Howdy gents. Well, I finally finished up my plenums. There is always something that takes more time to build templates etc than to do the actual project. This one is no exception. In order to cut 2 round holes in the plenum side and the fan mounts, I first had to build a routing jig to cut the holes. And it had to hold down 2 different size parts. The holes had to be the exact size of the INSIDE DIAMETER of the fan housing themself. There is only 1/16th in difference between the inside and outside of the fan housing. The only thing I could find to ride the router bit bearing on was the inside diameter of a plastic drain pipe. No big deal. I simply cut two pieces 3/4" long, cut a hole the in the middle of a piece of 3/4" plywood to hold both template rings precisely where the holes had to be in relationship to the piece being machined, and hot glued them in place. Took two hours to build the jig and only 4 minutes to route 2 holes in four pieces. Such is machining work. The same jig could be used for one or a thousand parts. In this case, only one plenum side and a fan mount per plenum were required. Here is a pic of the template jig.
Here is the finished side before glueing it on the plenun. Note the small piece of 703 at one end of the baffle inclosure. There is another piece at the other end of the 90 degree duct bend(can't see it here) to stop longitudinal standing waves. I don't care about vertical or sideways standing waves. At least thats the theory(these would be "modes" of the plenum inside dimensions I believe, but fan noise is what I'm trying to absorb)
Here is the "fan motor mount" with 1/2"x 5/16" weatherstripping foam applied to the back side. This(supposedly)will isolate fan motor vibration from the plenum itself. We'll see. I'm sure an engineer would calculate this stuff and test it. Well I'm no engineer
A tape job to spread a little contact cement on the plenum side and to the foam on the fan mount.
Here is the finished assembly
Here is the fans mounted(remember there are TWO assemblies)
And here is one plenum installed. I just slips into its position. Nothing to hold it but the 703 and some weather stripping "iso" pads at the junction to the plenum opening.
Now for the tough one. The exhaust fan "manifolds" and slot fans plenum. Good god, at this rate I'll finish about 2010.
