6/8 Wheel Extra Features

[Peter Matteson]

Originally Posted by Marc S.

As far as the width of the wheel, we on 973 noticed a big difference in traction with 2" wide wheels vs traditional 1" wide wheels.

In 2011 we used a wcd with 4" diameter, 2" wide weels, with a 3/16" center drop. The combination worked great. The drivetrain allowed us to switch from strict offensive play to strict defensive play with the ability to push every robot we came in contact with. Check out the cad for Titan in my signature. If you like what you see feel free to use our design(s) and pm us if you have any questions.

This is where my team started with the development of our current drive trains that we use. We started with IFI sheet metal 4" X 2" wheels. We then went to custom 4"x2" wheels. After that we did the math on the physics and realized that the difference wasn't that big between 2" wide and going down to 1" wide. Also we had greater variation in traction with various tread materials that we tried out, which is why we currently use 1" wide AM performance wheels with the best traction of all materials we tested. It's one less thing to make and 1" wide wheels package better.

[JamesCH95]

Originally Posted by MICHAELABICK

My guess is that because they were using 2 in thich wheels, they had an amount of turning scrub that they didn't like. By increasing the drop, they decreased that amount.

If only two axles are touching the ground, how does lifting the remaining axle further off of the ground help?

I'd bet it's more of a wheel wear concern.

[PAR_WIG1350]

Originally Posted by JamesCH95

If only two axles are touching the ground, how does lifting the remaining axle further off of the ground help?

I'd bet it's more of a wheel wear concern.

Sometimes, the drop is slight enough that the center wheels can sink in the carpet a bit and the wheels which are "off the ground" will make slight contact which can degrade performance slightly.

[IanW]

Originally Posted by PAR_WIG1350

Sometimes, the drop is slight enough that the center wheels can sink in the carpet a bit and the wheels which are "off the ground" will make slight contact which can degrade performance slightly.

We actually ran into this problem this year. We designed a .125" drop into our 6WD drivetrain, but found that we didn't like the turning once we actually got it running. Swapped out a pair of plactions for a pair of omnis on our competition and practice bots and it worked much better.
I'm not sure what exactly caused it to behave so poorly turning. My guesses were either the drop was insufficient and the wheels still scrubbed because the robot sunk into the carpet, or our chassis flexed, allowing all 6 wheels to contact the ground.

[JamesCH95]

I'd buy the chassis flex argument, or maybe if the target 1/8" drop was not reached for whatever reason. We've never had any issues using a 1/8" drop with 1in wide plaction wheels in a 6wd setup over the past couple years.

In the past we've seen the center set of wheels (skyway wheels FWIW) wear down to the point of negating whatever drop they had, and that was an issue.