Got a lot done today and really got into the heart of the beast. I added the bottom cold outlet since I wanted to be sure it would go in with the footing heights that I chose. It works. I then built the roof, the fan opening, the support ring, the venturi and got most of the fan drive built. It's really coming together and is a nice, not-so-long project which is refreshing.
To install the outlet, I doubled the floor thickness so there'd be some more stock to hold onto the pipe fitting.
I used 0.020" styrene for the roof. It's quite thin and overly flexible so it needed some structural support and doublings to firm it up. I use ABA to do the doubling.
To cut the hole (which BTW: is not centered, since I made a mental math error when I divided the length in half) using my special dividers that have a point on one leg and the other sharpened to a chisel edge so it can scribe the styrene. After scribing the diameter, I open up the center with the skinny razor saw and scribed radial lines to facilitate breaking out the inside piece. You have to pay attention when using these modified dividers. The chisel edge can wander inwards. I find it best to hold the dividers still and rotate the workpiece under it.
I cut a similar hole in the ABS that I was using underneath. I then added some Evergreen I-Beam stock for further stiffening.
On top, goes a thicker ring which supports the venturi and adds rigidity to the fan housing. I scribed this onto the 1/8" ABS included in the kit and roughed it out with a coping saw and then worked closer to the line with a jewelers saw.
After sawing I final shaped it with the Dremel and sanding drum for the i.d. and the belt sander for the o.d. I made a little sawing booboo and got over the i.d. line in one spot. I thought about redoing it, but decided it would really not be noticed and it was a lot of work to get it this far.
I used spray glue to adhere the venturi template to some 0.020" styrene and cut it out with a scissors. I left a bunch of stock off the end since I wanted to final fit it on the model. I used a piece of the same stock to form the joint reinforcement, and glued it similarly as I did with the transition piece of the Flare. I got it to fit perfectly and it exceeded my expectations since I was worried about this particular step.
While the venturi was setting up, I built the fan support structure out of two pieces of 1/8" X 1/4" styrene stock that I did a cross-lap joint. It's a lot easier to make a cross-lap in wood than styrene. First it's laid out, then using the thin razor saw to start the cuts, finished up in the miter box to half the depth. Then make a bunch of in-between cuts to make it easier to chisel out the waste.
After gluing them in position, I added brass pins since this is a pretty critical part and if it were to break loose, it would be really hard to fix. You can also see all the extra reinforcement added to strengthen the roof.
I used the hermaphrodite calipers to re-locate the center of the opening onto the fan frame since I didn't measure their location accurately when gluing. I then drilled a pilot and a #31 drilled hole to pass the 1/8" Plastruct #4 tubing which I'm going to use as the fan axle.
With this stuff all glued in, I test fit the now-dry venturi.
I have some Plastruct motors, but no fan pulleys, so I had to machine some. The piece of aluminum stock I used for the large fan pulley was a bit long to just hold in the chuck and it kept trying to pull out and do some major injury to me. So I hack sawed the part I was machining off the larger chunk and re-chucked it so I was cutting closer to the chuck and created a very passable 3-belt pulley.
I used some smaller stock for the motor pulley and it was much easier to machine without as much drama.
I made a little block mount to hold the motor to the support structure and again, used brass to pin it in place. This was a test fitting. I'm going to paint everything before adding the pulleys and the E-Z Line belting.
The roof doubling will also serve as a secure base for the hot water inlet which comes in from above through the roof. Next up will be to create the fan. I'm noodling whether to build it from styrene, brass, or a combination. With brass I could solder it together so it would be very secure and I would be easier to bend an airfoil shape for the blades, but it's much more difficult to work. It's not going to rotate and no-one can touch it, so styrene would work okay too. I still have to plan for the lighting on top. The prototype shows two lights on each module, and I'll need to built reinforcement for this as I go forward. The roof won't go on until everything is painted and ready to go since I need to install the black screening AFTER painting and the roof needs to be off to do this. I'm also working on how to best install the screening. I'll let my subconscious work on this for a little while and see what it comes up with. I don't know if it's unique to me, or people like me, but I will actually build what I'm doing in my mind in many different ways until I arrive at a reasonable solution. I pre-visualize a build kind of like Jack Nicklaus would pre-visualize playing a specific golf course.
As a refresher, here's the prototype. Notice the switchgear and electric wiring which could be nice to add. I don't know what that array of tubes do that are going up the side.
