question about the chassis

we are a new team and won an qualification for the dallas. we are building our machine. However we have some questions about the chassis. i think the chassis should be heavier so that the robot will be more stable, but our coach tole us to make the chassis lighter, or the rob may sink into the filed. So we are so confused,who can help us:confused:

My opinion is that it all depends on whether or not your planned drive train can handle it or not.

I don’t really think the amount of weight is too much of an issue if you support it well. The main thing I would be concerned about is having your weight be distributed throughout the robot so it is stable and not top heavy or anything like that.

The design of your robot should suit your game strategy. If you think speed, agility and acceleration is essential, you probably want a robot that is as light as possible. If you think this is a game that requires strength to both push other robots around or to resist the force of other robots pushing YOU, you would probably build a strong, heavy chassis.

Don’t worry about sinking into the field. That hasn’t been an issue in any competition Vex robot I’ve seen. If your robot is that heavy, something else (most likely the axles or motors) are going to fail before you have to worry about sinking into the floor.

For what it’s worth, in last year’s Quad Quandry game, power and weight were big winners. The final answer isn’t in this year, but I’m guessing the winners at Worlds will be fast and generally lighter.

I would suggest something that provides a good base for modification, as well as being robust. Because of the ramp, I would advise that the chassis of your robot weigh more than whatever you stick on top of it =). Aside from that, happy building:)

Sinking into the floor does happen and is very important if you are using the default tires on the 4" wheels (the tires have that little ridge around their edges - if it digs into the tiles, the bot becomes very hard to turn).

Sinking into the floor is also very easy to assess experimentally. Buy a package of tiles from somewhere and see what happens…


Here are a few specific examples:

*]If your drive train has all omni wheels, you want a heavy robot so you don’t get pushed around too much.
*]If your drive train has six wheels, with at least two omni-directional wheels, you want a heavy robot. The normal wheels are slightly smaller than the omnis, so the robot needs to sink in to give the normal wheels traction.
*]If your drive train has four wheels, with two of them omnis, you can choose to make it heavy or light, but it helps your turning if your center of mass is closer to the normal wheels.
*]If your drive train has all normal wheels, you want to make your robot as light as possible, because otherwise you won’t be able to turn very well.

Hopefully my reasoning is sound.

  • John