Egged on by adoring fans who demanded more aircraft videos, [ProjectAir] has decided to break the world record for rubber band powered aircraft… despite having never built a rubber band powered aircraft. Why rubber band power?
Before little two stroke motors became affordable, and long before electric motors and batteries were remotely possible, there weren’t a lot of options for powering your model aircraft. One technology that really took off was that of rubber band power. By winding a rubber band, it could store enough energy to turn a propeller for a short duration. With a 10 foot model taking the current world record, as you can see in the video below the break [ProjectAir] decided to see if he could beat it.
Starting with a successful free flight aircraft made of foam board, [ProjectAir] simply scaled it up to an eleven foot wing- one foot larger than the ten foot world record holder. Since there were now eight rubber band motors, a mechanism was created to release the propellers in sync, but this was problematic. Eventually a slightly heavy but solid solution was found.
[ProjectAir] did more testing, more problem solving, and through rapid iterations, he eventually was able to have a successful flight under radio control. His personal goal of a 12 second flight was exceeded, and then Guinness called! They’re interested in certifying his attempt as long as his plane can fly for at least 30 seconds- almost double his current ability. What will he do? Check the video, too, for [ProjectAir]’s challenge to the community to join him in trying to beat the world record. Sounds like fun!
Aside from powering world record attempting radio controlled aircraft, did you know that you can build a rubber band powered refrigerator? It’s true!
I built a rubber band powered Guillow balsa and tissue bi-plane around 25 years ago. It flew around 25 feet with a push.
That was amazing – Guillow selected the densest balsa and some really poor designs as they felt a significant part of their market was display-only models. What I learned from building them was to not build them – everyone else in the business had far better kits, but much worse marketing.
After couple of crashes and repairs, mine became a static display too!
B^)
The nice thing about Guillows kits was that the plans were included. With enough zoom on an analog photocopier you could scale the design and build a bigger version of your rubber powered plane that could be powered by an .049… at least, that was the plan. I laboriously transcribed and cut out all the balsa parts but never actually assembled it. Probably for the best – it probably would have just led to another Cox engine hitting the dirt :-)
Wonder if it would be a better strategy to use a huge propeller that is optimized for low speed, slow down the rubber band with a friction dampener, and reduce weight as much as possible? Or maybe setting off the rubber bands in series somehow with a latch that triggers when torque on the prior one’s shaft drops too low
Perhaps just bundle up all the rubber bands into one far more torqued-up mass, connect to a single prop through a stepped-up gearbox, and use a friction mechanism (possibly just the gearbox itself) to draw out the useful thrust period
I had a balsa model with single large balsa prop and it flew very, very well. I think it was called a “Gypsy”. It was a kit type aeroplane covered in tissue paper.
It took forever to wind it up and I recall we had to lube the rubber band to get best performance.
I’d put a torx socket or something on the hub of the propeller, then test the system to the max torque before breaking. Subtract 10-15% of that, set an electric drill toque limiter to that setting, and then wind it up with the drill.
Friction means loss of energy, and the available energy is already the limiting factor. Run time can be controlled by the size and design of the propeller (bigger will run slower). Run time can be doubled by tying two bands end-to-end on a longer frame (in series as you imply), or just using a band twice as long.
2 counter-rotating bands geared together might reduce the required strength and weight of the assembly that holds the bands, because both the net torque and the bending moment could be zeroed.
Twisting a rubber band is not how to store the maximum energy in the band because some portions will have less tension than others, perhaps no tension at all. Linear stretching should be the best, but that leaves the difficult problem of translating a small change in rubber band length to many propeller rotations.
I’ve seen surgical tubing used in slingshots, and it might be a good material choice for the rubber bands.
The world record for unpowered paper airplanes appears to be 29.2 seconds aloft. I’d think that by including a rubber band engine a much longer time could be achieved.
Would you believe: I think the duration record is around 60 minutes?
https://www.youtube.com/watch?v=pPUtKZ6UCB8
But this isn’t assembled with random rubber and dollar-tree foam board, as you can see. The wings of these serious planes are made by pouring a thin film on water and pulling it off with a frame. The covering is many times thinner (and lighter) than cling film. Everything is optimized to the tenth of a gram.
