Intro: Scooter 3spd Chainsaw Belt Drive
I built a gas powered inverted push scooter using a chainsaw for a motor, two customized pulleys, and v-belt. I later added patios instead of the foot pegs and an aluminum cover for the rear end. It worked great and my son would go about thiry miles an hour, and me being almost three times his weight went about 10-15 mph. I made a few changes to make things work and will try to list all the changes as it has been a couple years past, and I no longer have it.
Step 1: Later Mods Added for Safety and Comfort
I later added patios to stand on because the foot pegs were a bit uncomfortable after awhile. Then I added the fairing from aluminum sheet and painted it red to match the scooter. The fairing helps protect the rider from getting anything like feet, or, shoestrings caught up into the rear wheel assembly.
Step 2: Locate and Dissect a 3-spd 24" Bicycle Hub
This 3-spd hub I got from an old dillapidated 24" J.C. Penney's bicycle. I think I paid five or ten bucks for it. It was all rusty and everything, all I wanted was the 3-spd hub anyway. First I cut off all the spokes off of it. Then I took off the chain sprocket by removing the split clip on the outside of the sprocket. Then I put the sprocket end of the axle into the drill press hanging down. I then turned on the drill press and used a Dremel cut-off tool, and cut off the spoke holes and lip on the bottom end. Leaving the housing flush, and even with no lip at all. This is done so that the modified hub will slide into the modified plastic wheel hub from the rear wheel of the scooter. This is discussed in the next step.
Step 3: Modify the Plastic Scooter Wheel
This is where you will cut out the center of the hub of the wheel where you slide the hub into. Its been so long don't remember exactly how I did this. But, I think I put a narrow milling bit into my drill press and mount the wheel to the drill press table horizontally, and a bit off center, so that you can spin the wheel manually, and cut the inner diameter a little at a time. The diameter depends on how thick the 3-spd hub is. After the inside is cut out of the hub using plastic/ steel epoxy coated on both the plastic wheel and the 3-spd hub, slide the hub into the wheel and wipe off the excess, and then put it back into the drill press base horizontally, and slowly spin it, and tap where needed to balance it, so there isn't any wobble. Let set to dry.
On another note, you can also use one of the rear wheels thats on one of those childs 12" wheels. (little bikes) The custom pulley I make in the next step will work on either. Something happened to the milled wheel and will let you know what, later down in detail. Note the tire is not one of those knobby tires that are usually found on these push scooters. This tire is a low profile treaded tire that holds more air, and does not sway into turns. The knobby tires are taller and will sway and sometimes pop of the rim under heavy loads and higher speeds. The tires I bought can be found at some high end bicycle stores but only cost about $15. They are called Impac tires 12 1/2 x 1.75 .
Step 4: Make Custom Pulleys
In this step you will need two v-belt type pulleys. They can be bought at some hardware store or a TSC (Tractor Supply Store). I don't remember what size they are now, but one has to be larger than the sprocket. The sprocket will fit into the center of the pulley and bolted to it. The other will be larger than the 5 or 7 tooth gear on the chainsaw. First I counted how many teeth the sprocket had, measured the diameter center of each toothe and divided the numer of teeth into 360. On this particular sprocket there were 18 teeth , which figures out 20 deg. apart. I made a computer template from an Easy-cad program, taped it to the flat side of the pulley, and centered it. I first found a large bolt and washers and a nut and put it on the drill press horizontally and lined up the first of the eighteen holes. Drilled first hole, then I rotated it manually to the next hole and so on. The last step was to mill out the larger hole which should fit just slightly wider than the sprocket guts, but not the teeth. If your holes are lined up good the sprocket will fit perfectly. Then I used, I believe, 3/8ths in. nuts and bolts through each hole mounting the sprocket to it. Due to the space restrictions only 9 bolts can be used every other hole.
Step 5: Frame Modifications
The kids scooters normally comes with the frame hanging low, with a plastic platform, which you stand on. The platform must be removed, and the gooseneck disassembled, and the frame flipped over. This will look like an upside down "V". Reconnect the washers, bearings, etc, like they were originally. The rear brake mount will have to be cut off, and a new wider one made, and welded back on, because the 3-spd hub is a bit wider than the original wheel. The frame will also have to be stretched width wise, a bit wider to allow the hub to mount where it was originally. Drill the hole for the brake assembly. The handlebars will have to be raised to almost max height, because you'll be standing on the rear axle and holding the handlebars at a higher position for stability. You don't want to be leaning or put to much pressure on the handlebars, for safety reasons.
