Minibot climb rate

[Doug G]

Originally Posted by TGA Reaper

Question: What is the estimated ideal weight for the mini bot?

The first one we built was about 4 pounds. I think the final version we settle on will be more like 6-7 pounds.

[Hawiian Cadder]

i think my team intends to use surgical tubing to launch the mini-bot to the top in less time than 1 second. last years kicker on our robot only contacted the ball for 3 inches and was able to kick pretty far. i think we will be doing something similar for this.

[TGA Reaper]

Originally Posted by Doug G

The first one we built was about 4 pounds. I think the final version we settle on will be more like 6-7 pounds.

have you tried the heavier weight yet?

[indubitably]

What are the odds that a minibot launched by a slingshot will recieve a penalty?

I feel <G20> might be at risk as the slingshot might tap it after its initial release.

[JesseK]

Hmm, the calculations I'm getting from both of my 'drag race' calculators, adjusted for straight vertical ascent, comes out to just over 5 seconds. I'll investigate...

Originally Posted by indubitably

What are the odds that a minibot launched by a slingshot will recieve a penalty?

I feel <G20> might be at risk as the slingshot might tap it after its initial release.

Please use the other minibot threads for this question...

[billbo911]

Originally Posted by Doug G

The first one we built was about 4 pounds. I think the final version we settle on will be more like 6-7 pounds.

I'm curious Doug, what differences would cause your weight to increase 50-75%?

[mechE131]

I would reccomend someone go and look back at their statics, dynamics, mechatronics and material science textbooks; these calculations are a little on the flimsy side.

If I were a student, I would start with a free body diagram and account for all of the forces involved. Then factor the motor in with all included drivetrain factors.

You must then base a more practical time compared to your calculated "theoretical" time. Factor things in like manufacturing tolerances, material fatigue, material temperature change, etc. and read up on how they would effect your climb rate.

Then, after your minibot is built, compare the two calculated times with the experimental time; the time it actually takes the minibot to assend to the top of the both. Run several trials and make improvements.

[Sean Raia]

Originally Posted by Hawiian Cadder

i think my team intends to use surgical tubing to launch the mini-bot to the top in less time than 1 second. last years kicker on our robot only contacted the ball for 3 inches and was able to kick pretty far. i think we will be doing something similar for this.

WHAT is this obsession with using surgical tubing to launch your minibot?

You can use springs to launch it just as well if not better, they just have to be part of your main robot.

[MikeE]

Originally Posted by mechE131

I would reccomend someone go and look back at their statics, dynamics, mechatronics and material science textbooks;

This problem is a perfect example of one of the more selfish reasons I enjoy being a mentor on an FRC team: I have a reason to learn about other branches of Engineering outside of my original EE/ECE/CS training.

[My original back-of-the-envelope calculations gave a time of 8s with one motor, but I can now see how some of my initial assumptions were flawed.]

[GaryVoshol]

Originally Posted by Sean Raia

WHAT is this obsession with using surgical tubing to launch your minibot?

You can use springs to launch it just as well if not better, they just have to be part of your main robot.

Provided the rules allow the HOSTBOT to provide upward impetus to the MINIBOT. That is not yet established (either way) in the rules.

[Mike Schreiber]

Originally Posted by TGA Reaper

Question: What is the estimated ideal weight for the mini bot?

Ideally, I'd say massless...but I don't think even the best teams can pull that off, plus I'm not sure a massless minibot could press the sensor at the top... You want the minibot as light as you can make it while still having the mechanism you need to climb.

[JesseK]

I applied the equations in this whitepaper to JVN's Calculator (with some other mods as well) last night and came up with some interesting calculations. Over lunch today I further tested things, and have reached some conclusions:

A 5-lb minibot can reach the top in under 6 seconds
A 10-lb minibot will struggle to reach the top under 10 seconds
A 15-lb minibot probably won't make it to the top under 20 seconds ("probably" because there's a 10% fudge factor here)
There are only 5 gearing/wheel combinations that will even lift a 10-lb robot to the top in under 15 seconds, and all of those are well behind any of the 5-lb robot combinations.

Thus, the lighter the better.

[mechE131]

That model is only good for a situation where the normal force is exactly opposite of the force caused by weight (mass X acceleration due to gravity) and perpendicular to the resulting force (driving forward).

In the case of a "climbing" robot, the most suitable analytical situation would assume the normal force is perpendicular to the pole the robot is latched to.

I would recommend to all students draw a diagram of all the forces on their robots before using any calculators to see if the same situation applies.

[Gary Dillard]

So now that update 1 says we have to use the motors and controller, can someone answer the original question - does anyone have the weight of the required components (battery pack, controller, motor) so we can start doing some real calcs?

[billbo911]

Originally Posted by Gary Dillard

So now that update 1 says we have to use the motors and controller, can someone answer the original question - does anyone have the weight of the required components (battery pack, controller, motor) so we can start doing some real calcs?

Gary,
Which rule says that using the NXT is required?
<R92> does not say that currently.

<R92> The following items are the only permitted materials for use on the MINIBOTS:
A. TETRIX components,
B. no more than two motors (PN W739083),
C. exactly one 12V rechargeable NiMH battery pack identical to those supplied in the FTC kit of parts (PN W739057)
D. No more than one HiTechnic DC motor controllers,
E. No more than one NXT controller with the Bluetooth functionality disabled,....

Both D and E say "No more than one...". It does not say "One and only one".
I will admit, the rule can change. If they do, we will adjust.