Helicopters B

[TrueshotBarrage]

Our helicopter isn't working. We've made it just like it is supposed to, but it leaves the ground for about 2 seconds and falls down promptly, for a total of about 5~10 seconds. We've noticed making the rubber band have more tension (as in a shorter length) made it improve by a couple of seconds, but we were expecting for it to go at least 1 minute with our design. :< Thank you for any suggestions and tips

(and yes, we've tried different varieties of numbers of winds)

[jander14indoor]

Need more info to help. Also look back up this string.
Describe design. Weight, number of rotors, weight, number of blades, pitch of blades, weight, size of motor (length and width), number of winds, torque.
Basics, assuming you have a reasonable design and weight you either aren't winding your motor hard enough or you don't have a thick enough motor. You need MORE POWER!!!
Shorter motor just reduced weight, makes it easier to fly.

Regards,
Jeff Anderson
Livonia, MI

[TrueshotBarrage]

3 bladed rotors on top and bottom, spinning opposite directions. Blades are like sectors of a circle. Slanted in a way that is similar to a space diagonal of a cube. About 3~4 grams for the entire helicopter, not sure. For weight, I really can't say but I don't think that is the problem. Wings are light enough, we are using mylar for the covering. We are using .140 rubber bands. We are winding it for more than 2 minutes with a battery powered winder. Thanks in advance for any help.

[chalker7]

Weight is the single biggest factor in Helicopters success, the entire flight is essentially a math equation balancing weight against thrust. As long as thrust is more than weight, you'll go up. If thrust is less than the weight, you'll go down. Even 0.1 grams above minimum weight can have a significant impact on your times because rubber motors do not provide that much torque, meaning the rotors are limited in their thrust. I would highly suggest finding the actual weight of your helicopter.
Also, I would suggest switching from an electric winder to a hand-winder. The precise number of turns on your rubber band is pretty important and by hand winding you can count them. Additionally, you get a "feel" for the motor, after winding them for awhile you start to learn how hard you can wind, when they are about to break, etc.

[jander14indoor]

Let me second chalker7. With that description you aren't winding hard enough. If you are sure you are 3-4 grams the rest sounds like a reasonable design. It is capable of flying. That rubber should be thick enough.
Though the closer to 3.0 gm the better, PS, why can you only give a range, this is science, you should KNOW the mass, it is a CRITICAL parameter. If you haven't measured it, you might be surprised how heavy your helicopter is.

While I agree with chalker7 about hand winding, you can probably get the electric winder to work OK.
Do you lubricate your motors? If not, you must, you just can't get the winds into an unlubricated motor without it breaking prematurely. You don't need anything special, Armor-All or Son-of-a-Gun vinyl protectant from an auto supply store is fine.
Do you stretch wind? Many of the electric winders I've seen don't allow it. If not, you must. Stretch the motor to 3-4 times its relaxed length before you start winding. Put in about half the turns without moving. Last half of the turns as you slowly shorten the motor to the hook to hook length.
Do you have a counter on that winder? How many winds is two minutes? I suspect its not enough, the battery winders I've seen are slow. If not on the order of 1000 turns or more you aren't winding long enough. A motor that width 12-16 inch long loop should take 1000 to 1500 winds for a good flight.
If no counter, I suggest you wind 30 seconds and then manually unwind while counting turns. Then do the math to figure out how long it takes to wind 1000+ turns. Also, listen to the motor as you wind, does it slow down as you go. If so it will take longer than that test says.
Have you ever broken a lubricated motor? If not, you aren't winding hard enough. To win you WILL break motors.

So, back to my basic. Assuming the helicopter itself is reasonable (it sounds like it) you just don't have enough power. WIND HARDER! I'm always amazed supervising competition how many reasonable helicopters I see that get almost no time, hardly rise, but that are certainly capable of flying to the ceiling in most gyms. Almost always the problem is not winding hard enough.

Jeff Anderson
Livonia, MI

[Pele]

Hi, I was wondering if it was worth it to go for the single rotor bonus. Is the 10 percent bonus worth the lift sacrifices? Thank you

[ScienceGuy2000]

If you are an Ohio team headed to States on April 26th and you do not think that the French Field House with its rafters, cross-breeze and 48 ft. ceilings are an ideal venue for true performance rather than a game of chance, please consider expressing that concern ASAP. It appears no one has suggested that the venue is not ideal and so a change of venue is not being considered. It would be great to have the venue moved somewhere with a lower, unobstructed ceiling to allow for everyones hard work to determine results. Please consider requesting a change, and soon.

