Does anybody know where you can get a tank drive car, or how to make one. I don’t mean a go cart, I mean an actual car. Our team members have been using tank drive so much, they’ve come to the point where they have no other way of steering, myself included. So does anybody know these things?
I’m pretty sure you can’t get such a thing. Car steer because they are made for going in a straight line without a lot of stop and go. Robots have skid steer since a zero turn radius is useful and they stop and turn quite frequently. If you’re looking for a good industrial example of a skid-steer, check out a bobcat.
There is this for a laugh.
But in reality skid steer would be quite dangerous at high speeds and damaging to roads, plus everything is designed to handle a large turning radius that results from a car.
You might be able to buy one from a Tire Store. 
They would probably give you the car if you would promise to buy your first N sets of tires from them.
Every once in while somebody posts an M113 for sale on e-bay. They are quite reasonably priced, agile, configurable (APC, medical evac, command and control, engineer, utility, etc.). And the US government will be disposing of THOUSANDS of them over the next six years. These tracked vehicles are 1960’s era skid steer and some (all?) use the differential lever type steering you’re looking for… “tank drive”.
All modern agile tracked vehicles (military high mobility platforms) use a steering wheel, accelerator, and brake pedals. The newest ones might even start using a joystick. I don’t see them going back the two stick design, it’s not in any trade studies I’ve seen anyway.
Have any teams looked at user interface studies on “tank drive”? Our results from an early season test this year showed that independent up-down and left-right (axis 1 and 3) on a PlayStation style Logitech game pad was twice as fast for combined gross and precision movements. Our study involved at least 5 untrained users (users unfamiliar with the platform, not unfamiliar with various control methods) and the results were consistently half the time, even for those asking for “tank steer”. Why is “tank steer” so popular?
Seriously, there’s several major reasons why nearly all motor vehicles user Ackerman based steering instead of tank drive, including but not limited to cost, tire life, safety, ease of use, mechanical complexity, maintainability, etc.
Shoulda wired up an RC car controller to your robot, like we did…
(my old bulldozer has tank drive, complete with metal tracks, but steering requires using the brakes as well as pulling the steering clutches)
I didn’t intend to have the car “street legal”, just able drive with tank drive. A few of our senior and junior members (who have licenses) really want to try it out, and for some strange reason, our mentors said yes. So, they’re anxiously awaiting for me to send them this thread. I do like that tank one…
Think about how far the outside rim of a steering wheel moves when you drive a “normal” car. Then think about the levers you’d use to get this same action from a tank drive setup. Would the leverage ratio be the same? how would it work?
Easy. Build this years kit bot Jenny-rig a seat on it then put to control system in there lap.
But if you want to acctually want to drive something full size, a tank is your best bet (ps some tanks are street legal in France).
I know a Jenny-ring is 8675309 but what is a Jenny-rig ?
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This may very well be a big part of the future of racing, the ability the combine a traditional car system with hub motors to cause differential motion AND generate yaw would be very good in the corners indeed. Apparently a few Formula Student teams in Germany are working on exactly that.
Waaayyyy back when I was the drive coach on my old team, we did a study that showed that drivers all did better with “arcade drive” than with “tank drive” (then weren’t known as that back then). On that team, we forbode “tank drive” after that.
I’ve been wanting to go to independent fore/aft left/right for years. We finally did it this year, but NOT with two sticks. We use one stick for the fore/aft and a spring-loaded knob for the rotational movement of the robot. This setup was extremely intuitive the drive, and it even eliminates the “turning in the opposite direction while the robot is facing you” problem with a stick. I’m thinking we’ll stick with this configuration for a while.
To your knowledge, does this interface already have a unique name, and if not have you given it one that we could use here on the forums?
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No, we haven’t given it a name. We’ve been talking about using this interface since the 2008 game, but this is the first year we’ve actually done it.
Feel free to think of a good name. I’m not very good at coming up with names.
Chris,
Do you have any idea why using the knob works better than a joystick when the robot it facing the driver?
I have suggested a rotating control to our team several times, but none of the students seem interested. I just figured it was the gaming mentality coming out.
-Hugh
I know you addressed this question to Chris, but while you are waiting for him to answer…
It is because with the twisting action of the knob, the driver intuitively thinks of rotation as a clockwise/counterclockwise thing (which is independent of the orientation of the robot) rather than as a go_left/go_right thing.
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Excellent point! I didn’t think of that… Thanks Ether.
I will try that point with the students…
Any ideas for a good supplier of a centered spring return pot?
-Hugh