A Swing Set That Generates Electricity

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Introduction: A Swing Set That Generates Electricity

'Id just like to say first off that my electrical knowledge is very limited, and I'm sort of feeling my way around in the dark. If you have a better way of doing this, I'd love to hear about it. Also we are taking ideas for what to power.
*(UPDATE) The swing set performed well at the Bay area Makers Faire this past weekend 5/21/11. Having replaced the 44 tooth driven gear with a 112 tooth gear we were able to produce around 9 volts consistently. At 6 volts we had 0.3 Amps and 1.2 Watts. We were able to run 12 volt LEDs well, as well as 9 volt EL wire, and a 9 volt electric keyboard at the same time. We believe that with an additional gear reduction we will consistently produce 12 volts. Look for it deep in the outer Playa this year. Here is a video of it at the Makers Faire:

Also, this is my first Instructable so please bear with me. Hope you enjoy it.'

This project was done in Collaboration with and would not have been possible with-out my good friend Ryan Alpers.
Also I would like to thank Reid Johnston, Matt Gil, and Baker, and the good people at Bearing Agencies in SF for technical insight.
And Thank you to Cork Marcheschi for the use of his studio and equipment.

*(UPDATE)I wanted to make clear that the magnet rotor plates are very heavy and act as a flywheel, smoothing but not "bumping" the power. Also the chain does not move back and forth, but in a single direction. The swingers only affect the drive shaft when they swing forward, on their return trip the roller clutches freewheel back, also allowing the swingers to regain momentum. Thank you for all the interest! 

After building Hugh Piggott's http://www.scoraigwind.com/ Axial Flux permanent magnet motor and adapting it to a stationary bicycle, i wondered what else i could use to make small amounts of electricity. After polling friends and family for old play ground equipment, a friends parents donated an old swing set. It was built ages ago but super sturdy and after a little TLC it was ready for a new life.

The design was pretty straight forward, i used Mcmaster Carr and some local (San Francisco) companies for the machinery. It basically went together over a couple of weekends. I used Hugh Piggott's generator since i had already made it and like the design for low speed low torque applications, but i guess anything else like an alternator or treadmill motor would work as well.

Materials used included 4 pillow blocks, 4 roller clutches, 9ft of keyed drive shaft, standard steel tubing, around 20ft of angle iron, a lot of lag bolts washers and nuts, a rear bicycle hub with a disk brake attachment point, a couple single speed rear bike gears, some motorcycle chain, a bunch of shaft collars, 4 pipe collars, and a gear that fit the drive shaft.

tools used included a standard 110 mig welder, porta-band, files and rasps, rubber mallet, angle grinder, misc hand tools like screw drivers etc, drill press, hand drill, marine anti-rust spray, plumbers wrench, vise grips, and a motorcycle chain breaker and assembler.


Step 1: Deal With the Swing Set

We were lucky to have a swing set donated which made the project a lot easier and cheaper. A friends parents had inherited it when they bought their house. it had probably been sitting in the same place in the backyard since the bomb shelter it was above had been there.

In any event, it was 1/4' steel and built very ruggedly. Surprisingly after spraying some marine anti-rust into the joints and using a couple plumbers wrenches it came right apart.

After getting it back to our shop, we cleaned and removed as much built up rust flakes as we could. a stuck bolt led to drilling and re-tapping for a larger bolt, and all other hardware was replaced.

where some of the ends of the legs had warped over time where they went into the joints, we used an angle grinder to remove rust and round them out.

After re-assembling the swing it looked 30 years newer and went together and came apart effortlessly.

Step 2: Work Out the Design, Assemble Materials

originally we were interested in using a product called LED vision flex on the singing chains, to simulate a video by flashing a section of the image as it flew by. Due to time and money we decided to just make the juice and we figured we'd work out what to power after we knew it would work.

We settled on hanging a drive shaft a few inches below the top of the swing by pillow blocks, and to attach the swings to that by roller clutches, (or roller bearings as some say. Essentially ratchets). as the swingers swung forward they would turn the shaft forward, and when they swang back the roller clutches would freewheel and the momentum of the generator would keep moving forward. if the two swingers were out of sinc. then there would always be someone pushing the generator forward.

The generator was to be connected to the drive shaft by gears and chain.

The picture shows when we thought we would be able to fit 3 swingers.

The roller clutches which fit around the drive shaft were to be pressed into a standard pipe, and the swingers chain secured to the pipe. that way the weight would be distributed over the drive shaft and the swings would be removable.