Please see my post about this in the 'petition' thread:
http://www.scioly.org/phpBB3/viewtopic. ... 22#p257122

Ceiling condition has been a controversial issue for this event, as ceiling obstacles create uncontrolled conditions that cause non-deterministic outcomes for the helicopters. Here are my suggestions for dealing with it for future years.

1. Adjust the problem to make it an explicit requirement to handle ceiling obstacles and request students to apply their creativity to make sure that their helicopters don't get stuck.

2. If #1 cannot be done, then don't bring back the event. Helicopter is scheduled to be rotated out for 2014-2015 anyway. Don't bring it back, ever.

While it has been argued that handling unknown condition is part of real world engineering (e.g. the rovers that we send to Mars have to deal with many things that we still don't know or are not sure about the actual condition in Mars), Science Olympiad Helicopter is not a real world engineering project, and in my opinion as a practicing engineer, it is not reasonable to hold it to the same standard for real world engineering. In real world engineering, there would not be only 9 construction parameters to consider. There would be hundreds or even thousands of requirement that encompass everything from functional capabilities, performance, robustness, ease-of-manufacturing, serviceability, cost, schedule, etc... In real world engineering, you are seldom asked to achieve maximum performance, which is flight time in this case, as even NASA does not have the budget nor time to achieve maximum performance for its projects. Instead, requirements are typically specified as something that must meet a certain performance parameter at a certain cost. Requirements for helicopters would be something like "a helicopter that could stay in air for X minutes with a payload of A grams and a cost of B and a schedule target of C". In real world engineering, if navigating through ceiling obstacles is important, it would be specified as part of the formal requirement, and trade-offs against other requirements such as flight time performance would be allowed to be made.

To make helicopter something that resembles more closely to real world engineering, consider adding these to the problem statement:

---------------------------------

Construction Parameters

j. Helicopter shall be designed to navigate through obstacles in the ceiling and on the wall, which may include, but are not limited to air condition units, air condition vents, flags, retired jerseys, wires, pipes, ceiling support truss or i-beams, speakers, score boards, television, missing ceiling tiles, light fixtures, basketball board and its supporting structure, etc...

Scoring

e. Helicopter that fail to navigate ceiling obstacles and get stuck (defined as rotor no longer supporting the helicopter for more than 2 seconds) are placed in Tier 2.

---------------------------------

By writing the problem this way, at least the students know that they are required to design their helicopters to deal with the obstacles and they would have to evaluate the risks that their helicopters face and make the proper design trade-offs accordingly. The smart teams would do a better job anticipating the problem and test their helicopters at different places that present different obstacles. This is much better than leaving it to chance and pretending that the ceiling would be perfect, and when things don't turn out right, make an excuse that "all teams are subjected to the same uncontrolled condition so it is a fair competition". Students see through this sort of BS, as instead of a scientific competition, they get a game of chance. Instead of getting encouraged to do more science, we get crying kids whose months of work got wasted because they were unlucky, and in some cases, the misfortune affects the chance for entire teams to advance to state and national tournament.

My 2 cents. If you think I am writing this because my team's helicopter got stuck, you are way off. We have been both good and lucky. We just saw way too many kids from other teams who got affected by ridiculously challenging ceiling condition. The way that some adults conducted this event did not help either.

[Pele]

Probably speaking out of turn since I'm from Michigan, but...

We've found racquet ball courts work very well for helicopters.
Generally smooth ceilings.
Reasonably high.
Generally viewer friendly (not quite as nice as a big gym), but easy to limit inappropriate coaching. Especialy those glass walled ones.
No rafters to eat helicopters
Easy to have totally separate practice and timing areas if you can get a couple lined up side by side.
Smooth ceilings.

One issue, seems harder to get facilities to cut off air, but at least that's the same for everyone.

At the Michigan State Tournament we have a gym with a smooth ceiling that we use. Not the tallest gym, but preferred by most teams to limit helicopter eating rafters.

Now next year when gliders go to B and Wright Stuff comes back to C, you'll definetly want those tall, large sites back.

