6/8 Wheel Extra Features

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.

What kind of wheels, and what kind of tread? And any reason for using 3/16 drop over 1/8 drop? Did you feel it had an advantage? If so, what was it? Any disadvantage?

[MichaelBick]

Originally Posted by SuperNerd256

What kind of wheels, and what kind of tread? And any reason for using 3/16 drop over 1/8 drop? Did you feel it had an advantage? If so, what was it? Any disadvantage?

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.

[Clayton Yocom]

Originally Posted by topgun

I am confused on this. Can someone explain why having drop down casters would help with defense? Also, what do Drop Down Outer Wheels provide? Some pictures would help if possible.

Thanks.

Watch this http://www.youtube.com/watch?v=mhtdk...e_gdata_player video of us (45) and 111. We play defense so they cannot deploy their minibot. Interestingly enough, the T-Bone pin is crazy effective, and because we were soo good at pushing last year, they just could not get out of it.

[Hawiian Cadder]

Originally Posted by JesseK

Exercise caution in future years and apply the material for the year rather than using the "we always do it this way" way of thought. I'd be concerned that the outer axles would bend if it came off the bridge or bump incorrectly. Did you do any simulation or calculations to figure out the tensile stresses your axle could hold?

On a flat or predictable field like 2005, 2006, 2007, 2008, 2009, & 2011 this isn't a concern.

Our drive was setup so that there was about 1/4 of an inch between the wheels and the bearing blocks. This allowed for the lighter axles, bending was never an issue, one match we even drove off the 24 inch drop made by an unbalanced bridge with no damage to the axles. Keeping the axles short was critical to maintain a robust system.

Edit:
We did test the axles on an our off-season WCD, they were flawless and bending was minimal. We beefed up the axle wall thickness a bit for competition to ensure they would never break.

[Marc S.]

Originally Posted by SuperNerd256

What kind of wheels, and what kind of tread? And any reason for using 3/16 drop over 1/8 drop? Did you feel it had an advantage? If so, what was it? Any disadvantage?

The wheels are custom, we used blue rough top tread. The reason we went with 3/16" drop over 1/8" drop was to ensure better turning capability, less scrub on the raised wheel, etc. The advantages were that we could push every robot we came in contact with (even 469) without any fancy add-on's and without giving up offensive speed. There weren't any big disadvantages with the drive (the only thing that really gave us trouble was the 775 motors (which were removed before champs), if we use the design again we will use 550's in conjunction with the 4 cims).

Though for the moment, emperor swerve is working great for us, so it may be a while before you see 973 using the drive train again.

[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.