Gear Pullers and Presses - Electric Dreams

Posted May 29, 2009

As the number of new slot car enthusiasts we deal with increases we hear from some who are not familiar with gear pullers and presses. These simple but effective tools are a must for any racer who wants to change the pinion gears on his motors. Gear changes, of course, are an essential part of tuning cars for optimum performance on any particular track and power supply. Pullers and presses are designed to exert steady, even force to install or remove gears without damaging them or bending motor shafts.

Gear pullers consist of a framework with thin jaws that slide in on either side of the motor shaft between the pinion gear and the can or endbell. Most of the pullers used in slot car racing are circular in shape, similar to the one shown in Fig.1. A screw with a thin shaft on the end pushes on the end of the motor shaft and as the screw is tightened it drives the motor shaft back through the pinion gear until it has been driven all the way through and the gear is removed, as in Fig. 2.

Every gear press, regardless of what it looks like, is essentially a clamp, exerting controlled pressure on gear and shaft to press the gear into place. You can actually use some ordinary C-clamps as a gear press, as well as a bench vise or an arbor press. You can also use a drill press by simply chucking in a piece of bar stock to give you something to press with.

Many made-for-the-purpose gear presses are, in fact, modified c-clamps. The main modification is to provide holes or indentations to hold the end of the motor shaft and the gear firmly in proper alignment, ensuring that the gear is pressed on completely straight and the motor shaft is not subjected to sideways bending forces. Gear presses also have a hole drilled in one end, as shown in Fig. 3, to allow the end of the shaft to be pressed past the end of the pinion gear. This allows the pinion to be placed properly to engage the teeth of driven gears in motor installations where the exact positioning of the motor may vary. It also allows the shaft to extend past the pinion gear to engage an alignment ring on the crown gear, as used on virtually every in-line RTR car.

To press on a gear, place the motor and gear into the gear press as shown in fig. 3. Then, begin turning the screw, applying even pressure. The screw will press the end of the motor shaft through the gear and beyond, if needed for the particular gear installation, as shown in Fig.4.

Always be sure the motor is placed in the press with the gear end facing away from the screw. If you get it in backwards you can end up pressing the shaft through the motor, as shown in Fig. 5. Some people have used this method successfully to convert can-drive motors to endbell drive and vice-versa, but you don’t want to do that when it isn’t part of the plan, and it does carry substantial risk of damaging the motor.

Some manufacturers make a single tool that combines the functions of both puller and press. These have the advantage of compactness and allow you to carry one tool in your race case instead of two, but these combination tools are not always as durable as the separate ones and may not accommodate as large a range of motor sizes. It’s also worth noting that virtually all motors presently used in 1:32 and 1:24 scale slot car racing at all levels have .078″ shafts (the exception is the FF motors, which have a smaller-diameter shaft), so once you acquire a good puller and press they will serve you no matter what kind of racing you get into.

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Electric Dream Team

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