<snip> like these tiny blowers that take a month to arrive from China. <snip>
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I know it's kind of a Mickey-Mouse-ish solution, and the output might be somewhat anemic compared to the ones you're trying to order from the Far East, but Academy sporting goods sells personal fans that work on the centrifugal principle (those weird little boxes that hang from a cord around one's neck). Also might have to do some major modification to their housings to make them fit with your design, but at least they aren't all the way over in China.
Indeed. I had not seen those. Thank you for the suggestion! The other solution was to look at rubber camping mattress inflators. The time is prohibitive online. I sorely miss being able to go to Radio Shack /Fry's, what have you and being able to prototype in a day. This online shopping thing is not all that it's cracked up to be.
On the other hand, I have good news: Texas will begin Phase 1c this 15th of March. That includes anyone over 50, which means I'm old enough to get the vaccine!
Also, I have finally achieved positive pressure inside the mask. It's very close now to becoming functional.
I started by chopping off the top of the threaded cap and gluing another PVC cap to make a larger stagnation chamber. Then I increased the diameter of the tube and chopped the length quite a bit. I noticed that the plastic spigot (you can see that glued at the top of the little tank/stagnant chamber) was in fact a standard 1/2 inch copper pipe diameter.
That is in fact its purpose. It was a plastic spigot to PEX adapter. Which means the outer diameter is compatible with many couplers plastic or copper. I got a half inch vinyl pipe and I used the plastic coupler as a quick disconnect for the mask.
On the opposite end, I used a large diameter lamp threaded rod, which happens to hold tightly to the vinyl tube and can be screwed into the wood... Being very careful not to split the wood, as it is rather narrow on that side of the mask.
I found that with proper sealing around the face à diameter of 0.9cm to 1.1cm at the inlet was enough to increase flow into the mask.
The pressure is such that air will escape through any nook and cranny left open around your face. You want to seal all around your face and open a hole large enough to be an exhaust (it will be filtered with a single layer of 3M spun melt). I can feel air continuously escaping through the outlet and increasing as I exhale air from my lungs. What I still need to prove is that even if I inhale that nothing will come in through the exhaust. I could also build a valve if I need to, like in the 3M masks. But I'm hoping I have enough pressure to not need it (I will have to do an experiment.
For the sealer around the face I, sliced the pipe insulation in half to use in both sides, because after the Texas snow storm there is very little insulation left. There are very few pipe accessories left in the shops, actually. But it turned out to OK. For the strap, I recycled the plastic helmet head band, attached with 3M double sided foam tape (the super sticky kind) , and screwed it to the wooden frame. I recycled part of the headband from the 3M visor and used it as a rubber cushion also, attached with 3M tape. Inspired by the helmet headband system I used a parachute belt as a simple vertical headband that goes over the top of your head. The plastic horizontal band goes over the ears and I modified the back strap with a heavy duty snap button. This insures that the mask is securely tied and is as easy to put on and take off as any other mask. It's actually very comfortable and secure. The soft foam easily adapts to spectacle wire frames. If the glasses become misaligned, you can straighten them just by pulling the "hooks" of the frame being your ears. No need to take the mask off.
There was no need for insulation at the bottom. The wood frame is heavily lacquered and fits perfectly over my chin. Part of the weight of the mask rests on my chin. In fact you have to allow the chin to slide a bit so you can talk, but I find the system works perfectly. I had to put a little extra foam on the headband to adapt to the temples, but otherwise the profile I cut on the frame was perfect. It should be much more comfortable than my old mask.
I received the ultraviolet LED strip. It's powered by a 5 volts source and in fact you can cut it in segments, each powered by 5V.i don't think I'll want to cut it though. I'll try to coil it inside the cannister. There are two types of LED modules. The fancy brass-looking modules emit the invisible UV-C light. The white modules emit the visible UV-A light. I taped the strip to a square wooden dowel, so I can experiment with it. I have yet to find a UV reactive material to play with, so I can confirm it's working. Otherwise, the UV-A LEDs produce a blue-purple light.
It's looking good so far. The filters are trivial, because they're the same type I make for the other mask. Left to do is confirm positive pressure during inhalation, test UV-C lights, finish vertical head band and then start work on the battery. During the snowstorm, I had to fineagle a 12 V to USB adapter to use to recharge my phone. During the storm I realized that the 12v auto cigarette lighter adapter you buy at the pharmacy is actually a solid voltage regulator on a chip. This allows you to covert any DC voltage from 24 volts down to 9v (or even lower) to 5v for a USB power connection. I successfully ran my phone on a 9v battery. So I found that my handheld inflator uses an 11 V 2000 mAh battery, which with the voltage regulator could function as a 4000 mAh 5v battery. I could even use AAA, AA, C or D size batteries provided I can make the regulator work with 6v
So things are looking good! Naturally now that the vaccine is around the corner...
Cheers!
