Working on a possible design for next year, I was just curious aboot which way is easier to steer:
This is with tank steering, so one set runs backwards, the other goes forwards.
My logic tells me that having the wheels 30" apart (instead of 24") means that they’ll produce a greater turning force (torque) around the axis of rotation (the centre of the bot). So I just want a bit of confirmation on that.
I’m guessing you mean all 4 wheels are going to be the driving wheels?
For example, no castors in the front or back of the robot?
There are some good White Paper on Drive systems…and one explains the physics behind tank drive…check them out, and you will get more that you asked for!!! in a good way oh course
Yep.
Chris Hibner created a GREAT whitepaper which very simply lays out the physics behind drivetrain turning. Check it out.
Props to Chris.
JV
For the basics, wheels on the 24 side will have much easier turning than the 30…because of their distance apart. This can make a big difference based on the wheels your using. If you plan on using pneumatic wheels like the ones provided in the kit, your best off going with 24. Even that isn’t too great. We did tests with different wheels on a robot this year, and were barely able to turn with those the 24" way. All they did were skip, and eat up our battery.
Definitely make your robot wider than it is long if you want it to turn well.
sorry, but aren’t the dimensions 30 by 36, not 24 by 30?
slaps head…yes…it’s too late for me to notice such an insignificant detail 
… so that’s why everyone’s bot seemed so much bigger than ours… 
just kidding.
Well see, I figured since most of you were in the states (in Canada myself), I had to take the exchange rate into account.
But yeah, all four wheels are driving. And what I’m doing is developing a crab drive for the robot, so I can choose which wheels turn the robot, so depending on how we build the robot, we can make the software choose to orientate the wheels to turn either with the front/back or the side wheels.
putting the wheels on the 30" side makes the robot turn earsier nd be more controllable
Just for reference, when doing track drive as long as your distance between you tracks is longer than the length of your track touching the ground then you will turn well(assuming that your tracks have good traction and do not slip alot). I believe this same principle applies to wheels also…correct me if Im wrong.
-Pat
You aren’t wrong, but I believe FizMan was talking about a “crab drive”. In that case, I’m not sure why you care much about tank steering because you can just turn your wheels to turn like a real car, or even cooler, move by translation by having all the wheels have the same orientation relative to the robot and changing that orientation.
I wish Max, I wish. Unfortunately, the way I’m developing the drive, that’s not possible. But the benefit of the crab drive is, assuming the game won’t demand it much, we won’t need to turn often.
FizMan, That sounds like you are talking about translating, not turning. How would you move in more than one dimension without turning? By translating, I mean point all 4 wheels in the direction you want to go, and drive.
Oh yes, we are translating for the most part. BUT… unless the game is beyond my scope of comprehension, I’m going to assume that being able to TURN the robot as well will be undoubtably required… (for example, orientating the robot so that your bar hanging hook is pointed in the right direction)