Jeff Anderson
Livonia, MI

Agreed. Racquet ball courts are ideal for helicopters. When the event is held in a gym about 50 percent of the helicopters get stuck in the rafters. This leaves a lot up to chance. With a smooth ceiling, nothing gets stuck, which is ideal.

[Bazinga+]

hah, you guys should have sen the helicopter place for NY state tournament... it was a gym and there were nly 2 safe places were to launch it and they were both about a meter by a meter, so pretty much if ur heli wasnt stable, you are in trouble.

[jander14indoor]

Ceilings, I've been reluctant to respond, but felt the need to say something. I did write the original version of these rules, influence others, and have a particular view on uncertainty that tends to get in the rules.

Now I like ideal flying conditions just as much as anyone and as Michigan State Director use my influence to secure them when possible for our state tournament. But sorry folks, it just doesn't always happen. MSU, where our tournament is held, has a field house almost as nice as the Armory at Univ of Illinois. More floor space, slightly shorter ceiling at 60 ft or so. Never been able to hold a flying event there because its just too expensive to rent for the day. So we've had to go with second or sometimes third best.

Let me quote the relevant rule 4.a
"The event must be held indoors. Tournament officials must announce the room dimensions (approximate length, width and ceiling height) in advance of the competition. Tournament officials and the Event Supervisor are urged to minimize the effects of environmental factors such as air curents. Rooms with minimal ceiling obstructions are preferred over very high ceilings."

Folks, note key words. Must vs urged vs preferred. ONLY "must" is translated as a mandatory item. The others are optional. This is fairly consistent across SO rules. THAT BY ITSELF should be enough to warn you that you will NOT always experience ideal conditions. We don't use the rules to tell you how to solve the problem. You need to read them carefully. Do not look for words in the construction part of the rules that tells you this. This also is pretty consistent across SO rules for the construction events. Example, Robocross. We tell you the playing field has a quarter round in it, we don't tell you under construction that you'll need to cross a quarter round. We also allow a range of surfaces for the play field, we don't tell you you have to deal with that variety under device construction. I've heard folks complain in the wheel events about the floor being different from what they practiced on. Sorry, not specified in the rules, you should have recognized that and practiced on different surfaces.

So, look for any place in the rules where things are not tied down and PLAN for it to change. DON'T assume the conditions at your school will be replicated at the tournament site.

Now, lets talk about how big a problem it is and how you a competitor or coach can manage it.

I've yet to be at a competition where 50% of the helicopters can reach the ceiling, let alone bounce around long enough to get caught in the rafters. And of those that reach the ceiling, I've never seen 50% get stuck. I'm generally the only guy in the room with a 40 foot pole, so I am pretty aware of how often they get caught.

I fly these things regularly at demos and have little trouble reaching most ceilings. I certainly don't get stuck 50% of the time. Far less.

Is part of the problem that students just aren't taught well to choose their launch point? I'm often dismayed with where a team chooses to launch, sometimes repeatedly, under the worst hazard. At the Michigan tournament we found a reasonably tall student gym with smooth acoustic ceiling tiles, nothing to get tangled in. Of course in a gym the size of several basketball courts there were a couple of missing tiles. So what happens, TWO teams launched right under the holes and flew up into them. Is that the fault of the site or the tournament orzanizers? Sorry, I think not. Competitors, LOOK UP! Find the LEAST congested area and lauch there, even if you have to give up height.

And someone mentioned stability. That's something under your control as a competitor, not unimportant for duration, why wouldn't you make your helicopter stable? If not, a poorer placing should (and will) be one of the consequences. Regardless of ceiling type.

What else can you do.

In Wright Stuff it used to be a bragging point to be able to fly a long NO-TOUCH flight at specific, well-controlled, heights. Has the emphasis on smooth ceilings misled students into blasting into the ceiling and depending on bouncing around for max time? Perhaps they need to work on maximizing time to a target height without touching like Wright Stuff? Then you can choose to fly a good, but not great time just under the rafters for one flight and go for broke into the rafters on your second flight. And balance that against ceiling conditions.

Does everyone bring at least two GOOD helicopters? Depending on one good helicopter is just asking for problems without even looking at the ceiling. Part of what I try to teach when I run coaching sessions is how to consistently build your helicopters. That way its not luck that you have one great helicopter you can't replicate. The science and technology we are trying to teach with this event almost require you to build multiple great helicopters to succeed.

Hope that helps both from an understanding and a what to do point of view,
Jeff Anderson
Livonia, MI