Which is a better bot?

Lynxmotion Rovers, Sumo, and Tracked
1

I am building my first sumo bot. I am wondering about my design.
My only restriction is 4lbs.

With you guys experiencd which is a better sumo bot.

2wd
4wd
6wd
tank tracks

thanks for any help. my next post will be about motors.

2

chuksauce,

I’d vote for the 4 wheel drive just because all of mine have been 4 wheel drive.

         Rick Brooks
3

chuksause,

How about a more complete reply?

I’ve never been successful getting the weight distribution right on a 2 wheel sumo. Whatever weight that you put on the front scoop will reduce pushing power. Then, when you are pushing on another sumo, the weight distribution can change to almost anything.

The major disadvantage of 4 wheel drive is turning speed. I’ve never had a problem with the ability of a sumo to turn. In every case, I’ve had to slow down the turn rate to give the sensors a chance to respond. Keeping the track width the same as the wheel base helps, but even long, narrow four wheel drive sumos turn good enough.

Ah, six wheel drive. Try one. Then take off the middle two wheels and see if you loose any performance. Report back and we will compare results.

Tank track sumos…where are you going to get tracks that come anywhere close to the traction of Lynxmotion molded urethane tires? Think about the real reason that vehicles use tacks.

Since you are going to ask, use four GHM-12 motors with a 17 cell battery pack. See Excuse II at Brooksbots.com. Although I wasn’t trying to build it light (it is in the 3KG class) it presently weights 4 lbs. 3.4 oz. It has four GHM-12 motors, urethane tires, and 17 Kokam 1050 ma-hr batteries. Using light weight design and proper materials and I am sure that it could be made under 4 pounds.

Hope that helps.

      Rick Brooks
4

In my opinion, it really doesn’t matter. I run both 2 and 4 wheel sumo’s and they both work just as well, when they work.

In most cases, the problems I see with robots is that the don’t work very well. Sensors don’t see the edge, Sensors don’t see the other robot, microcontrollers reset, batteries go dead, wheels fall off, software does provide flexibility to change based on robots, etc.

It doesn’t matter how many wheels you have if your robot has any of the above problems.

My recommendation is to pick something that you like, and spend the rest of the time making the robot completely reliable.

Pete

5

check out the thread about my tracked sumo. I have no experience with the urethane tires, but i find they the lynxmotion tracks offered more traction than typical neoprene sumo tires. I wouldnt rule out tracks completly, i find them to be jsut as manouverable and they can drive off of a wedge when you get hit.

6

I saw the video that you provided a few days ago and in the video you could see the wheeled sumo’s tires slowly spinning forward while it was being pushed backwards. There is simply more surface area with the track system and it makes it hard for the opposing sumo to push against a tracked sumo. Also the tracks spread the weight along the length of the tracks rather than only on the small foot print of the round tires–that small area that is actually touching the surface–so tracks seem very effective based on what that video showed.

Reliability I would have to agree is perhaps THE MOST important of any design.

7

yep,

interestingly enough, we where both underweight. the tracked bot weighs in at 1.9 kg and wheeled bot weighed 2.2 kg. so tracks have much more traction in my opinion.

8

The thing you have to realize is neoprene sumo tires are not even remotely close to urethane tires in the traction department. Urethane tires have to be clean to work properly, but they provide enormous traction when they are.

Seeker 2, my mini-sumo, has never lost a head-on pushing match with another mini-sumo.

  • Jon
9

clean is also paramount for tracks as well, I would be interested to see the outcome of a 3kg urethane vs tracked robot tug o war.

10

I am only guessing, but I bet the tracked vehicle wouldn’t be prone to “hop” as much as a wheeled bot can in serious pushing matches. Just a guess though…

11

One of the key pieces of building a good sumo robot is fore and aft balance. Too much weight over the wheels and they stall. To little, and they hop. Just the right amount, and they spin with lots of pushing power.

Seeker 2, mainly through luck, has really good balance, which makes it a really good pusher.

  • Jon
12

In reality, it really doesn’t matter about tracked sumos or wheeled sumos. The key to a successful sumo is one that works! In must stay in the ring, must not reset on its own, and when it “sees” its opponent, it responds they way you expect it to.

Over 90% of the sumos I see in competiton, and I have seen hundreds of them (not counting the ones in Japan) fail in at least one of the above 4 points. And their failure points cause them to lose the matches. It is unusual to see a robot that is successful in the above 4 points lose due to traction issues.

Pete