Hello Forums!
Our Team is currently having some issues with our drive train overheating during long-ish periods of driving. Our Specks
6 Motor Drive
Blue (600) RPM Motors
450 RPM to 2.75 Omni & Traction Wheels Building Techniques
Used Screw Joints
Used Shoulder Screws to Build Frame Issues
After around 20 minutes of driving, the robot stops turning and takes way longer to accelerate, with our motors ranging from 40* C on one side to 60*C on the other.
So with this in mind, I was wondering what some issues could be with our base… Should we use grease on the axles? Is this a common amount of time for blue motors to overheat?
Of constant driving? That’s actually pretty good, seeing as competitions take place in 2 minute-sprints. Our drivetrain overheats after around 30 minutes.
Other than lowering your robot weight or decreasing your gearing speed, there’s nothing really much you can do about it. However, (and I assume you have mitigated friction as much as possible), you shouldn’t really do any of these, as overheating after 20 minutes is quite okay at a competition.
If you’re concerned about how it will affect your performance at a competition, you can use hot swap motors, or between matches use fans to blow cool air across the motors (like the infamous “more leaf blowers”).
If the temperatures are that different on either side - that is kind of concerning (unless you’re going in circles), as it shows you have an excessive amount of friction on one side.
My gut is that you have a lot of friction with regards to moving parts. Sure it seems like a good idea to use screw joints - but not always everywhere, AND screw joints have different assembly techniques that differ from when they were used in lifts as pivot points vs axles. If you are using screws in axles, do recall that screws are spiral wedges that sometimes like to bind to material they are interfaced with… think a drill bit cutting into the material vs rotating around a matched thread of a nut.
Back to topic at hand - if running 20 minutes to push your bot around with friction with low torque gearing (blue) to get benefit of speed (until you hit something, or another bot pushes you in competition) - it may work in 2 minute match, but 20 minutes continuous, you may be pushing it. No one goes 10 matches back to back.
Grease where moving things makes sense - but really tiny amounts, think of small, you need a lot less. Dripping on competition tiles uncool!
What you do not mention is weight of your robot, actions the robot is performing (for example, pushing mobile stake across whole diagonal of field while being pushed in opposite direction by two opposing alliance robots!).
In summary - build quality is key - not employing every new cool technique and configuration you heard on some post or viewed on YouTube.
You are doing right thing to ask for technical guidance on the forum. I wish you and your team a great season!
Given your drivetrain - yes, it is possible and common for a drivetrain to overheat in this amount of time. Your friction and gearing does contribute a bit to overheating, but after continuous driving of 20 minutes, the drivetrain is bound to overheat, and as a result can suffer some issues.
I would recommend implementing a temperature checker or program to monitor it, and also not drive while it’s overheating(the motors can be damaged). You can add specific types of grease onto the axle, but not DIRECTLY onto the motor( per ). Hope this helps!
Honestly, your drive train sounds completely fine! After 20 minutes of driving, even a very well-constructed base (which it sounds like you have) will start to overheat after this much driving. Just give your robot a short period to rest, and it should be good to run again. Also, I would advise you to stop running your robot before the motors reach the 40-60°C mark, as you may risk damaging the motors.
Assuming you’ve checked all friction points, 20 minutes actually seem quite normal for that spec of drive also assuming you have a robot weight of like 14-16 pounds. Really a burnout time of over 15 minutes should be good even in really heavy competition use. Personally, I haven’t had problems in competition as long as burnout time was above 10 minutes but that is just my experience. Since you did mention temperature, FYI VEX motors “burn-out” that is the software limits the motor power at about 55 degrees C. The only thing that might be concerning is the fact that the sides of the drive differ by 20 C in temperature. 40 C means that one side is just warm after a few minutes of driving which is normal. (25 C is about idle, turned on for a while, not running temp).
In other words, 20 minutes is fine, and I would say lube is not necessary in most applications assuming everything is built correctly and friction is kept to a minimum.