Step 6: Motor Mount
First you will need two right angle brackets, a turnbuckle and two eye bolts. They can be found at most hardware stores. The angle brackets I found in the lumber hanger/brackets area. Turn buckles are usually used to stretch, or pull fencing, or door frames tighter. Most commonly screen doors. Also buy a long steel rod or pin 6 to 8 inches long.
The yellow seen in the first pic is the belly of the chainsaw where the gas tank was. DRAIN the fuel tank, and connect and mount an auxiliary weed eater type fuel tank on the handlebars.
Place the brackets edge to edge, where a seam is in the center. Drill 3 or 4 holes in each bracket base and one larger one in the same area for the rod or pin thru each side. Then place over the chainsaw housing and drill thru each hole in the bracket into the chainsaw housing. Screw self tapping machine screws to hold everything together. Slide the rod/pin thru one side of the bracket, and then thru one eye bolt, and then tru the other side bracket. I believe I cut a groove around both ends of the rod or pin, just outside the brackets, and put cir-clips/keepers on there to keep it from sliding out. Screw in the turn buckle to the end of the first eye bolt.
Drill a hole the diameter of the shaft of the second eye bolt thru the frame brace where the platform used to be mounted as seen in the second picture. Slide the eye bolt thru the drilled hole and connect to the other end of the turn buckle. The turn buckle is used to keep the v-belt pulled tight and the motor upward on the frame. Ideally if the rod /pin had rollers on the ends it would make it easier to tighten. (less friction)
In the later mods, I took off the stunt/trick pegs and replaced with patios and made a red aluminum shroud/housing to cover this entire area seen in the third picture. The velcro is glued to the frame brace where the other eye bolt goes thru as seen the the top edge in the third picture. The third picture is what you should be close to seeing when this step is done.
Step 7: 3-spd Axle Set-up
This is where I made a mistake to some degree. I chose a three speed axle from a J.C. Penney bicycle where the chain is pulled out, to change gears by a cable that comes straight out. The problem with this is that you have a cable bowing out from the side about where you feet are and its way to easy to snag on something as you go by, or slip/trip off the pegs or patios and get your foot caught in it and get dragged, etc. So what I did was just select one of the three gears by pulling on the chain and leaving it there. Also I wasn't at that time sure how I was gonna tighten up a peg with a cable going, or coming out of it. What I found out later is that if I used one of those little kids, 12" bicycle wheels, with the sprocket attached, it gave about the same torque, or speed as the second gear did. Dooh! The modified pulley still would fit that sprocket as well. Now on second thought, I may have just used that 12" bicycle wheel sprocket and all, or tried one of those Sears 3-spd bicycle sprockets, where to change gears, you turn a grip on the handle bars and it pulls a cable that runs parallel or flush with the wheel and changes gears with a ratchet type mechanism. This would all be neat, and snug under the patios. One, if they have the money, might try one of those Shimano hubs with 3, or 7 gears, but they are quite expensive. I believe the Penney's one was a Sturmy-Archer.
Step 8: Finishing UP
Now at this point you will need a v-belt. I think I used one around 54" long, I really am not sure, now. Remember you have a little play with the length and the turn buckle. I believe I bought two belts till I got the right length. Connect the belt around the bigger pulley, and the other end around the smaller one at the top, by lowering the whole motor. You may have to disconnect one end from the eye bolts to do this. Then reconnect the eye bolt and tighten. Fuel up and your almost ready to go. Oh, I used some of that fuel additive for weed eaters gas so they don't smoke. Smokeless, AHhh... This is a pull start chainsaw and one other problem I had was getting it started. You see the carburetor is upside down as well. So naturally the fuel wants to flow out. I put a shut off valve in the fuel line when not used and when starting, turned it open and shot a burst of starting fluid up into the carb. THEN, pulled the cord to get it started. Once it started running, all was ok. There-in that was the major-ist? problem I think I had. Wish I could've figured out a way around it, because it more, or less, had to be that way because of the direction I needed for momentum. Well, I think thats it. I will be around if there's questions.
Oh, this project came in at under one hundred dollars. A donated 20 something year old chainsaw, five dollar scooter with wheels (yard sale), two fifteen dollar tires (new), I think ten dollars for the used J. C. Penney bike (yard sale), used gas tank (had), bought v-belts, fuel line, starting fluid, brackets, screws, eye bolts, 2 pulleys and the plastic/steel epoxy. What a bargain, huh?
Oh and the answer to what happened to the Hub? Well the hub itself had oil in it and had gradually over time seeped out and got between the bonds of the epoxy and came loose while ridng. Very scary. Thats when I discovered that the little kids 12" bicycle wheel would work. I kept thinking I really am having to much fun with this and I gotta get it going some how again soon. And everything fit. Yahooee.... :)