Rotor Egg Drop B

[ckssv07]

What would a competitive time be

our most recent devices have been getting times between 3.6-4.8 seconds. these are mostly prototypes, as in builkt from inferior materials and one was slightly oversized. (I should not be in metric mastery .) but remember that with higher drag comes lower stability

I am thinking that if you are going to quote time, I would want to see the accompanied height along with the quoted time, otherwise, it does not mean much.

It was a three meter drop.

[hogger]

It was a three meter drop.

The rule says minimum of five meters. You should at least try at that height or at least find out what height would be at the competition if that is possible.

[ckssv07]

It was a three meter drop.

The rule says minimum of five meters. You should at least try at that height or at least find out what height would be at the competition if that is possible.

3.6->~6.12
4.8->~8.16most likely times for 6 meters

[hogger]

It was a three meter drop.

The rule says minimum of five meters. You should at least try at that height or at least find out what height would be at the competition if that is possible.

3.6->~6.12
4.8->~8.16most likely times for 6 meters

You might be closed but It is definitely not linear, you can't assume double the time with double height. More importantly, will the egg breaks at 6 meters when it may have survived 3 meters fall. You don't know for sure until you have tried.

[ckssv07]

You are right it does not double, but over many testings, it has become apparent that every three meters, the time is multiplied by about 1.6,1.7 from the previous drop. It is not always true, because something can happen to the device after a certain height. The egg should not break because i have made others that have been a lot faster, and they had still survived, but if for some reason it picks up a considerable amount of speed at the end, then the egg could break.

[hogger]

You are right it does not double, but over many testings, it has become apparent that every three meters, the time is multiplied by about 1.6,1.7 from the previous drop. It is not always true, because something can happen to the device after a certain height. The egg should not break because i have made others that have been a lot faster, and they had still survived, but if for some reason it picks up a considerable amount of speed at the end, then the egg could break.

Using constant factor to estimate time again is also not right. The helicopter speeds up really quickly when you first drop it, then the rotor engages and the acceleration due to gravity is countered by the lift force of the spinning rotor. The behavior of the velocity and acceleration varies based on how the rotor behaves, it is not a simple linear equation that can be described be a simple factor, in other words very complicated and not very predictable for small distance like 3 meters and use it to extrapolate to larger distance.

Lastly, why not test it at greater heights instead of thinking or predicting that it should behave certain ways.

[ckssv07]

I know it is just an approximation. Our newer rotors tend to take a circular path downward, instead of straight down, and all the staircases we have at school that are larger than 3meters are just barely large enough to accomodate the rotor, and we do not want to take any chances, but we will be testing them from greater heights soon, so i will keep you posted.

[jander14indoor]

Hi Jeff,

Do you have any tip with grocery bag covering? Do you use solder iron to cut the edges like film or do you just cut it with a knife? I am going to have to move away from film, film is way too expensive for this event and probably overkill.

Pretty much the same as for mylar films exept you can cut with a SHARP knife. Make sure you weigh your bags as select the lightest, a lot of variation out there.

You might be closed but It is definitely not linear, you can't assume double the time with double height. More importantly, will the egg breaks at 6 meters when it may have survived 3 meters fall. You don't know for sure until you have tried.

Actually, once you hit terminal velocity (which you want to get to quickly) with rotors a full speed, it is pretty linear with height. And you are no more likely to break an egg at 20 meters than 5, assuming you hit terminal velocity at 5. Terminal velocity is the fixed speed you reach for your system, additional height will not increase it.

Jeff Anderson
Livonia, MI

[hogger]

Actually, once you hit terminal velocity (which you want to get to quickly) with rotors a full speed, it is pretty linear with height. And you are no more likely to break an egg at 20 meters than 5, assuming you hit terminal velocity at 5. Terminal velocity is the fixed speed you reach for your system, additional height will not increase it.

Jeff Anderson
Livonia, MI

Yes exactly. But the device might not have even been closed to reach terminal velocity at 3 meters and still accelerating so when he tests it at 5 or at 20 meters, it could just as well break the egg.

Thanks for the tip on grocery bag covering.

[balasg]

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

Look for any instruction for wrightstuff construction, there should be instruction on how to cover the wings. Depending on how you make your rotor, it should be similar. You may need to roll the rotor surface on top of the tissue as you try to get the all the edges to be glued to the paper.

http://www.youtube.com/watch?v=CkADhiyD2z4
https://soinc.org/sites/default/files/u ... iad5.0.pdf

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