10-Minute Tech: Crank It Up… and Down

Illustration by William Tipton

Here’s my work-around for a troublesome manual crank to raise and lower the screw-type scissor jacks on my trailer. I bought a reasonably priced used 12-volt battery-powered cordless drill with a 19mm socket adapter and attached a two-conductor cable that will reach from the scissor jacks to the trailer’s battery. The drill has a two-speed selector and sufficient torque to raise the jacks a few turns past “tight.” A rechargeable cordless drill was not practical because the battery would not last long enough, and I did not have a way to charge it.

One caution is to determine the polarity of the drill’s battery terminals, since they are not marked (an old battery would give a clue, but we didn’t get one with the used drill). We determined polarity by using a current-limited power supply, so as not to damage the drill-speed control, which is polarity-sensitive (a 6-volt battery could also be used to ascertain when you have the positive and negative terminals identified). The manufacturers do not mark the terminals, as they assume you will use the battery pack they sell for the drill.

Once you are certain of polarity, the connections can be made to the two-conductor cable.

Warren Shulz | Griffith, Indiana




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