz-in. This is consistent with measurements we have made in the past.
Is it possible that your test isn’t accurately measuring the torque? Can you post some pictures of your setup and provide a more detailed description of what you’re doing (e.g. diameter of the adapter, the weight you are lifting, etc)? How confident are you in your power supply’s ability to deliver as much power as the motor is trying to draw? One thing to note is that the stall torque of the motor will go down as it heats up, so please make sure you give your motor time to cool off between your tests.