Re: 6/8 Wheel Extra Features
 

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?

Re: 6/8 Wheel Extra Features
 

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.

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.

Re: 6/8 Wheel Extra Features
 

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.

Re: 6/8 Wheel Extra Features
 

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. ;)

Re: 6/8 Wheel Extra Features
 

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.

Re: 6/8 Wheel Extra Features
 

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.

Re: 6/8 Wheel Extra Features
 

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.

Re: 6/8 Wheel Extra Features
 

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.

Re: 6/8 Wheel Extra Features
 

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.