Re: Minibot climb rate
 

Does rule include using surgical tubing as a drive belt and a friction surface on the wheel?

Re: Minibot climb rate
 

We smoked a motor hitting the top of the pole and not shutting off...probably a maximum of about 3 seconds of full voltage on a jammed motor.

This happened on the very first occurrence.

My suggestion is make sure you put in the motor cutoffs at the end of the race or make sure your wheel contacts are slippery enough to keep that motor turning.

I'm glad we ordered two extra motors. I expect many teams will fry motors before getting a working minibot. ::ouch::

---

BTW, our prototype uses solder on the motor contacts and uses standard tab and receptacle electrical connectors- not wire nuts.

If they didn't want us to use solder, then it would have been nice for them to supply Tetrix "DC Motor power cables". http://www.legoeducation.us/store/detail.aspx?ID=1629

Re: Minibot climb rate
 

Nope - I meant "surgical tubing to store energy" rather than "surgical tubing". If the tubing isn't storing energy there's no rule broken.

Re: Minibot climb rate
 

as a referance, Today, team 2200 made it to the top (no top plate yet) of the pole in 2.6 seconds, with a minibot that weighed 4.9lbs. and we still have LOTS of room to save weight.

Re: Minibot climb rate
 

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

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

Re: Minibot climb rate
 

I too am curious to know what the sub 3 second mini-bots are using for gearing. Thank you to the few people who shared videos! No proof like video!

Re: Minibot climb rate
 

And gravity!

Re: Minibot climb rate
 

Can anyone give hints on haw to make the climb rate as fast as possible any ideas will bee much appriciated

Re: Minibot climb rate
 

Some quick math and some analysis of the torque/stall curves for the motors have shown us that the most optimal gearing rate is .5/1 please check my math. Additionally using this gearing rate we found that a robot if carefully constructed can weight about 5-6 pounds. This gets you to the top in about 4.0-4.75 seconds. This has been pretty much confirmed by our present prototype minibot design.

These individuals claiming 2-3 seconds I have questioned unless the robot is like 3 pounds or they are direct driving but with that said you direct drive the motors get really close to stalling after only a few pounds. I would love to see a video of a team beating 4.0 seconds

Re: Minibot climb rate
 

your 5-6 pounds is way wrong.

Start with only what you need and then make that lighter. I'm certain that 4# is possible and teams will do better than that.

With standard out of the kit parts and not modified we got to 3 seconds and < 5#.

You are missing something.

Re: Minibot climb rate
 

No ladders, no poles on the field, look at the Q&A forum. Keep working!

Re: Minibot climb rate
 

OK let me check your math, 2 ways

Suppose your minibot weighs 5 pounds, you use 2 motors with a .5:1 gear ratio, and you use 4 inch diameter wheels (using nominal numbers and ignoring start up and inefficiencies for now). The robot exerts a torque on the wheel of 10 inch pounds (weight times radius), and the gear ratio makes the torque on the motors 20 inch pounds, or 10 inch pounds on each motor. Looking at the motor curve, they run at 77.8 rpm at 10 inch pounds load (sorry, I always work in English units). 77.8 rpm on the motor divided by the gear ratio and divided by 60 gives you 2.593 revs per second at the wheel, times pi times the diameter gives you 33 inches per second up the pole. If you start at the top of the line (30 inches off of the floor) you have to travel 92.25 inches (122 minus 30 plus 1/4), which equals 2.83 seconds.

Now for optimum performance (tweaking the gearbox and/or the wheel diameter), you want to run the motors at peak power which is 9.36 Watts times 2 or 18.72 watts, which converts to 165.67 inch pounds per second. Moving 5 pounds times 92.25 inches and dividing by the power gives you 2.784 seconds feasible.

So you can see that for a robot less than 5 pounds, even including some inefficiencies 3 seconds is absolutely feasible.

Re: Minibot climb rate
 

Do the math. Save the world!

Re: Minibot climb rate
 

The "little bits" here and there can kill you on the mini-bot. Our initial prototypes were 0.5 lbs heavier than we estimated (5 lbs). We had "geared" to be on peak power for those runs, but the 10% heavy also meant we needed about 10% more torque which took us down about 10% in power. Thus the 10% more weight would have added about 22% (1.1/0.9=1.21), but weight there is more... This 10% more mass also added additional friction which meant more torque, and again lower speeds therefore (1.15/0.85=1.35). Thus a mini-bot that we thought would climb in a little over 3 seconds ended up taking over 4 seconds (3.25 * 1.35 = 4.4 seconds). With certain mini-bot designs, a little weight can kill the performance for that design. This was initially very frustrating, but after review it is much more encouraging.

