Helicopter schematic diagram
The winch reel for copter "Y"
Each motor turns a drum that is a winch for the control lines (Figure 4). The diameter of each
area that winds up a line affects the speed of motion. Most of my lines wind onto .770”
diameter, which gives the speed that I want. When you use a larger diameter winch, this puts a
heavier load on the motor. By using a counterweight, the motor just moves the load and does
not have to lift it all. So then at the same time that the winch is winding up control lines that
raise the helicopter, part of the winch is unwinding a line going to a counterweight. This
counterweight lightens the load for the motor, and also balances the system so that when the
power goes off the copter remains in position instead of crashing. If the winch area for the
counterweight is turned to a smaller diameter, then the weight will not travel as far. This will also
require more weight, but means that the path of the traveling counterweight is shorter and can fit
into a smaller area. I used a block with one counterweight to reduce the counterweight travel to
half the distance.

The motor controlling the “X” direction turns a drum that pulls the trolley toward it. The line
attaches to the trolley, continues to an idler pulley, and then returns to the drum where it
unwinds on another part of the drum. The ball-bearing idler pulley keeps tension in the line with
a spring. As the line winds in one spot and unwinds in another, the pulley moves about 1/4” as
it keeps tension on the line. The line is 50 lb.-test multifilament “Spiderwire Stealth” fishing line
(Wal-Mart). This multifilament line is thin, strong, Teflon lubricated, and it is limp: it has no
“springiness” to make it misbehave. The action of the “Y” mechanism makes the trolley want to
go to the left, so a counterweight pulls the trolley to the right to offset this.
bee counterweight
The motor controlling the “Y” direction winds up 3 lines (16 lb Spiderwire) on its drum winch to raise the
helicopter, while unwinding another 50 lb. line going to a counterweight. The lifting lines attach to three points
on the helicopter, and then lead up to a “Y” shaped yoke, where the lines turn around pulleys, lead to more
turning pulleys in the center of the yoke, and then go to the winch. Since the yoke rotates as the helicopter
travels, the turning pulleys in the center of the yoke keep the relative lengths of the lines from changing, which
keeps the copter level while flying. The lines attach to the helicopter by going through a hole and attaching to
a lead crimp-on fishing weight. When the copter lands, the weights can drop and keep tension on the lines so
that they all stay on their pulleys. All of the pulleys use ball bearings.

The trolley is made of pieces of brass soldered together, with 6 bearings to ride the rail: two on top and two
each on front and back. I tried making this trolley with a brass sleeve to ride the rail (as I did the elevator and
rescue device), but there was too much friction. The helicopter rotation arm puts the center of weight off
center from the rail, and the ball bearings are needed to make it travel smoothly enough.

The “X” motor also connects to a potentiometer, so that I can measure the position of the trolley with a
Stamp. This is only for cases where power is lost, so that when power is restored the copter can find its way
back home. Otherwise, it is almost sure to crash when the power goes on. One way the power can go off is
when someone thinks that the way to turn off electrical things is to unplug them (been there, done that). To
ensure that this can’t happen during normal operation (turning it off with the switch), a relay holds the power
on to the stamps and motors until the copter lands. The spot lights and ball-lift motor turn off, but the
helicopter finishes its journey before all shuts off. This feature was disabled during most of the development
of this project, when I wanted the copter to stop if I switched it off.