to use self-tapping screws. This allows me to disassemble
the project if required to either make changes or do repairs.
I’m also able to completely take it apart if I no longer need
it so that I can reuse the parts in another project.
Using wood in your builds can certainly be a viable
option in some situations. It’s easy to work with too and
most of us have had opportunities already to become
familiar with its characteristics. It’s readily available from any
hardware store, and many of us have a stock in the garage
ready to use in our projects. I bet you already have most if
not all the tools you need to convert those scraps of wood
into some viable props. Even if you don’t have any handy,
it’s not expensive and comes in a wide variety of sizes and
Using wood does have its drawbacks, however. You
want to be certain to seal it from the elements thoroughly
to prevent it from warping and degrading. Holes have a
tendency to expand with extended use, causing the
movements to get sloppy. In order to gain sufficient
strength and rigidity, you often have to use bigger lumber
which increases the weight. More weight often means
larger motors or higher air pressure to get the desired
Although it’s tempting to use screws, I’d suggest you
use bolts with locknuts whenever possible. Especially with
very active props, screws tend to work loose and the results
could be a disaster. If you have to use screws, make sure
they are of sufficient strength and quality.
Even though drywall screws are quick and easy to use,
they should only be used in the prototype stages. When
constructing your final build, please replace them. I’m guilty
of breaking this rule myself, and had a pneumatic prop
shear three drywall screws off on a hinge. The resulting
effect was impressive for about two seconds and then
required an extensive repair. Never again!
This is probably the material I reach for the most often
as I love its versatility. You can work it with common hand
tools if that’s all you have at your disposal and still get very
good results. It’s sufficiently strong for most of my designs
and the light weight means I can often get the movement
I’m after with a much smaller motor than if I was working
with a heavier material.
Aluminum and steel can both be purchased from most
big box hardware stores, but I suggest you check to see if
you have any retail metal shops in your area. I’m fortunate
enough that we have one nearby, and I make a trip with
the truck whenever I get low and stock up. The price
savings can be substantial, and the selection of sizes,
shapes, and thicknesses is much larger.
There are some times when there’s no choice but to go
with steel. The majority of my projects that use pneumatics
are constructed with it. Its strength is hard to beat when
you’re expecting a prop to stand up to the abuse
pneumatics can inflict. Steel is also my material of choice
when constructing especially large projects. Sometimes it’s
the only way to get the required rigidity without having to
add a vast amount of bracing.
If steel is that great, why don’t I always use it, you ask?
For one, it is heavy. Secondly, it can require some
specialized tools and skills to shape it to your needs. Many
times, you can drill and bolt together your creation, but
being able to weld will definitely improve your results. Many
community colleges and local maker spaces offer classes on
learning to weld, which would certainly shorten the
learning curve. Once you learn to weld, there’s no going
Drilling steel can be challenging in itself and a
benchtop drill press will be a substantial improvement over
a hand drill. With either tool, make sure to use some oil on
the drill site to extend your drill bit life and simplify the job.
SERVO 07.2015 45
Figure 1. A 1” PVC prop joint from Spider Hill Prop Works.
Figure 2. Slider rig built from wood and drawer slides.