After a couple of false starts where things went awry with my first weld and I had to cut the two pieces apart and start again, things went well. It's not going to sound impressive but what took all day was welding 4 pieces of steel angle into a rectangle and then adding 4 pieces of flat steel as a flange.
I tested my ventilation unit today. I simply placed the fan inside, powered it up and a reassuring roar of air came through. That roar was quite reduced when the filter was put in place but it still came though as a good breeze. I didn't measure how many seconds it took to fill a Walmart bag but probably it would not have been many.
It was ludicrously hot today. Inside the bus it was a scorching 104F. If it were not for my white roof and heat extraction fans, it could well have been much warmer.
While I tested my ventilation unit, I also tried it with some corrugated dryer tubing. The air whizzed merrily out of a 5 foot coil. I'm probably going to use dryer tubing to connect the ventilation unit to the floor vent (which is a sink drain tube with a stainless steel strainer top from Lowes -hiss, spit). I'm not anticipating huge amounts of air being injected but with air being blown in and air being blown out, there should be much more airflow.
One thing I neglected to do was to add a back support for my ventilation unit. It's way too heavy to have it hanging off the skirt. In fact, it might be better just to hang the whole thing from the ribs and have the whole weight supported that way while it's bolted to the skirt for the inlet and filter access.
Another (simpler) design would have been to have the filter and fan units separated and the inlet just being a louvered pipe coming out of the skirt. As it is, I have a ten pound monster that would probably survive an atomic blast.
My welding is 100% better now that I can see what I'm doing. My auto darkening helmet has made an impressive difference. Though I wait for my welds to cool I also play safe these days (after more than a couple of burns) and use a non contact thermometer.
This model tops out at around boiling point. I could have paid more to have one that measured up to 2,000 degrees but honestly I don't need to know that. Anything over 90F is untouchably hot anyway.
As I knocked off for the day, I had the most ferocious hand cramp. I'm guessing this has something to do with not enough fluids and a ludicrously hot day. Tomorrow, if I have time (it's supposed to rain) I might add supports to my ventilation unit and make a start on putting a hinge on the door and putting a louvered vent cover on.