rotodynes

Rotodynes are very difficult to make but cost almost nothing




Launching is difficult too



This is how you make the wings



It is important to tape them securely at top & bottom and at each end to the drinking straw as otherwise they tend to deform in flight. You won't see them deform because they spin too quickly.
This is how you make the hub



Print the following for a pattern

This is a punch for making the jets in the drinking straws; although this can be done by hand it's a bit fiddley.



Putting a three inch rubber band round the balloon before you inflate it will increase the balloon's power a lot.



This is quite difficult because the band tends to slip as you inflate the balloon, you have to adjust it continuously.

This is an alternative method for making the hub



It is less fiddley than the original method & seems to work quite well, I think there is less energy loss although there is about a one gram weight penalty. Extra weight isn't so critical in the middle because it doesn't stop the wings accelarating when you launch it. Only 7 from the science museum although in my experience they only work a few times with the special balloons supplied, they now seem to have a ring-around-the-rotor I don't know if this helps with stability and/or endurance.

rotodyne doesn't work? Neither did mine for the first 5 years! Try a rubber band helicopter instead. That won't work either!
youtube
Sud-Ouest Djinn
modern version
showing tip vortexes
focke-wulf triebflugel
related idea, looks fun, much easier to do
interesting things to do with balloons


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my email is davidvwilliamson@hotmail.com