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#1
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Re: Rookie Team 3729's minibot
That's exactly what our minibot looks like and how it works.
If you are a good team, you will copy this robot. |
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#2
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Re: Rookie Team 3729's minibot
We tried direct driving off the motor a 3/16 shaft with sergical tubing over it and it smoked the motor. I would like to see a close up.
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#3
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Re: Rookie Team 3729's minibot
![]() Ask and ye shall receive |
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#4
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Re: Rookie Team 3729's minibot
Quote:
The other parameter is the right amount of normal force on the pole- for a 2 lb robot, you want about 4 lbs of normal force to hold the surgical tubing of the wheels to the pole. Too much and the motors are loaded down by friction. Vamfun did nice simulations... http://www.chiefdelphi.com/forums/sh...6&postcount=16 Last edited by boomergeek : 12-03-2011 at 07:08. |
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#5
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Re: Rookie Team 3729's minibot
Quote:
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#6
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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. Last edited by rcmolloy : 12-03-2011 at 09:03. |
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#7
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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.
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#8
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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... |
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#9
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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).
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#10
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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! |
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#11
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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.
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#12
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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.
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#13
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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.
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#14
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Re: Rookie Team 3729's minibot
You need to change that avatar!!!!! - Team #3729
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#15
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Re: Rookie Team 3729's minibot
How did you attach the surgical tubing to the shaft? Ours keeps spinning off.
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