Page 10 - November December 2014

A HOME MADE WHEEL PAINTING JIG Terry McDonald
One of the more tedious jobs I found when weathering a wagon was painting the wheels, I usually finished with as much paint on my hands as on the object! On various forums I saw mention, and even once a picture, of a dedicated jig in which to hold the wheels whilst being painted. So I started thinking about this and rooted in my scrap metal box for suitable bits of plate for making a jig. I found some bits of 1.5 mm thick aluminium alloy plate that were of a suitable size. I stuck two similar pieces together with double-sided tape and squared them off before drilling four holes of a size to accommodate HO 33" wheels. As I was having trouble securing them to the drill press plate, they didn’t look very pretty as far as alignment was concerned. I then drilled 6BA clearance sized holes in the four corners and fastened the plates together with 6BA nuts and bolts using lengths of brass tubing as spacers to prevent the plates squeezing the wheels out of gauge. This assembly worked surprisingly well, although assembling the whole lot was a bit akin to balancing a ball bearing on a razor-blade edge! Obviously a better system was needed, so I had a long talk with my brother who was a professional engineer (I was a chemist and my engineering skills are limited to say the least). We decided that (1) the brass tube spacers were no good and blocks would be better; (2) the holes needed to be tapered to fit the taper on the wheels better; (3) it would be better if the jig would stand up on its back face with sufficient clearance for the pointed end of the axles.
Another search of the scrap boxes found some more plate and some scraps of ali block. Nuts and bolts were no problem, as we were both aero-modellers for many years so we had stacks of BA sizes, principally 6BA. Around this size, 3 mm metric or 4-40 UNC would serve equally well.
Two jigs were needed, one for 33" and one for 36" wheels in HO scale; then came the problem of finding (a) a drill for the 36" size and (b) a suitable taper reamer for each hole size. Problem
(a) was due to the fact that my drill sets finished at 10 mm and the odd larger sizes I had were not suitable. My brother’s enormous collection of drills finally gave up one in the correct size, though I think it was some very obscure Imperial size in reality (he had a habit of buying up old workshop collections of tools). No such luck with the reamers, though, even some adjustable reamers he had were nowhere near the size needed. Then the flash of inspiration, he tried a bodger’s special, better known as a sheet metal taper reamer. It worked, so now it came down to drilling the holes using his milling machine. After taper reaming, it is as well to stamp a mark on the outside faces of the sheet for obvious reasons. A bit of fiddling with the nuts and bolts and we were there. As I have arthritis in my hands I turned up some knurled brass rod and tapped it 6BA to make easier fastening than fitting small nuts. I have appended photos of the 36" wheel jig, as the other (which had rosewood spacers) is covered in paint. In use it is easy to assemble – lay it on its back, then place the wheels into their holes and put the top on, fasten down the screws and start painting. I have used both spray and brush painting techniques and they work. Of course you have to clean the axle bearing ends and there is always some leakage onto the wheel rim, which can easily be removed. Take my word, it is a lot quicker than painting them individually.
Please excuse any errors in my drawings, I am no draughtsman. The dimensions are what we used due to the material we had to hand; the only critical dimension is that of the spacing blocks so they do not compress the wheels on the axles when tightened up. It would also be possible to make the plates from some hard plastic sheet or material such as paxolin; we simply used what we had, our Yorkshire blood stopped us well short of buying new metal!!
10 ROUNDHOUSE