Helicopters B

[Pianoman159]

How difficult is the Da Vinci Helicopter Model to construct?

[jander14indoor]

Depends on how you approach it, I can think of a couple of simple approaches.

That begs the question of WHY you'd want to as other than an interesting exercise? Aerodynamically its just NOT a very good vertical lift system.

Jeff Anderson
Livonia, MI

[isaysroar]

To connect the lower rotor you simply glue to the side of your frame away from your rubber band. You only add one hub inbetween the wing. Good question though. I had the same problem.

[isaysroar]

How difficult is the Da Vinci Helicopter Model to construct?

Well I've done some research and I think that to make one you need to put the rubber band inside the tubing in the middle of the propellers to make it work. But otherwise I think its going to be a big challenge to get it working. Is it even legal in the competetion?

[mrsteven]

Well... yes. its legal.
The question still remains "why?"
Its not an effective design and it would just be a pain.

Maybe a fun exercise, as Jeff said before, but in this competition it would not be worth the effort for the results you'll see.

[Maxwellc007]

Thanks everyone for the tips. We actually RANKED!!!!!For my rookie year on the event, that's GREAT!

[rmp509]

how does rubber work. thin vs thick? is thick more power and thin more turns? please help

[jander14indoor]

how does rubber work. thin vs thick? is thick more power and thin more turns? please help

This will make more sense if you test some things yourself. Make some motors of various widths and lengths. Make at least two of each width and in two lengths.
For example, make up some 3/32, 1/8 and 5/32 inch wide motors, two each of a 4 and 8 inch loop. That should give you twelve motors. Luibricate them.
For the next step you really need a torque meter, but can just count winds (though the data you get will be much less rich).
- Wind one motor of each length and width until it breaks. Use the same stretch wind procedure. If you have a torque meter take torque data every 10 turns. until you break. Plot the data.
- If you are using a torque meter, wind the second motor of each length the same way, but stop winding at 90% of breaking turns or better torque. If no torque meter just wind the second motor till it breaks. Again, take data.
- UNWIND the second motor, again taking torque data every 10 turns. Plot that data.

Here's some of the stuff you should see (But really, you should do this yourself, not just trust my word. That's a key element of science, the ability to replicate experimental results):
- An 8 inch motor will take twice the turns (on average) to break over a 4 inch motor. It will take twice the turns (on average) to get to the same torque. If you tested more points you'd find that for a given width motor turns is directly proportional to length so you can talk in terms of 'turns per inch'. Handy as you change motor length you can easily predict maximum turns.
- As motors get thicker, they take less turns per inch. There's a formula somewhere on the web, it is not linear, but is predictible with the formula.
- If you plot the torque vs turns, the area under the curve is the energy stored in the motor.
- You'll find that for the same mass motor it stores the same energy whether its a short, fat motor or a long, skinny motor. Fat motor will have less turns, but higher torque.
- You'll see the shape of the curve is like a sideways S, rising steeply in torque with the first few turns. Leveling off for a while, then rising sharply again as you approach the breaking point. This makes it possible after winding lots of motors to have a feel for when a motor is about to break.
- You'll see that the unwind curve is always below the wind curve. You fly on the unwind curve. You don't get all the energy back you put in. A property called hysterisis, a result of entropy, or why perpetual motion machines don't work and can't work.

Not a short answer, but if you read carefully you should find what you asked for. If not, feel free to ask clarifying questions.

Jeff Anderson
Livonia, MI

[rmp509]

so if a motor is shorter it will have more torque than a longer rubberbecause it is less ruber stretched out over the same distance right? but this will also run out quicker because less rubber is less turns. Also a thinner motor will allow more turns than a thicker rubber but will not produce as much torque? did i understand this correctly? sorry but your answer was a little to advanced for me. i got a time of 1:45 at invitationals but i want to hit the 2 and a half minute mark and i believe it is possible because i am at around 2 minutes right now. i am just trying to understand the actual concept behind the changes in rubber. Thanks for your help!

how does rubber work. thin vs thick? is thick more power and thin more turns? please help

This will make more sense if you test some things yourself. Make some motors of various widths and lengths. Make at least two of each width and in two lengths.
For example, make up some 3/32, 1/8 and 5/32 inch wide motors, two each of a 4 and 8 inch loop. That should give you twelve motors. Luibricate them.
For the next step you really need a torque meter, but can just count winds (though the data you get will be much less rich).
- Wind one motor of each length and width until it breaks. Use the same stretch wind procedure. If you have a torque meter take torque data every 10 turns. until you break. Plot the data.
- If you are using a torque meter, wind the second motor of each length the same way, but stop winding at 90% of breaking turns or better torque. If no torque meter just wind the second motor till it breaks. Again, take data.
- UNWIND the second motor, again taking torque data every 10 turns. Plot that data.

Here's some of the stuff you should see (But really, you should do this yourself, not just trust my word. That's a key element of science, the ability to replicate experimental results):
- An 8 inch motor will take twice the turns (on average) to break over a 4 inch motor. It will take twice the turns (on average) to get to the same torque. If you tested more points you'd find that for a given width motor turns is directly proportional to length so you can talk in terms of 'turns per inch'. Handy as you change motor length you can easily predict maximum turns.
- As motors get thicker, they take less turns per inch. There's a formula somewhere on the web, it is not linear, but is predictible with the formula.
- If you plot the torque vs turns, the area under the curve is the energy stored in the motor.
- You'll find that for the same mass motor it stores the same energy whether its a short, fat motor or a long, skinny motor. Fat motor will have less turns, but higher torque.
- You'll see the shape of the curve is like a sideways S, rising steeply in torque with the first few turns. Leveling off for a while, then rising sharply again as you approach the breaking point. This makes it possible after winding lots of motors to have a feel for when a motor is about to break.
- You'll see that the unwind curve is always below the wind curve. You fly on the unwind curve. You don't get all the energy back you put in. A property called hysterisis, a result of entropy, or why perpetual motion machines don't work and can't work.

Not a short answer, but if you read carefully you should find what you asked for. If not, feel free to ask clarifying questions.

Jeff Anderson
Livonia, MI

[jander14indoor]

Your first sentence is wrong. Has NOTHING to do with stretch or length on the motor stick. I'm talking about the length of the rubber loop itself.

A shorter motor of the same width will have less turns than the longer motor, but the SAME power.

A fatter motor of the same length will have less turns, but MORE power.

Whether it runs out faster actually depends on the rotors.

Note, when I'm talking turns I'm talking max turns to breaking a given motor. NOT what you wound on.

Go try some of the tests I mentioned, you'll learn a lot and it will make more sense because it is your experience then, not my words, however correct they may be. Or may NOT be, in science, while you have to have a level of trust, a level of healthy skepticism is important too. I'm not trying to mislead you or anything, just questioning the experts when data differs from theory is important.

Jeff Anderson
Livonia, MI

PS, those times are pretty good, its time to attack these advanced concepts if you intend to improve more.