The Bike Riding Skeleton

We love Halloween props, but we love the ones that move even more. There is that fun mystery, when we see an effect and wonder, "how did they do that?". If we add in the ability to untether our creation and let it roam free, then another tool is added to our ability to wow the viewer. A skeleton doing normal human motion always gets a smile, especially when the mechanism is hidden. Ok, let's go.

The theme to this project was to make a skeleton ride a bike somehow. A trike is the easiest and probably the best way as far as stability, but we would have to fashion some sort of drive mechanism. Chains and motor mounting adds to the time and complexity of the project. A training wheel bike would have the same complex motor issue and even less stability. The less common bike is the sidecar design. Here we have the answer to stability and simplified motor drive as we can use a kid's electric scooter driving the sidecar wheel. No motor work is needed on the bike itself, just a framework between the bike and e-scooter base.

Cost is always an issue in the design of a prop and this one is no exception. Estimated cost was about $400 but many parts were acquired over time from other past projects. The biggest outlay was in the steering servo and motor controller. Fortunately for us, these parts are easy to move to other projects after Halloween, so it's an investment in equipment for other radio controlled projects. A pawn shop was the source for the bike. The scooter motor and wheel with chain was found in the trash. Radio gear was Amazon order as was speed control and servo. Details in the lists.

There is no metal work or welding in this project, but we do need the general tools most homes would have. Screwdrivers, drill, hand saw, sandpaper are a must. It is better yet to use a vice, drill press, table saw and sander.

Sheetrock Screws, Paint, Hose Clamps, Duct Tape, Zip Ties, Various Bolts and Nuts, 1x2 inch Wood Strips, tools like Vice, Hand Saw, Drill and Drill Bits, Small wrenches, Small Sockets, Screwdrivers and assorted extras.

Steering servo

This is the ASMC high power servo for the bike steering. It has a wide operating voltage that can be supplied to it from 12 volts up to 24 volts. It also regulates a 5 volt output back to the radio receiver so this eliminates the need for another battery to power the radio. Link is to Amazon, about $60.

Radio Control

The FlySky FS-GT2 radio was used for control. It uses AA batteries and can run for several hours. Also around $60 at Amazon.

Speed Controller

To control motor speed we have to have a speed controller. The SyRen 10 from Dimension Engineering worked great. It's a true 10 amp controller works from 12 to 24 volts and has overload protection. About $49.99.

Batteries

Power is provided by battery such as this lipo used r/c cars, planes and drones. It does require special chargers and support equipment if they are new to you. This is what was on hand. This one is about $30 from HobbyKing.

Cardboard Tube

This is the sidecar part shaped like a bomb, a QUIKRETE 12-in Tube Form about $18. It is intended to be form to pour concrete into and peel off once it has set. Be advised the inside has a waxy coating, so it won't accept glue. The outside is ok to paint though. Screws going through it will need support on the inside.

The motor was acquired as a junked scooter and the bike purchased from pawn shop for $20. Other odds and ends we need are hose clamps, zip wire ties, various bolts and sheetrock screws, paint, skeletons, tape and other odds and ends.

To get around having to weld and drill and do all the hard shop stuff to the bike, wooden "hard points" were fitted using automotive hose clamps. So where we need to secure onto the bike, a piece of 1"x2" wood was clamped onto the frame. This is plenty strong and can be repositioned or removed later for storage or whatever. After removing the brake cables, 3 points were settled upon to place the hard points. One at the seat post, another on the top bar near the steering neck and a last one low, near the rear sprocket. Be sure to allow the pedals to move freely around without hitting, and our skeleton has to be able to move and be clear to pedal.

A complete scooter drive unit wasn't available at the time of construction, so a box was fashioned to house the motor and rear axle from a junked scooter. People toss them when the electronics fail, but the motors are tough. The project would progress much faster with a more complete scooter base to bolt onto. As long as the chain is straight on and not too loose, it works great. So, positioning the scooter base near the bike we channel our inner carpenter spirit, as this isn't an exact science. We want to get a stiff frame from only a few pieces as to not distract from the visual effect. Holes are piloted with a drill before adding sheetrock screws. Be sure to not leave any sharp points protruding. Squares and triangle structure are the design shape we look for. Pieces were tried and sometimes removed. Mostly scrap wood, some from last Halloween was used and clamped here and there testing different angles. Each bike type is different so there is no set plan. This bike needed an extension along the top bar all the way to the back of the rear tire. measuring from the edge of the bike frame, the scooter was about 24 inches to the side. Our scooter was mounted parallel, tracking straight on with no toe in or out. The scooter wheel was only a little behind the bike rear axle. The bike came out mostly straight up only leaning right slightly.

