Vic and Sue Thies “Too Much Fun Railroad” includes an area dedicated to the Wizard of Oz/Emerald City that includes Professor Marvel’s balloon hanging from a line. Vic asked me if I could animate the balloon to make it rise/return to earth.
“Well of course I can!” Hmmm…, Easier said than done only using what is at hand.
Without a worm drive motor on hand, I figured that the balloon would need a counterweight, otherwise when it goes up and stops, it would probably start to unspool under its own weight until the switch disengages, making it go up again, then starting to unspool again, etc., etc. etc. until it was time to reverse and come down. …And wouldn’t that be fun!
I used a piece of 2" x 4" for a chassis to contain the motor and pulleys. A pulley on either end supports the balloon and counterweight (will probably be the wicked witch and her flying monkeys, or…), and a pulley in the center shuffles the two weights back and forth. All of these pulleys are made from plastic train wheels. The center “drive” pulley has a couple USA Train traction tires on it to eliminate the slippage from the 80# test fishing line.
A donated motor drives the assembly using a belt drive and I made the driven pulley on my lathe to attain ~10:1 reduction. The motor is mounted on two vertical uprights like the spindle between equal length “A-arms” on a car allowing it to move back and forth through an arc for tension adjustment.
The lines that holds the balloon and counterweight weights pass through “trip switches” to stop the ascent. As the balloon rises, a lever pulls the switch opening the circuit until the electronics tell the balloon to decend.
I had a stroke of genius that allows instantaneous, infinite adjustment in the X, Y, and Z axis, as well as allow for rotation in the X-Y plane, all vital to having the lines centered within the levers. This also allows the switch/lever assemblies to “break away” and reposition themselves rather than breaking, if for some reason the balloon does not stop. I’ll let you guys ponder this one until I get some pics up.
The electronics consist of a 555 chip in oscillator mode running a relay to forward/reverse the drive motor for ascent/decent. A dc-dc voltage converter reduces the motor voltage to keep the balloon from becoming a rocket.
Pics in a day or two.