Re: Minibot climb rate
 

I would also like to know what gearing others are using. Our minibot is taking 4-4.5 seconds to climb the pole with no extra gearing.

Re: Minibot climb rate
 

I think that you are forgetting about torque!!!

Re: Minibot climb rate
 

It would appear that a "reachin' stick" is not allowed per the rules

http://forums.usfirst.org/showthread.php?t=16331

You can't carry anything functional into the arena except the operator console.

So now, getting the robot to come down off of the tower seems like a pretty important part of the design.

Re: Minibot climb rate
 

So you have a reaching stick on a tether attached to the operator console :rolleyes:

In all seriousness, i think last year 1114 had a special fixture device to let them pull the bot off the post.
I think in 2007 648 had a hand crank to move the arm down after a match

In 2007 we used my multitool to release a little catch and lower the lift

Hope they don't go TSA style for people entering the playing area :rolleyes:

Re: Minibot climb rate
 

Team 2130 is right on par with other times posted. :) Only tested the prototype though!

Re: Minibot climb rate
 

Same here, the motors start to smoke pretty fast. Wonder if any real damage was done... check the resistance of the non-smoked motor, and then check the motor that smoked for any difference? this might work...hmm...

Re: Minibot climb rate
 

Let's take a second and do some *wait for it* real engineering.

:ahh: :ahh:

To get the climb times we want, we have to run the TETRIX motors at 50% of their stall torque. Depending on gearing and weight, the robot will not run at perfectly 50%, so most bots are either on the close-to-stall or further-from-stall side of the power curve. A 0.5:1 ratio with 3" wheels is slightly on the closer-to-stall side for a 5-lb minibot, by my calculations anyways.

Given the experiences we've had with Banebots 550/545 and Fischer-Price 9012 motors, I'd say the burn out at stall of an TETRIX motor is perfectly aligned with what should happen. If we run the FP9012 at 50% of stall 100% of the time, it seems like simply thinking bad thoughts at the motor will burn it out when it hits a bump.

So Chris, you should be happy that your TETRIX motor smoked. It means you didn't do the engineering first -- and that fact will inevitably be a invaluable lesson at some point in your engineering career. It also means the sky isn't falling (whew).

If we're so concerned about motor (and wallet) longevity, the perfectly viable option is to not gear the thing for peak power. On the field, I'm sure we'd get 10 points every time we deployed; in the Elims, that's typically much better than a 50% chance the minibot nets either 30 points or 0 points (depending on how angry the motors are you keep running them so hot).

Re: Minibot climb rate
 

We are right at 3 seconds with 5# minibot.

On our way to a 3.5# minibot and less slip. I think 2 seconds just might be necessary to win the race.

Will start to play with the 4-way switches tomorrow cause right now we have to catch the bot while the gears are turning .... not a good answer!

Re: Minibot climb rate
 

Ok I know this is coming a little late, but i don't know if the whole shoot the bot up the pole is completely legal. I say this b/c i found out that compressing air inside a tube of PVC isnt legal. i dont know if shooting the bot will work well at all, simply because you need to line the shoot up, and get a correct power/weight ratio. mess that up and you wont hit the button. too much and you could miss. also with surgical tubing, it wears out after awhile. go into too many rounds and you minibot will start to fail. all in all, if you can create a system that would shoot the bot up, and then catch and climb the pole, shoot me a line @ Chris@Team3266.org

Re: Minibot climb rate
 

I have a hard time believing a lot of these times (no pun intended). I really don't think this many teams could reach a time of under 3 seconds already unless you've only focused on the minibot. i also believe that
A. Some people have been hitting stop on their stopwatches before it reaches the top
B. The "2 second minibot"'s will probably be hard to deploy.
C. Those minibot's do not/ cannot consistently get under 3 seconds.
Right now our best time is 3.57 seconds. Weight is roughly 4 pounds, consisting of two motors, chains, surgical tubing, wheels, etc.
Very very very reliable deployment, now just working on deploying mechanism placement on the bot.

Re: Minibot climb rate
 

Yes, it is a little late, about 3 or 4 Team Updates late. Flinging the MINIBOT has been completely outlawed. You can only use the Tetrix motors as a source of propelling the MINIBOT up the TOWER.

You need to keep watch on Team Updates: http://www.usfirst.org/roboticsprogr...nt.aspx?id=450 Else, you are going to be building a robot for playing a game that doesn't exist anymore.

Re: Minibot climb rate
 

Don't worry, it wasn't my engineering.. :)

I'm thinking along those lines - winning the minibot race isn't as important as being in it!

Direct driving two 4" wheels (not sure on one for each wheel or both mechanically linked to a lower "gearbox") seems simple, robust, lighter, and less likely to blow up Tetrix motors. Now to get the darn thing to come DOWN the pole...

Re: Minibot climb rate
 

With 4" wheels the motors will backdrive easily, the way we get ours down is by putting some long bolts on the bottomside of the robot. next get a pole and attach a ziptie in a large loop at the top, use it to gently pull on the bottom of the minibot and it should backdrive all the way down.
Here is a video of our minibot prototype:
http://www.youtube.com/watch?v=8IKLSgfXqcM

Re: Minibot climb rate
 

Right now our robot uses just one motor and 4" wheels and back drives on the way down way too fast. However when we shunt the motor, after it switches off at the top, it comes down nice and slow. If teams haven't figured out how to get it back down safely, I suggest you add a dpst switch that turns off motor power and at the same time connects the two ends of the motor together for a slow return.

Re: Minibot climb rate
 

Our minibot prototype is getting to the top in just about 4 seconds (3.9ish)

now while we realize there is quite a bit of human error involved with the timing devices, it is a pretty solid baseline to work off of.

Here is the video(yes we are actually providing proof of the climb:rolleyes: )
http://www.youtube.com/watch?v=R24GD8FIt9Q