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Re: pic: Team 195 driving base 2007
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Re: pic: Team 195 driving base 2007
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I won't repeat all the arguments here, but you can find discussion about it here, and it would appear that a few of your mentors are quite familiar with 6wd systems. You'll also notice that most well-designed tank tread robots have a middle wheel that's slightly lower than the outer wheels, making it essentially a "lowered wheel" 6wd system There is nothing here that says this is the ONLY way to do 6wd. Your team is living proof of that. I'm just trying to present the reasoning behind the lowered wheel. Many MANY teams use this design, so they can't all be wrong. |
Re: pic: Team 195 driving base 2007
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http://www.chiefdelphi.com/media/photos/26869 We only been doing wheel for two year so I am no expert but this system works. it is lowering the center wheel a little. We did tank track before that and also had a center wheel http://www.chiefdelphi.com/media/photos/18792 I think our robots has proven to have power so what he is doing is a good way |
Re: pic: Team 195 driving base 2007
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By lowering the center wheel, you effectively create two 4WDs with a shared center wheel. Each of these has a wheelbase roughly 1/2 of that of the same drivetrain with coplanar wheels. Also, closer the center of mass of your robot is to the center wheel, further it is away from the center of area of both of the wheelbases. Additionally, the traction and width factors should be the same as if you had a coplanar 6WD, and you still achieve many of the other benefits of a 6WD. (Thanks to Chris Hibner for this terrific white paper on the physics of turning with a 4WD). |
Re: pic: Team 195 driving base 2007
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On the other hand, when you do a 6wd and don't lower your middle wheel, the robot is trying to turn on 6 different points. Depending on the friction you create with the wheel/tread you are using, it is very hard to turn unless you lower your middle wheel. While lowering the middle wheel, lots of team work on their CG. If the CG is low and the weight is distributed properly throughout the robot, while turning, the robot turns on 2 (middle) or 4 wheels (using only 4 different points to turn), creating less friction. At the same time, there are always 4 wheels touching the ground. I know wedgetop compresses, so if the weight is distributed properly, you get all 6 wheels touching the ground while going straight or back even if you lower your wheel. It also depends on the team how much they lower their middle wheels. I have seen teams do 1/16, 1/8, 3/16, 1/4, even 3/8 and lot of teams have been successful doing it too. I sure would like to know how does a team turn without lowering their middle wheels. If there is anyone out there with a proper answer with reasonings behind it, please post. Now back to topic... As always, 195's chassis looks awesome. I am digging those wheels. Can't wait to see you guys in person. Let's not burn a victor out right before the final match this time. =) |
Re: pic: Team 195 driving base 2007
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Re: pic: Team 195 driving base 2007
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What I'd really like to see is an eight wheel drive, with 4 centralized drive wheels that are in contact with the ground all of the time, except when accelerating hard in one direction, or pushed from the top. The front 2 and back 2 would be raised up a bit (1/8" or so), be smaller (to reduce weight), and probably unpowered. This would have the benefits of a long drivetrain, be stable (none of the rocking back and forth I'm guessing you get with a 6WD), and have a more predictable center of turning. |
Re: pic: Team 195 driving base 2007
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