Want to make your bike create sparks as you drive?
One way I found is to add on a Wimshurst machine, an electrostatic machine that produces sparks. The cool thing is that the Wimshurst machine works by rotating two disks, normally using a hand crank... but connect it up to your bike pedals and now you rotate the disks as you pedal! To make it cooler, this one even uses a 3D printed sprocket!
Put the spark in front and it's a flashing, and audible signal for oncoming bikers and pedestrians that gets their attention. And if any bugs get attracted to it, they get zapped, instead of flying into your face!
This won a runner up prize in the Instructables Bicycle Contest. Thanks to everyone who voted for it!
Step 1: Watch the Video!
WARNING: The shock from this spark is high voltage and with some current but lasts for only a few millionths of a second. It is more painful than rubbing your feet on a carpet and getting a shock when you touch a doorknob, but leaves no lasting effect. It may be harmful if you have a pacemaker or heart condition though. In general, it's pretty harmless on a bike like this.
Step 2: Take Apart the Wimshurst Machine
Take it apart. Usually you need only a screw driver and a wrench or pliers. If you want to be sure that you get one that you can take apart and mount it to your bike like I did, then use the photos of mine to find the same one online. A lot of places sell this same model, or one with color differences.
Step 3: Remount the Disk Assembly
The disk assembly consists of the two disks, the pulleys, the belts, a hand crank and the support structure. Cut out a new wooden base that fits just the disk assembly and bolt the disk assembly to it.
Step 4: 3D Print a Sprocket and Replace the Hand Crank
Normally you make the Wimshurst machine's disks rotate by turning a hand crank. But the magic here is that we replace that hand crank with a sprocket that we can attach a bicycle chain to. And surprisingly enough, a 3D printed plastic (PLA) sprocket works just fine! I designed mine in Blender, free 3D modelling software. Watch the above video to see how I did it.
I've attached the STL file and in case you want it, and the .blend file too. You may or may not have to scale it once you load the STL into a program like MakerWare. In MakerWare, if you go to Scale it, the dimensions should X: 59.57mm, Y: 60.19mm, Z: 22.22mm. After you've printed it you'll have to sand down both sides of the teeth to make them fit in the chain holes, but it'll be obvious what you need to do. You don't have to sand between the teeth.
My hand crank will rotate the disks in one direction, and turning it in the other direction unscrews the hand crank from the disk assembly. As you can see in the photo, the hand crank has threads. Bring it to a hardware store and find a bolt with matching threads. At Home Depot I found a bolt with M6 (metric) threads matched. The length of the bolt, not including the head is 1 3/16 inches/3cm.
I designed my 3D printed sprocket to have a hole in it. I drilled the hole larger for the bolt but such that the fit was tight enough to have to be screwed in using a pair of pliers, but not impossibly tight.
The result then screws into the disk assembly and when turned in the right direction, turns the disks. Luckily it's also the direction that the pedals turn when the sprocket is on the correct side for the chain to connect to the pedal's sprocket.
Step 5: Mount the Disk Assembly to the Bike
I found that the disk assembly fit nicely inside the open area just below me on the bike as shown in the photos. Note that I have a touring bike/road bike and so there's lots of room there. Though you don't want the space to be so small that the Wimshurst machine parts touch the bike frame. Make sure there'll be a good inch/few centimeters distance.
To mount it, get some aluminum bar, around 1/8 inch/3mm thick and 3/4 inch/2cm wide. This can be found in many hardware stores such as Home Depot, Lowes, ... as metal bar or moulding. I had some scrap lying around that already had a few holes in it but it was still usable.
Cut two pieces roughly 10 inches/26 cm long and put them in a vice and hammer them into a 'V' shape. Each leg of the 'V' is roughly the same length (5 inches/13cm). Note that if you bike is different then you'll have to come up with your own dimensions and positioning that works for you.
Mount them to the bike frame using hose clamps. You want the angles of the 'V's to be such that two legs of them form a flat face where the disk assembly can be attached to.
