Sometimes
the project I work on is decided by what I’m currently excited about. Sometimes a project is at a really exciting
stage where a lot is getting done. Other
days I feel like there are external circumstances that have to be taken into
consideration like if the summer is ending and I’m working on a longboard. Finishing a longboard in the winter is fine
but I can’t ride it until spring.
Sometimes I talk with someone about a particular project and later I
enact the things I talked about. At
lunch I talked with the person behind the Tennis Ball Launcher contest and
showed off what I had already built.
That
evening I planned to continue work on the ESPeri.Impass, as I had been for the
last several days, so I bought parts at a hardware store and was pretty excited
about improving the new design. However,
when I got to the hack space I realized that I had forgotten the Impass
materials at my apartment. Everything
except the parts I just bought was sitting on the table next to my bed. So, suffice to say, I worked on the Tennis Ball
Launcher because those parts were handy.
I
guess there’s an advantage to a messy car, I would have been out of luck if
that project wasn’t close.
Enough
background.
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2”
PVC was cut to obtain two pieces 30” long.
It was cut on a radial arm saw.
The goal was to make larger diameter replacements for the 1 ½” PVC
already cut and drilled for this project.
Marks were made 1” from the end to be drilled to 5/16” for the carriage
bolts which hold the bungee cord. The
5/16” holes were drilled all the way through the PVC pipe. Care was taken to keep the holes on the same
plane. One end was drilled then a bolt
was inserted so an accurate ling-of-sign could be drawn at the opposite end of
the pipe. A second hole was drilled 28”
away which is a longer distance than the first pipes. This caused more tension on the bungee.
Cutting the PVC into 30" pieces
The hole location is 1" from the end just like the first version
The holes are drilled all the way through the PVC pipes
Lining up the holes at the far end based on the location of the first bolt
Measuring 1" from the back end
Keeping
the pipes close to identical was done by inserting a long 5/16” bolt through the
first holes then copying the other end ensuring the holes in both tubes were
the same distance. The second end was
marked by twisting a bolt through the first pipe, which had all the bolt holes
drilled, and pencil marking on the second pipe.
The pipes are fastened together with a long 5/16" bolt
Pencil marks are made to drill the same distance from the first hole
The holes will be very close to the same distance on each pipe
The
next step was drilling 7/8” holes in the PVC for the pulleys and bungee to pass
through. The holes from the first pipes
were copied by laying the pipes together and making marks where the holes began
and ended. The 7/8” drill bit was lined
up to make the edge stop at the mark. A
rotary tool with a sanding drum was used to complete the hole and smooth over
the edges of the hole.
Marking the holes based on the first version
Two 7/8" drill bits. The Forstner bit on the left was used in this project
Two holes made with the Forstner bit
A sanding drum in a Dremel is used to finish the holes
The sanding was done in a vacuum tube to minimize dust
The bungee
was reinstalled along with the pulleys.
There is considerably more tension on the bungee cords. It may be important to redrill the holes at
one end of the PVC and lessen the tension.
It would also be possible to install a variable tension system to
make the power adjustable.
To
do:
- Build: Ramp (1/2 pipe)
Handle
Trigger
Mounting
Well ball sling
- Attach release mechanism
- Test
- Refine
- Document
Journal page 2
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