Make Spoked Wheels

Model Airplane News, Mar 2004 by Sparks, Keith

Cheap and easy scale secret

Much has been written about how to create spoked wheels. The problem with most methods is that they require extensive trim work, and the result is often limited in strength. So when I need a set of scale wheels for one of my park flyers, I construct my own using PVC pipe. It's tough, cheap, easy to work with and comes in many sizes.

A well-stocked hardware store will have most of the parts you'll need for this project, with the exception of the threading fixture; you'll have to make that yourself. The absence of dimensions is intentional here. It's more important to keep things simple and to allow your own personal preferences to prevail. With that said, here are the basic steps involved in creating your own inexpensive spoked wheels.

1 Mount a hole saw on a hand drill and wrap enough masking tape around the saw so it fits tightly inside the PVC pipe. Mount the pipe on the saw, then turn the hand drill on to rotate the pipe, allowing you to make evenly spaced scratches in the pipe. A divider works well for this, but it isn't necessary. Next, use a hacksaw blade to cut slots in the pipe to form the individual rims. (Note: do not use a pipe that is longer than 6 inches; it would require support at the other end.)

2 For the finished wheel to look right, the spoke holes should be centered. A slight groove helps to keep the drill bit centered and will later serve as a guide for the thread. Use the corner edge of a small file to make the "V" grooves.

3 To determine the proper locations of the holes for the spokes, wrap a piece of card stock once around the pipe, and then trim it to size. Lay the card stock flat on a table, and make 28 evenly spaced marks on the card. Then wrap the card back around the pipe and transfer the marks to the end of the pipe. Drill the holes where the lines intersect the "V" groove. (Note: nest the pipe against the handle of a sanding bar or anything with a 90-degree angle. This ensures that the lines run parallel to the pipe.) The number of holes can vary from 28, but the total must be divisible by four.

4 After you've drilled the holes, use a saw to separate the rims from each other, and slightly sand the sides. The rims are then ready for the router. Use a PVC fitting to protect your fingers from the router bit while routing the rims' inside radiuses.

5 Use a block of wood to make the threading fixture. Hold the rim centered and squared over the axle post. The clothespins are not required here, but they do come in handy.

The axle hubs are made out of two aluminum tubes and two washers. The hub itself slides over the bearing and is held in place with a light crimp or dent. The washers must be a close fit over the bearing so that they will not slide over the hub. You can then install the whole assembly on the threading fixture by placing it into the axle post.

6 Threading the rim is easier than it looks. I use 8-pound-test monofilament line. Start by making a double knot in the line, then thread it through the first hole in the rim, looping it around the axle post below the washer at the bottom of the axle and out through the third hole in the rim. Pull the line just taut enough to take out the slack. Next, thread the line into the second hole, over the washer at the top of the axle and back out through the fourth hole. That's it! Continue this sequence until you have worked your way around the rim.

7 To set the spoke tension, place the threading tool in your hand, and wrap the excess line around your finger to keep the line tight while you work. Use forceps to tug on the lines leading to the third and fourth holes, and work your way around the rim until all the slack is gone. Next, lay the line into the groove in the rim and apply CA to hold it in place. (Note: if the forceps have "teeth," cover them with masking tape to prevent damage to the line.)

Remove the wheel from the jig and give it a spin test. Any small defects can be fixed at this point. When you are satisfied with the quality of the wheel, use CA to lock down the remaining lines at the rim grooves and at the washers.

8 For your tires, cut strips of foam rubber to match the width and circumference of your wheels. If you have difficulty finding suitable foam rubber for your wheels, you can buy large foam wheels at your hobby shop and cut them to make strips of foam. Cut the strips so that they will fit the rim snugly, and bond the ends of the strips with CA.

9 With the foam in place on the rim, pull back the rubber slightly to expose half of the rim surface. Apply CA to the rim, working around one side and then the other. (A coffee stirrer works well here.)

10 Next, place the extra axle bearing in a Dremel tool or drill and spin it at a low-speed setting; use sandpaper to sand the tire to shape. (Note: if you choose to shape the tire at a high speed, use piano wire through the axle bearing for support, and please use caution.)

11 To cut away the extra axle bearing, place it on the edge of the table and use a razor to roll the bearing. The weak point will enable you to break the excess away.