Weed Eater Powered Scooter

Sometimes I find that my projects are defined by the things that I find.... Please read next.

This project was also inspired by something I wanted to learn. I always wanted to learn to weld and this potential project was further motivation. I picked up a wire feed welder off Craigslist last year after searching a while. I chose to go the practical application route rather then spend $ on classes and books to learn the technical background of how it works. As the saying goes: You listen, you hear, you look you see, you do, you understand"... or something like that. So after practicing a bit on some random scraps, and getting some hands on pointers from some people who knew what they were doing I dove right in with my first welding project.

Step 1: Pieces and Parts

Found this scooter in our garage (actually I found it at a garage sale a couple years ago, cheap)

Found this bicycle rear wheel in a dumpster

Found this string trimmer at a garage sale.

Found out that inside this $2 chair (from a surplus store) there are lengths of 7/8" dia. 1/8" wall thickness tube steel reinforcing inside the 1" tube steel frame.

Found I couldn't stop thinking about mounting the weed eater engine to the scooter.

Step 2: Tools

Welder: Just got this last fall and still learning to use it so forgive the quality of my welds.

Metal Chop saw: for cutting angles.

Angle grinder: with cutting and sanding wheels.

A bevy of hand tools, to numerous to explain. This was a figure it out as you go along project the number of tools only exceeded by the number of failed strategies.

Step 3: The Challenges and First Steps (Freewheel Hub)

I looked for other designs online most involved attaching a spindle to the motor and having it friction drive the rear wheel. This would have been much easier than the strategy I employed. I wanted the scooter to have a chain drive. This meant the engine had to have a clutch so it could be started in idle and the rear wheel needed to be able to coast when not accelerating (freewheel)

There were probably easier ways of doing it but I went the free and cheap route. If a project is to be judged based on what you learn in the process then this one was way up there for me. Hindsight being 20/20 I would have done many things differently but this project represents the forging ahead.

I needed a big sprocket on the tire and a small one on the engine. I did the math and was afraid a 6,000 rpm weed engine would translate to a very fast scooter (it didn't by the way and I will be upgrading in the future)

the large sprocket came from a used crank from a bicycle shop.

I got the freewheel hub out of a rear bicycle wheel.

the wheel was the existing wheel from the back of the scooter.

had a couple discs made so I could weld sprockets from the salvaged cassette to the disks and bold the discs to the large sprocket. i used a combination of existing spacers that came from the cassette and acrylic disks I cut out to locate the sprocket and mount it to the freewheel hub

Step 4: Attaching Hub to Tire

I drilled, cut, filed and sanded the existing tire hub and JB welded the new hub to the exiting tire.

Step 5: Attaching Sprocket to Drive

Note: some string trimmers have a centripetal clutch, some do not. my first efforts were involved trying to figure out how to put a chainsaw clutch on a trimmer without a clutch (big challenge) and then I found a trimmer with a clutch at a garage sale for $15.... problem solved.

I cut a length of black pipe that fit snugly over the drive shaft (and clutch cover) added a washer as a spacer and to center the small sprocket and welded it all together (a couple times)

Step 6: Measurements and Design

Turns out that the mounting width of new rear tire is a couple inches wider than the mounts on the scooter.

So I built a temporary framework to get measurements and lay out the design, then drafted it to get the cut angles and dimensions of the frame.

Step 7: Marking and Cutting the Tube Steel

Then using the tube steel salvaged from inside the base of the $2 chair I cut the pieces to length.

I struggled a bit to figure out how to make parallel angle cuts on tube steel. the technique I came up with involved cutting the angles on a square pieces of wood, holding the tube steel tight against the angle then finding the high point by placing the tube between two adjacent then running a file across the three to find the high point. I then marked down the center line with a sharpie and piece of angle. I am sure there is someone out there that has a better way of doing this. If you are them and you have read this far please explain in the comments section.

Step 8: Learning to Weld

Then the welding started. I picked up a 120v Hobart 140 last fall because I always wanted one. This was my first legitimate effort to put something together with it, as is obvious looking at the quality of the welds. but they are getting better and I am excited about the future possibilities in working with steel.

I cut the axle mounts out of a piece of 1/8" flat stock with and angle grinder and cutting disk and sloppily welded that to the frame.

I cut out the motor mounting plat and welded that the the frame. (sorry missed taking a pic of the mount welded to the frame.

Step 9: Attaching the Tail End

The front and back were aligned, clamped together and welded.

Step 10: Cleaning Up the Mess

I ground off the major chunks of my crappy weld job then cheated with a little hastily applied Bondo.

After a coat of closely matching paint it didn't look half bad.

I cut the foot board and backstop out of 1/2" plywood and painted it. This scooter has a foot board about 6" longer than the original so an adult or large child or adult that acts like a large child can stand on it.

Step 11: Motor and Throttle

I JB welded the eyelet to the motor casing as the other half of the casing has been removed.

the thumb shift button and derailleur cable was salvaged off an old scrap bike, withe the derailleur cable bolt modified with a couple bored out washers was used to tie the new cable and the motor throttle cable together. I zipped tied the cables to the bike frame.

Step 12: Finished!

Well it wasn't as simple as all that, it was a lot of trial and error; and it took about 4 times longer that i thought it would and i didn't describe all the FAILs. As it took longer than I thought it would and today is the deadline for the make it move challenge contest the instructions are a bit less detailed than I would like them. But I learned a tremendous amount by making it and if success were based on how much I learned I would have to call the project very, very successful. It doesn't go nearly as fast as I thought it would (faster than a jog, slower than a sprint) which is ok I guess and I am still having some challenges with the chain and sprocket alignment. I plan to reduce the size of the sprocket on the wheel by using the large sprocket from the original cassette and some the acrylic spacers. Also plan to add some clips to hold the axle square when tightening the nuts. this should speed things up and refine the sprocket to sprocket alignment a little better. But that is for next week.

Step 13:

Well that clutch didn't last last long, probably should have known better note the blue (burnt up clutch) color.

Went back to the chainsaw clutch and thought a axle for the clutch would be a good idea.

After the existing clutch was removed a 3/8"-24 thread on the motor spindle was revealed.

Used a 3/8"-24 threaded coupling and a couple 3/8"-24 bolts,

Took the plunge and dremmled off the small end of the shaft. Can't ever go back to the original clutch and drum now!

Had to grind the coupling down it was a bit to long.

Had the left over end of the scooter thought that would make a good support for the other side of the axle. marked it and cut it,

3/8"-24 all thread turned out to be unobtainium. had to weld to bolts together to get the length. ground it smooth.

Once the axle was added found that it was a bit easier to square the motor to the wheel (hmm hadn't thought of that earlier)

Welded the clutch shoe to the axle, then had an "oh crap" moment as the weld did not allow the clutch and drum to fit together properly. put it the drill press and filed and sand clothed it till it fit pretty good and spun smoothly.

Welded the sprocket to the drum cassette (that the chainsaw chain usually fits in) wrapped tape around it to get it centered in the sprocket. unconventional probably but it worked.

Then it started to rain, then thunder then lightning. Wont get to test it tonight.

Put bearings and the appropriate bushings on the other end of the axle collar lock on one side and nut on the other side. Last pic is how it all goes together. hope it works but its storming outside and I wanted to get this posted by the deadline.