Whoa! Disc brakes for shelf models and slot cars, by Mike Sells

Disc brakes have been common usage on racing cars of all sorts since the middle 1950's but it's been difficult to model them realistically in 1/32 scale for several reasons: first, the number of kits detailed enough to contain brake parts have been few and far between and second, nearly all of the aftermarket parts are for 1/24 scale (too big) or 1/43 (too small). To be honest, until the advent of NINCO's gorgeous classic wire wheels and the FLY large diameter BBS and OZ wheels as well as some of the better kit wheels, one couldn't see the discs through the wheels anyway. Finding something "just right" to use behind the wire wheels on the Aston Martin DB4GT has occupied me recently and a similar solution, suitably altered, works just as well for the modern GT and sports cars.

"Classic" disc brakes; that is, solid rotors used with wire wheels or '60's spoked wheels, are simply flat, solid discs with a hole in the middle to suit the wheel hub and a brake caliper on the outer edge. The MPC/Airfix Porsche 917 kit provides excellent disc brake parts that work very well for some applications but the diameter is too small to suit the NINCO wire wheels. Replicas & Miniatures Company of Maryland casts small 1/24 scale resin "Street Rod Brake Calipers" (RM-35C) so appropriate discs were the hard part until I visited the hardware store across the street from the office over my lunch hour, acquiring an assortment of steel washers and aluminum pop rivet backing plates that looked like they might work. Washers to fit #8 screws were the best outside diameter (3/8" or 9.5 mm) but they not fit the NINCO hub diameter. One can drill out the centers of the washers or use a pointed grinding bit in the Dremel, working from both sides at once until the washer is a slip fit on the hub. The washer gets hot so take your time, keeping a small basin of water handy for periodic cooling. As my Aston is a shelf model, I drilled out the hubs to accept a combination styrene tubing inner part mated to an aluminum tubing outer part sized to fit the #8 washer. By grinding the original hub down to within 2 mm of the spokes, a ledge is formed to glue the brake rotor to, holding the caliper and rotor the correct distance from the wheel. I do NOT recommend this for slot racers! Paint the calipers metallic gray, glue to the rotor and install in the finished wheel. The wheels on my shelf models do not turn so it's easy to rotate the calipers to the correct position when installing the wheels but those used on slot cars will have to rotate with the wheels.

Drum brakes, used on earlier racers and many Ferraris as they were the last to convert to discs, can be modeled by installing just the washer behind the wheels. Use a slightly larger diameter washer than the ones used for the disc brake rotors as the drums were as large as would fit in the wheels - as the outside diameter increases, so will the inside so grinding may not be required in this case. These were usually painted the same color as the chassis or the body. Finned brake drums are another matter entirely!

Modern racers use vented discs of larger diameter than the classic style. Detail Master's 1/24 #DM 2231 11" drilled discs work perfectly for many contemporary slot car wheels but require some surgery to install. The package contains four outer and two inner discs - sufficient to build a pair of vented discs - but only one outer disc will be used on each wheel so one set will detail an entire car. FLY's OZ wheels as used on the Marcos look fantastic with the drilled rotors because they are the most visible. I have included examples of modified wheels by several makers; some are more successful than others. The NINCO rally style wheels are smaller in diameter and use the notched center part of the etched brake set but another set would be required for the second pair. I dispensed with calipers because there isn't room to install them.

Remove all four tires from the wheel set, taking care not to wear the markings off if possible. The step in the wheel for the tire mounting will act as a guide for most wheels but in some cases, the NINCO wheels for example, the spokes are set back far enough that one needs to leave more of the outer wheel. If so, chuck an axle into the Dremel, put the wheel on the end and using a thin, fine tooth razor saw held perpendicular to the wheel rim, cut a shallow groove in the wheel 1/16" or so behind the tire mounting step. This gives you an even guide to use in cutting the outer rim and spokes from the main part of the wheel. There should still be plenty of hub left for strength after cutting. Sand the wheel and the wheel spokes flat and smooth with 400 grit wet paper. Clean up any debris from the cutting operation, continuing until you have modified all four wheels. The FLY Panoz/Viper wheels also need some of the tire mounting rim removed with the spokes but the original style deep dish FLY Porsche GT1 wheels have very shallow spokes so cut only the outer, gold part of the spokes from the inner hub. Install the tire on the rim and glue the disc to the main part of the wheel with super glue, centering it in the opening. Glue the outer spokes to the brake rotor, aligning the spokes and centering them in the tire. This technique puts the brake rotor out close to the wheel where it can be seen. I hope you'll agree that the wheels look much more finished and realistic this way. Now, if there were only some way to get them to glow red…. One more tip: there is no particular reason to re-install the same outer wheel that was cut off originally. The diameter of the replacement must be very nearly the same and of approximately the same depth but other wheels may well meet the requirements, perhaps those from 1/24 scale model kits or after market parts? The chrome 5 spoke wheel from Monogram's 1/32 Ferrari 512 TR is especially suited to this use. If the wheel center you wish to use is smaller than the original, simply cut a ring from large styrene or brass tubing that fits the outside diameter of the wheel insert. Paint flat black so it gives the illusion of a wider tire sidewall and glue to the inner wheel. Glue the detailed wheel insert in place and you're done. If you find that a given wheel just doesn't look right - too many spokes to show off the disc or strictly an artistic judgement - glue the spokes back to the wheel as it was originally.