Okay this very much could be a stupid question but would it be possible to instead have a center tracerwheel attached to your drive you have your tracer wheel be a flexwheel to prevent pushing from the side? I currently have two tracer wheels in the middle of mu drive train since all 4 wheels are direct drive but I need some kind of way to prevent side pushing so i was wondering if I could just swap out the omniwheel on the tracer wheel for a flex wheel and solve it that way. I have no idea if this is stupid or not but I have never seen any team do this so I was just wondering. Thanks ahead of time!
I should add that whenever I say I want to use a flexwheel I mean one of those car tyre 60A flex wheels not the squishy 30A ones
Yes I do know that but I would really like to keep my 4 wheel direct drive if possible so do you think having the tracer wheel be a traction would be possible?
I am dumb…. But what’s a tracer wheel?
Tracking wheel? Traction wheel?
Or this tracing wheel?
Edit: when @RoboCatz mentioned 6 wheel drive train, it really means 6 wheels, but only 4 of the wheels are powered.
6 Likes
A tracer wheel is a nonpowered wheel that has an encoder on it to track how much it rotates. This is usually put on some mount that is able to pivot down onto the ground and with rubber bands it is able to always maintain contact to the floor so you can use odometry without the motor encoders since the wheels that are powered can slip.
Also are you sure about that becuase I feel like I have definitely seen robots that have had their middle traction wheel powered
We normally call this tracking wheels, and not tracer wheels.
Anyway, back to whether you want to power your pair of middle wheels, it is totally up to you whether you want a 6-motor or 4-motor drivetrain.
So obviously if you want a 4-motor drive, then you only power the pair of front and back wheels. And just use the traction wheels in the middle unpowered.
And yes - I am very very sure.
11 Likes
You are missing something here. Wheels don’t have to be connected to a motor to be powered. Add two tracking wheels in the middle-ish of your drivetrain. If you want to power them, add gears from the axle in your motor to the axle through the tracking wheel. A lot of people recommend gearing your drive motors to each other even without a tracking wheel, since that way if one wheel lifts off the ground, the other wheel is still powered. You very well may have seen robots with three wheels on each side and all of them powered. That would be a 6-wheel, 6-motor drive. You have a 4-wheel, 4-motor drive. You can have a 6-wheel, 4-motor drive by gearing a middle wheel to to one or both of the drive motors on that side. Or you can have a free-spinning tracking wheel in the middle.
You are right. 1) Not being pushed from the side is good. 2) Ignorance is not the same as stupidity. (Why does everyone say they’re stupid? If they are, we can all tell anyway.)
6 Likes
Ohhh, now I understand what you mean. My team actually tried this in Change Up as our smaller Omni wheels had not yet arrived, yet we still wanted to have encoder wheels for a more accurate autonomous.
(You should be able to see them poking through beneath the intake roller).
What we found, is that if you have any slop in the encoder wheel joint at all, the encoder wheel can slip and “spread out”. This can affect your autonomous routines and can prevent your robot from driving properly straight. This actually impaired our robot’s movement during matches and prevented us from doing well in the robot skills challenge. Another issue is if they are not perfectly co-axial with your robot’s center of turning (especially if you already use traction wheels on your robot), your robot’s motion will be impaired (especially turning-wise).
So, to answer your question, I would much rather prefer using Omni wheels on your encoder wheels, and save the tractions for the actual drivetrain (this is why many teams use 6 wheel drivetrains where the middle wheel is a traction wheel). If you don’t want to be pushed from the side, then I would recommend sticking with a 6 wheel drivetrains with middle traction wheels.
2 Likes