When you're a kid, there are few things more fun that exploring on your big wheel. As an adult, I'm much too large to fit into any kind of kid's toy, so I built my own. I made this big wheel to participate in San Francisco's annual Bring Your Own Big Wheel race, which is a downhill event held on the twistiest street in the city.

To make by own big wheel I reused parts from my horse bike that I made for my Lone Ranger Costume a few years ago. The horse is optional, but since the race is an excuse to dress up and look crazy I thought it was a good addition.

Here's a video of me making the big wheel, and some racing footage at the end

I managed to find spectator video that showed me racing down the hill, I compiled clips from these two_videos into the animation below.

I salvaged as much as I could for this build, buying only the wood dining chair for the seat for $8.

Ready? Let's make!

Step 1: Find Your Horse

The first step was to bring horse bike out of retirement. This silly ride had a good run, but was gathering dust in storage and was ripe for be remixed into a new project. If you don't have a horse (what's wrong with you?) you can search the classifieds like I did, or buy one online, ditto with the BMX bike. Both items are inexpensive enough second hand, so shop around.

Horse bike had the plastic horse screwed to a wooden block that replaced the seat on the bike. Removing a few long screws uncoupled the horse from the bike, and a tug to break the Velcro bond removed the horse completely.

With the horse and bike separated I could assess the components and what needed to be modified.

Step 2: Cut Frame

The bike frame was cut down using a portable metal bandsaw. At this stage I didn't know exactly how the big wheel was going to look, so I cut the frame with as much additional tubing as possible, allowing me more options later on if the design needed it.

The bike frame was secured in a bench vise, and then the bandsaw made quick work of cutting through the thin walled tube steel frame.

Step 3: Sketch Ideas

With the front of the bike separated I could sketch out ideas for how the bike would look. Placing the bike front o n a large sheet of butcher paper, I sketched out a rough shape of the frame using a marker.

I also sat on the ground with the bike front to get an estimate on the dimensions to go along with the sketches. With some sketches to guide me, I turned to cleaning up the frame in preparation for welding.

Step 4: Clean Up Frame Cuts

The frame had burs from cutting that were easily removed using a deburring tool. These tools make short work of removing any sharp metal fragments from the edge of cut metal, leaving a smooth edge.

Before welding an extension to the frame the bike tubing would need to be cleaned up to remove any paint and bring the frame down to bare metal.

Using a grinder I prepped about 2" from the cut end of the frame, grinding away paint until I got down to bare metal.

Step 5: Measure + Source Tubing

To make an extension of the existing bike frame I measured the frame tube diameter and looked for some similar tube steel that could be welded together with the frame.

Since the bike frame was steel, I looked for tube steel that was as close in diameter as possible. The tubing was going to be welded together, so i was looking for tube stock that would slip over or into the bike frame and make the connection more rigid.

Step 6: Bend Tube

I have access to a hydraulic tube bender, so used that to make the bend in the tube stock.

From my sketch I estimated a 140° bend from the existing bike frame to translate from diagonal to horizontal, where I would be seated. Using a tube bender is very satisfying and really not hard to do, however from the picture you can see there's a kink in my bend and not a smooth transition as it should be.

Step 7: Weld Bent Tube to Frame

Once the tube stock has been bent to shape it was inserted into the bike frame until fully seated, then a mark was made where the cut end of the frame fell on the bent tube stock.

The tube stock was removed and clamped in a vise and a grinding disc was moved over the place that was marked to clean the stock in this location from any mill scale or debris, making it ready for welding.

After, the tube stock was placed back into the bike frame and the two were welded together.

I started by tack welding the parts in place, then finished up welding the entire circumference.

Almost all welds are ground down smooth and covered with some kind of paint, so there's no points for having a pretty weld. My weld was ugly as sin, but after a few minutes with a grinding wheel looks great!

I used a rough grit grinding wheel to knock down the high spots of my weld, then finished up with a finer grit grinding wheel to blend the two welded pieces of metal together.

