Rotor Egg Drop B

[jander14indoor]

Thank you to all those who responded to my question.

We actuall did something very similar to your suggestions, but had a problem with the condenser paper:
We spritzed it and two days later ironed it, but the ironing caused to to have very many wrinkles. For the frame we are using bolas wood. It is just the wrinkles many the paper look horrendous...

Anything to do?

Thank you,
GAB

You'll never get all the wrinkles out, doesn't really matter. Just iron until you get lots of small wrinkles and fairly flat.

Note, if you have areas with wrinkles and smooth areas, then you didn't spritz it evenly and some areas have shrunk more than others. Lay out flat on the towel again, spritz and soak evenly. GENTLY spread out evenly while wet. It can be done with care. Make sure you don't have wet layers of tissue touching each other, when dry they will stick tight.

Let dry and re-iron.

PS, all this hassle is why I recommend looking for LIGHT grocery bags. You can find them if you look. You can find ones that approach condenser paper in weight. Used the same way, glued the same way, but very stable with temp and humidity changes.

Jeff Anderson
Livonia, MI

[sofan]

I'm coaching the rotor egg drop, and my team is currently confused on how to attach our blades to the hub. Any suggestions? We're currently using carbon fiber rods that are bent into tear drop shaped blades with the veggie bagging covering them. We followed the instructions on http://fc.niskyschools.org/~psherman/03 ... gDropNotes but all they say is to use fixtures to attach the blades at the pitch angle and we have no idea how to do that. Any suggestions?

On mine, I made 8 blades and connected them by a rod. Something like + with a X in it overlapping. Basically an X and a + on it. Worked pretty good. You could use that as a starting point.

Did you keep all the blades flat? If not, how did you make the blades all connected at certain pitch angle? Btw, what is the best pitch angle to provide the maximum lifting power?

I kept mine all at the same angle. about uhhh.... 45 degrees pointing down?

[sofan]

Hi Guys,
A friend and I are doing Rotor Egg Drop this year. Our teacher would not order us the kit, but got us condenser paper. It is a lot more fragile than I expected.

How am I supposed to use it? I know it is for the wings, but how do I make it work?

Thank you,
GB

You would probably use it to cover the wings, once you made the frame for the wings.

[John999]

I was at the Solon Invitational this past Saturday and watched the Rotor Egg Drop. I thought it was a very well run event.

Some observations:

The event used releases on pulleys near the gym ceiling to drop the devices. The judges would have the kids attach a ring to the top of their rotor, and then insert the ring into the release. The judge would raise the device and release by rope to the ceiling and then drop the rotor. This was a much better situation than dropping in a stairwell. They had 8 meters of height for the drop. Most of the devices did not have a good way to attach the ring to the top of the rotor and had to rely on tape to hold the ring. I recommend that all teams at least have a small string loop at the top of their rotor for ring attachment. The teams that had this were quickly able to attach the ring. You never know if a similar setup may be used at your Regional, State, or National competition.

Some teams were found to be in violation of the 51cm cube rule, 3e. They had constructed their device to assume the cube was at a 45 degree angle to the floor. I thought they had a great idea, however, at this competition the rule was interpreted to assume that the cube had one face on the floor and they were moved down to tier 3-4. I think the teams had it right given the rule wording. I submitted a question regarding 3e to the FAQ sight. I hope to hear back soon as the first regionals in our state are only 11 days away. FYI, I've never had a question answered, just the loud sound of crickets.

[chalker7]

The event used releases on pulleys near the gym ceiling to drop the devices. The judges would have the kids attach a ring to the top of their rotor, and then insert the ring into the release. The judge would raise the device and release by rope to the ceiling and then drop the rotor. This was a much better situation than dropping in a stairwell. They had 8 meters of height for the drop. Most of the devices did not have a good way to attach the ring to the top of the rotor and had to rely on tape to hold the ring. I recommend that all teams at least have a small string loop at the top of their rotor for ring attachment. The teams that had this were quickly able to attach the ring. You never know if a similar setup may be used at your Regional, State, or National competition.

I cannot speak to Regional or State tournaments, but typically the National competition will follow the letter of the written rules book and any subsequent official clarifications and/or FAQs. This is not official, but if there is no mention of a ring attachment in any of those locations, it is very unlikely to be used at Nationals.

I hope to hear back soon as the first regionals in our state are only 11 days away. FYI, I've never had a question answered, just the loud sound of crickets.

You've never gotten a response? How many questions have you submitted? While the responses can sometimes take a couple of weeks (remember, there are a number of people involved in this process, almost all of whom are volunteering their time,) I haven't heard of them being completely dropped.

[JMDugan]

My student is using a knex hub, attaching his rotors with knex sticks. He is preventing it from sliding down the balsa center stick via a piece of tape that prevents it from sliding down but not from rotating.

It is only a white knex "star", nothing else -- is there any way this could be considered a commercial rotor, which would be a construction violation?

He got tier 4'd at an invitational, but in that case he used a whole rotor setup made of knex -- my fault I guess for not realizing that would be considered a commercial rotor -- I just thought he was clever and made something that rotated out of knex.

Is he in the clear with his new design?

[jander14indoor]

My student is using a knex hub, a<SNIP repetition of details>
Is he in the clear with his new design?

Sorry, but there is no way anyone on this forum can give you anything but an opinion. Any answers we give are not official and can be overruled by the event supervisors at your competition.

