Rotor Egg Drop B

[thehydrogenpoptart]

So what tends to be the winning time at Regionals, States, Nationals etc?

[OlyRocks2013]

For this event, how do you use the balsa to create a blade? Should the two blades be directly connected or no?

[jander14indoor]

For this event, how do you use the balsa to create a blade? Should the two blades be directly connected or no?

There are several ways to make a blade, lots of discussion in the helicopter threads. For all of these you are essentially making a giant propellor. It might help to have a propellor handy to look at as you do this.

Easiest (but heavy), take two planks or long rectangles of wood and connect them like a flat X at the center (when looked at along the planks, one plank is one bar of X, other is other bar). Hmm, for a start, planks about 1/16 thick by two inches wide by 12 inches long. That will give you one rotor with two blades. If you want four blades, just stack them on top of each other rotating the first set from the second by 90 degrees

Slightly better and lighter, sand the planks to an airfoil shape.

Much lighter, though still not best aerodynamically, make a retangular frame about the same size from 3/32 sticks of balsa and cover with light tissue. Again connect at center to a flat X.

About the same light weight, but better aerodynamics. Take two long pieces, maybe 1/8 square, about 70 cm long (just short of the diagonal of the 50 cm box). Pin one securely to a building board covered with wax paper. Mark the exact center. Take the second piece (again with the exact center marked) and fixture it above the first but rotated to make an X. Make sure the centers are exactly above each other. The upper piece (called a spar) should be consistently say 2 cm above the building board. The tips should be seperated say 5-8 cm on both ends. Now, here's the tricky part. Connect the two spars with ribs running from top to bottom. One at each end. Another about 3/4 radius. Another about 1/2 radius, and a final at 1/4 radius. Add a final spar at the exact center. When the glues all dry cover the blades from the 1/4 radius out to full radius. The center is open.

OK, now that you have a rotor, how do you attach it/them. You need some sort of bearing at the center you can run a wire through so that the rotor spins nicely around the center. Attach the wire to a stick and slide the rotor on the top, securing it so it can spin. If you have two counter rotating props, add another wire to the other end of the stick (the wires should be in line), slide on the rotor and make a loop in the bottom wire. Use light string to attach the loop to the egg cup.

I've been a little vague on dimensions because that's part of the challenge. What propellor shape slows the egg the most?

Oh, and in all of this WEIGHT is your enemy. Keep things light.

Jeff Anderson
Livonia, MI

[2017Kortman]

I'm building a rotor egg drop device with two individually spinning rotors. They spin in opposite directions. How do I attach them together while still allowing them to spin in opposite directions?

[retired1]

With a piece of thin piano wire vertically thru the dead center of each rotor, 90angle at the top with washes between the rotor and the 90, spacers between the two rotors and the wire attached to your load structure.

[bbcourt13]

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?

[sofan]

I'm building a rotor egg drop device with two individually spinning rotors. They spin in opposite directions. How do I attach them together while still allowing them to spin in opposite directions?

washers may be a big factor in weight. So do what retired said but I recommend not using washers.

[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.

[retired1]

I'm building a rotor egg drop device with two individually spinning rotors. They spin in opposite directions. How do I attach them together while still allowing them to spin in opposite directions?

washers may be a big factor in weight. So do what retired said but I recommend not using washers.

Washer was generic, by shape. Pieces of tubing. tiny beads, nylon or teflon washers if you have. For some, I steal sequins from the wife's sewing kit.

[ckssv07]

What would a competitive time be