Detailed specs for "29:1 Metal Gearmotor 37Dx52L" item #1103

I’ve 3 questions on this motor 29:1 Metal Gearmotor 37Dx52L, item #1103

Question 1:
I need to know the Torque value at free run speed for this gearmotor (item 1103). In details: can a single 1103 gearmotor drive about 1,5Kg load without damage itself?

Question 2:
The gears inside the gearbox are metal-made, or there are some plastic-made gears?

Question 3:
Output shaft has the ball-bearing?


Answer 1:
The torque at free-run speed should be zero since it is measured with no load on the shaft. You can get a general idea of the torque at various other speeds by approximating a linear relationship between zero torque at full speed and the stall torque at stall. Also, the torque and speed will vary proportionally with the voltage.

I cannot determine if your load would be appropriate for these motors because the load you have given is a weight and is not a torque. We generally recommend not loading the motor with more than 30% of the stall torque.

Answer 2:
All the gears in our metal gearmotor are metal.

Answer 3:
There are no ball bearings on the output shafts of our metal gearmotors.

- Grant

Oh, really? That’s surprising. You might want to mention that the gearboxes are bushing-output-type on the product page, because ball bearings are almost an assumed standard for me…

From our experience, ball bearings are not a standard thing in motors of this type. Have you seen other companies use ball bearings in their motors, but not list them as a feature because it is considered standard? If so, could you provide some links to those motors?

- Grant

My point was that most of them specify that they uses bearings! Now it makes sense that you also don’t rate for axial load…

Hi, jwatte.

Can you elaborate on why ball bearings are an assumed standard for you? As far as I know, ball bearings are not common on the classes of motors we carry, so I would be interested to hear if your experience is very different.

- Ben

When I’ve looked at motors “in general,” gearboxes typically have a bearing output shaft. Those are likely from higher-cost sites than your motors – what I know of mechanical engineering, I’ve learned from motion control company white papers and such like.
When I’ve separately looked at hobby servos in the same price class as the motors you supply, they also are typically billed with ball bearings on the output spline. (Those systems are integrated motor + gearbox + encoder + driver, so one more piece than your motor + gearbox + encoder option.)
So, I wouldn’t expect the micro metal gearmotor, or the solarbotics plastic motor, to have an output bearing. (On the micro metal, I can even see that’s not the case :slight_smile:
But for a $40 inch-and-a-half motor rated at 60 Watts and up to 250 ozin of torque, my mind lept to that conclusion. It might have not been justified to do that, but that’s what it did, and that’s why I was surprised learning otherwise. (also, without the encoder, I guess it’s a $25 motor…)
The good news: This counts as this weeks “really, never assume anything” incident for me. I keep having to remind myself of this.

Also, ServoCity apparently has some $28 and $40 motors that have (dual) ball bearings.

I’m not sure if these are what you are talking about, but if so, I think they probably use cast gears instead of machined gears to reduce cost, which is why they can be a similar price to ours while including ball bearings.

- Ben

Excuse me… Jwatte said the correct thing: I mean the Axial Load. Can I apply 1,5Kg of load without damage the gears?

Unfortunately, as jwatte mentioned, we do not have that motor characterized for axial load, so I do not know what effect an axial load would have on the gears.

- Grant


Imho, bearing or not, the output shaft of a small DC motor should hardly ever be put under high axial load. However, creating a wheeled robot with bearing supported drive shafts and axles all over is not an easy or inexpensive task for a novice. Since almost all Pololu motors are shown with with wheels attached directly to the output shaft, I reckon it would be good idea to post some best-practices on the kind of load you can put on a simple robot platform (i.e. per motor/wheel attached).


It sounds like you might be talking more about radial loading on the motor shaft and not axial loading. I suspect that loading too much on the motor shaft in either radial or axial directions is not a good thing. Many times with smaller robots where the load is small, you can connect the wheel directly to the motor shaft. When the robot gets larger or the loads get larger, you do want to avoid having the loads directly on the motor shaft. As you point out though, this is often not an easy or inexpensive task for someone who does not have the experience. Most of the things we carry fall into the small robot category, but we will keep your suggestion in mind.

- Grant

@grant: You’re absolutely right - I was indeed referring to radial load. Just got carried away with the discussion on axial load :smiley: Thanks for the nice reply