All in all the finished product came out very similar. which i don't usually expect.

Step 3: Assemble the Generator

Like I said I decided to use Hugh Piggott's generator http://www.scoraigwind.com/ for this project because i had already built it, and liked it. but you could adapt a lot of different stuff to it.

As anyone who is familiar with Hugh Piggott's generator knows, it was designed to sit on a wheel hub from a cavalier or something. When i built it, instead of going for the wind turbine i opted to addapt it for a stationary bicycle. I actually got the idea to use a standard rear bicycle hub with disc brake mount from a website a long time ago, and it worked quite well.

There is a picture of the hub with out the stator and magnet rotors on it sitting in its eventual mount. in the picture you can see the aluminum scrap plate that i machined to mount to the disc brake attachment point and the holes where the lag bolts for the rotors attach. To get the rotors though i had to grind down the flanges on the hub. A pity, i don't like destroying things.

The beauty of this system is that it already has built in bearings and a massive amount of free parts like single speed gears readily available. Which made finding chain etc easy. I wasn't sure if the disc brake could handle the weight of the magnet rotors which weigh at least 45 mounds, but the hub takes it like a champ. I think using a mountain bike bub (which is more likely to have the disc brake attachment anyway) is the way to go because it may be beefier.

basically, the magnet rotors sandwich an independently mounted stator with the copper coils, and the magnet rotors spin around it and the magic electricity fairies do their thing.

the other pictures are the stator mounted on the swing, the assembled generator, and a magnet rotor mounted to the hub.

Step 4: Attach the Drive Shaft

The design called for the drive shaft to be mounted as close to the top of the swing as possible to minimize contorting the shaft, and to give as much clearance to the swinger as possible. (it really was a child's set so we were only looking at 8 feet max)

The drive shaft needed to stick out one of the sides of the swing to allow the gear to rotate and the generator to be mounted so the shaft had to be just lower than the joint where the swings legs attached.

I set the top of the swing set upside down on a level surface with the legs removed. Pieces of angle iron were cut to the length of the pillow blocks and drilled, then the pillow blocks bolted to them.

The pillow blocks and attached pieces of angle iron were then pressed onto the drive shaft and the drive shaft coupled together. two blocks and angle iron were welded to the joints on the swing at equal points to make the shaft level.

Next the remaining pillow blocks were supported by additional pieces of angle iron beveled to fit the swing set and after eyeball leveled, welded to the swing.

The drive shaft was then removed from the pillow blocks by de-coupling and sliding out.



Step 5: Assemble the Swingers Chain Attachments

I didn't really know what to call this step but basically, this is where the roller bearings/clutches were pressed into a pipe and the swingers chain attached.

The roller bearing/clutch act like a ratchet allowing the swinger to turn the shaft in one direction and let the shaft freewheel in the other.

I used a piece of pipe with a slightly smaller Inner Diameter then the Outer Diameter of the roller bearings.

The roller bearings were about an inch and a half wide so i cut the pipes 5 inches wider then the width of my shoulders.

After filing the weld ribbon on the inside of the pipe down to make the interior smooth and only slightly smaller than the Outer Diameter of the roller bearings. We used a half round file.

We then cut short pieces of scrap 2x4, and a hole was cut slightly smaller then the OD of the pipe. These blocks were then cut in half and used to hold the pipes vertically in a table vise without destroying the pipes.

once very secure in the vise, a Portaband (hand held steel bandsaw) was used to cut vertical lines length-wise on either side of the pipe, about the length of the roller bearings.

The roller bearing was then placed on top of the pipe while still in the vise, and with a wooden block on top of the bearing gently knocked into the pipe with a rubber mallet.

WARNING! when you put the second bearing into the other side be very sure that the bearings roll and stop in the same direction as the other side. They can be removed but you might not notice until you wonder why the shaft wont turn.

Plumbers clamps (circular steel belts with a screw that tightens) and hooks for the swingers chain were then tightened around the outside of the pipe and the roller clutches. (these were later welded after they tended to slip while swinging.







Step 6: Assemble Drive System

To assemble the drive system,

Take the completed pipes with swing attachment and pressed roller clutches,

A shaft collar for each side of the pipes, pillow blocks, and gear,

And the Gear,

And slide the drive shaft back through everything. Tighten the shaft collars after everything is where it should be, with the drive shaft sticking out one side and the gear on the outside.

Be sure to leave room for flailing arms and legs when swinging. on an eight foot wide swing, we found two adults fit.