Back to some more iterations.

Re: Minibot climb rate
 

Check your math. The short story is -- equations only tell us where to start with MINIBOT prototyping, yet only real prototypes will tell us if the theory is sound.

The problem with such simple Power->Torque conversion in this case is that it does not account for the increased time the MINIBOT will take to get to its max speed under a higher torque load. Kinematic equations are non-linear with that respect when combined with the inverse relationship of an electric motor's speed-versus-torque relationship, thus analyzing a distance-versus-time chart between the two options may surprise you.

The problem is, distance-versus-time isn't quite as straight forward as it seems. In my analysis, I have to piecewise the graphs into acceleration sections and max-speed sections based upon the calculated time it take to accelerate to max speed under load.

So while I don't claim to have my calculations be 100% precise to real-world conditions, they do show that MINIBOTS with a 0.5:1 ratio with 4" wheels and a 5-lbs of weight will spend over 75% of their climb time in the acceleration phase, resulting in a 6+ second climb. 0.5:1 ratios with 3" wheels have 4-4.5 second climbs (50% of which is acceleration). Direct-drive 4" wheels have about the same times due to greater efficiency motor-to-pole coupled with less mass due to no gearing (all else equal), even though its max speed is technically slower than 0.5:1x3" wheels on a flat field.

Actually, putting a 0.5:1 ratio on the MINIBOT puts it's torque load twice as close (ish) to stall as direct drive does.

Re: Minibot climb rate
 

That doesn't pass the sanity check. If it takes 3-4 seconds to get to 33 inches per second, that's an acceleration of about 10 inches per second^2, or .03 g's. It doesn't start with a load of 0 g's, it starts with 1g plus acceleration, so that's about 3% reduction in available power using your numbers.

Re: Minibot climb rate
 

I'll ditto Gary here. Check your math on this one. I was thinking along similar lines two weeks ago and whipped up a spreadsheet to do all the numerical integration for me. The acceleration phase was stupidly short, in the tenths of a second. But we don't need a complicated spreadsheet to tell us that. If we gear for peak power, that's 1/2 stall torque. So full stall torque is 2 times the weight of the bot, is 1 g instantaneous acceleration at the beginning. When you get up to half your final speed, you're still doing 0.5g. At 3/4 final speed, it's still 1/4g, and so on.

In fact, if you toss out friction, this is a very nice linear system to model. The fact that your torque/force decreases linearly with your speed makes it just another damping term, so it actually works out to a simple mass-damper system with an external force. So if I wasn't so lazy, I could tell you the exact time constant based solely off the robot's mass and motor characteristics.

Re: Minibot climb rate
 

...... And then... there was this

http://www.youtube.com/watch?v=sO4uNj44oZE

I'm SOOOOOOoooo envious!

Steve

Re: Minibot climb rate
 

Don't believe everything you see...all may not be as it seems. See the other related thread highlighting 1625's minibot climb. Do you clearly see the 1.5 lb. battery on the skyrocketing minibot? Do you vaguely see it?

Re: Minibot climb rate
 

Right towards the end of its climb, you can see the battery fly up past the robot and fall down.

Or some other relatively heavy objected connected via wires.

- Sunny

Re: Minibot climb rate
 

You are correct... could be an "illegal" minibot.... I STILL envy that speed...Or maybe it's the Mythbuster-ish destruction that occurs when it slams into the top! COOL!

Steve

Re: Minibot climb rate
 

It is my assumption that "direct drive" in this thread refers to driving a wheel directly from the motor shaft. In other words, without the Tetrix gearbox attached. Is this correct?

My team is considering the idea of doing away with the tetrix gearbox. But I don't like the looks of that 2.5 mm motor shaft.

Re: Minibot climb rate
 

I believe when everyone says direct drive, they mean with the tetrix gearbox, considering you cannot alter the motors (which I assume means the gearbox connected also).

If I am wrong, please smite me. Thats what I meant whenever I said directly driven.

Re: Minibot climb rate
 

*smite*

http://forums.usfirst.org/showthread.php?t=16187

ye of little faith...:rolleyes:

Re: Minibot climb rate
 

I meant a direct drive off the stock gearmotor, not motor sans gearbox.

The latter could be done but for my team at least it's beyond our capabilities.

Re: Minibot climb rate
 

I propose that from here on in we specify what we mean when we say "direct drive."

