There are a handful of robots out there this year that have exceptional speed, but don’t seem to have sacrificed acceleration. Team 27, Rush, is one that comes to mind, as is Raider Robotics Team 25 and Simbotics team 1114. I believe their bots are also close to the 120 limit.
My question is this - to those teams that seem to have exceptionally fast drive trains - what is your setup? I believe Rush uses dewalts, but I haven’t been close to their bot to see if they use 4 cims + 4 dewalts and shift them.
To get things started, we use 4 cims and 2 AndyMark supershifters. I’m guessing around 13-14 actual fps (we were very similar to Thunderchickens speed-wise).
We have custom gearboxes built around two cims and dewalt transmissions (horribly inefficent and slightly unnecessary, AndyMarks next year). We have three speed shifting, but have a lot of trouble maintaining the gearboxes from breaking. Come see the design in Atlanta if you can.
1075 uses a custom tank tread with the guts of an andymark shifter, and 2 cims that live INSIDE the track… whole thing comes on and off in 5 minutes, and nobody can outpush us… not that that really matters this year.
We use the toughboxes and the KOP wheels and our theoretical top speed is about 11 feet per second but we really do about 10.5 or so. The reduction we used made is so that the robot has to have almost 3/4 of the pwm value to get moving so it’s kinda difficult (and loud) to get moving for low speed maneuvers. We’ve found that it’s plenty fast for what we’re using and puts very little strain in the four cims powering it.
Team 141 is using two cims per side with direct drive via timing belts driving custom six inch wheels. The reduction is around three to one, I do not know the exact numbers. In theory we can run 18-20 fps. When the drivers decide to run laps we can usually turn them in seven to eight seconds on a full field provided there are big enough openings on the field that we can get through. As long as there are openings we have been able to get through them without slowing down significantly.
Also a lot the team with high tops speeds use two speed transmissions. I would also guess that some of them use automatic shifting software to always have the drive train running at max efficiency.
The problems alot of teams are having with bots that are at weight limit, is that when you gear up the drivetrain to a crazy speed (20 fps lets say) you have to factor in acceleration time and the space provided to accelerate, therefore many teams with robots capable of reaching that speed never really do. (however teams with smaller and lighter bots cough148*cough, have a significantly reduced acceleration time due to their lesser inertia)
To combat the acceleration problems we use 2 cims and a fp per side with a max speed of roughly 16 fps.
On 1986’s drivtrain, we use mecanum wheels that are connected to the CIM motors with a simple 6:1 reduction using sprockets and chain. Each wheel has its own suspension assembly that is easily removed and replaced, and only 2 wires and 2 bolts need to be removed. This set up gives us a theoretical speed of 23 fps but in reality, its closer to 20fps.
To keep our speed so high and still have insane acceleration, our robot weighs under 80 lbs with bumpers and the battery. We could also lower this another 10-15 pounds by removing our modular ball knock-down device.
You were close. We use 2 CIMs coupled into one dewalt per side. This direct drives our middle wheel, and we have chain running from there to our front and back wheels (6WD). We use AndyMark off the shelf 6" wheels and the middle one is lowered about an eigth inch for turning. We also use servo shifting. Our problem has been our drive shaft breaking. It happened in the quarters and semis at detroit, thank goodness for 47 and 453 winning one on their own. We have a plan to fix this for GLR and hope to be working much better.
We use 6 inch omni wheels and a CIM + banebot 12:1 transmission for each wheel, because they make for good pods lol (our famous linkage and all). and we reach roughly 10.5ft/sec
We have a 4x6 differential (tank) drive system. There are 2 cims/side mated to supershifters. The maximum speed in a straight line on a linoleum floor (observed) is 18ft/sec, but with the shifters our track speed (with traffic) is still a good haul at about 12.75ft/sec.
Don’t believe me for speed? Just watch our rear data center. It displays the robot’s overall vector velocity in ft/sec by default in teleoperated mode. :]
For us, it was AndyMark Super Shifters and 6WD. Off the gearbox, we went 24:22 (or was it 25:22?) to skinned-and-treaded AM FIRST wheels (diameter about 5.5" in the end). I realize it’s a little counterintuitive to gear back up in chain and sprockets, but it was a little cheaper than fiddling with extra shafts and we wanted to use the onboard encoder. The end result was around 13 fps (could’ve sworn it was 14, though a re-check of the spreadsheet says otherwise), enough to be one of the fastest robots at Chesapeake*.
*We thought we were doing well to get seven laps in a match. Then, after packing up and sitting down to watch eliminations, 2016 goes and clocks nine. Showoffs.
I’d venture to say that teams 254 and 968 have the fastest drivetrains this year; both in terms of max speed and acceleration. They are running 4 CIMs and 2 FPs through a modified AM transmission.
254’s robot was so fast at SVR that it was actually hard for their drivers to control it. After they removed the FP’s it became more controllable and their game-play improved.
As for us, I can tell you were not going to do 2 CIMs again. Acceleration is horrible.
48 currently runs one A-M SuperShifter powered by 2 CIM’s direct driving a 4" Brecoflex halftrack pulley on each side of the bot. Tread thickness adds .25" x 2 to that to yield a total driven wheel diameter of about 4.5".
Custom 25T:40T final drive gear ratio yields theoretical 16.2 fps in high gear per JVN’s spreadsheet. No load taching of the right side gearbox output in the pit yielded 770 RPM or roughly 15.11 fps. Obviously actual performance is somewhat south of that, but it’s still fast enough for our liking!
When we added the gearbox mods in Pittsburgh, the right side drivetrain gave us problems with breaker popping until we cleaned and realigned the boxes. We ran well with no major problems at Buckeye (at least in teleop mode). We were one of the fastest and most productive lappers at the event. The halftracks (with four passive outbound omnis providing stability) turn beautifully and provide excellent straight-line control.
Ya, we have done surprisingly well with custom gearboxes. We used two CIM motors on a 3.57:1 Gear reduction. Same as an AM Stackerbox… but this is a double motor stackerbox.
Ya, we have done surprisingly well with custom gearboxes. We used two