I am thinking 4WD is the way to go this year, but am not sure whether to make it long or wide. We did a 4wd wide in 2004, 2009, and several other years, and it works great. It’s nice and mobile (though not as much as an omnidirecitonal drive train like mecanum). The increased width between the wheel lines decreases the friction while turning, while retaining the same pushing force and sideways friction. The axis of rotation is centered in the middle of the robot. It’s good for pushing too, if done correctly. In 2009, we had traction control, and the combination of drive train, sensors, and software allowed us to basically push any robot we chose. It was nice. The only concern is the chance to fall over backwards if accelerating suddenly. That can be remedied by making sure heavy components are at the bottom of the robot.
I am very torn on this game. My original intent was to be a shooter/balancer due to the new qualifying ranking system which weighs autonomous higher. But considering how hard that actually is to make it in consistently, I changed my mind to a defensive/feeder/balancer bot. That will hinder our performance in the ranking, but potentially give us a better chance of actually winning matches. So the wide 4 wheel would be great, but to minimize slippage, I was thinking of going wide 8 wheel, but that won’t go over the bump.
Our team on kick off day built the 4 wheel wide version of the kit frame.
Photo/Video here: http://www.youtube.com/watch?v=AnIGjPHzkBk&feature=youtu.be
In a short test of driving it around, it seemed pretty nimble and quick.
Might gear it lower however.
We did have it go over a 2x4 seemed to be okay.
Another advantage to going with 4 wide is that the 6 wdr with the middle wheel being lower then the other ones making the bot rocking back and forth when the bot is shooting
That would depend on where your weight is centered at. The ball isnt going to create much rock if any if your weight is centered low and to the front.
Also on the four wheel drive, my team had a four wheel drive in 2010 and we had trouble steering. You want to try to keep your wheels as close together as possible while still being stable. Otherwise you end up dragging the wheels across the floor making it difficult to turn. That was with the standard rubber 6 in" wheels.
Our 2010 robot used a 4 wheel swerve drive with 2 modes. One mode is strictly translating in a crab drive mode, but the other is with the wheels straight operating as a wide base 4WD. It uses 6" FIRST wheels. Here’s a video of it playing breakaway:
When the robot is moving sideways that won’t give you a good idea about the maneuverability of what you are thinking of. But when the robot is moving strictly forward/backward and turning, that is exactly the type of maneuverability you are interested in seeing! It may be tough looking at the video for the first time to differentiate between when its in swerve vs. tank mode, but it’s there!
