The second summer that I worked at the PennDot I made a vacuum chamber. My boss Seth Pelepko came to me and told me about an experiment or series of experiments he was wanting to try that required a vacuum chamber, which the lab did not have and would most likely be unwilling to spend such large amounts of money on, so he asked me if he thought that I could design and build a vacuum chamber for him. Well, at first I told him that I'd have to think about it and I'd get back to him.

I had heard of the chambers in passing in a science class at some point but only had the vaguest idea of what one actually was, so I hurried to my computer and looked up information on how they worked and what all of the components were. I was able to find a few websites where individuals had made their own chamber cheaply for various projects and after a day or two I was convinced that the project was at least possible, which Seth was glad to hear. I asked if I could have an intern work with me on the project and he gave me the list of interns in the building, allowing me to pick one, talk to them, and begin. With minimal design help from a fellow intern, and a lot of construction help from a full-time employee Mark Bitner, I was able to complete the project by the time I left that summer.

As you can see from the pictures below, the chamber is a mix of spare parts we found out in the garage that used to be parts of old equipment. The total cost of the chamber was $0.

This is the idea behind the chamber: PennDot drills cores of concrete from the road and test them in various ways to see how many air voids are in the concrete. The voids will effect the usability of the roads in various ways. If a core is halved it will sit in the vacuum chamber. When the air is removed from the chamber, an epoxy will be introduced to coat the flat section of the half-cylinder. This epoxy will have a special chemical in it which makes it glow under a UV light. When air is slowly re-introduced to the chamber, the epoxy will settle into the air voids. Once the core is dry and the epoxy is set, the core would be placed under a UV light where the voids could more easily be observed. Furthermore, a photograph could be taken of the core which would be put into an image processing program that another employee was developing in his spare time. This program would select all of the voids based on their color, and calculate the percentage of the specimen that was void space. This was the basic idea behind the experiments which Seth wanted to carry out.

The chamber presented some interesting design challenges. First and foremost, it had to be a secure vacuum chamber. In addition to that, the core needed a place to sit stably, but with easy cleanup. The chamber needed to be easily assembled for use but still air-tight, and able to withstand the vacuum pressure. The epoxy itself was a challenge. It could not be used on the core ahead of time because the time needed to create a sufficient vacuum in the chamber was greater than the time the epoxy was allowed to sit around. If the epoxy were mixed at the beginning of the process, by the time it could be used it would be hardened and useless. Therefore, I had to create a way to introduce the epoxy from outside the chamber without breaking the vacuum seal, and this too needed to be sufficiently easy to clean up.

This is a photo of the whole chamber in all its glory. There is a container on the top to hold the epoxy. A valve beneath it is opened and the epoxy is allowed to drip through. Since the liquid is blocking the way of air, the vacuum is maintained, and the valve may be shut before air enters the system. The epoxy then falls into a trough which can be dumped onto the core. In the bottom of the chamber is a holder for the core.

This is a close-up of the pressure dial. A hose leads from inside the chamber to the outside, to be attached to the vacuum aparatus It passes a simple pressure gage to judge when adequate pressure is reached for the experiment. The black thing beneath that can be pressed to slowly allow the vacuum to be broken in a slow, manually controlled manner.

Here is a close-up of the dumping mechanism. There is a handle outside the chamber that can be turned to dump the trough. The vacuum is mainted by use of the rubber stopper surrounding the metal rod.

When the side panel is removed (to remove the core), the trough would necessarily fall. It is kept up by use of a simple kick stand.

This is just a fun picture of the chamber stand which reads "Hogentogler". We found this metal peice in the garage from some old mystery equipment so we have no idea what it used to be but the named seemed silly and fun.