Example, to me commercial rotor means something designed to be sold and bought as a rotor. Example, a rotor assembly from a commercial model RC helicopter. So building a rotor from random KNEX parts would not violate the rules, same for the hub you mention. Obviously the event supervisor at your invitational thought different. There is no way we can predict how the supervisor at your regional will rule.

The only way to get official rules that you might be able to use at a tournament in an appeal is to submit your question to the NSO website for a clarification for FAQ answer.

Jeff Anderson
Livonia, MI

[wlsguy]

My student is using a knex hub, a<SNIP repetition of details>
Is he in the clear with his new design?

Sorry, but there is no way anyone on this forum can give you anything but an opinion. Any answers we give are not official and can be overruled by the event supervisors at your competition.....

I agree but you may want pose the thought with the event supervisor the rules prohibit "commercial rotor assemblies" not "commerical parts" used to make the assembly. If Knex are not permitted then you could easily argue anything purchased and used to make the assembly would also be prohibited.
Every team would fail this test since no one grew their own balsa wood or made their own paper / plastic for the parts of their rotors.

[Pengu8]

heyo!!!
Just some quick questions here

Right now my district is having their contest next Saturday (omg!) and I got nothing for my rotor egg drop.
I am right now on my paper prototype. It has 4 big blades on top assembled in a + shape. with 3 smaller blades on the bottom assembled in a Y shape. They are flat and I didn't twist the blades. I thought that not twisting the blades will make it go slower. I also observed that if you put the paper blades up in a direction too high it wont work or fall to quickly like a tornado shape when it falls down. It works pretty well and all, but imo it goes a bit too fast? It lands smoothly and I used a clip on the bottom to act like an egg and when it landed from my stairs it made a little click sound. It was ok. I tried to mimic the sound of it hitting the ground and try to measure how much force it was, it doesn't look like it would do much damage.
I have a few questions before I make mines on real material though.

How do I make my rotors rotate in opposite direction? I looked at your guys response to this but i don't get that piano wire and that 90 degree angle part. btw I'm using 4 big blades on the top and 3 smaller blades on the bottom of it.
ALSO.. DO they HAVE to rotate? It's called rotor egg drop for a reason but I'm not sure if my blades really need to rotate or stay immobile. It doesn't say much in the rules and I'm kind of confused. Yy dad told me that if I rotate it then it would make some kind of air vacuum and make the egg drop more slowly rather than the blades being immobile. I still think it doesn't matter. Help and clarify please!

Secondly, What is the best shape for the blade? Is it a rectangle, curved at the end, or pointed, etc.? I did mines curved at the end and it worked a bit.
Third, the egg holder thing. Do I have to make a contraption on the bottom or can I tape the cup to my stick? I don't like adding extra weight and I don't like it looking like it is only held by tape. I only have ONE shot at this thing and if I screw up I'm doomed!!

fourth, best material for blade skeleton? I was thinking of using some thing copper wire wrapped around some plastic wrap you would use to store food and all. My teacher said that that won't work and that it would be too heavy. So what would be best? Would it be the traditional balsa wood for the skeleton and the food wrapping thing or something else? I need clarification. Thank you guys!

[jander14indoor]

<SNIP>Right now my district is having their contest next Saturday (omg!) and I got nothing for my rotor egg drop. <SNIP>
How do I make my rotors rotate in opposite direction? <SNIP>
ALSO.. DO they HAVE to rotate? It's called rotor egg drop for a reason but I'm not sure if my blades really need to rotate or stay immobile. <SNIP>
Secondly, What is the best shape for the blade? Is it a rectangle, curved at the end, or pointed, etc.? <SNIP>
Third, the egg holder thing. Do I have to make a contraption on the bottom or can I tape the cup to my stick? I don't like adding extra weight and I don't like it looking like it is only held by tape. I only have ONE shot at this thing and if I screw up I'm doomed!!

fourth, best material for blade skeleton? <SNIP>

Wow, kind of last minute, but...

Start with the usual, this is opinion, not official, not a clarification, etc...

To make the rotors go in opposite directions (counter rotate) they have to be pitched in opposite directions. Hmmm, how to describe. For the top rotor, look along a blade from the outside towards the center. All the blades on this rotor should tilt from lower left to upper right. For the bottom rotor the blades should tilt from upper right to lower left. Or vice versa for each rotor.

Do they have to rotate? Well, opinion again, but the rule seems pretty clear, para 3.a The device must use wings or blades that rotate around a central axis to slow the descent of the egg, using aerodynamic principles of a helicopter rotor in unpowered "autorotation" mode. Hmm, sounds like your rotors better rotate.

Blade shape. The last thing you need to worry about at this point. You need to get your rotors rotating with the blades at the 'best' angle, as you are right, flat won't rotate, too steep won't slow things much. Use whatever shape you can build quick and get testing angle. IF you have time after that, rounded tips have less drag. Ideal is probably an eliptical shapped blade. When looking from the top.

Egg holder, you are right to keep it light and simple. My suggestion would be to have three strings below your bottom rotor. Use the tape to hold the string to the egg holder cup. PS, you should be thinking in terms of multiple tries beforehand, not ONE shot. Besides testing with just dead weight equivalent to an egg, you should drop a real egg or two to give you confidence.

Rotor frame. Your coach is right, a copper frame will be HEAVY. Its actually pretty hard to beat balsa for lightness AND strength. And don't use food wrap, TOO HEAVY. Instead, check out plastic shopping bags or produce bags. Its easy to find coverings that are strong enough and much lighter than food wrap.

Jeff Anderson
Livonia, MI