Rookie team drive tream idea

[Max Lobovsky]

Originally Posted by Solace

Ok, here goes

The two chips are not quite as powerful as the drills. I think that the drills give you a little under 350 watts and the chips give a bit over 250 watts. The next highest motor in power capabilities is I think the fischer price motors, with something like 200 watts. (don't quote me on the numbers).

That being said, the chips are more useable. The are more symmetrical than the drills, so they run at the same speed in both forward and reverse. Its a lot easier to make the robot run in a straight line that way. They are also a lot easier to mount, and are much harder to overheat. You can run them longer and harder without ever having to worry about hooking up cooling fans and heat sinks.

The good thing about worm gear transmissions is that you can't backdrive them. The bad thing is that you can't backdrive them. It's a mixed blessing. There isn't really any aspect of this years game that requires you to hold your ground in a pushing match, so it probably wouldn't be that useful. Also, you wouldn't believe how much harder it is to simply transport your robot when you can't just push it along the ground.

The skyway wheels will provide traction.....up to a point. They will be good enough for driving around, but they will not be able to stand up to a higher traction wheel, such as a pneumatic. However, unless you see yourself doing a whole lot of bashing against other robots, that won't pose a problem. On the plus side, having low traction wheels allows you to turn easier.

The best gearing to put into your transmission is, believe it or not, almost entire determined by the kind of wheels you are using, and the geometry in which you make your wheel base. Basically, you want to be able to drive as fast as possible while still retaining your ability to turn quickly.

Just for comparison, last year 571 used a four wheel tank drive drive train, powered by both the chips and the drills. We had 2 high traction 8" pneumatic tires and 2 low traction 8" skyway wheels. The bot topped out at about 12 ft/sec while retaining its ability to turn. This relatively high top speed let us outrace most other opponents, but came back to bite us in a way as well. though we could still turn at a reasonable speed, the process of turning drained an excessivly large amount of battery power (we couldn't turn at all until we replaced the back pneumatic wheels with the lower traction skyway ones). Learning from last year, this year we are going with the more versatile 6 wheel drive base in order to make turning easier in high gears.

In your case, running only on chips, I would not suggest running on any wheels that had a whole lot more traction than the skyways. 8ft/sec, while not blazingly fast, is fast enough to keep up with most of the competition. While i would not suggest using a worm-gear transmission, i don't really have any basis for making that suggestion other than personal preference.

I'm sorry, i confused the Skyway with the new 12" pneumatics they are giving us. I guess that means we need to trade out two of 'em for lower traction ones.

I don't understand how bots have such a huge range in power in their drive trains. I believe FIRST suggests a simple drive train with the Fischer-Price yet some teams, like you, will have nearly quadruple that power. What do we really need?