I recently decided that a high voltage relay would be a necessary component for a successful can crusher (i.e., one that does not destroy its power supply) along with a triggered spark gap. Recently, while cruising E-Bay for "high voltage", I came across an auction for a Ross Engineering high voltage relay (40,000 volts, two pole, single throw). Unfortunately, I was outbid (it sold for $102.50). However, the pictures of the relay gave me some ideas and I proceeded to design and build my own. The parts all came from McMaster-Carr.
These two drawings show the relay from the side
and top, respectively. The three frame pieces were cut from a 12"
x 24" x 1/2" sheet of polycarbonate. The swing arm and bearings were
made from 1 1/2" x 1/2" ultrahigh molecular weight polyethylene bar.
The axle is a 1.6" length of 1/2" (actually, it is sold "oversized for
finishing", it is really 35/64" diameter) UHMWPE rod. The fixed contacts
are 1 1/2" lengths of 1/2" copper rod, which I rounded on one end (with
files and polishing pads) and drilled to accept banana jacks (5/32") on
the other. The moving contact is a 4" length of 1/2" copper rod with
rounded ends and a divot drilled into the center to help the nylon locking
screw hold it in the swing arm. The solenoid is pull style with a
twelve volt coil, rated for intermittent service (70 seconds maximum on
time). It provides a maximum pull of 100 ounces, at 1/8" travel.
Maximum travel is 1", at which point the force drops to about 20 ounces.
The solenoid is connected to the swing arm with a two axle link made from
two lengths of 1/2" square nylon bar and two pieces of 1/8" steel rod.
The nylon link arms were drilled about 3/8" deep to accept the rod.
They fit snugly between the two long rails of the frame and since they
are not drilled through the rods do not come into contact with the frame
(which they would scratch). The lower link axle is prevented from
riding forward on the bottom of the swing arm by a 6-32 screw located in
the bottom of the swing arm 2" from the swing arm axle center. The
frame, bearings, solenoid and contacts are all held together with 8-32