Motors petering out?

We are running a pitching machine style setup for or robot. Using the regular 393 motors with turbo gears. All of a sudden, they cease to run… They don’t feel that hot. Check with a multi meter we have a steady 7 volts. Any ideas?

Do your motors return to normal operation if you don’t use them for 10 minutes or so?

What you are describing sounds like they might be overheating the motor internal PTCs and that can happen without the motors feeling hot on the outside, at least at first. In other words, it can take a while for the heat inside a motor to get conducted to the casing.

Does this happen to the motors when lose? It sound like the PTC’s are tripping for sure.

I hate to say it but… Try reducing friction? Check dem shafts, bearings etc

The community could better help you if we had more detail. How many motors? Single or double flywheel? I suspect if your running turbo gears, your not getting enough torque, and the PTCs are tripping. Let us know so we can better advice you.

We are having a similar problem. After running and shooting for about 30-50 seconds, they slow all the way down and start twitching. To me, it seems like some kind of breaker issue but I don’t know if it is our expander or the internal motor breakers causing it. Our flywheel setup is built very well (in my opinion) in that we were very careful to use brand new shafts etc., but we did just increase the ratio to a 28:1 rather than a 23:1 with 4 inch wheels.

Can I ask how many motors you are using? Whether your flywheel is double or single? What type of motors are you using?

Yes. we are using 4 motors, horizontal double flywheel with a total gearing of 28.8 : 1. For the majority of the year so far, we’ve had a 23:1 gearing which we had almost no problems with but wanted to see if we could get a faster turnaround shot time for full court shooting. We are probably going to try a 25.6 : 1 because we are pretty sure out motor breakers are tripping. Our wheels are a lot heavier than most.

You could always try using 2 motors instead of one. To do this, all you need to do is attatch a metal gear to each of the motors and put one in the middle. The middle will be your output gear while the 2 motors act as our input.

I know this is an older post, but for any future vex users, our team was seeing this same problem and it turns out it was the vex cortex that was tripping it’s PTC sensors.

The tell-tale sign was the motors “petering” after some seconds of operation but did not warm when touched. All four motors were connected to the 1st group of motor pins on the cortex: pins (2-5)
In a nutshell the cortex has two PTC (thermal fuses) dedicated for the motor pins. One is for pins 1-5, the other for pins 6-10. You should spread your load as evenly possible (similar to buying houses in monopoly).

Simply balancing them out between the two cortex PTC groups fixed the issue. i.e. 2 in pins 2-5, the other two in pins 6-9.