My team is in the same boat regarding technical ability to use the motor shaft. On the other hand, I cracked open the tetrix gear box last night. With some moderate machining capability, one could signicantly modify the ratio of the gearbox. I took a couple of photos that I will try to put up this evening (CST).

I would love to use the internal gearbox alone for several reasons. Not the least of which is that two of our wheels and a driven tetrix gear came loose on our first climb test.

Re: Minibot climb rate
 

Here's an internal view of the Tetrix gearbox:



It looks possible to mate the brass helical gear to the 40T gear on the output shaft, with a little bit of machining. Sorry this post is a day late.

Re: Minibot climb rate
 

Or a just a case of skepticism with the treatment being a clearer video with close up? ;)

Re: Minibot climb rate
 

Thanks for the pic. How many teeth on the gear on the input shaft that mates to the 26 tooth gear?

Re: Minibot climb rate
 

Math would say 10. (40/10)*(25/15)*(30/10)*(26/10)=52:1

Re: Minibot climb rate
 

10 teeth on the helical gear on the motor shaft. This makes the ratio input 52:1 output for the gearbox and motor as assembled. Mating the 10 tooth element of the 26:10 brass gear to the 40 tooth output shaft gear would yield
input 10.4:1 output for the same assembly.

Re: Minibot climb rate
 

That is exactly what we did (using only an inexpensive mill and lathe and a dremel), and it works great.

Re: Minibot climb rate
 

Do the gains in efficiency offset the lower torque output of the motor, or is this an "experts only" mod for teams that make custom 2" wheels?

How dramatic is the speed gain? 1625-dramatic?

Re: Minibot climb rate
 

The dyno data showed a ~60% increase in output power. That makes it 1625 fast. You would definitely have to do some custom gearing and probably custom wheels (custom wheels will remove the necessity for some of the gear ratio). The big thing is to get the gear/wheel combo right so your reflected torque to the motor is ~50% of stall.

Re: Minibot climb rate
 

Here's a tip, whether or not you chose to modify the gearbox. We found in years past that cleaning the stock grease from our NBD gearboxes and using light lithium grease had a noticeable improvement in output (efficiency). It looks like this gearbox is pretty clean - don't know if it was that way when you opened it, but even if it was well lubed it might be a good idea to clean it out and put in lithium grease. (which per update 5 is an allowable material).

Re: Minibot climb rate
 

Hmm....

I imagine for a 1:1 (pre mod) reduction it's more efficient to leave the gearbox as is than to take out half the stages and compensate for the speed increase with Tetrix gears.

But for a 0.5:1 (pre mod) - that could be interesting.

Re: Minibot climb rate
 

Wow.

We are 4.5 with a 1 second deployer. We havent tested our other two mini bots yet. 2:1 gear ratio, magnet holding method.

Re: Minibot climb rate
 

not to show off or anything... but this is our minibot... water bottles attached to simulate battery weight.. 3.4 seconds!

http://www.youtube.com/watch?v=UqPyHQqQtYk

Re: Minibot climb rate
 

http://www.youtube.com/watch?v=UqPyHQqQtYk

water bottles attached to simulate battery weight

Re: Minibot climb rate
 

nice job.

Re: Minibot climb rate
 

Looks like a nice start!

Re: Minibot climb rate
 

Does anyone know the weight of the individual tetrix parts like the large gear=xlbs, motors=ylbs sort of thing?

Re: Minibot climb rate
 

According to our scale in the shop battery is 1 lb 5.1 oz and motor is 7.0 oz.

Re: Minibot climb rate
 

Answer to this question is in this thread. It would be helpful to read the whole thread.

Re: Minibot climb rate
 

our minibot climb the pole in approximately 2.5 sec , a little less.
with all the wight on it , the battery is attached to the minibot.
you welcome to see it in the post:
http://www.chiefdelphi.com/forums/sh...threadid=90373
hope for comments on it .:)

Re: Minibot climb rate
 

The photo was taken seconds after opening the box for the first time. It was quite clean and lubrication was pretty light.

Re: Minibot climb rate
 

Considering the use of tiny helical gears I think adding more lubrication will help even unmodified gearmotors.

Re: Minibot climb rate
 

I looked at one of the transmissions we had, and I didn't notice any lubrication. It may have been there, but I couldn't see it or really feel it.

Does anyone have a good grease for these guys? I'd imagine you'd want a pretty light grease.

Re: Minibot climb rate
 

Has anyone tried the Thermal-Protected DC Motor Power Cable yet? If my memory is correct it's set for 2.4 amps, which is lower then some of the motor current draw that I've seen people post. I assume it will work for a short time at a current draw of above 2.4 amps, so I'm curious whether it works for other people.

