Making Hidden Wheel Retainers for Scale Models
In Scale Modeling, the wheels often have hub caps. All too often, the common wheels we normally use don't allow adequate clearance for the "store bought" hardware available we use to mount the wheels. So, the solution is actually a simple one, but requires a bit of soldering and tube cutting. But don't worry, it's really not hard, and after all, we're modelers, and making things is what modelers do, right? Here's how the whole process works.....
For the smaller Park Flyer type airplanes I fly, 1/16" and 3/32" wire landing gear axles are typically sufficient, but the common light foam wheel sizes come with holes drilled in the hubs for 1/8" or 5/32" wire axles. To make the wheels work on the smaller axles, one or more spacers will be required to re-size the hole. Typically, if you have 3/32", 1/8", and 5/32" O. D. brass tubing on hand you'll be in good shape. And typically, only 2 sizes of washers will be needed; a #2 washer fits the 3/32" O. D. tube, and a #4 washer will fit the 1/8" O. D. tube. The spacers are cut from various sizes of brass tube to the proper length using either a small tubing cutter, or by rolling the tube under an X-Acto knife blade to score it, then break it off.
The way the system works is to retain the wheel on the axle by way of a washer soldered to a brass tube, then the keeper is retained on the axle by way of a single wheel collar on the inboard side of the wheel. This way, after the hub cap is glued in place, it won't have to be removed should the wheel need to come off for any reason.
Here are the tools you'll need to get the parts made up. So let's get started....
1- Cut the appropriate sizes of brass tube to length to fit the axle to the hole size of the wheel. The bearing tubes should be cut to the width of the wheel hub. The smallest tube should be cut approximately 5/16" longer then the width of the wheel hub to accommodate the washer being soldered to the out-board end, and the width of the wheel collar on the in-board end.
2- Make up a drilling jig by drilling the appropriate size hole in a piece of scrap wood and slip the axle tube into the hole, leaving about 1/32" protruding. Slip the washer over the tube and solder in place using a lead free solder such as Stay-Brite.
3- Remove the tube from the jig. Then using a Dremel rotary tool with a Cut-off wheel, grind a slot in the other end of the tube to receive the set screw in the wheel collar that will hold the whole thing in place. Clamp the tube lightly in a vice to cut the slot. Don't over-tighten the vice or it'll crush the tube and it won't fit over the axle.
4- Now that the axle assemblies are prepared, slip the bearing tubes over the keeper tube, fit all that into the wheel and slip the collar over the inboard end. Tighten the set screw just enough to prevent the collar from falling off the tube. And with that, the wheels are ready to mount on the axles.
5- To mount the wheels onto the model, cut the axle to length, just enough so that it won't protrude past the outside wheel hub. Slip the wheel assembly back onto the axle and snug the wheel collar.
6- Now you can make up your hub caps from whatever items you find work best. I like to use those little plastic seals from Orange Juice cartons, or for an even more versatile item to fit those less common sizes, the domed bottom of an aluminum beverage can can be cut to any size using a drafting Circle Template to mark the proper size on the aluminum, then trimmed to size using a scissors. The caps are glued in place with Pacer Canopy 560 glue, so that in the event that the cap does need to be removed, the glue can be softened with plain water and the cap removed without damage to either itself or the wheel.
And that's all there is to it. A simple solution to an age old problem, and requires only common modeling tools to accomplish. As always, the first time to do one of these it'll probably be a bit of a challenge, but after the first one, you'll know what you're doing and you'll be able to knock out the next one in no time flat.