Sumo Bots C (NY Trial)

[LukeThomas]

I am pretty divided on the subject of what body shape I should use this year, my partners and I would like to use either a pyramid with a flat top, or a square box with 4 wheels protruding out of the top and bottom in case of a flip.
The main question is would it be advantageous to have a square box with the most surface area touching the other bot, or is it advantageous to have a body that the other bot cannot push?
What are you guys using for your bot this year?

Any help is EXTREMELY appreciated

[captbilly]

Is there a SUmo BOt event this year, I can't find it anywhere in the Rules Manual.

[Dark Sabre]

It is a trial event in some states.

[LukeThomas]

Yea, Its a trial event in new York, though the event description isn't in the booklet. It can be found Here http://soinc.org/sites/default/files/up ... BOTS09.pdf
So back to my question...Any Ideas?

[gh]

The pyramid thing is much more difficult that you'd think. Last year, I started with 1/8 inch plastic sheet and cut it to the right outline, so I had four side panels and one on top for mounting stuff. The four panels then need to be beveled on the edges by hand with a file and sandpaper, and welded together with solvent cement. I added some glue to fill in the chinks. The red outlines below are the volumes that had to be filed down:


Getting those darn bevel angles right was a real pain.

The process would be different if I used sheet metal or mounting brackets to hold the side panels to the top panel and to each other. But, you still need to get all four sides to lie flat on the floor and also make that whole "armor skirt" assembly adjustable on top of your chassis (the part with motors and wheels). All in all, it needs a lot of planning, calculation and drawing, followed by a ton of manual labor and tedious tweaking.

I'd recommend a regular old wedge with two wheels. It's the easiest to control, the scoop fits against the ground, and you don't have to worry about alignment of the wheels to the floor. It's not the most efficient, but it works. You're really not likely to be flipped if you design it to have a low center of gravity.

[LukeThomas]

But I'm afraid that if I build a scoop then I will have no real pushing power, the opponent will just slide off



Hopefully I'll see you at west point if all goes well

[iiamkevin091]

Man, after competing against you guys.

you kind of make me want to ditch the vex kit, haha. i just cannot deal with the weak motors.

hehe...i got kind of lucky the first round, of our best out of three match.

i should have put the battery top on, but ohh wells.

i guess i will see you guys at westpoint. and btw are you guys at stuy planning on keeping the same two wheel design?

[iiamkevin091]

After our performance at regionals, I am currently debating along with my coach whether we should change our design

Right now we are using a four-wheel design. And it is working fairly well, just I feel not well enough for states.

We are also using vex kits, They are simple and fast to build but very limited.

My feelings are:

Four Wheels:
Better over all handling
Greater stability
Less vulnerable on the sides

Two Wheels:
Ability to achieve low angle of scoop
Possibility of operating on both sides if flipped.
Would have to buy new parts, do not feel two vex motors would suffice
Very vulnerable on sides
Scoop might catch on the ply wood
much harder to balance

Is the lower angle and ability to operate on both sides worth it?

As of now, building a two-wheeler definitely seems much more difficult, and would require a lot of work.

However, the Stuyvesant built one seem almost perfect in design. I would opt for large wheels.
It would be very hard to create a two-wheeler, comparable to stuy's with our limited funding.

I think the S.O office might possibly chew my head off if i ask for $500 for more equipment. LOL
We are after all a budget school, lol we should get an award for Penny Winners, haha.

What do you guys think?

Also, Stuyvesant, what kind of tires did you use?
It was insanely hard to push event after getting the bot on our scoop?

[gh]

After our performance at regionals, I am currently debating along with my coach whether we should change our design

Definitely ditch the Vex.

Right now we are using a four-wheel design. And it is working fairly well, just I feel not well enough for states.

Four wheels > two wheels. My original plan was to build a four-wheel design (I would have done six if I had time to). The one you saw was a backup design. It was just a copy of our 2007 States design.

Four Wheels:
Better over all handling

Nope, it has terrible maneuverability. See the Cons for Skid-Steer at http://www.roboticsindia.com/modules.ph ... cle&sid=29. I had four wheels and sticky tires last year, and turning was an ugly operation.

Greater stability

Maybe, maybe not. I never did testing on this.

Less vulnerable on the sides

I assume you think this is because there's twice as much surface area contacting the floor as does a two-wheel bot, so I guess it would be better, but the wider side profile really makes it not worth it.

Two Wheels:
Ability to achieve low angle of scoop

That's really about how well you can pack components and how big your wheels are.

Possibility of operating on both sides if flipped.

No reason why this wouldn't work with four wheels.

But there's just no point. The field is so small, you wouldn't get a chance to move around after being inverted anyways.

Would have to buy new parts, do not feel two vex motors would suffice

Four won't cut it either. I'm using 550-size motors, which means that the can of the motor is 55mm long. Try opening up a Vex motor and compare with the puny el cheapo Mabuchi or whatever is in there.

Very vulnerable on sides

Everything is vulnerable on its sides. But the scioly competition's dimensions are such that almost all matches are head-to-head. I design to push forward, not to defend sideways.

Scoop might catch on the ply wood

Bigger problem is the scoop pivoting about the wheels as it rides on the wood.

much harder to balance

Yep. The biggest disadvantage to the two wheels are that part of the robot's weight is resting on the scoop, not the wheels, and that means less pushing power. I tried to counteract it by placing the battery pack behind the motors so as to distribute the weight over the wheels better. I thought that would be what loses me the tourney, not that somebody would get under. Unfortunately, you seemed to have figured out our secret for the scoop and outdone us in that regard.

As of now, building a two-wheeler definitely seems much more difficult, and would require a lot of work.

As I said, two wheels was a backup plan. It was supposed to be easier to build than the four wheeled one, because I didn't have time to make the original design. I built everything the night before competition (had an interview after school, so I basically didn't sleep Friday night).

However, the Stuyvesant built one seem almost perfect in design. I would opt for large wheels.
It would be very hard to create a two-wheeler, comparable to stuy's with our limited funding.

Eh, you'd be surprised at how little money the team gets and how much is wasted on useless things (ie, stuff other than building events :P). The major parts in the bot (batteries, motor controller, motors, wheels, chassis fabrication in order of descending cost) is about $300, with other knickknacks like shipping, lube (don't ask), and stuff destroyed in the process of building the thing not included.

Also, Stuyvesant, what kind of tires did you use?
It was insanely hard to push event after getting the bot on our scoop?

It would have been impossible if I hadn't moved the battery behind the wheels. Once the front of my bot gets lifted over a certain angle, the robot stops riding on the wheels and starts skidding on the battery pack instead. If it weren't for that and I had maintained traction, I would have driven OVER your bot instead. Great job on scoop though. My partner took high-speed video of all my matches and I can see two things that really put me at a disadvantage (probably unintentionally): you always went for my left side, which is not only weaker in pushing power, but also a bit off the ground, and you seemed to have actually practiced before (I never practiced driving in three years of doing this event).

As for tires, you probably don't want to bother trying what I did, which was completely insane. I basically made wheels that didn't mount ONTO the motors, but OVER them. They were just plastic tubing. So then I made a mold around that assembly and poured in a soft rubber compound from an art store. Then I had to destroy the mold to get the wheel out, since the mold is stuck to the rubber.

However, the results are awesome:

That's the wheel and motor stuck to a WALL.

[gh]

Oh right, videos: http://www.geekshavefeelings.com/harpy- ... -2009.html

You might want to check out the last two just to see what the design could do with better electronics. Match 4 might be interesting, since you can see a brief moment when neither bot is over the other but I'm still pushing the other back.