Wheels

[iSnoopy]

I would really like to have omni-wheels for our robot. Maneuvering around is probably the key point and positioning ourselves to shoot the ball is probably the most important feature.

[Jaimtrocity]

im not sure wt omni-wheels means, but i feel like having 2 motored wheels in front & 1 free wheel in back (centered) would be good. the prob with 4 wheels would be that you have 2 connect up either all wheels 2 a motor which may be weak & or hard, or you do 2 wheeldrive, which would be dragging 2 wheels, instead of 1 (which i suggest)
having 1 wheel taht is free is also nice for turning on  a dime, since you only have to turn 2 wheel instead of possibly 4. In this case, 6 wheels is out of the Q, cause we dunt need speed or power here like last year, 3 is my ideal here! 

[iSnoopy]

6 wheels benefit for climbing over the bar as we have more contact and climbing power. 6 wheels also benefit in that it has more speed and speed is very important in this game. we have to fight for the balls and the speed will definitely put us in control. unfortunately, we aren't experienced enough to have swivel wheels (like cars) in that we can adjust the wheel direction. i agree that power isn't need to drive the robot as we won't be needing a big tank.

[Jaimtrocity]

but it just occured 2 me, if we are going over bumps, which it seems like we are, then 3 wheels has very little power & it would be very difficult to climb the bump. Is the only wheel system we can do for the bump 6 wheels? because you have already shown that 6 wheels has problems....

beter just to go under tower?

& any spelling mistakes, i tried very hard this time!

[JAYHYUNKIM]

...We can do FOUR wheels.

[iSnoopy]

we can do any realistic number of wheels
moving a post

a demonstration of omni wheels: The Amazing AIRTRAX Omni-Directional Wheels

[SakifNoor]

maneuvering is great but most of the less maneuverable bots will save time going over ramps rather than having to go under the towers.  It is all a trade off.
a huge 6 wheel bot can probably get over the ramps easily though it may have a bit of an issue turning (though this is not significantly more than a 4 wheel if the center two are lowered enough to allow the bot to rock on these wheels a bit.)

maneuverability also often sacrifices the ability to push.  for example omni wheels have negligible lateral resistance to motion which is the very reason they make turning easier.  They also get shoved from the side easier.  If you intend to go super maneuverable, I suggest you focus on speed and try to make the robot small (though not necessarily light beyond a point since reducing weight reduces traction) so that it can slip away and not be tackled as easily.

Also something to consider:  Maneuvering with the ball will be rather difficult given the only 3" to get any hold rule.  If you are to become super maneuverable, this does not necessarily mean you will be moving like that when you have a ball.  To use maneuverability, you will probably be going for a ball, knocking it in the correct direction then going through a tunnel to finish the job or depending on an ally to finish it.  Going super maneuverable->needs a good kick/shoot whereas a less maneuverable bot can play defense (just generic get in the way), or center hog (to get scored balls that reentered moving favorably with a good method of getting balls over bumps), or goalie (the one bot the alliance can have guarding the enemy goals).

[JAYHYUNKIM]

The second issue that SakifNoor just mentioned has been a worry of mine as well, but I thought you guys all worked it out by placing the indent in some creative, useful way. Therefore, I didn't say anything...but the indent does seem too small for it to have a proper hold/placement on the ball.

Right now, I think large four wheels will be ideal? I'm not entirely sure.
It seems we're going on the offensive right now, so I think we should go maneuverable, and through the tower (have small wheels will create more space in between, thus increasing the chance of the "stuck-on-the-bump" dilemma presented in the other thread "Clear or Climb")

Let me know what you think. It seems we're not finalized on anything yet, Alec.

[iSnoopy]

yeah, it does seem so. I may send an email concerning the design of the robot.

over all, on the update 2 of the robot...i dont understand the 2 wheels perpendicular :S

[SakifNoor]

yeah, it does seem so. I may send an email concerning the design of the robot.

over all, on the update 2 of the robot...i dont understand the 2 wheels perpendicular :S

If it were powered, it would let you guys turn a bit easier and that is an approach i guess.  Not the one I would take, but it does seem good for all except shoving other bots and climbing ramps, though think it may be able to get away with not getting stuck on a ramp if it were shoved up there.

Its bad for shoving bots because: a frontal shove will remove some weight from the front wheels simply because the point of impact (the bumper) is above the wheels' axis of rotation.  This means your front may even be lifted up off the carpet if pushed from the front, leaving your only option to turn with your back wheel (this is why it should be powered) and escape.  You can never win a front to front shoving match with a standard 4 driven wheel box bot, but you can escape pretty well.  That means your offensive scoring system (kicker or whatever) MUST be good, since you have only a small defensive capability, and that only if your front is extremely heavy and since you cannot use 2 cims each on driving those two wheels because you risk not having one to power the back.

Also, if you are using a CIM for the back, do you have the 3 gearboxes ready?

I mean in theory you could do a 4 cim drive in 2 gearboxes for the front two wheels... but then your only real option left is to use a FP with gearbox to power the back...and FPs to drive are extremely tricky since they overheat and they burn out when stalled...CIMS can survive at stall rather well whereas the FPs cannot.  You might get away with one of the wormed motors but they are rather slow and you will have t o write a program that turns them as needed when you turn with the front two wheels (since they cannot be backdriven)...otherwise your back wheels will drag when you turn with any worm using motor.

So unless you are doing a 3 cim 3 gearbox drive, I would advise against perpendicular omnis in the back.  Not driving the back wheels impairs you in shoving and escaping from shoving considerably, and FPs in drivetrain die easily.