Step 7: Mount the Stator

the stator used in my generator was mounted independently of the rotors which if not dealt with correctly could have caused some problems with chain tension.

to account for experimenting with different gear ratios and not wanting the hassle of a chain tensioner, the distance between the generator and the immovable drive shaft gear had to be dynamic.

This led to the stator and the rotors being independently mounted on the same movable rig. where the rig was bolted to the swing legs, the angle iron had short "drop outs" cut to ease chain tensioning.

Besure to mount the stator as verticaly as possible, to account for the angle of the swing legs. This was accomplished with the use of a lot of washers.


Step 8: Mount the Rotors

The distance to the center of the stator was known, so with the magnet rotors taken off the hub a level mount was fabricated to hold the hub in the center of the stator. It was then welded so that it would move with the stator and thus adjust chain tension.

The second picture is of the whole generator mount removed and fully assembled.

The generator mounted is then bolted to the swing.

Step 9: Attach the Chain

Move the drive shaft gear to be vertically over the generator gear and insert the key into both slots, then tighten the shaft collars.

Using a motorcycle chain breaker and assembler tool, the chain is wrapped around both gears and the generator mount is moved up or down on the "drop outs" (like on a single speed bike right?) to adjust the chain tension.

The motorcycle chain is wider than bicycle chain but the same pitch as single speed. so that it didn't rattle or try to jump off a used two single speed gears with a spacer in between which fit very nicely. The drive shaft gear was the correct width.

Step 10: Enslave the Children of the Earth ( I Mean Swing)

It doesn't produce enough electricity to where the effort in keeping children swinging on it to make power would pay off, but gather some people none-the less.

It should at this point make some juice.

possible problems may be shorting the wires, or slipping roller clutches or swinger chain attachments.

In terms of swinger chain length, We found the sweet spot for power, was with pretty short chains, removing the impetus to make a huge swing. We believe that the shorter the chain the faster the drive shaft turns as there is less difference to cover for the swinger and the drive shaft has a fixed difference to turn. However if the chain is too short it is very hard to get into the swing, and more importantly very difficult to sustain momentum while swinging.

We got it producing around 4.5 to 6 volts DC with two large adults swinging hard.

The generator makes AC and some bridge rectifiers convert it to DC, that is the box of wires hanging out of the stator.

In the past this generator produced 12 - 13 V and ran a 300W inverter when attached to a stationary bicycle, though it could not be sustained for any comfortable amount of time. So I believe that in going with a 44/13 gear ration I was a little too optimistic. I am traveling for a few months but for those of you who might have thought this would make a good Burning Man project, your right, and we hope to get a stronger gear ratio on it by then.

As it is, we can not hope to power the mega sound system or persistence of vision video flashes we were hoping for, but we feel confident that it could at least light up some LED's and look pretty.

If you have read this and are interested I'd love to hear any ideas for what to power and how.

Hope you enjoyed my first Instructable.

Best,
Cleveland

Video coming soon...

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83 Comments

We are also designing/building a swingset generator for a senior design project. Everything is going well, but I am having trouble locating roller clutches that are fine enough and still relatively cheap. We don't begin the purchasing process until January so I still have time, but I was wondering where you got your roller clutches!

1 reply

Cool, Bearing Agencies in San Francisco on 9th st.

I just read all 83 comments and I am blown away! What amazing things can be created when so many brilliant minds share thoughts and ideas. I am so impressed. We need other great minds working on everything it would take to get us all of the grid if that is our desire. I have no doubt that it could be done especially with internet sharing like you have done here. Way to go!!!

Congratulations!! You've done something I've always wanted to do, but only accomplished perhaps on rare occasions after a show storm {help shoveling...} -

YOU'VE HARNESSED KID-POWER!! *AND* made it FUN!! You ought to get a Nobel Prize or something.

I was highly skeptical when I initially landed on this instructable; however, after a careful read.......VERY GOOD JOB!!

If you placed an additional generative device on the opposite side of the swing, it would allow energy to be produced in both swinging directions with very little modification to your i'ble here.

sir i m orvil diaz doing mechanical engg final sem!!1 we r doing des project of urs for our final semester...sirr we plzz u to gve us some more knoledge abt des...sir cn we meet on fb??

We're planning on using a similar set-up and this is pretty much where we're headed with the Math for this...