Re: Minibot climb rate
 

We used the tetrix motor cables last night. They worked great, and did not trip to the best of my knowledge. Judging by time, it was pretty close to the peak power point.

Re: Minibot climb rate
 

Be careful, you can not use one four-way switch to reverse your motors. You need to use two Three-Way Switches or one Double pole-Double throw Switch. I did electrical work for 9.5 years.
Mentor Mac mccubbin99@live.com
240-405-9213 301-831-0407
Mt.Airy,Md. Team 686

Re: Minibot climb rate
 

Apparently the GDC thinks otherwise

From Team Update #7:

Re: Minibot climb rate
 

This circuit should be correct for using a 4 way switch to reverse the motors.

Dean

Re: Minibot climb rate
 

Yes a 4 way switch will reverse your motors, the key is to put the battery connections on one color screws (we used the black) and the motor on the other color screws. Doesn't matter which is which just that both leads of a respective item are connected to the same color screws. If you want to change which direction of the sw is up and which is down reverse the motor leads. It is also possible to wire it so that one of the motors works in brake mode while the other has power in the "down" mode.

Re: Minibot climb rate
 

Here's a couple updates. This is a picture of the bot in it's functional state. We'll be tweaking on it a bit, but it works as planned.



Our goal was a sub 5 second robot. Currently, and without much fine tuning yet, we are at 4.5 second from the platform to the top of the pole without the sensoe plate.

http://www.youtube.com/watch?v=HnKO-nry2EA

Re: Minibot climb rate
 

We hit 2.71 seconds today (including the battery and all necessary switches), and that's without our new custom wheels (which aren't back from the CnC mill group yet). We were very excited, as prior to this we had been stuck at around 4.5 seconds!

Re: Minibot climb rate
 

what did you use to have the minibot turn on when it hits the pole. we're using magnets also.

Re: Minibot climb rate
 

There is a polycarbonate rod the extends past the magnet. When the magnet pulls the bot to the pole, it pushed the rod back, which in turn closes the main electrical switch.

Re: Minibot climb rate
 

um... where's your battery? we tried magnets in the early stages of our design and they would work just fine untill we put the battery on and the whole thing would fall right off.

Re: Minibot climb rate
 

I think this was discussed as not allowed on several other threads. Plus team updates it was also clarified. Maybe someone could help post those rules. ( psst I am at work)

Re: Minibot climb rate
 

If you look at the date on the original post (10th of jan) you should notice that team update one which disallowed the use of surgical tubing for upward movement was released the day after I posted that.

and yes, surgical rubber is not a legal source of energy to climb the pole per the current rules as G19 states.

Re: Minibot climb rate
 

Watch the video. The battery is opposite the motors.

Re: Minibot climb rate
 

I have taken a different approach to estimating the theoretical minimum time possible for the mini-bot to reach the top of the 10 ft pole.

Rather than the using the power output from the motor, I used the rated no-load speed of the Tetrix motors (152 to 154 rpm) to estimate the shortest time possible. This rpm for the motor would produce a Motor Rotation Time for one revolution of 0.39 seconds in an idea world with no load (battery, motors, framework, etc.).

This means that a 3 inch wheel directly attached to the motor would require 4.96 seconds to reach the top of the 10 foot pole. Similarly, a 4 inch wheel would reduce this time to 3.72 seconds. Using a 1:3 gear train would reduce these times to 1.65 and 1.24 seconds respecively, but reduce the effective power of the motors to lift.

Motor rotation time = (60 sec/ 1 minute)* (1 Minute / 154 revolutions)
= 0.39sec/rev

Revolutions to top = (Pole Hieght) / (diameter of Wheel * Pi)
= (120 inches) / (4 inches * 3.1415)
= 9.55 revolutions of the 4" wheel

Time to top = (Revolutions to Top) * (Motor Rotation Time)
= (9.55 rev) * (0.39 sec/rev)
= 3.72 sec for a 4" wheel to reach the top of the poe.

Re: Minibot climb rate
 

Clocked in at 1.7 Seconds tonight! :D

Re: Minibot climb rate
 

our minibot goes up the pole in just under 6 seconds if the wheels don't slip, actual test of real minibot and real pole.

we can deploy and climb the pole in under 10 seconds under software control; it works about half the time. the other half the alignment isn't quite right and it doesn't work.

jw

Re: Minibot climb rate
 

We are flirting with 3.5 second climbs on a fresh battery.

http://www.flickr.com/photos/ukweli/5466703933/

Re: Minibot climb rate
 

We were able to modify the Tetrix gearbox with no special tools / machines - we just had to stake the ID of the large gear to get it to press on to the top of the output shaft at the position of the gear attached to the brass gear

Re: Minibot climb rate
 

What was the resulting gear ratio? And what does "stake the ID mean"?

