48 SERVO 11.2015
it cost me to get started?” It may seem like an excessive
amount of “stuff,” but like with most new projects, you
need the proper equipment to do it right.
My suggestion when shopping for a compressor is to
buy a larger model than you think you will need. Once you
own one, you will find many other uses for it. Nail guns,
staplers, and grinders ... oh my, more cool new tools to
buy! I often wonder how I ever got anything built without
the use of air!
Check the power requirements and be sure you have
the electrical capacity to support your chosen compressor.
They come in both 120V and 240V models. I run two large
120V compressors for my Halloween display and had to
add two dedicated 20A breakers to run them. For me, the
expense was money well spent. However, you must factor
this in when deciding on the extent that you will utilize
pneumatics. Make sure your service has sufficient amps and
that you use appropriately sized extension cords.
Another factor to consider is the CFM, or cubic feet per
minute. The higher the better — especially if you plan to use
it for other work projects, like running air wrenches.
Expansion chamber mufflers and intake silencer filters
are available that can help mitigate the noise created by
your compressor. There are commercially made units, as
well as some do-it-yourself models, so check what may be
available for the unit you choose.
When shopping for a compressor, you will need to
decide if you are going to go with an oiled or oilless model.
The oil free units are usually less expensive, but can be
considerably louder. For anything but occasional and light
use, I would recommend going with a unit that uses oil.
The maintenance is a bit more and the unit itself is heavier,
but the added durability and quieter operation will be
worth it in the long run.
New units have the benefit of coming with a warranty,
but you may want to check for used models. I have seen
many on Craigslist that would fit the requirements of the
DIY prop builder at a substantial cost savings over a new
A solenoid is an electrically operated valve that plays a
crucial role in our system by controlling the airflow to our
cylinders. By switching the power on and off, we can either
extend or retract the cylinder shaft by alternating the
airflow between the two outlet ports.
There are plenty of choices when shopping for
solenoids. They come in a variety of sizes, with two to five
ports. Port sizes also vary, so check the flow rates of the
different models and choose one that fits your design
You must also decide if you will use 12 VDC, 24 VDC,
or 110 VAC to power them. It is much easier to swap
things around if necessary if your entire system uses the
same voltage. I prefer to use 12 VDC as they are safer to
have in an environment where my guests could conceivably
come in contact with them.
My preference is to use four-way five-port solenoids.
These are the most useful and the unneeded ports can
always be plugged. When designing my props, I like to plan
for the future as something I build today will one day be
dismantled and the parts incorporated into a new project
Here again, you have many configurations to choose
from as cylinders come in different designs, mounting
options, and fitting sizes. The style most commonly used
when building animated characters are the cylindrical
models which is what we will focus on here.
Single-acting cylinders have one air inlet that allows for
the cylinder shaft to move in one direction — usually out —
and then use gravity or a spring to return it to its original
Most of mine are double-acting cylinders as these
provide me with the widest range of control when
incorporating them into the body mechanisms of my
characters. These have two air inlets which allow you to
control the airflow in both directions (Figure 2).
Stroke length and bore size need to be fit to the design
requirements of each build. Larger bore sizes are more
powerful but require more air, so you want to select a
model that will do the job but not waste air.
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Figure 1. A four-way, five-port solenoid.