Non-FRC Bot

[EricH]

Originally Posted by drakesword

I think treads would be good at traction but not much more.

Incorrect, actually. Treads are often used when the surface that needs to be crossed is marshy, somewhat swampy, unstable, dirty, or sandy, or some combination of those.

The objective is to spread out the weight so that the pressure is less so that you don't sink down into whatever it is you're trying to cross. Think snowshoes--if you're not wearing them, you break through any crust the snow has on it and go knee-, shin-, or ankle-deep until you get to the point at which the snow under your foot will support you. If you're wearing snowshoes, you go much less deep, because there is more snow to take your weight. Tank tracks take the entire weight of the vehicle and spread it out over the length of the vehicle by some width that, for a large military tank, could easily be a yard or two (taking both treads together).

For sand, it may not be as much of an issue, but it's still worth looking at. There's a reason a lot of heavy construction equipment and tanks use treads. An awful lot of small, light military/police-type robots use treads.

Large wheels are also an option, especially if you want car-type steering. Just make sure that they're big enough to let the robot scoot over the top of the sand as much as possible, or that the robot is heavy enough and has enough ground clearance to pack the sand behind it.

[drakesword]

Originally Posted by EricH

Incorrect, actually. Treads are often used when the surface that needs to be crossed is marshy, somewhat swampy, unstable, dirty, or sandy, or some combination of those.

The objective is to spread out the weight so that the pressure is less so that you don't sink down into whatever it is you're trying to cross. Think snowshoes--if you're not wearing them, you break through any crust the snow has on it and go knee-, shin-, or ankle-deep until you get to the point at which the snow under your foot will support you. If you're wearing snowshoes, you go much less deep, because there is more snow to take your weight. Tank tracks take the entire weight of the vehicle and spread it out over the length of the vehicle by some width that, for a large military tank, could easily be a yard or two (taking both treads together).

For sand, it may not be as much of an issue, but it's still worth looking at. There's a reason a lot of heavy construction equipment and tanks use treads. An awful lot of small, light military/police-type robots use treads.

Large wheels are also an option, especially if you want car-type steering. Just make sure that they're big enough to let the robot scoot over the top of the sand as much as possible, or that the robot is heavy enough and has enough ground clearance to pack the sand behind it.

True sir but the issue of endurance remains. Being a medium to small bot any ort of tread that will withstand sand over a long period of time would have to be most likely steel which would be rather heavy compared to the overall objective of the robot.

[MrForbes]

Plastic or rubber treads would probably work well and last a long time. I expect the treads would cost more than pneumatic tires and wheels, and the mechanism to support them in proper alignment would be harder to build, and more complicated and expensive, and difficult to make sand resistant.

Although the steel treads on my 1940s vintage International Harvester crawler do still work after all this time....

[Tobot]

Nasa has been dealing with sand for a long time. They prefer the rocker-bogie suspension.

Another function that tracks can allow is climbing of square-edged obstacles like steps and stairs.

[drakesword]

Originally Posted by Tobot

Nasa has been dealing with sand for a long time. They prefer the rocker-bogie suspension.

Another function that tracks can allow is climbing of square-edged obstacles like steps and stairs.

We did a modified version of that for the breakaway game except we had 8 sets of wheels each half had their own articulating point rather then 1 articulating 1 solid

[Tytus Gerrish]

Originally Posted by Tobot

Nasa has been dealing with sand for a long time. They prefer the rocker-bogie suspension.

Another function that tracks can allow is climbing of square-edged obstacles like steps and stairs.

Yes, but they have a robot on mars that's stuck in the sand and hopefully hibernating right now.

[PAR_WIG1350]

Originally Posted by Tytus Gerrish

Yes, but they have a robot on mars that's stuck in the sand and hopefully hibernating right now.

But keep in mind, it did last much longer than it was designed to.

[drakesword]

@All

I like the enthusiasm that everyone has. A couple of points that I need to make first before I continue work.

I am limited in my fabrication skill. I have experience repairing and modifying things but very little in building something completely from scratch.

I am able to weld so having a ridged frame is not an issue.

I believe the best way to go about this would be to modify an existing platform or to build a simple one. Then go on to make an advance chassis or modify the existing one to increase capabilities.

So here are the options in my eyes.

Option 1) Build a square 4 wheel chassis
Option 2) Mount a system to the Go-kart chassis utilizing the current drive train
Option 3) Mount a system to the Go-kart chasis converting it to all electric

Advantages to each
1) Can build to any need. Can spin rather then turn.
2) Simplest to build (add a servo for throttle and a motor for steering). Potentially could go further then 1 or 3
3) More controllable then 2 yet simpler then 1

Disadvantages
1) More time from build start to run
2) Another area of failure with the engine. Unable to spin.
3) More power drain then 2 and less capable then 1

[MrForbes]

Would the range of the wireless control system affect your decision? Will it operate autonomously some of the time?

I think you'd probably be happiest with a skid steer robot....much easier to get out of sticky spots. And since you are not sitting in the vehicle when you're driving it, you will probably get into more sticky spots than you expect

[drakesword]

Originally Posted by squirrel

Would the range of the wireless control system affect your decision? Will it operate autonomously some of the time?

I think you'd probably be happiest with a skid steer robot....much easier to get out of sticky spots. And since you are not sitting in the vehicle when you're driving it, you will probably get into more sticky spots than you expect

Ideally it would be autonomous with manual backup.

[EricH]

I've got an idea. If the go-kart chassis is anything like I think it is, tear the current drivetrain off of it entirely, and put a 4WD skid steer on instead. Also weld on a belly pan to help keep sand out of the internals, if there isn't a pan already.

The go-kart tires might work OK for use on sand, too, if the robot is fairly light.