Minibot climb rate

[klmx30302]

Originally Posted by Bruceb

What type of gearing are most of you advanced minibotters using?
Bruce

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.

[rbaker8734]

Originally Posted by billbo911

I looks like your numbers and mine are spot on. I took a different approach, but the result is the same within .1 seconds.

Just so others can see where I got my numbers, I ran it through the JVN Calculator.

I think that you are forgetting about torque!!!

[Gary Dillard]

Originally Posted by Kevin Sevcik

Nor do we have to cart a reachin' stick out on the field after every match to get our minibot down.

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.

[Aren_Hill]

Originally Posted by Gary Dillard

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

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

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

[awesomegeek166]

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

[Numbers]

Originally Posted by Chris is me

So... we saw smoke when we made our bare bones minibot try to climb, with a modest overgear (0.5:1). These things can't be stalled for even a half second, apparently? I have no idea what smoked or whether or not the motors still worked, but if the motors are that delicate...

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...

[JesseK]

Originally Posted by Chris is me

So... we saw smoke when we made our bare bones minibot try to climb, with a modest overgear (0.5:1). These things can't be stalled for even a half second, apparently? I have no idea what smoked or whether or not the motors still worked, but if the motors are that delicate...

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



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).

[cmass]

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!

[chris janney]

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

[Duke461]

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.

[GaryVoshol]

Originally Posted by chris janney

Ok I know this is coming a little late ...

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.

[Chris is me]

Originally Posted by JesseK

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

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).

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...

[klmx30302]

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

[Doug G]

Originally Posted by klmx30302

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

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.

[McGurky]

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 )
http://www.youtube.com/watch?v=R24GD8FIt9Q