Several threads discuss wheels, friction and traction.
I propose moving a robot around like a swamp boat. A 27" fan on each end, driven by 2 CIM motors each, with steering vanes, might allow for a far greater acceleration than wheels on the ground.
You’d still have wheels of course - I am not proposing a hovercraft (or eels) - they would just be mounted as casters, with no function other than supporting the weight of the robot against the playing field.
Two fans running in the same direction would push the robot. To slow down, reverse them both (no need to turn around). Run them both blowing outward, maybe you can blow moon rocks away from your trailer as the other alliance lobs them to try to score…
Steering is a little bit poor however. For this, we use a horizontal reaction wheel (think bicycle wheel with a heavy rim, spinning parallel to the floor). Driven by two FP motors at about half speed (to allow speed headroom both faster and slower), you would slow it down quickly - conservation of momentum would cause the rest of the robot to spin in the opposite direction. The same effect would occur, but in the other direction, but sharply accelerating the wheel. the wheel would be brought back to idle speed somewhat slower than during a steering maneuver.
An alternative to this would be a vertical flywheel (the axle would be horizontal) in the center of the robot which is turned opposite the direction you want to steer the robot. Gyroscopic effect would work to keep the wheel from moving, so the robot beneath it would move instead. This idea is not mine, I give credit to C J Reeves.
Thoughts and comments on these ideas are requested, along with other ideas for propulsion not involving driving wheels.
Anyway: The battery will certainly allow four 2.5" CIMs to be driven to near maximum output - our robot does that almost every year. Maybe we’ll be near the limit after 2:20, but that also depends upon how it is driven. The real question is whether this will provide more propulsive force than 4 or 6 (or x) wheels on the graound, driven conventionally.
In '06 we were contemplating a robot with fans that would sit underneath the goal and attempt to blow the poof balls away. The poof had a bit too much mass, but in this application… it will be interesting to see how much air movement is required to deflect an orbit ball.
Of course, once you’ve got the fans, you could also use them to suck air from underneath the robot to increase your traction.
Also, does it seem conceivable that you could have the fans blowing overtop of your trailer all the time to stop all/some balls from being scored? Does this seem like a cheat of the game?
Mathematically, this concept is possible. You’d need some extremely high-volume fans (4000 cubic feet per minute for 50N), and as your trailer filled up you’d lose a lot of your propulsion. The size of the fan required rules out quick reverses, not to mention that the structure of your robot ahead of the fan would reduce its efficiency.
I’m not sure why you’d want your wheels undriven though. You might as well make use of the 26 newtons of frictional force that the wheels provide. There’s no good reason to simply have them be casters when they can provide as much propulsion as a big fan.
To see someone who ran the numbers, read drkiraco’s post here
I wouldn’t think it would be cheating, but it would have to be pretty powerful to stop them if they are being directly dumped into your trailer…
it might work but it would have to be very very powerful, which means heavy most of the time…
we have begun to descus the options of a fan boat type effect, but u have to remember those huge fan boats have very poor acceleration on the water, and from what we saw in the kickoff video the robots could accelerate just with some slipping and stuff. the fan you would use on your robot would be even smaller, and probally have less power to work with you can only pull 40 amps at max. the fans ability seems doubtful to be any better than wheels.
then for the power situation but if using my past experience becuse last year we where using 4 CIMS to move a robot (120lbs) on wheels with high friction/wieght and a pnuematic system. this drained most of our battery last year. but if we where to use only the fan idea it would be 1-4 CIMs moving at most 5 pounds of fan blades (im being very heavy). Then with no other major draw of power the batterys most likely won’t have a problem with this type of drive train.
At Bongle, did the 26 Newtons of frictional force come from each wheel, or from all of the wheels together, and how heavy was the robot? Anyways, a mentor and I had the same idea of having fans blowing like in a swamp boat. We calculated that a battery with an 18AH life would be capable of holding out for the length of the match, with a bit of time left over.
On blowing balls away from the trailer, could you use pneumatic tubing to direct the force and just dump pressure from a tank to create an air jet of some sort?
You can use a pipe-like thing to direct the air. But anything regarding pneumatic tubing, or air ultimately from the on-board compressor simply does not have enough volume to be useful in this way.
I don’t know why it would violate any rules, assuming the safety aspects were covered. An increase in “weight” (more accurately, downforce) would provide more friction and therefore traction.
Interesting idea…
Big fans… Maybe. Depends on the coating and the weight of the robot. Seems conviecable but you’l have to work out the number of wheels (do we have to use wheels are can we use like little bearing things?) for the least friction…
Why a big fan though? By not build a series of duct fans like on the Big RC Jets? Build a nice fat one or custom make a few by gearings the motor out and making it run 2-3 duct fans. That way you could direct the fans. You could either go for downforce or for power…
<R06>
ROBOTs must use ROVER WHEELS (as supplied in the 2009 Kit Of Parts and/or their equivalent as provided by the supplying vendor) to provide traction between the ROBOT and the ARENA.<snip>
Yes, you can only use the specified wheels, nothing else.
1124 ran a small test with a large downward facing fan (it was powered by a .25hp motor, about 26" in diameter, so it probably wouldnt fit on a robot), but that fan and the downforce it provided gave a significant boost in the amount of friction between the robot and the ground. it actually became hard to push (we dont have the proper instruments to give you guys how much force was required to move it, but it was a lot more than without the fan turned on)
- tis the question
