Coupling a Few Hundred Rubber Bands Together

Hi, I believe there was a nice link to a home made rubber powered car from an old DIY magazine, somewhere in this thread.

Have fun

Del

This is a great "Modern Mechanix" story. I just wish the Figures were included. I can envision several ways of matching the verbal descriptions to hardware implementations. This story reminds me of reading "Modern Machinist" and the old "Popular Mechanics" about 50 or 60 years ago.

How about a rubber inner tube for a bicycle instead?

Instead of twisting up a bundle of bands, you might think about a rod that is used as a shaft to turn a small set of gears to run your prop. The bands could be cut and wrapped around the rod all down its length side by side then attached to a parallel rod as the anchor point. This would allow all of the bands to apply even work down the length of the shaft and if geared right will allow a mechanical resistance to regulate your energy expenditure. The use of a lightweight extended armature will allow the combined force of that many rubber bands to be distributed over a wider area and prevent the necessity of a large, heavy frame due to a big bundle of twisted rubber.

Thats a very big model you are building! You might be best using the rubber from Spear guns. The ends come with screw on fittings which you could screw one end to a fixed board and the other screw directly to a gear drive to the propellor. you can use them as a series of sun gears around a central output gear. You can also place an inside ring gear around them to give double wind effect and more speed to the propellor. Old printers, photocopiers VCR's etc should have most of the gears you need inside.

It is indeed an interesting challenge to get the energy in stretched rubber bands to power something. But getting a hundred pounds off the ground sounds like a bit too much for rubber energy. I would have thought you would have a better chance if you tried to power a bicycle using rubber strain energy. The challenge is to connect the groups of stretched bands to the driving mechanism in sequence as each set gives up the energy in it. Have you tried to find out the energy density in stretched rubber bands ? Is it better than in steel springs ?

hello everyone,

have you considered using bungi cords. when you open one up, they are nothing but massed rubber bands.

I think fishing tackle shops sell thick elastic for bait catapults.

This may not match your requirements, but, you may be better off going for a bungee launched glider.

Instead of having the rubber bands on the inside of your model, have them on the outside as your catapult, then you need less structural bracing to stop your model collapsing under the huge forces of the rubber bands, also no need for the battery bank to rewind the thing once the bands let loose

Substitute surgical latex tubing for the rubber bands. You will experience a considerable improvement in performance.

Modern rubber bands are full of talc and other fillers that seriously compromise their elastomeric integrity, and give them a very short life.

The genius of rubber-band motors for lightweight model aircraft is that the rubber band (the motor) doubles and re-doubles as it is wound without requiring much more force as the motor is wound up. The force applied to the propeller during flight also remains fairly constant . The length of time one of these things will run depends on how long the rubber is, and how many times it will re-double without breaking.

If you plan to make a motor that will keep a hundred pound airplane aloft for very long, put a guard around the rubber band. If it breaks, it will leave a serious welt.

I'm surprised that no one has posted a link to the Rubber Bandit (http://www.rubberbandit.org/). But the power-to-weight of ordinary rubber bands probably won't make them a bargain; the suggestions about surgical tubing are good, or go to actual model airplane rubber (used to come on spools, and you bought as much as you needed in a continuous piece, nice and uniform, and lubed it with green soap). Google "Tan sport" or "Tru torque" (or both).

several ofthe leads sound promising. i like the model airplane rubber in rolls. i like surgical tubing. i like the bunggie catapult. launch it with the bunggie catapult, then once momentum starts to fade, release rubber band propeller. would it work with two propellers. one on each end of the rubber bands. lock one tighten the other lock it. release both locks, both propellers spin, have one counter rotating. one pulling one pushing. also another thought. how about additional propellers mounted on the wings. each with its own rubber band power. you could release them all at the same time, or sequentialy.

"...how about additional propellers mounted on the wings. each with its own rubber band power?"

Their blades would need to be foldable or otherwise stowed to avoid a serious drag penalty. And no, freewheeling is NOT the answer - a pinwheeling prop may actually consume more energy than a stationary one (though the tests I'm aware of were done on conventional airplanes, where it would be rotating an engine against compression). Might as well go whole-hog, and stow the main propeller(s)' blades, too, when power runs out, for the same reason. They could even be jettisoned, if weight-&-balance are manageable, and it's possible to assure that they won't impinge on structure or control surfaces when released. Wing-mounted booms (essentially, mini-fuselages in tubular form) would offer length and structure for the additional rubber motors, but avoiding interference between adjacent prop discs gets complicated by the need to un-stow and possibly re-stow blades. Complications are not a good thing, here!

In my distant youth, there was of course the continuous rubber band available in spools. Often several bands were geared together to run the propeller. Still, I doubt the aircraft ever weighed more than a pound or so.

If you want a 100 lb. payload vehicle, why not try compressed air? (Models powered by C02 "Sparklet" cartridges were common for a while) A small IC engine could be converted, and a SCUBA tank should provide plenty of energy.

Have you thought to use a lead screw threaded through the prop and compressing an substance into the fuselage or tube. When the energy is released the lead screw could rotate and extend through the threaded prop.

May be hazardous though...