In step 10, you mention the length of the chains affecting the speed of the drive shaft turning...
The length of a pendulum directly affects the time taken for that pendulum to complete one "swing cycle" or "period"... the longer the pendulum the longer the time taken to complete one period.
There's a mathematical formula to calculate this period - it's

T=2π√L/g

where:
T =
period
π = 3.142 (Pi)
L = the length of the pendulum
g = 9.81  (gravitational acceleration)


there's a website with an automatic calculator here http://easycalculation.com/physics/classical-physics/simple-pendulum.php

A 2 meter long pendulum takes 2.84 seconds to complete 1 period, which gives 21.1 periods per minute.

Based on a swing arc of 90 degrees, work out the amount of travel made by a point on the circumference of the pivot gear, "x"....  x = (πd)/4   where d=diameter of the gear.
Work out the circumference of the smaller gear, "y".... y = πd
Divide x by y to get the amount of revolutions made by the smaller gear for 1 pendulum swing, and then multiply that by the periods per minute to get the rpm figure for swinging at a 90 degree arc.

For us, using the rim of a bike wheel at the pivot to drive a toothed or V belt which in turn drives a BMX freewheel, and using a 1.5 meter pendulum, the Math gives us an rpm of around 90 at the freewheel, which is perfect for our purposes.

Variables:
Length of pendulum
Diameter of pivot gear
Diameter of smaller gear
Swing arc degrees

We've set ourselves a deadline of 2 weeks from today to get this up and running and will post details of results when we have them.

1 reply

Hey Azizas,

Thanks you very much for taking the time to reply with those calculations! I am very excited to see how your project turns out.

I would expect since the pendulum in this case is a self powered swinger, and not simply gravity, the timing will be different than your formula would suggest. Since the arc will be generally be longer than 90 degrees, and the swinger can speed up and slowdown as they wish.

That said, I think those calculations will be a great starting point.

I also agree with you that the solid bars will reduce thrust loss in each chain link.

I am beginning to build the second version of the swing set now and am only useing car parts and bicycle parts as would be available in developing nations. Having learned the lessons of the first prototype i think that this second one will be more efficient, cheaper to build, and easier to source parts for, taking it out of the realm of an art project and into a possible source of power.

Please let me know how your project goes, i am very interested in seeing your results.

Thanks,
Cleveland

I like this.

In looking for a motive power source for our project, we came up with and discussed this idea. We've done enough of the Math to know that it's viable for us.
We don't have the access to the type of parts and engineering that you have, though, and will be making this from readily available components - mainly bicycle parts.
A 27" bike wheel at the pivot driving a BMX style freewheel would give around 2 rotations of the freewheel for one pendulum swing - flywheel regulated to try to avoid too much variation in output - that's what we're aiming for.
Nice to see that the idea can work.

A thought, if I may... as an offshoot of this, if you ditched the electrical generation side, you could power most anything requiring a low rpm rotational movement if you add weight to the swing seat to up the torque generated.
Also, solid bars instead of chains would be a definite efficiency improvement.

You have a good, solid project here - all the best of luck with it!

Aziza's Place, Cambodia
https://www.instructables.com/id/Coil-Pump-V20-testing-rig/

Nice project you are really thinking outside the box. Have you tried a fixed bar instead of the chain, that would allow you to put maximum torque to the thrust bearings and would allow you to drop the seat height back down to give a longer swing stroke. If you check out the mythbusters video of is it possible to 360 on a swing they point out that the you can only 360 on a fixed bar. seems you loose a percentage of your possible thrust on every link in your chain. with a fixed bar you get 100% Adding a massive flywheel something like a car wheel with the tire filled with concrete, would be slow to get going but would store a mass of energy to keep the generator going a a decent speed on your back swing. fixed arms combined with a flywheel would be my 2 cent worth. Fantastic post. Andy.

1 reply

I think you are on the money with this Dr. An added advantage of fixed bars would be the swings could possibly be permanently "fixed" to the bar in phase with each other which we have found to be the most effective swinging. if they were fixed we wouldn't need to deal with loss of thrust with the ratchet bearings... of course then you'd have these steel bars swinging pretty quickly even if only one was being swung...

Brilliant! Energy from humans. When do you think it will become self aware ?

Brilliant! I've often thought of an electricity generating treadmill for pets. So they could earn their keep while I'm at work. 10 minutes of treading drops out a morsel or two of food. :D

hey you could scrounge the one one way clutch from old bikes

dude hook it up to a flashing light display and bring it to the burn!

1 reply

Look for it in the deep playa, it'll come alive when you swing.

Too Darn Cool! Leave it to you California Swingers... LOL