Shooter Prototype – The final shooter looks different than this, but is of a similar idea. (Much faster wheels, more rugged design – this one was cobbled together from our orbit ball shooter from The Game Which Shall Not Be Named and some scrap wood.)
Octocanum barrier hopping – Aside from the spaghetti wiring, this is our finalized drive train! There is virtually no stress on the wheels as they traverse the barrier, and the octodrive gives us the maneuverability we want with the pushing power we will almost definitely need!
Hopper/Conveyor – Our primary goal was extreme consistency in feeding balls to the (unmounted) shooter; also, our hopper is easy to retrofit into a vertical hopper for dunking (if we ultimately fail in achieving the shooting accuracy we need to be successful in that strategy).
Aside from the drive train, our goal is that everything is modular and can be removed/replaced/retrofitted in less than ten minutes.
I love the drive train you guys came up with. I have never been a fan of mechanum drives but the fact that you paired it up with some tread wheels should make it pretty effective.
I know team 217 and 148 had Nanodrive back in 2010 which is essentially the same concept, just be careful on your weight. I know those teams had to remove their hanging arm because their drivetrain was too heavy.
In team 148’s case in 2010 they did not remove the hanging arm because of being overweight, rather they wanted to distribute the weight more evenly to avoid flipping when speeding over the bumps. They also thought in the time it would take to hang they could simply score more goals to accommodate opposing hangers.
My team was thinking about doing a similar drivetrain, but decided on mecanum only. Looks great and good luck!
The traction wheels are geared very low as well. (I’ll be cagey about just how low, but lets just say we want to be able to power through any defense that gets thrown at us!)
However, please don’t give us credit for the octocanum drive idea – we stole it quite shamelessly from 488. Mind you, there are some important differences (gear ratio, wheel placement, pod shape), so we made it our own, but the credit for the original idea goes to them.
Also – as for not loving mecanum wheels: they’re expensive, quirky, and require tight control of your robot’s CG. They also allow your robot to be controlled exactly like a first person shooter with almost no modification to the programming. Their primary flaw – the lack of pushing power – is truly a significant and non-trivial drawback, and anyone who says otherwise certainly hasn’t had our experience with them (and this will be our fourth year using them). In many game applications I would not recommend them, but in some I would. Octocanum removes this drawback but adds in weight management and battery management issues, as well as sheer expense – we would not have been able to afford it this year without the very generous donation from Gates.
That’s a great heads-up for anyone looking to implement an octocanum drive. The drive train system (including pneumatics, compressor, electronics, frame, etc.) is just under 80 lbs – the heaviest we’ve ever had by a great deal! Our projected robot weight without protective coating stuff (lexan, etc) is 108 lbs with all systems (bridge manipulator, ball intake, conveyor, and shooter) – this gives us a little wiggle room for a few more sensors or brackets or whatnot, and will allow us to add weight (steel blocks) to get to 120 lbs in a strategic manner to ensure that our CG is dead-center and below the frame.
If you have any other questions, I’d be happy to answer them!
I am good friends with one of the people on the design team of the hanging arm on 217. They informed me that the hanging arm put them overweight. However, they did redesign it to make it within weight, but that is when the comment you brought up came into effect. Either that or 148 and 217 just had different reasons for their decisions…or perhaps I was misinformed, who knows?
In any case, why did your team decide to go just mechanum? Too complicated or too heavy?
I’m absolutely in love with Octocanum. It’s one of my favorite drive systems! I think it’s awesome 1551 is bringing it to the field this year. The shooter and elevation system are looking really good too. I can’t wait to see it go to work on the court!
Best of luck, and I can’t wait to see the Grapes of Wrath is action at Finger Lakes!
It’s not the mechanical stuff that worries me – it’s the programming. Aim and rpm control are just absolutely critical if you’re going to build a robot that can make baskets, and both problems are harder than they look.
We have a contingency plan, but we’d rather not go to it.
We had an octocanum drive in design stages but didn’t like the technical risk, having not finished a prototype in the off-season. Plus, we do not see the clear traction disadvantages that others do. A mecanum will get pushed back if one is crazy enough to challenge a 6-wheeled beast head-on but that does not happen all that often. Quite often we just slide a little at the last minute, catch the defensive bot on its corner (while it is pivoting to get to us) and spin them around or we spin around them. Most of the time we just give a little head fake and go right around them, it is pretty funny to watch. These maneuvers steal time but pushing contests between powerful bots do not consume zero time. No doubt our experiences will be less true should we ever get anywhere near Einstein but thats a nice problem to have. Our bot can gather balls from all 4 sides and the key is a safe area, hopefully these factors make it harder to defend us -we’ll see.