Some commercial slotcar sets have a Turbo-Boost feature - a brief spurt of higher than normal voltage that can be used once (or a limited number of times) per race .

I can think of two possible ways to do it:
- a capacitor that discharges and then takes a while to charge, and
- a separate higher voltage power source that can be momentarily applied to the track (there would have to be some timing cutoff and/or counting device to keep it from being used too long or too often).

Does anybody have a simple circuit that could be added to a conventional 20-volt rheostat-controller HO system for Tjets and MTs, that would give that feature? Something that could give the feel of that last-minute drafting move in close races.

-- D

A capacitor won't charge up to more than the maximum applied voltage. What you need is basically a step-up transformer, or booster coil. The theory of operation follows the way traditional automotive coils work, where you energize (or charge) a primary coil with a 12V source and then discharge it through transformer coupling to a much higher wind secondary coil that is adjacent to the primary coil. The voltage step up is directly proportional to the ratio of winding turns between the primary and secondary. So you would need a booster coil that will take 20V up to say 30V or so.

The transformation between the primary and secondary only takes place when the magnetic field in the primary coil is changing, which will take place when the boost button is pressed and the primary winding field collapses. This effect is momentary in a DC circuit.

That's the theory. All you have to do is find the parts and come up with a switching circuit that allows the secondary winding voltage to be delivered to the car when the button is pressed. A side effect is that the primary coil also introduces inductance into the controller. But you would be putting a large resistor on the primary coil charge side anyway to limit how often the effect can be used, so the impact on your controller behavior would be minimal if designed right.

Thyristor capacitor. Charges up over a few seconds (makes a high pitched whistle while charging) can be rigged to discharge via a momentary switch.

I saw a controller like this a long time ago, I'm nearly certain it was from AFX, had a button at the back labeled "Turbo Boost" I think. It's been at least 20 years since I saw one though.

Didnt Tyco have some sort of turbo boost in the 80 s?