Re: Rookie Team 3729's minibot
 

This is not new news guys. Many teams have competed in Week 1 with the same thing. It's good that a rookie caught on though. It's upsetting because by champs most teams will have the same minibot. More importantly, how much does it weigh?

Also, good luck finding a good deployment. It seems like only 4 out of 40 teams with the same mini have been able to deploy it.

Re: Rookie Team 3729's minibot
 

Robert is right, not new news. Even though 3729 is a rookie team, it doesn't lack horsepower. It's main mentor (me) has five years FIRST experience and has mentored teams to a regional win and two trips to Atlanta. The other mentors are engineers in aerospace. The students are very sharp and were very trainable to the ways of FIRST. They learned so fast that they helped two other FIRST teams with design. One other thing, it doesn't hurt to have a full fledged CNC machine shop as a major sponsor. :D

Re: Rookie Team 3729's minibot
 

Our team as prototyped a similar design, but can't seem to get the minibot to raise off the ground.

We used surgical tubing to cover 1/2 OD rods, but when it is turned on, all that happens are spinning shafts going nowhere...

Re: Rookie Team 3729's minibot
 

To get traction on the pole you have to have a normal force. The normal force comes from an interference fit. For example the pole OD is 1.75 inch. The distance between the rollers has to be something less than 1.75 inch. The less it is the more normal force. You have to experiment with what works for you. Another concern is the OD of the shaft. 1/2 inch could be too big. I know 3/8 inch and 1/4 inch work for about 3 lb minibots. 1/2 inch may stall the motors. Another way of saying this is your drive ratio needs to be tuned to your robot (it's weight).

Re: Rookie Team 3729's minibot
 

Hey! We're a team in atlanta, 2420, and are trying to implement this design. Our original was too heavy and clunky. With only a few days left, we're in desperate need. If you don't mind my asking, I'd like to get some specs from you.

1. Do you have a drawing of dimensions? We tried to mimic your minibot from the description in the thread and sort of have the same idea. However, our lexan keeps flexing and forces the robot to come off. Where exactly are your reinforcement pipes?

2. How far is the inner spacing in between the output shafts? Currently the inside space between the shafts is a bit under 1.75". After hours of testing, we've decided that this is too small as the motors keep stalling out. Our next plan of action for today is to, keep the spacing at a minimum of 1.75" and slightly slant them towards each other. We think if the motors are slightly biased towards the center, the minibot won't fall backwards as easily.

3. How close was the battery to the motors? Does the proximity serve as a reinforcement for the lexan? There's about an inch or more in between the motors and the battery. This allows for a lot of flexibility and we're trying to get around this.

4. What magnets did you use? We're going to test out some ceramic hard drive magnets today b/c they're really strong.

Anything information really helps. Thanks!

Re: Rookie Team 3729's minibot
 

Is their any possible why to attach the minibot with 2 motors with surgerical tubing? and make it light as possible.... My team is having troubles finding a way to attach the minibot so I was wondering if you guys can help.

Re: Rookie Team 3729's minibot
 

t.ngo, we use the syrgical tubing as the traction media on the aluminum axles. What holds the minibot on the pole are magnets. There are a lot of variables to manipulate to make the 'whole system' work. There are tons of information here on CD that tell you 'how to do' everything you need. If you have any specific questions just ask.

Re: Rookie Team 3729's minibot
 

If you mean 2 motors and a shaftless piece of surgical tubing between them, don't waste the motors, it can't support the battery. If your tubing has axles and you just want to connect the motors, use the holes in the front of the motor that the gearboxes were held on with. If you are trying to connect the axles to the motor, drill them out on a lathe and press fit them.

Re: Rookie Team 3729's minibot
 

You need to change that avatar!!!!! - Team #3729

Re: Rookie Team 3729's minibot
 

How did you attach the surgical tubing to the shaft? Ours keeps spinning off.

Re: Rookie Team 3729's minibot
 

First of all we use 3/8 inch OD tubing on a 3/8 inch shaft. That means the tubing is going to have to stretch quite a bit, but once its on it is not going to slip. We put it on two ways. The first way is to run really hot tap water over the tubing and then push it on the shaft. At competition you don't have hot water. We wipe the shafts with Clorox disenfectant sheets (get tem at the grocery store) and push the tubing on. The liquid is probably alconol. Doesn't work as well as hot water but you can do it in the pits.

Re: Rookie Team 3729's minibot
 

Alcohol works pretty good for getting the surgical tubing on the shafts. It also dries quickly without leaving any sort of residue. Get the tubing started onto the shaft. Hold the shaft and tubing vertical with the tubing pointing up. Fill the tubing with alcohol. Pinch the tubing and push down quickly. The tubing will "inflate" due to the pressure from the alcohol and slip over the shaft with almost no friction. The position of the tubing can be adjusted for a few minutes until the alcohol is all squished out or evaporates.

We forgot to bring some to the practice day so we had the meet organizers make an announcement asking if any other teams had any alcohol. It got some funny looks. :yikes: