Quote:
Originally Posted by LeelandS
So, here's my take on 8WD vs 6WD. Now, this is only coming from what I've read perviously and seen out of a 6WD, so take all this with a grain of salt. Maybe a teaspoon.
6WD
Wins:
Lighter and simpler than 8WD, obviously due to one less set of wheels.
Yeah, that's pretty much it.
8WD
Wins
-More maneuverable. With 6WD, the turning radius of your robot, I believe, becomes centered between the center wheels and whatever outer wheels the robot is sitting on. With 8WD, it's in the center of the robot.
-Able to overhang. On a 6WD, the robot is sitting on 4 wheels at a time. The center ones, and a set of outer ones. These outer wheels are set out at the far ends of the robot. When you start to try and overhang, as soon as one set of wheels comes off the surface you're on, the robot is going to start tipping that way. With 8WDs center wheels, the robot still rests on 4, but the weight distribution of the robot along those 4 wheels is more centralised. As long as those 4 wheels are still in contact with the surface, you shouldn't tip over. Weight distribution on both of these is a huge factor, so you saw some teams on 6WD and West Coast able to overhang, but I believe this rule generally holds true.
-With the raised wheel set and a sloped chassis, overcoming obstacles is much easier.
Anyone finds flaws in this, please tell me. Writing down wrong information then having CD correct me is usually how I learn here  |
I dont mean to be rude but some of the things you have said here are wrong. :$ And i dont want people to be miss informed when designing a robot chassis.
I have designed many chassis and have been the driver for a couple years now, so I have experience with the 6WD vs 8WD. Though we have never used a 8WD.
6WD chassis do not spin on the middle wheels and what ever else wheel/s it is on. They spin only on the Center wheels, and (if you picture this it will help) "rock" back and forth from the back and front wheels. Making the middle wheels the "Axis" for the turning. In 8WD it is a little different how it moves. It moves with the 4 center wheels, and eliminates the "rock". And makes it a little smoother chassis. But the rock may or may not be a problem depending on how much it rocks. For example this year a 6WD could have made your shot off, by the slightest little bit. 8WD might (most likely) Eliminate that problem.
You contradicted yourself in the second point IMO. As long as 4 of your 6 (in a 6WD) wheels are on the bridge you should not tip. Depends on your COG though. With 8WD you do not have a center wheel to support your robot on the bridge. When 4 wheels are in contact, however (if COG is in center) you have (if wheels are evenly spaced) more than half your robot off of the bridge, and you know what that means...
(I Know I am terrible at explaining things, so sorry)