pic: One-day Minibot

[sanddrag]

Originally Posted by Jeffy

How is the plate for turn-on connected to that switch?

It's a special type of limit switch that I had a few of sitting around. The little plate is spot-welded on, from the factory.

To clear up any confusion, I'd like to explain my thought process behind this design. I find it silly I need to defend myself here, but nonetheless, here's my response.

If you look at the Russian Buran shuttle, many people would claim they stole it from the United States, when in fact, both countries had done proper engineering and arrived at very similar conclusions, independently.

When I built this, I did not have any pictures of any other teams' minibots with me. Interestingly enough, I have never even seen up-close the minibots of the teams of individuals in this thread who have taken issue with me posting this design. Yes, I saw the general concept of the fast minibots at San Diego. But so did hundreds of other people watching in the stands. This minibot design is a logical conclusion of proper engineering and physics principals. To think that anyone with an understanding of such principals would not arrive at a similar conclusion is preposterous. It is not an optimal conclusion, nor the only conclusion, but is is certainly a logical one. I don't think anyone with an understanding of physics would disagree.

From the minute the rules came out that said you couldn't launch the minibot, and all that was required was a motor and a battery, that's all that I wanted to send up the pole (well, two motors, more power). Why have mass you don't need?

Physics principals say less mass makes for less force (weight) which makes for less work and a shorter time to complete the work, if the available power is fixed (which it is). I'll post a writeup on this in a separate thread. And of course, to be realistic, you need something to provide a frictional force to the pole (for propulsion), you need a switch to turn it on, a switch to turn it off, some means of providing normal force to the pole, and a "stick" to hold it all together. WHY any team would choose to send more than this up the pole is beyond reasoning. They clearly do not understand the physics involved. So, that's how this design came to be. What is the least amount of "stuff" we can send up the pole. I've been saying this since day 1.

Regarding removing the gearheads, I had been looking for data since Day 1. At some point, CD user Richard was gracious enough to stick a motor on a dyno, and post the results. Anyone who read these results would have concluded, the gear-head needs to come off. And hence, a smaller "wheel" follows, additionally reducing mass.

I hadn't worked on the minibot much at all for the build season. I had many ideas of how it should be, but I never got around to doing anything about it. I was too busy with work, personal projects, and other parts of the robot. Our team has a culture of letting the students go their own way, letting them fail, then learning why the failure occurred. It's not a culture I agree with, but it's how we do it here. Anyhow, we had several new freshmen students working on a minibot the whole season. They built a large, heavy minibot. Clearly they didn't understand the Physics involved, nor had they done any math on it. It's slow, and difficult to deploy. However, my students did not understand what was deficient about their design. So, I decided to build this to prove a point.

As a team, we went to San Diego to watch the regional, and see what works and what doesn't. Clearly, small light minibots work. So, I embarked on an endeavor to see how quickly I could build one, for my own amusement.

I dug around through about 200 lbs of scrap metal, found a piece of C-channel, looked at it, and thought "hmm, this might work"

I went to 3 hardware stores, looked at every type of switch they sell, picked one and thought "hmm, this might work"

I looked at the rules and thought "what allowed materials can I use for tires?" I saw latex tubing on the list and thought "hrmm, this might work"

I opened a web browser and started searching for strong magnets. After an hour or so of searching, I found something cheap that looked decent and thought "hrmm, I have no idea if this'll work, but it's cheap enough to try."

As for an on switch riding against the pole, that's already an idea we'd had for many weeks.

But, I don't see any point in debating who came up with what ideas first. The winners will be the ones who have refined their design, which I have not.

On the topic of sharing designs. When I was young, and not-well informed about how the good robots work so well, and how the good teams do what they do, I learned from Chief Delphi. I learned not by constant wonder, and frustration, but by abundant sharing, and examples graciously provided by others. At events, I learned how things work by people showing me up close. The reason I've posted what I've come up with here, is for the teams who maybe don't have a physics teacher or engineer to help them, or for the teams who maybe got down such a narrow path of thinking, they never considered something like this.

Some will choose to copy the design. But, I don't feel I've given anything away. Engineering is no secret, it's math. I could have not posted this. That's always a choice. But who does that benefit? Perhaps a select few who were hoping that nobody else could do the math (which Ether has so kindly posted here on CD, for all to benefit from). What is the greater good?

This is something anyone who can do a little math can figure out. It's something a dad with tools in his garage can build. However, the winners will be the teams that can iterate and refine their designs to the least mass and optimal performance.