I built an RC/Robot platform using 4 of these 1000rpm motors for a 4 wheel drive system. I am using a Radiolink controller and receiver and 2x Hobby Wing Quickrun 880 duel motor controllers, 1 for each side and a 3S battery pack. I did about 6 test runs, -5 min each and notice this motors get really hot. On my last test run I noticed 2 motors completely stopped running. I tried switching motor controllers, checking voltages, etc, they are just plain dead.
I double checked all my calculations and based on stall torque my max weight should be under 27 lbs and I am right at about 11 lbs which is way under the max for 4 of these motors. The motors themselves weight 2 lbs themselves combined, so the payload is only 9 lbs above the motors. So as you can imagine I am pretty frustrated I spend $130 bucks for these and to have them fail in under an hour.
Is there something I could have done wrong? I know stalling is a big deal and I think it only got stuck once or twice, but I never held down power for more than a second and rarely ever drove it full blast. My max output on the battery charged was 12.6v so I should be within tolerance. Basically similar to the wild thumber build that used 7.2v motors, so I thought this one with 12v motors would be way more beefy.
I’m sorry to hear you are having trouble with your motors. I am not sure how you did your max weight calculation, but the results you observed of the motors overheating and rapidly failing indicates the applied loads were beyond what they could tolerate. Just looking at the size of your wheels and hearing the robot is 11 pounds, 10:1 sounds way too low. A general rule of thumb for brushed DC motors operation is to keep continuously applied loads under around 25% of the stall torque, which keeps the average current under around 25% of the stall current. I suspect that your motors were drawing significantly more current than this; did you measure that?
If you want to use the 37D gearmotors in this application, you would probably need to go with higher gear ratios capable of delivering more torque at lower currents, though this will reduce the speed. Also, please note that your current chassis weight is approaching the upper limit of what is reasonable for radial loads on the motors, which is generally around 1-1.5 kgf. For heavier loads, we would recommend decoupling the weight of the chassis from the motor shafts.
Wow, I had no idea. I had ChatGPT do the calculations and I just reran them and now its saying the max weight of 7lbs. Guess I shouldn’t have trusted it. I was also reading the stall torque wrong, I was thinking it was saying 25% under stall, aka running it at 75%. Not running it 25%, 75% away from stall.
So are RC motors just way more torque? I was looking at some but a lot of them don’t list their torque ratings with is kind of aggravating, but I have seen so many of them that can tow a person on a skateboard or start to tow a pickup truck.
But if I wanted to stick with the 37D and shed a little weight, what would you recommend? 30:1 ratio?
Or what would be the next bump up for different motors? Should I look more into RC? Although RC would have to be geared down, so it wouldn’t work for my design.
ChatGPT is a language model that is essentially just guessing what you want to hear, so it is not a good tool for something like this.
“RC motors” is such a broad categorization that it’s hard to say anything specific about them, but if you want to compare our 37D gearmotors to the RC car motor from the video you posted, the order of magnitude price difference and the fact it is a brushless rather than brushed DC motor are indicators that these are just two different classes of motor.
Instead of just guessing at what motors you need, my recommendation is that you try to estimate and characterize the actual loads your application will exert on the motors. If you are not sure where to start with that, then reading this “Force and torque” blog post might be helpful. For a more advanced overview of the topic that is specific to four-wheel-drive robots chassis, you might look at this article: “The Art and Science of Selecting Robot Motors.”
Cool, I will check it out. ChatGPT has come a long way, its more than just language. I think I wasn’t specific enough when I asked my question a few months ago when I was planning the project. It was also version 3.5, not the new 4o model. Here is the results which is probably more accurate.
That answer is still fundamentally wrong in multiple ways. I strongly encourage you to be skeptical of any results you get from AI that you cannot judge the correctness of yourself.
Agreed, and also incredibly misleading. That is partly due to the “confidence” of the bot’s prose, especially given that the bot (if assumed to employ human reasoning) so completely misunderstands or misinterprets the question. What a travesty!
However, I’m glad to see this example, which I’ve saved, because it could serve as a basis for demonstrating to students how far these bots have to go. Or used as a homework question!
Ya, that is unfortunate, it seemed pretty convincing. I come from an IT / Game Design background and it gets python and C# pretty well. Usually just needs some minor tweaks or revisions. It saves me a lot of time on code that would take me hours it does in seconds. Physics I guess not so well, which is something I always struggled with.
