Re: pic: One-day Minibot
 

I can understand how you can be upset if you see pictures online of a similar design that you spent a lot of time working on. But, if you attended a public event (where everyone and anyone can see your robot and take pictures of it), I don't think you can complain if someone talks about your design or even posts pictures of it on a public website. It's just a nature of the beast.

Re: pic: One-day Minibot
 

I think the issue is with someone else posting their design. If the team wanted their design revealed, they would have posted it themselves.

Re: pic: One-day Minibot
 

If I understand correctly, this design was built by the original poster. As he mentioned it was inspired by a few other team's designs, but he gave them their credit as it was due. It may apprear to be the same, but it's not exactly the same, which makes it the Op's design.

Re: pic: One-day Minibot
 

I think he's suggesting it isn't gracious to essentially post another team's design..

Anyway, I think so many minibots at this point have such similar designs that he could have been inspired by quite a number of teams, some who wouldn't be upset at all. At this point, as someone mentioned, it's worth more to optimise than to express dissatisfaction with loose-lipped miniboteers.

Re: pic: One-day Minibot
 

Agreed! This design is "inspired" by our back-up minibot. Oh wait... we never used that minibot, or even brought it to a competition....

Re: pic: One-day Minibot
 

We're happy to share our design philosophy, design decisions, and the processes we used to get to our current solution. We do hesitate, however, to post detailed pictures and designs of things during the current season to both ensure learning takes place, but also to maintain a competitive advantage. Ask any team and they'll tell you we're the first to explain all about our robot design and any details about it.

The bottom-line is that we're happy to give you the tools you need to build a successful mini-bot, but prefer doing so in a way that further enables you later. We must also not forget that this is a competition. The unfortunate thing about this year is that the simplest mini-bots will be the most successful (and the easiest to copy). When a significant majority of some of the early regionals could have been won with a single first place mini-bot, their importance cannot be over emphasized. Copying, sharing, posting pictures or detailed CAD of other teams robots without their consent is neither inspiring nor should it be considered GP.

While our issues here are not really that big of a deal, the benefits and takeaways from this thread could have been achieved through a different and more discrete means.

Re: pic: One-day Minibot
 

I personally don't like to have to make shafts for all the spare motors, especially for these motors and the task at hand. I try to use motors as they come out of the box. Replacement is much easier. We use double set screws with a Loctite adhesive that is advertised for polycarbonate. In addition, since the motor shaft does not come through the back of the motor, you risk damaging the rear bushing pressing your drive shaft onto the motor shaft. If you still insist on removing the pinion gear, I suggest making a push plate that will go in the area between the back of the pinion and the front of the motor housing. However, you still have the problem pushing the drive shaft onto the motor shaft. I would rather use that same push plate to press the drive shaft directly onto the pinion gear.

Nice design - quick build and effective. However, by St. Louis, consistency with deployment and dependability are likely going to be the deciding factors. You can only lighten so much, push the amps only so far, before you plateau with the minibot design. We're saving our best for St. Louis. :) :)

Re: pic: One-day Minibot
 

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.

Re: pic: One-day Minibot
 

I did exactly that to remove the gear. Did it years ago with FP motors too. I never considered a press plate to push a shaft directly on the gear, without loading the motor shaft. Great idea! I'll have to keep that one in mind.

I was a little worried about pushing the shaft, when it doesn't go all the way through the motor, but it appears to have turned out okay.

Re: pic: One-day Minibot
 

Studying and understanding successful designs is an excellent way to learn. The students who spent time on their own team's minibot will learn a great deal when they see a design that is much faster than they came up with. They will begin to understand where their thought process was limited and maybe will know a bit more about how to approach the next problem that comes along. The students on our team spent about half the build season working on versions of the minibot with the NXT Brick as part of the minibot! When we got to KC, our minibot was only a 2 second minibot. However, our deploy system works pretty well and we won KC with that 2 second minibot. (Information on our robot including deploy have been on our team's website since the end of the build season so if you're looking for deploy ideas feel free to go there.)

Re: pic: One-day Minibot
 

I don't disagree with that, but do feel that an explanation of the reasoning behind design decisions will almost always result in a more thorough understanding of the solution than analysis alone can obtain.

Re: pic: One-day Minibot
 

xx

Re: pic: One-day Minibot
 

The specific details of the interactions were not posted here, nor do they need to be.

I do not disagree with the spirit or intent of the post, and have a long history with Dave personally and did not intend to discredit his teaching or work. I said what I needed to say, and it seems that we are in agreement over a good majority of everything else. However, as far as simplicity and logic are concerned; the simplest solutions are sometimes the ones requiring the most iteration, refinement, and time. The designs that make you say "Why didn't I think of that?" are usually from the people who thought of everything else, designed it, built it, had it fail, and then iterated until they were successful. Logic and reasoning don't always translate into simplicity, even when keeping minimalism in mind.

Re: pic: One-day Minibot
 

There are pinion pullers designed specifically for removing pinions. Pulls it right off easily w/o and damage and only costs a few dollars. However we removed them a couple of different ways w/o any damage to the rest of the motor because we didn't want to wait for the mentor who had the pinion puller at home. The simplest method to do it w/o a pinion puller is to cut a slot slightly wider than the shaft in a plate that is larger than the motor. Then slide the motor on the plate, support the plate with the open jaws of a vise or some blocks and use a small diameter drift to drive the motor out of the pinion. Be sure to have someone ready to catch the motor. Grinding or filing the pinion most of but not all the way to the shaft will allow it to slide off easily also.

No worry about pressing the new "wheel" on the shaft when I did autopsy on motors with broken tabs and burnt inductors I found out that the CE bushing is a ball end type bushing fully supported by the brush plate. So as long as the amount of force is not great enough to bend the motor shaft and you support it on the bushing bump on the brush plate and not the case or terminals the motor shouldn't be damaged.

Re: pic: One-day Minibot
 

Is there an A in Q&A that tells us definitely that the pinion is not part of the motor? There has been a lot of traffic about pressing things onto the motor shaft, but I don't recall anything about the pinion being a Tetrix part and thereby modifiable.:confused: