Minibot climb rate

[billbo911]

We have not received our FTC parts yet, obviously because the orders went in today . I have a couple quick questions and then a result of quick calculations based on assumptions.

What are the weights of the following items?:

NXT controller, Tetrix motor, 12v battery pack, HiTechnic motor controller.

I did some very ballpark calculations based on ideal situations. If we can build a robot weighing less than 5 Lbs, it should be able to climb the pole in less than 7 seconds.

Does that sound right?

[Brandon Holley]

Originally Posted by billbo911

We have not received our FTC parts yet, obviously because the orders went in today . I have a couple quick questions and then a result of quick calculations based on assumptions.

What are the weights of the following items?:

NXT controller, Tetrix motor, 12v battery pack, HiTechnic motor controller.

I did some very ballpark calculations based on ideal situations. If we can build a robot weighing less than 5 Lbs, it should be able to climb the pole in less than 7 seconds.

Does that sound right?

What are you basing your calculations on? Overall output of the motors (ie: power)?

-Brando

[billbo911]

Originally Posted by Brandon Holley

What are you basing your calculations on? Overall output of the motors (ie: power)?

-Brando

Yep! I chose to run the calculations close the motor's max efficiency. I also chose to use the largest wheel I could find that appeared to be legal.

[Chris Hibner]

This calculation is actually very easy using the work-energy thorem.

Power = Work / Time

Work = weight * height

Therefore:

Time = (weight * height) / Power


Example:

Motor power: 8.43 W (Tetrix motor)
Efficiency: 0.85
Weight: 5 lb * 4.4545 N/lb = 22.27 N
Height to climb: 2.1 m
assume gearing for peak power.

then:

Time = (22.27 N * 2.1 m) / (8.43 W * 0.85)

Time = 6.53 sec

This is the FASTEST time. If you make the wheel big enough that the torque on the motor causes the motor to move away from the peak power point, the minibot will climb SLOWER, not faster. In other words, bigger wheels aren't always better.

[billbo911]

Originally Posted by Chris Hibner

This calculation is actually very easy using the work-energy thorem.

Power = Work / Time

Work = weight * height

Therefore:

Time = (weight * height) / Power


Example:

Motor power: 8.43 W (Tetrix motor)
Efficiency: 0.85
Weight: 5 lb * 4.4545 N/lb = 22.27 N
Height to climb: 2.1 m
assume gearing for peak power.

then:

Time = (22.27 N * 2.1 m) / (8.43 W * 0.85)

Time = 6.53 sec

This is the FASTEST time. If you make the wheel big enough that the torque on the motor causes the motor to move away from the peak power point, the minibot will climb SLOWER, not faster. In other words, bigger wheels aren't always better.

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.

[BornaE]

Seems like everyone is forgetting the possible use of surgical tubing to shoot that bot up the pole much much faster.

Also you can use 2 TETRIX motors.

[billbo911]

Originally Posted by BornaE

Seems like everyone is forgetting the possible use of surgical tubing to shoot that bot up the pole much much faster.

Also you can use 2 TETRIX motors.

Who says we are forgetting?

[Jibs]

Originally Posted by BornaE

Seems like everyone is forgetting the possible use of surgical tubing to shoot that bot up the pole much much faster.

Also you can use 2 TETRIX motors.

So the calculation above is based off one motor?

[TGA Reaper]

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

[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.

[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.

[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...