Step 8: Trim Bent Pipe

I deliberately left the bent pipe long to give me the most material to design with. After testing out the length of pipe compared to how long my legs are, I marked a spot to trim the pipe.

Using the portable metal bandsaw I trimmed the bent pipe.

Step 9: Seat and Axle Support

The seat will sit on the bent frame, but will need some support to keep it steady. Within the seat support openings will be made to feed the axle rod through, which the wheels will be attached to later.

I used 1½" scrap bar stock, cut to about 7" in length. I measured in about 1" and made a ½" opening through both sections of square stock.

The openings were deburred to make a smooth portal for the axle to fit without any resistance.

Step 10: More Welding

The seat brackets were spaces away from the bent tube, then welded in place using short sections of flat steel stock.

An axle opening was drilled into the bent tube and then the axle was fed through the seat supports and bent tube. All welds were cleaned up with a grinding wheel, the the entire surface was worked over with conditioning discs to give a nice surface for painting.

Step 11: Paint

Before installing the seat and wheels I used spray paint primer to cover the entire metal frame, using tape to mask off areas that I didn't want to paint.

After the primer has dried I applied 2 coats of flat black spray paint to the entire bike, waiting about 30 minutes between coats.

Step 12: Seat

I had intended to make make a low profile seat to go with this build, but then i happened upon an inexpensive chair at a thrift store. Thinking about how silly this build already was, I knew having a mash-up of styles wouldn't hurt the aesthetic.

Holes were drilled into the seat, then each opening was countersunk. These openings in the seat will correspond to the steel frame underneath, and long bolts will hold the seat securely to the frame.

Step 13: Lathe Wheel Bushings

The small chunky plastic wheels used at the back of this big wheel are from a broken Power Wheels cart for kids.

The ½" axle fit inside the wheels, but there was a lot of play in the wheels and they needed some support to run smoothly on the axle. I machined aluminum bushings that fit into the Power Wheel openings, and have a ½" hole drilled through the center.

Starting with 1½" aluminum bar stock, I machined down to the diameter of the Power Wheel wheel openings.

After turning the outside to the right diameter, I used the tailstock to drill an opening into the aluminium bar stock.

From left to right: I started using the center drill to begin the opening, then stepped up drill bit diameters until I reached my goal of ½"

When I had the center drilled out I used the parting tool to make 2 bushings from the machined aluminium stock, parting at 1" sections.

Here's what my two machined aluminum bushings looked like after parting and deburring.

Step 14: Install Wheel Bushings

The bushings were made slightly oversize to ensure a tight interference fit into to wheel opening. I used a deadblow mallet to pound the bushings into the plastic wheels until fully seated.

The wheels were then fitted onto the axles.

To stop the wheels coming off I used hose clamps to secure them in place while still allowing rotation.

I had originally intended to create a slit in the end of the axle and spread the partially bisected ends open to secure the wheels, but this proved too difficult to accomplish. You can see the slit I created in the image above.

Step 15: Cut + Screw That Horse

With the big wheel fabrication done the last part to make this ride complete is to add back on the majestic horse.

The existing horse was much too large for the big wheel, so I used a saw and cut the rear legs off. The horse was placed over the bike frame and screwed into the wooden seat with long screws with big washers on them to hold the horse in place.

To further steady the horse along the frame I used long zip ties, sometimes daisy chained together, to secure the horse to the bike.

The bike is complete! The tire was pumped up, the brakes calibrated, and the horse fed a sugar cube. This big wheel is ready to hit the slopes!

Step 16: Ride Into the Sunset!

My big wheel was entered into the Bring Your Own Big Wheel (or, BYOBW), an annual race down San Francisco's windiest street. A fun fact I learned: despite popular notion, Vermont street (where this event is now held) is the windiest street in San Francisco and not the famous Lombard Street. Neat!

There's no winner in this wacky race, just good times with fellow big kids who love doing crazy things. The sticker souvenir is always a good reminder when things get too serious: never grow up.

Happy making!