Our servo doesn't have a proper case around it. So one was fashioned from thin plywood. One photo has the dimensions used. An arm was also made from the same ply scrap piece and the servo assembly screwed down to a nice spot just in front of the bike's seat. A clear path was needed to the handlebars for the "pushrod". Just a small pvc pipe where the ends were heated, smashed in a vise until cool and drilled. Two wooden pieces were clamped around the handlebars and the pvc pushrod secured with bolt and washers, making sure it was free to pivot.

So our skeleton has to sit up but be flexible enough to pedal and steer. The shoulder, elbow, hips and knees had the ratcheting plastic bushing removed or flipped so they could freely move. It takes some effort but the same hardware was reinstalled to keep the hinge actions intact. The spine was modified so he could turn a little left and right. In operation, it doesn't seem spinal surgery was needed. The arms took up most of the action.

A pvc pipe was fitted through a hole in the seat and bolted to our hard point under the seat. The skeleton sits with the pipe extending through the pelvis to about the rib cage and zip ties secure the lower spine to it. This is the only true support for the skeleton so it has to be strong. The feet are secured to the pedals with zip ties. It was a mistake to remove the ratchets from the ankle as they were too floppy so they were put back. A short pvc pipe was used to beef up the wrists as they are rather thin. Zip ties were used here as well.

The idea was to place the Battery, Electronic Speed Controller and Receiver in the sidecar above the motor. The only long wire leads would be to the steering servo. The leads to the motor should not be too long as this is bad form and can cause issues. Speaking of bad form, the Receiver was mounted next to the ESC but had no issues. This says a lot for the quality of the electronics. A 20 amp fuse and high current switch should be mounted between the battery and power leads. A switch was not used as plugging in the battery was considered the switch. In hindsight, that is dumb. We were lucky this time. In the future, a way to remove power quickly is a must.

All power connector were the "Deans T Connector" type. No reason for this other than we got lots of them and that is the kind used here. Battery is connected to a Y, where power goes to the ESC and to the Steering Servo. This is the unregulated battery power. 5 volts is supplied by the Steering servo and by the ESC. It back feeds to the receiver through the channel 1 and channel 2 signal harness. Finally, the motor leads are terminated in the screw down lugs on the ESC. The ESC dip switches were set to "simple r/c" as in it's instruction booklet.

Receiver has a "binding plug" so follow the instructions or check YouTube for a video on binding the transmitter to the receiver.

ESC Holder

This holder was printed from Thingiverse to protect the ESC. Holes were drilled so it could screw down easily to our wood plate in the sidecar.

Originally, the sidecar was to be a small barrel. After the tube was purchased, it seemed a shame to cut it down to size. A clear bowl of roughly the same diameter was found in the lucky scrap pile so it became the bunker buster sidecar for our dog skeleton. The idea was to make only 3 bolt points so as to make it easy to adjust and remove. So one bolt up from the motor assembly on the bottom, another from an angled arm up front and the third was just a clamp inside the tube in the back. I was a bit wobbly, but it worked ok. Using a scrap cardboard piece as a straightedge, we marked where our "cockpit" would be. We CAREFULLY cut the area out using short shallow cuts. Gloves and patience are a must. An additional area was opened up behind the cockpit for a hatch to access the electronics and battery. Additional wood supports screwed in where needed for looks or strength as was needed. Dark green spray paint was added. The bowl on the nose was screwed on with 1/4 inch sheet metal screws. Here is where it started to look cool. A scrap piece of plastic split wire loom was placed around the cockpit edge and shoelace was threaded around it through holes drilled in the tube as "cockpit coaming".

This thing needed fins to look right. Plywood scrap was held up against the back and a pencil pulled around the inside of the tube gave the right diameter to cut a round plug to fit in from the back. The picture explains it better, we fashioned a few blocks on the disk to screw in through the tube and to hold the fins. Fins are 1/4 inch sticks hot glued to simple cardboard sheets from 12 pack soda boxes. Fins are then screwed onto the blocks on the disk. More green spray paint for the fins. Yellow duct tape made a good trim and a hinge for the radio access hatch.

The red rear reflector was added, safety first.

All wood parts were painted with cheap water based acrylic craft paint like Hobby Lobby sells. A single strip of peel and stick light emitting diodes was added for ground effect lighting. The skeleton dog has batteries in his head so he barks and growls. Duct tape is a good source of decoration and we used yellow caution and checkerboard.

So overall cost would be about $350 to $400. It's unfair really to just spout that number because much of this project is parts accumulated over time, scrounged or repurposed.

So our skeleton project worked great! He got lots of compliments and suffered no major malfunctions. The reflectors on the pedals added a nice effect. Funny too because we never even put air in the tires! Our local law enforcement came by and was ok with it as we are residential and no thru traffic. It was fun hearing kids exclaim loudly and grown-ups stopping to video and laugh. What was really cool this year was there were 2 driving skeletons projects. A little "mini me" trike from last year.

Now, what do we do for Christmas?