TIA

Re: Minibot climb rate
 

If you look at the output shaft you'll see that in the area where the gear is pressed on the shaft is "knurled" or has ridges formed in it to create the press fit. So I assume he means that they used a chisel or punch to deform (stake) the ID (inside diameter) of the gear so it will press on the un-knurled portion of the shaft where it will mesh with the input gear.



The mod of making the first gear mesh with the gear on the output shaft results in a 10.4 to 1 ratio instead of the factory 52 to 1.

Another way to accomplish this IF you have a lathe is to machine a spacer that fits on the output shaft between the gear and case so that it meshes with the input gear. On the motor end of the output shaft you need to turn it down the same amount as the length of the spacer so it will fit in the case.

In addition to increasing the output speed ~5x it reduces the drag in the trans aprox 50% by removing 2 gear interfaces. Make sure you don't loose the spacer on top of the input gear and remove the spacers on the other shaft, there is a small one on the shaft under the 25:10 gear.

Re: Minibot climb rate
 

Why keep that silly gearbox? Take it all the way off, and you can be seeing times in the 1.4-1.8 range. Most of the gains are due to the loss of weight of the huge wheels, and the gearboxes, not the raising of efficiency.

Re: Minibot climb rate
 

That is fundamentally untrue, and easy to demonstrate as untrue.

Our current minibot is in the 1.8 second range (and very consistent, thank you), and even when we add excess weight just to see what it does with it, it's still faster.

Reducing weight matters, but increasing efficiency matters a whole lot, too. It's not a dichotomy, here -- both are important!

Re: Minibot climb rate
 

Thanks for proving me wrong. I was just inferring, so apologies, and I learned something!

Re: Minibot climb rate
 

I know it's not fast, but it's reliable. We are thrilled it is ready for Sacramento.
http://www.youtube.com/watch?v=AVx7oFAyfjg

Re: Minibot climb rate
 

in order to climb the pole, you dont need the wheels and with this you can cut the weight of the minibot. Just suggesting. :)

Re: Minibot climb rate
 

We were consistently getting ~1.2 seconds. We got our minibot measured by team 1279 at the DC regional and got a higher accuracy measurement:



Our deployment arm, when it was working properly :(, was taking ~0.2 seconds to get the bot on the pole, so total time was ~1.27 seconds.

Below is a photo of the bot, which uses a cnc machined chassis. Our goal was to use only the minimum of materials necessary to hold the components in place. Weight came in at 2.5 lb.

Re: Minibot climb rate
 

meet richard.

not the fastest liger in the forest but hes around 2.2s and stupidly reliable.
it seems like its one of the most machined minibots out there!

Re: Minibot climb rate
 

our mini bot helped us get up the pole in under 2 seconds with deployment so that got us back to back wins

Re: Minibot climb rate
 

I know 968's minibot is exteremly fast. They get like .7 seconds with the dployment. Well that is what was said, but if you saw it in really time their minbot was up when the clock still said 9. This minibot helped them win the LA regional. their minibots somewhere around a one seconds minibot.

Re: Minibot climb rate
 

Thats prety impressive. If you don't mind, what roller size did you use?

Re: Minibot climb rate
 

The axles are 3/8" aluminum, drilled to fit the motor shaft (we removed the spiral gear). The "tires" are 1/2" OD surgical tubing.

Re: Minibot climb rate
 

What's the blue broom-hook thing at the top made of ?

Re: Minibot climb rate
 

if you're referring to the clip, its actually blue pvc pipe!

Re: Minibot climb rate
 

are you using the stock 52:1 gearbox? and are those 4" wheels ?

Re: Minibot climb rate
 

Based on a quick comparison in proportions to the opening in their deployment system, my guess is they are 4.6 inch. It looks like they are made of PVC and wrapped with surgical tubing.

Re: Minibot climb rate
 

Stock gearboxes, I modded some gearboxes to 10:1 but I didn't invest much thought into them after. The wheels are actually around 5.5", the picture angle is misleading. They use a 4" to 3" PVC pipe fitting for the wheel rim and its 3/8's surgical tubing. Im pleased with the way they came out, and can safely say its a unique design (unlike many little screamer bots out there).