*Fan In A Drum* April 7, 2005 A friend asked if I'd be willing to make a saferoom fan for them. Seeing how I made one not that long ago, I figured that it would be a simple thing to make another one. Unfortunately, neither of us was able to find an ammo can that was the same size that I had used before. Seems the ammo can I had used was a "30 MM" can and the common cans currently found in surplus stores are the "20 MM" variety. Having already bought the fan from Grainger (#4C447), I set out to find a suitable container for the unit. I knew that I could build a wooden box that would have worked just fine, but I really liked the ammo can idea as is was stronger, more rugged and provided a more secure seal that needed less maintenance. After trying every metal can in the local surplus stores, I found a sealable drum that would fit the fan, so I decided to see if it would work. (For reference, this drum had cost the same as the 20 MM ammo can.) The military sealable drum. (The roll of paper towels is for size reference.) I have no idea what the drum was originally used for, but it has a gasket seal on the lid and seals with a brass bolt and nut on the drum ring. It looked like a great container for this purpose, but it posed a couple of issues on how the intake and exhaust was going to work. I finally decided that everything could be accomplished with some PVC piping. The first thing I did was set upon mounting the fan. I decided to mount the fan on a slight angle, so that the drum could be used to (hopefully) store all the Fan-In-A-Drum (FIAD) and saferoom items inside. I also hoped that the offset would allow the fan to be more efficient since there was more "room" on the intake side. I have
no real way of knowing if it helped or not. Here is the lid, showing the markings for the fan mounting points, and the first holes drilled to allow cutting. As with the first fan, the only power tools I had to work with were a drill and a jigsaw. These worked well enough that I didn't entertain the notion of buying other tools, though I'm certain there are easier ways of cutting. All cutting was followed up with a grinding stone and wire brush on the drill to make sure that there were no sharp edges or burrs. Now for the tricky part. The lid of the drum wasn't large enough to accommodate two PVC flanges, so I had to modify them in order to get them on the lid. PVC is a relatively soft plastic and was easy to modify. As you can see in the pictures below, the modifications were fairly simple. On one of the flanges, I had to remove a little extra in order to mount the bolts for the fan flush to the lid (yellow arrows). The picture on the left shows the PVC flange the and knockout plug that had to be removed. The right picture shows an unmodified flange and one after modification. Even after modification, the PVC flanges would only fit on the lid in a certain way, so I had to mark the lid so I
knew exactly where the flanges would go. I also had to do a lot of test fitting to ensure that everything could be bolted into place without interfering with the other bolts or the fan. These images show some of the markings used to make sure that the flanges would fit. The picture on the right show the lid after all the intake, exhaust and bolt holes were made. It also shows the cord mount for the fan cord. Once the holes were all made and everything test fitted together, it was time to wire the fan. It's a simple wiring job to do. The Grainger fans need a small length of wire to attach to the ground mount. After attaching a wire clamp to the frame, I threaded the cord through and attached the wires. I used wire nuts so that it would be easier to access the wires if the need ever arose. A before and after set of pictures showing the fan wiring. Note the yellow arrow that shows the extra wire on the ground mount. This wire is connected to the green wire of the AC cord. Once the fan was wired up, all that was left to do was assemble everything making sure to apply a liberal amount of silicone to all potential leak points. Not thinking it through, I attached the fan first, which turned out to be a mistake as I couldn't access all of the bolts for the PVC flanges (the fan was in the way of, at least, one of the bolts). After removing the fan and the silicone, I attached the PVC flanges, then reinstalled the fan.
Showing the lid assembly with everything attached. The left picture shows what it looks like underneath, the right picture shows what it looks like on top. Once I finished putting all the hardware together, the only thing that was left was to put the rest of the PVC piping on it. For shipping and storage purposes, the PVC pipes were not siliconed in place. When the fan is needed, it will be a simple matter to silicone the joints or to use the metallic duct tape to seal any potential leakages at the pipe joints. This configuration takes full advantage of the latest thinking on the Rubicon about being able to use any HEPA filter available. All that's needed to be done is simply create whatever housing that is needed to hold the filter and attach it to the upper PVC mount. One could even go as far as to create several of these filter housings, each with its own PVC mount in order to make very rapid filter changes. Though, considering how long most HEPA filters are rated for, I doubt that such extra housings would be necessary.
Here is the finished unit. The picture on the right shows the PVC in a little closer detail. In the below picture, a piece of (very oversized) wood and a Holmes HAPF600D HEPA filter sit atop the PVC mount where the filter would go. You can also see the bead of silicone that has been added to all seams for extra leak protection. The picture on the right is the silicone I use (for reference).
In many ways, I prefer this FIAD to the FIAC due to its design. As already noted, the ability to mount different filters on it has distinct advantages, plus the height of the filter above the ground should help prevent it from having to filter out the heavier particulates. This unit is also much quieter than the FIAC. This design also allows for a variety of hookups. A length of PVC pip can be attached to the exhaust portion to increase the distance of the unit from the shelter, if that would be needed for any reason. Also, it would be fairly easy to route the intake portion through an exterior wall or window and mount the filter on the outside of the house/shelter. Seeing how well this worked, I would think that any steel drum would have similar results, as long as it had an airtight seal.