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This sounds an awful lot like our first year :o
This is usually because you are putting too much strain on the motors. You may want to consider using a different design for the arm or gearing for more torque.
Some helpful links:
A common problem for newcomers is forgetting to use a bearing flat on the axle to the motor. This significantly reduces the amount of friction the motor needs to overcome. Not sure if this is your issue but just throwing it out there.
An excessive load on the motors can kill the batteries very rapidly. A 393 Motor can pull up to 4.8 amps when stalled (ie given full power but not able to move). According to some battery load tests, this means that with 2 strained motors, you’ll be encountering issues after like 2 minutes with the 2000mAh batteries.
Also, it is not unusual to have to change batteries fairly often. We use the 3000mAh and generally change them after every 1-2 practice matches. In other words, 2-4 minutes of use.
Most likely related to the battery. VEXNet is infamous for behaving poorly without enough voltage. You may want to try using a 9V battery backup as it helps with intermittent connection issues.
Also, we typically don’t run our robots connected to vexnet for “a few minutes.” You should really only use vexnet for when you need to run the robot wirelessly and turn the robot off while working on it. We also use the orange tether cable for just quick tests where we don’t need the wireless.
Robotics is extremely frustrating. Our first year we didn’t score a single point in any competition and the second year we had countless problems. I realize it seems like “I have so many problems now, I’m just gonna have more later,” but really it’s more like:
- Tons of issues at the start
- Most of the issues get fixed, everything works fine
- Nothing works at competition
I very well may be wrong on some of this but fixing these problems is where I’d start. If you have pictures of the robot, we would be more than happy to point out specific things we notice may need changing.
I hope you get this all squared away and have an excellent season!