Revolving Pneumatic/Electricity joint

A power drill and a valve from VW Beetle makes a nice lathe.

Attach a 35mm x 35mm piece of circuitboard to the valve
with 2-sided carpeting tape.

Make a groove thru the copper with a sharp file.

Drill a 6.5mm hole in the middle of the ring.
File the circuitboard to 32mm x 32mm so that
the hole is exactly in the middle.
Drill 2 holes and solder 2 wires to them.
Use a temporary solder mask.

Peel off the mask.

Some testing.

File off the inner teeth from a turntable.
A piece of Lego flex-pipe is the upper part of the pneumatic joint.

Cut a 1mm slice of Lego-hose.

Put that slice around the pipe. It's a gasket.

Put a piece of 5mm silicone hose on them.

Here is the lower part of the pneumatic joint.

The silicone hose fits perfectly to a 1 x 1 round brick.
Make sure that the hole in the stud of the brick is round and not
an octogon.

Connect the brick to the pneumatic t-joint.

Place the circuitboard on the brick.

Modify 2 pulleys.

Lead 2 thin wires thru the holes.

Put some white vaseline to the silicone hose and to the wires.
(Don't use silicone grease because it isolates the electricity.)

Now the joint is ready to be closed carefully.

These instructions are simplyfied. Make tests and don't
expect your first joint to be a success. I've made some of
these to my rides and not all of them have worked at the first time.
The electricity connection may break if there are scratches or
solder tin on the track of the wires on the circuitboard.