It was a good week of prototyping. We took a previous year’s drivetrain and replicated the wheel spacing we planned to use this year. With AndyMark 7.65" diameter wheels we can handle both the defenses we’ve had time to build. The drivetrain shown has a crate of CIMs strapped on top to give a total robot weight of 121 lbs. Yes, it is top heavy, and yes a rookie driver tipped the bot, and yes, the tote shattered.
The shooter prototype was slapped together to let us know if a wheeled shooter showed any promise.
Looks great! Mind sharing what wheel base and wheel track you’re showing? We’ve been trying to figure out the best spacing but we haven’t seen a traverse as clean as that.
It seems like your top heaviness is probably helping you over the rock wall. Keeps you wheels up longer so the front ones hit the wall at a better angle. I’d be interested how things work with a lower CoM closer to what you’d normally be running.
Also I probably don’t have to remind you that shooting a single brand new ball consistently does not make a consistent shooter.
This testing was primarily to see if our standard drop would work, or if we were in for a redesign. The tire pressures are whatever they ended up when pumping up with a hand bicycle pump. Next step is to use a compressor with a real pressure gauge. We’ll play with the pressures in the center vs outside wheels to see how that effects the current draw when rotating in place. I can confirm that these wheels definitely scrub more than Colson wheels. We have Colsons on the way, too, and could switch to those, but we’re liking the shock absorption of the pneumatic tires.
Yeah, we tried the hard rubber first and I don’t think many of us were fans. I have a couple reservations around us diving headfirst into the school of WCD design for this years drivetrain. The ability to absorb shock with those wheels and a couple other mechanical tricks we are looking at to assuage my fears should do the trick. We did some of this work too, but I’m pretty sure the only video anyone got today was me eating chili near the drill press.
Also our 2012 wheeled shooter is in a cold dark circle of hell along with our MK Is for 2013 shooter actuation, 2014 drive, and 2015… everything. We’re kicking around some blue sky plans to solve the inevitable ball consistency problem; I can only imagine the damage some robots are going to inflict on them this year.
Have you tested that drive base on the moat? Our initial pre-built concept chassis had a similar wheel spacing and we just got caught up. We thought the rock wall would give use the biggest problem, but the spacing of the moat can cause the chassis to sit on the moat ends and have the wheels free spinning. The rock wall was no problem. The moat was deceptively challenging for us. Our new prototype robot will have the wheels closer. Hopefully, our new spacing will be perfect and we can use that spacing for building the next two robots (practice and competition).
That is hilariously and horrifyingly terrible. Can’t wait to see how our prototype is handling the moat when I get back to houston. Also, I’m told using steel for the 1.5x2.5 bars makes things even harder. So you might want to try that.
This looks great! May I ask what amount of center drop you have on the drivetrain, , what diameter the Colson shooter wheel is, and how much you are gearing up the CIM?
I believe one key to some of the defenses this year is to drive you bot like you stole it.
For instance, hit the mote with a bit more authority and you may just own it.
I wouldn’t want to deprive your students of the feeling of accomplishment they will have when they build their own prototypes.
<edit> Oops. Looks like Nate has no such compunctions… I will say that the prototype drivetrain is from our 2014 robot, and we plan for the 2016 drive rails to be of the same design as the 2015 drive rails. The CAD for these bots can be downloaded from FRCdesigns.com
We’re thinking about drown-down pads (or similar) to assist in stability and angle adjustment for high goal shots. Strategic placement could also mean they assist with getting stuck in the moat. Our prototyping drive base didn’t get stuck unless it skewed far left/right, but that base was also 3" too long w.r.t. the current actual CAD design.
