A hole is drilled in the center of the bar, and tapped for an 8-32 thread. Use a "gun tap" and you can chuck it in your variable speed drill and
run it through in one pass with the drill, as the chips are ejected out ahead of the tap. Two 3/8" long screws will clamp the track. The clamping
pieces are each made from a 1/2" long piece of 1/2" x 1/2" steel angle 1/8" thick, with one part cut short and a groove made for the wire. A #16
hole is drilled in the clamping piece: the hole needs to be bigger than the screw to allow for some play in the angle of the piece. Cross hatches
are cut in the surface of the bar with an abrasive disk in a Dremel tool. These allow for very secure clamping of the wire, and keep it all from
A piece of 1/8" diameter steel rod is welded or brazed to the end of the bar, to clamp the cross pieces. Small vise-grip pliers clamp the cross
piece to the rod, and allow lots of flexibility on how the cross piece is positioned.
It is very handy to have about 8 of these jigs.
Ball is ready to be
embedded in plaster.
The small box is
sliced, the big wall
holds it together.
Ball Bouncing Pad
The ball bouncing off of the pad is one of the most popular features of my RBS's. The most important part
of this pad is the slice of a Superball®.
If you just try to cut the ball in a saw, if you don't have a way to hold the ball stable then you may get a
very bad cut, and also jam or mangle the ball in the blade. I found the solution by embedding the ball in
plaster before cutting it on a table saw.
A small box just big enough to hold the ball is made out of 1/2" plywood, with one wall of the box a larger
piece of plywood. When the box is eventually cut, the bigger wall of the box doesn't get cut all the way
through and holds it together until the ball is completely cut.
The ball will be cut into 3 pieces: the middle piece to become the pad, and two end pieces that will be
discarded. For each section of the ball to be cut, 4 brass nails are pressed into the ball, so that the nails will
go into the corners of the box, and not be in the path of the saw blade. The nails are brass, so that if you
make a mistake in nail placement, the saw blade will not get harmed. Two nails are also put inside of the
box (before the box is assembled) to hold the center piece after it is cut.
The ball is put in the box, and the box is then filled with plaster. I used dental stone for the plaster, and
Fix-All would work well, too. Use wax paper as a temporary bottom for the box until the plaster sets. Let
the plaster harden and dry overnight. Then the ball can be cut on the table saw, leaving a nice disk that is
ready to use.
The pad is mounted to a disk made of 1/2" thick steel. This thick piece of steel is needed to give a solid
mass under the pad. A ring is made of plastic to circle the pad and help hold it in place. The the ring and
the pad are glued to the steel disk, using epoxy glue after first roughening the top of the steel disk and the
bottom of the plastic ring with #60 sandpaper. Put a thin layer of glue on each surface to be glued, place
them together and seat them firmly but do not clamp (epoxy does not like the film thickness to be too thin).
A great set of bells can be made from hole saws. They are made of the right alloy to make a very nice
ringing tone when struck by a ball. (The tiniest ones don't sound quite as good.) Harbor Freight has a set
for a low price. The saws are held in place by screws that only hold them loosely. My rack to hold them
has bumpers on the left side, so that a ball cannot miss any of the bells on the way down. A drawing shows
how they are attached.
pdf Drawing of
Inside of the base