... I'd rework my coaster bike design

A lot of folks have been taking me up on my offer for suggestions on how to build a wooden coaster bike. So, it's taken a few days, but I finally have a collection of suggestions and a pdf of patterns that I feel comfortable releasing to the public.

Coaster Bike Advice

The first step is to decide what kind of wheels you’re going to have: wood, plastic, or metal. This decision will shape the rest of the bike design. Here are my thoughts on the three basic wheel choices: wooden, plastic, and metal.

Wooden Wheels
Wood wheels are the best looking and since you’ll have to fabricate them, their characteristics can very flexible. However, not everybody has access to either a lathe or a drill press – tools that I think you’d have to use to make decently round wheels. Wooden wheels will require some sort of hub or bearing to spin on the axle. Look on ebay for a couple of either 1/4“ or 3/8“inner diameter bearings. Wooden wheels also require some sort of tread or other gripping surface. You could cut up a bike tire and use the tread from it, but you’d have a seam in the tread that might be a bit noticeable. I’ve wondered of a can of Plasti-Dip could be used to paint a tread on a wooden wheel – it might work.

Plastic Wheels
Plastic wheels are a faster build option because you don’t have to fabricate the wheel. However, most plastic wheels (like metal wheels) are made to fit a 1/2“ axle (the standard for lawn mowers). This means you’ll have to use a thicker (or in my case, redesigned) front fork to accommodate an axle that large, or you’ll need to buy some bushings to make a smaller axle fit inside the wheel bearings (in hind-sight, this is probably what I should have done). Plastic wheels (again, like metal wheels) are also wider than wooden wheels and will require a wider front (and rear) fork design. This will affect the styling of the bike. The reason I avoided plastic wheels was that I didn’t like the look of plastic. However since I completed the project, I’ve wondered if a plastic wheel with a pair of round wooden (probably made from a thin sheet of luan) hubcaps would look OK.

Metal Wheels
Metal wheels have pretty much the same characteristics as plastic ones except they are heavier and look nicer. Metal wheels also give you the option of pneumatic tires, which aren’t really necessary, but are certainly cool. I’ve also seen a coaster bike online that had a pneumatic wheel on what seemed like a wooden hub. I think a similar wheel could be made from taking the wheels off a small child’s bicycle and cutting out the spokes and fitting a wooden circle in its place – but that’s probably just as much work as making a wooden wheel from scratch.

Construction Suggestions

After making the first bike with metal wheels, I’ve pretty much decided that I should have gone with wooden wheels. For that reason, my suggestions and the accompanying patterns will be based on the assumption that the builder is making the bike with wooden wheels.

Wheels
To make a set of wooden wheels, you’re going to need either a lathe or a drill press. I suggest making the wheels out of 3/4" plywood, because a bike with a wider wheel will be easier to balance. Someone with a lathe can probably whip out a 10” wheel in a few minutes. However, I only have a drill press, so I’d probably have to rough cut a circle with either a jigsaw or a bandsaw, and then drill a center hole, attach a bolt through it, and chuck the bolt into my drill press. Then, I could spin the circle while using a rasp and some sandpaper to smooth the circle into a wheel. Once the wheel is nice and round, I’d drill a bigger hole in the center to set one of the bearings into. I bet a couple of thin 2” luan circles (with axles holes in the center) glued onto either side of the wheel would be enough to hold the bearings in.

Front Forks
I think making the front fork out of 3/4" plywood would be sufficient to hold a 3/8” axle bolt.

When I cut out my first attempt at the front forks, I had a lot of trouble with the edge of the plywood chipping. I think it might be worth clamping a sheet of luan on either side of the plywood to help reduce chipping.

Also in my first attempt at the front forks, I ran the pivot bolt up from the wheel well into the fork. I now think it’s a better idea to run the bolt from the top of the fork down. This way, the bolt head can be hidden by the handlebars.

Bike Frame
In my design, I used 3/4" plywood for each side of the frame. I now believe that using 1/2" is a better option for the frame. The bike will be lighter, and the thickness of the frame at the front fork pivot will better match the thickness of the wheels.

I originally used wood screws to sandwich the two frame pieces together. This means that one side shows the screws and the other doesn’t. In this new design I suggest using counter-sunk bolts driven into some wood insert nuts. (This is probably a picky detail, but I think it looks better.)

The front fork's pivot bolt sits within a hole drilled through the frame cross-section. I suggest inserting a pair of bushings on both ends of the hole to keep the wood fibers from getting reamed out.

I also suggest reinforcing the area of the frame where the pivot bolt attaches with a plywood wedge.

Another small detail that I'd like to change is the front of the frame where the two half meet. In the original design, the frame had a rounded leading edge. This made getting the two halves flush together troublesome as I had to do a lot of precise sanding to accommodate for the curved edge. A flat edge would fit together nicely with little to no extra sanding. I've updated this detail in the plans.

Seat
In my design, I have two thin wedges glued to either side of the frame that the seat support slides between. It was a lot of hassle to get those wedges into just the right spot to correctly hold the seat support. In this new design, I suggest securing a piece of wood onto the front edge of the seat support and use that to secure the seat post to the frame.

I also redesigned the seat support to be a little more “stylin”. The longer seat also acts as a rear wheel fender.

Axles
In my original design, the axles were 1/2" steel bolts with the heads cut off. The axles were kept in place by friction, and I noticed that they tended to work loose after a few days of riding. To correct the problem, I put some hot glue where the axle contacts the wood, and that seemed to work. However, I think a better design would be to use wood insert nuts and possibly a few drops of hot glue for good measure.

Final Thoughts

I hope these suggestions help. If you get stuck, please refer to the final three pages of the patterns pdf file. I’ve drawn some diagrams of how I’m envisioning this new design fitting together.