A howto from Josh Finn: https://forum.flitetest.com/index.php?threads%2Ffullfilling-the-dream-the-ultimate-rubber-powered-airplane.39145%2F
(The dobs of hot glue in the OP video weigh as much as Josh’s entire plane…)
And then tuned. Josh uses specific rubber that unloads slowly and consistently. And then he designs the propeller so that it puts out the longest duration of just exactly the thrust needed to spiral up to the top of the space he’s got to fly in — and this may be the ultimate constraint. There’s a lot of tuning dedication, and at 30-40 minutes per flight…
I’ve watched a bunch of Josh’s free flight / rubber videos. It’s absolutely bonkers, and somehow lovely watching him and others shepherd these floaty things around. Try to remember that it’s not running in slow-mo.
https://www.youtube.com/watch?v=kBhm3NHAbKY&t=0s
This. Thanks for providing links.
Aha, Sandia labs is on it. Good luck beating them lol
Indoor free flight rubber powered duration contests are the realm of wily old farts. Props are made if built up balsa and cling wrap. All up weight is a few grams, half the rubber band.
Like car bracket racing. Kids should show up to learn, not expect to be competitive until they’ve studied the last 75 years of work.
He must be going for the record for the biggest rubber band powered airplane. I have a half memory of one that carried a human though, so I think he’s going to be working for a long time.
Unclear what this record, very specifically is for. Rubber powered aircraft fly slow and in circles for like an hour. It’s mesmerizing. The tech is incredible with gossamer materials and amazing airfoil shapes, super slow spinning props that change shape with the force applied to match flight characteristics and as the rubber winds down, and BUNCH of other factors.
Do you have a link to what you are referring to? Maybe they are lighter than air models, using helium?
The world record for heavier than air rubber band airplanes is 2 minutes 8 seconds. This project is far from it, but still a nice start.
I guarantee that 2:08 is incorrect, since I made a kit in highschool that performed about that good. You are referring to: https://www.guinnessworldrecords.com/world-records/375787-longest-time-for-a-rubber-band-powered-model-aircraft-to-remain-in-the-air
But, I think “Model aircraft” may mean “remote controlled” or possibly that it’s a model of a real aircraft.
The ones the other commentor talked about are heavier than air (no helium) but generally weight something insane like just a gram or two.
>”On Sept. 3, 2017, Brett flew his craft for 32 minutes, 9 seconds, eclipsing the previous record for a flight above 100 feet by about 2.5 minutes. ”
https://www.sandia.gov/labnews/2018/11/21/f1d/
More like half an hour:
https://www.sandia.gov/labnews/2018/11/21/f1d/
The official world record planes are all to a standard, with rules, a governing body, etc and, I believe, is about a half hour. Like F1 racing kinda with the rules. “Unofficial” flights over an hour are definitely occurring. Vis: https://www.youtube.com/watch?v=pPUtKZ6UCB8. I know what a blimp is, LOL, these are not lighter than air, I’ve seen them in person.
https://www.wired.com/story/how-much-energy-can-you-store-in-a-rubber-band/ says the energy stored is 1.6 J/g for stretching and 6.6 J/g for twisting. Composite structure free flight model airplanes can have glide ratios up to 1:30.
If the aircraft had 25% of its weight in rubber bands charged to their full capacity, it would have enough energy to rise to height of 170 meters or to glide horizontally for 5 kilometers.
A ridiculously high result of course, but it shows that most of the energy gets lost into inefficiencies and there is potentially a lot of room for improvement.
I can see three immediate problems with the first version of the prop release mechanism. (@ 07:40)
The first is that the system is untested, and [ProjectAir] is too anxious to fly the aircraft.
The release mechanism looks quite usable, but it needs some tweaking and testing, and that needs attention.
So the solution to the first is to put some effort into testing and modifying the prop release mechanism.
