Rear with Battery Holder in center. The things that look like there could be wheel 5 and 6 be mounted will get a toughbox mini with a winch to lift us up
Closer view of toughbox mini with mini Cim and wheel mount
Frame dimensions 29.46x29.46 in. The square holes hold some 1/2in 16 gauge square aluminum tubing. Its held in place to the frame with 8-32 bolts and lock nuts. All Inventor and STL files at
Right now the team wants tank drive. But the holders will fit Mecanum too and omnis will fit too it just takes the 4 bolts of the toughbox mini to pull the wheel off and put another one in so that is something that could be done between matches if we wanted too. (of course with the necessary change in code)
Can you elaborate / explain the construction technique here? What is the white boxy stuff? Why is it boxes not triangles? Is the intent to reinforce it with aluminum box tube inside? If so what does the white framing accomplish?
No problem we did not weigh it with wheels and gearboxes yet Without wheels and gearboxes it weighs 9 lb about 6.5 lb of plastic the rest is the 1/2in aluminum tubing. We went to the 1/2in 16 gauge square cause its much stiffer than a hex churro and much lighter and its easier to mount it the COP Wheels are 0.6lb so add 2.5 that makes 11.5 4 mini CIM are about 8 lb so that makes 19 and I have no idea what a toughbox mini weighs but I guess 2-3 lb so probably close to 30ish lb
The white boxy stuff is HIPS Plastic its 3d Printed. Its boxy cause it gets 1 square tube shoved into it. So now you have a compound plastic/aluminum frame the reason we did it is cause we have 3d printers not much else but hand tools. 3DP is accurate and tough if done right. The aluminum is there to reinforce and cut down printing time You are looking at about 60-70 hours printing time (we got 2 printers) so you can print it in about 2 days (or longer or shorter depending how many printers you have)
No 3DP wheels because they did not get finished in off season. We are working on a 3dp HUB with a hypocycloidal 3DP gearbox inside so you can mount the motor directly to the hub and then 6 and 8 in “rims” that are either regular wheels or mecanum or omnis. But that might happen next year
I’ve seen examples, and even done myself, printing “nodes” for purchased extrusion (plain or 80/20) to connect to with either bolts or adhesive. I’m interested to see how this will pan out. Could be more flexible to design around in the long run.
Have you considered switching to 3dprinting only the corner brackets, and using 2x1? It should cut down your printing time by a large factor while the 2x1 could make it easier to mount a 3DP bearing block or something.
Are your wheels not chained together? If you get in a pushing match and one side of your drivetrain lifts off the ground, you’re essentially losing half of your drivetrain power, making you extremely susceptible to being pushed and not making you a very efficient defender.
It was considered. But this way we can mount something pretty much anywhere and right now the printing is not the bottle neck the bottle neck is the “comitte meetings” with the team trying to make up their mind how to make the shooter etc
No it always was intended 4 wheels Version one had a straight piece in where gearbox 5 and 6 mounts are then it was decided to make 2 winches so we can shift the center of gravity to balance the beam so as we have already printed spares it was found that we could 3DP a winch that fits into the wheel holder and use one of those so we pulled the frame apart and put those gearbox holders in and the winch/climber mount is going to get done as soon as my designers finish the mono-myth paper and get back onto inventor
Instead of being chained together we opted to give each wheel its own motor. even with them being chained if one side lifts up you loose that side. Now one mini cim with a wheel has enough torque that the wheel will spin out before the motor will get in a range where it pops a fuse So each wheel touching the ground will always have more potential power than it can need. IOW the limited factor will be the grip the wheel has on the floor
Assuming your using the lowest Toughbox ratio (12.8:1), it does not look like you are traction limited with 4 miniCIMs, unless you are under 105lbs with bumpers and a battery. Additionally, this leads me to a few beliefs:
a. If someone plays defense on you, they will easily be able to push you around.
b. If you attempt to play defense on someone, your robot is either too light or your drivetrain is too underpowered to play effective defense.
c. Unless you are very very light, you won’t be agile enough to avoid defense
An easy solution would be to step up to 4 full sized CIMs, if not one of the brushless motors.
Also, second, a perfectly square 4w traction robot may or may not turn, and if it does, it will draw a considerable amount of current in doing so.
We will see and changing wheels is not that big a deal. We had that setup before and we ran that 2007-2009, 2010-2019 where mecanum. But its something the kids discuss
in the past we have spun wheels against a wall with mini Cims at about 30 Amps with a 120lb robot when the weight limit was that. If this year is different we can add a 2nd mini CIM to each gearbox. Now at the time it is estimated that minus battery and bumpers our Robot will be 70-80 lb. So we can make it any weight between that and the 125 limit by simply adding weight. We have some 1/2 in solid square mild steel bars laying around and easily could fill each one of those squares. But currently it is an argument to either go to the limit or make it as light as possible to be nimble. There is even some discussion to 3DP some weight plate mounts (for weight lifters under the frame and add/subtract weight as desired and have it re-inspected weighed during a competition. So come to it at 125 then remove lets say 50lb if we decide to and have it reinspected etc. At an off season event we played defense with a 60ish lb plastic robot - of course not to well but the point was to really bash it around to see if the plastic will last and it did.