Before you can bolt the disk assembly in place, you first need to make matching holes in the disk assembly's wooden base and the 'V' pieces. To do that, with the 'V's in place on the bike, I used a C clamp to mount the disk assembly temporarily to them and drill the necessary holes through the wood base and the 'V' peices at the same time. Then I removed it all and enlarged the holes in the 'V' pieces into slots for adjustability. Then I put the 'V's back on and bolted it the disk assembly to it.
Step 6: Make New Collectors
The collectors on a normal Wimshurst machine are integrated into the Leyden jars. But on the bike the Leyden jars are far from everything else, so new collectors need to be made. To do that start with some 10 AWG insulated wire. You want it to be stiff and the insulation helps prevent short circuiting to the bike frame and your leg.
Add brushes in whatever way duplicates the brushes that come with the original collectors. In my case the original brushes are just short tips of thin, bare wire, so I stripped some multi-stranded wire and soldered that to the 10 AWG wire. To connect to them later, attach a ring connector to one end of each collector.
Cut a piece of wood that you can mount the collectors to using cable ties. Hot glue another piece of wood to the disk assembly and bolt the collectors to that.
Step 7: Put the Chain on the Sprockets
Get a bicycle chain and open it up using a chain disassembly tool. Remove however many links needed to get it the required length. Wrap it around the big sprocket at the pedals and around the 3D printed sprocket. Change the position of the disk assembly on the bike if necessary. Reassemble the chain. In the photo I'm using channel locks, but pliers will also work.
Step 8: Mount the Leyden Jars and Spark Gap
To mount the Leyden jars to the front of the bike make the wood and aluminum bar part shown in the photos. My Leyden jars were simply bolted to the original Wimshurst machine base from underneath so a similar support structure is needed. Cut three pieces of wood and screw together in a 'U' shape. The base of the 'U' is where the Leyden jars will be bolted onto and must be wide enough such that when the Leyden jars are attached, they will be spaced out enough to make an easy to adjust spark gap. In my case I made it around 7 inches/17cm long. The length of the legs can be however long you want the Leyden jars to be sticking out forward.
Cut and bend two more pieces of aluminum bar at a 90 degree angle with sides around 1 inch/3cm long. In the photos, to bend a piece I put it in a vice and hammer it to shape using a dead blow hammer. Clamping it to the edge of a table and hitting it with a regular hammer also works fine.
Bolt the aluminum bar pieces onto the ends of the legs of the 'U', but do it such that there's a gap between the aluminum bar and the wood where the bar hangs over the side of the wood.
Before bolting the Leyden jars onto the base of the 'U', prepare a wire with ring connectors on either end. This is to electrically connect the two Leyden jars together. Bolt the Leyden jars onto the base of the 'U' while putting the ring connectors under the nuts.
Put another hose clamp loosely on the front steering column section of the bike frame. Insert the aluminum bars into the hose clamp and tighten the clamp. That holds the Leyden jars in place.
Step 9: Connect the Collectors to the Leyden Jars
Prepare two long, fairly stiff, insulated wires to connect each collector to a Leyden jar. Make sure they're long enough such that they can be at least two inches/3cm from anything else and each other, to prevent sparks along their length should the insulation break down.
Connect ring connectors to one end of each and connect them to the ring connectors you'd put on the collectors. I used nylon bolts for this. Using metal bolts increases the chance of coming into electrical contact or making sparks with other parts.
Do whatever is necessary to connect the other ends of the wires to the Leyden jars. In my case I stripped around 2 inches/3cm bare and inserted them into a hole at the top of each Leyden jar and fixed them in place by tightening a screw.
Step 10: Go for a Ride!
The things you can check if there are problems are the same as for a normal Wimshurst machine. The disks must not have any dust on them. If they do, clean them with rubbing alchohol. Make sure the electrical connections between the Leyden jars and the collectors are good. Make sure the outer cylinders of the Leyden jars are well electrically connected to each other. Wimshurst machine don't work well in humid air.
Obviously the spark looks best at dusk or night. Be safe and watch for people's expressions as they hear and see your sparks as you approach and pass them. Have fun!