Servo - November 2015

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.

Air Compressor

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 unit.

Solenoids

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 requirements.

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 (Figure 1).

Cylinders

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 position.

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.