Today we decided to change from mecanum wheels to a 1:3 speed ratio on 4 inch high traction wheels. However, this is my first time working with chain on a drivetrain. I heard clicking, but i’m not sure if i should be worried. We drove the estimated 5 pound robot for about 10 minutes without any overheating. Should i worry about the drivetrain? And if so, any ideas on what may cause the clicking?
-previously with the mecanum drive there was no clicking
-the chain is NOT restrained with an object
-each wheel is individually chained
-no side of the drive is stronger than the other(if it is, it wasn’t noticable after we traveled 12 feet straight across)
-we use arcade drive
-Chain was not carelessly angled
Does it sound like the clicking is coming from just one wheel? Usually when we hear that it means that it is time to replace the internal gears of the motor.
The problem is that you replaced wheels with omni-directional capability with high-traction wheels that do not easily roll sideways. You are putting a big load on your drive train which is causing the chain to slip. If you had gears, you would like be hearing a similar sound from skipping gears. I would replace two of your traction wheels with regular 4" omnidirectional wheels.
A couple of other questions – is your 5-pound robot a Sack Attack competition 'bot? How did you bring one in that light? The lightest good competition robots I’ve seen were in Elevation, and weighed right around 8 pounds. Five pounds is crazy-light, unless it is pretty much just a chassis and wheels.
Another question, if you are gearing from 6-tooth to 18-tooth sprockets, your top speed is really high. Again, you are unlikely to build a successful competition robot with that gear ratio, but you could do it in a “for fun” robot. And last, chain slip is a lot more common on smaller sprockets than big ones. I would consider using larger sprockets, or, even better, spur gears.
I can check that tomorrow. It did not sound when the drive was elevated or we had mecanum wheels.
We do not. I probably phrased that detail poorly on my first post. I have a feeling this could be the problem, but just wanted to make sure.
I have a feeling the chain might be a bit loose cause it’s fairly close together. the second could be an issue. It uses the 18 and 6 teeth sprockets
I forgot if i heard this problem while turning(though i’m fairly certain it continued), but i know for sure this problem occurred when driving forward. Also, the drivetrain is wider than it is long. We wanted to stay away from omnis due to dirt.
To answer your questions, this is a “For Fun” robot that we plan on using for relay for life. Since we’re driving it around the track, i’m worried that dirt and mud will jam up the omni wheels (there might be rain this friday).
Another concern is that we plan to run the batteries dry. I know many robots had issues controlling a 2:1 ratio on 4 inch wheels, but i don’t know if the motors have the endurance to run an hour
I would switch out the 6 tooth sprockets because they can allow the chain to slip more easily. Is it clicking when the robot is accelerating / decelerating or just during normal use?
Accelerating. Clicking stopped as the top speed was reached.
Anyhow we took the robot to the track and it went extremely smoothly. Each charge allowed the robot to travel a bit over a lap around the track. There were no issues with chain slippage. Also surprisingly, there were no issues with overheating. For future reference, i would add non slip pad to the high traction wheels. Due to the vibrations, many keps nuts and collars fell apart.
If the clicking is at a slower rate (1 click per seconds, say), it is more likely your chain slipping. However if it sounds rapid, it is most likely the internal gears on the motor.
One method of checking the integrity of the motor’s internal gears is the turn your robot off and push the robot around. Accelerate it more quickly that it could normally do, and you should be able to tell quite easily if it is the internal gears (they will sounds horrible and click rapidly). However, do not be too rough, as this can also further trash your motor’s gears.
Either way this sounds like a fun project! As an off-season build we plan on testing out various drives and gear ratios using all 10 393’s and see what is the theoretical top speed of a VEX robot. My money’s on 8 feet/second.