I don't know about the winners of Nationals, but I know my team did very well with a single-motor drive. We used one Chiaphua motor with a two-speed gearbox and never had any problems. We were one of the fastest and one of the most powerful robots around- all from a one-motor drive. It was all in the gearing. It goes to show, though, just like 255's did, that you don't have to be complex to be successful.

2 years ago (Bridge Balance year) 'da Bears did that on accident.

We swung our arm back and started goign forward to the balanced ramp. (Was balanced because it hit another team's bot on it's way down. Anyways, in a wheelie on our tank drive we were also bringing up the arm to vertical.

The sizes were justright so as we went forward (still in wheelie) we got on the bridge, arm finished it's forward motion (thus throwing center of gravity forward) and slammed down the bridge for us.


We have a video I took of this match somewhere..

How did it steer with only one motor?

It was one motor per side. I guess I left that part out. It would be a little hard to steer with one motor.

After last year's competition we spent part of the summer developing a new drive transmission design for our robot ED. The drive features a 1:4 ratio between low and high gears, 250rpm and 1000rpm peak power output speeds, up to 65 ft-lbs of torqe, uses the Bosch and Chiaphua motors found in the 2002 kit of parts, and an 8-millisecond response time to shift gears. The prinicpal feature is that the design can be constructed with hand tools, a lathe, and a mill. No CNC, wire EDM, castings, or carbon-carbon componsite construction capabilities are required (hopefully putting it within the reach of most teams)! We play-tested Version 1.0 of the drive system at the Maryland State Fair competition at the end of the summer, and refined Version 2.0 during the fall.

Rather than keep it as a secret, we are making the design available to any teams that want it. It is posted in the White Papers Section. Download it, build it, improve on it, or just look at the pretty pictures - it's all up to you. All we ask is that you let us know about any feedback, and if you do improve on the design, please post your improvements so the entire FIRST community may benefit and improve their capabilities. In the mean time, we are off thinking about Version 3.0 for the 2003 season...

-dave

As Big Mike siid- this past season we used the Chiaphuas (chalupas- atwoods- chihuahuas- whatever) to drive our wheels.

The biggest problems was getting the gears (of unusual configuration) to work with the normal gear types we had available.

The solution was to machine out a reg spec gear such that the bore of the arbor was minutely smaller than the external diameter of the motor arbor. Then we froze the motors and heated the gear such that the expansion/contraction of the two allowed for the shaft to snugly fit into the gear bore when pressed on. As the two slowly came back to room temperature thermal expansion and contraction formed a snug fit which never failed us.

Of course the gears were built into a configuration which came to about 32/1 if I recall and in the wheel housing the load is shifted to sprockets which actually drive the wheels. That way, in the event of something fouling the drive train, the weakest point is the chain and that is easily repaired.

We also designed our machine to grab two goals on the run. Our two extrudable hooks were preset by software to come out as we fly towards the gap between two goals. They sit on tracks in the chassis and are held forward by a shock absorber. So as the robot hits the goals and grabs them, the impact is shifted to the shocks and the chassis stays together. The momentum of the whole system now is moving forward and inertia slams the 290 lb system into whatever is in the way. Inertia can be a good thing!!

Sorry if this is long- I really like that machine!!

WC