The second problem I see is that all the cords were tied to the same rock. Pulling the pins out works much better if you pull them out straight. This means tying all the cords to some broomstick. Also: don’t just yank the plane backwards to pull the pins out. Take a few second to align the plane with the direction of the cords and then give it a “calibrated” tug backwards.
Third problem is that it takes apparently twenty minutes to wind the rubber bands. This gets tedious quickly and lowers the incentive to do many tests. Get a cordless drill or another electric motor to improve on the winding effort.
Some other ideas for improvements:
Lowering the force to pull the pins may help. If the locking is done further from the center of the prop, the force on the pin is lower.
If you stay with a servo controlled release. It should be quite doable to use only a single servo and lightweight yarn, but guiding it properly takes some design effort (this plane is clearly a quick build).
Another option is to put the plane on some kind of frame. For example, if the propellers are bigger then the height of the plane, the propellers can be started by just picking it up from a flat surface. A piece of 2 meters long U-profile can hold the propellers static.
The rubber bands look like they can be wound much further and store more energy. How far they can go needs some extra testing (which has of course already been done by lot’s of people in the last 150+ years…
Does doubling up the rubber bands (so distance front to back is halved) improve energy storage? (or energy to weight ratio, as the tube for the frame can be halved) Optimizing the rubber motor is an art in itself.
Add an extra ring to the rubber band that always stays open, so it’s easier to transfer the band from the winding mechanism to the propellers, or better: Attach the winding mechanism to the front of the propellers, so it does not have to be disassembled at all.
If the rubber bands can be mounted in the center of a tube, it does not exert a bending force on the frame. A very thin walled tube would be ideal. Rubber is also affected by the grease that humans excrete though their pores. That is why rubber bands often have talcum powder. This absorbs that grease so it does not affect the rubber as much. If it’s in an enclosed tube, you would not have to touch it at all.
I wish you lots of luck and success with further experiments.
What are the requirements for the record I wonder. Like, can it fly indoors? Find a large done stadium to borrow.
Can it use more rubber bands? Chain them together to make a longer rubber band.
Does it have to be remote controlled? If not, tune it to fly in a large circle without guidance/electronics.
Construction wise, carbon fiber, balsawood, and thin films like mylar should make it way lighter, which should result in longer flight time.
Honestly doesn’t sound that hard to beat depending on the requirements.
Umm, contest rubber comes in lengths, not loops, you knot the end after making the band loop you need, be it 2 or multi strand. Strength to resist the pull force is kinda important otherwise you could use couch bands. Not a bad first attempt especially a what if scenerio.
Interesting posts. For those into rubber powered free flight, check out maxfliart https://www.youtube.com/channel/UC5lXh5HZ62N8s7urLVoOVxg Beautiful builds and some of the most relaxing, beautiful content on YouTube
Yes indeed, loved the comment about old farts and the art of indoor freeflight.
When I was young but outgrowing the competiveness of keeping up with the Joneses on the RC field and just the over complication of staying high tech, my friends and I would have our religious weekly outing on Tuesday nights where we would meet in Garden Grove for a evening at the Crystal Cathedral gymnasium where all the old farts practiced their arts with their aircraft . Ten minutes flights were very much an unfortunate norm as craft would hit the ceiling and crash before completing their duration. Like someone mentioned it was like bracket racing where they would count windings and consult a slide rule and adjust wing and incidence , prop pitch and a little bit of breath and an eyeball warp of a control surface before hitting the stopwatch and proclaiming an estimated duration time…. I remember seeing one old guy that had a duration of 18 minutes as this craft circled at just above eye level, only to have the man stomp his craft to smithereens for failing his estimated duration by a few tenths of a second !!! It was crazy and refreshing thing to watch as a spectator. We did build some rudimentary planes that were a far cry from the performance that these guys flew. But it was fun going back to the basics of tissue paper and balsa.
The thin buytl nitrate water dip covering was amazing as was much of the other tricks and precision tools of the trade. With gear reduction winding counters, strain gauges, grain scales and all manner dial indicating measuring devices.
Definately an art form practiced by those of a greatest generation.
Much like other forms of hobby like some of the control line crowd and tether cars too!