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Portable Air Conditioner Awning Window HVAC #6: Supply/Return

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Blog entry by DevinT posted 03-29-2021 01:17 AM 576 reads 0 times favorited 7 comments Add to Favorites Watch
« Part 5: Mistakes were made Part 6 of Portable Air Conditioner Awning Window HVAC series Part 7: Thermal curtains, Banksy, and Gee Fix »

The air conditioner that we settled on was a dual-hose kind. That means that there is a separate hose for the supply air and the return air. There are to be 2 holes in the shelf for the ductwork.

However, we have a slight problem. If we attach the ductwork to holes created in the shelf, then it will technically be compressed by 3/8” when we swap the 3/4” ply for 1 1/8” walnut. This does not seem like a problem, but it is for the design and function of this system I am building to go around the AC unit.

Quick-Links to videos found in-order below:
  1. https://twitter.com/freebsdfrau/status/1313656503690166273
  2. https://twitter.com/freebsdfrau/status/1314387824200740865
  3. https://twitter.com/freebsdfrau/status/1314394563348320256
  4. https://twitter.com/freebsdfrau/status/1315101079034458114
  5. https://twitter.com/freebsdfrau/status/1315102554133393408
  6. https://twitter.com/freebsdfrau/status/1316182664051740672
  7. https://twitter.com/freebsdfrau/status/1316183311316705280
  8. https://twitter.com/freebsdfrau/status/1316183506079289344
  9. https://twitter.com/freebsdfrau/status/1316183900696141824
  10. https://twitter.com/freebsdfrau/status/1316543635693871105
  11. https://twitter.com/freebsdfrau/status/1316546122186252288
  12. https://twitter.com/freebsdfrau/status/1316552828819664896
  13. https://twitter.com/freebsdfrau/status/1317317870443876352

So, before I can make the duct holes in the shelf, I will need to make 3/8” risers for the duct connector so that it connects at the proper height, equivalent to the final product dimensions.

I didn’t need anything super flat for these risers because the duct is flexible and a I could tolerate being even up to 1/32” out of co-planer for these risers. Somehow, I found a store that had 3/8” pine ply. It certainly wasn’t pretty but it was cheap and was perfect for the job. Bought a whole sheet and had the store cut it down so I could fit it into my tiny car.

(video) https://twitter.com/freebsdfrau/status/1313656503690166273

(below image) It’s not pretty stuff, but will be more than functional.

(below 4 images) I measured the ductwork (diameter and bend radii).




(below image) and added 1” to give me some material to screw the duct flange into (flange not shown). I used a large compass to draw the rings that I would use for duct risers onto the 3/8” ply. I positioned the ring around a knot so that I wouldn’t have to worry about it.

(below 6 images) I really wanted this piece to stay down after routing it out, so I transcribed the circles to the 3/4” ply spoil board and laid a bunch of double-stick tape within the boundaries.






(below 2 images) I clamped everything down, made a little barrier to separate the tools from the sawdust, and put a nail into the center of the ring (you’ll see why in a bit).


(below 2 images) I have a Milescraft small circle router compass jig. That nail we put into the center of the ring? The compass rides on that to swing a circle of pre-determined distance.


But, you know the Ryobi router doesn’t plunge and I’m a little bit uncomfortable turning the micro-adjust wheel while it is operating (or at least, I was at the time, so I piloted a hole for the router bit before using the compass).

(below 2 images) The bit is a 1/4” compression bit from Align Carbide. Pretty much the most affordable compression bit I’ve ever seen and it does a really nice job on so many things that I throw at it. It even creates a really nice matte finish on acrylic edges when jointing at the router table—but I digress.


(below 5 images) Using a spade bit I measured a point where the outer diameter met the ring from the waste side. That is where I would pilot before plunging the spade bit.





(below 3 images) I inserted the router into the jig, swung it around to align the bit with the hole I created with the spade bit, and plunged it into the material manually while still off. I could now start the router in-air at the proper depth and sweep into the material to make the 2 cuts to form a ring.



(below 3 images) I laid down another pilot for the spade, which still had my depth-stop painter’s tape ready to go, and made another hole for the outer cut.



(below 2 images) This cut has the same center as the last one, so all I did was extend the jig to make a wider diameter sweeping motion.


(below image) Used my putty knife to free the ring, and voila! One duct riser.

(below 2 images) And now I have one of those boards where you put your face into for silly pictures (if I ever wanted one) and the spoil board is no longer virgin.


(below image) I flipped the board around and marked out positions for the second ring, made a pilot for the router bit, and got everything set up.

Here is the inner ring cut: (video) https://twitter.com/freebsdfrau/status/1314387824200740865
Here is the outer ring cut: (video) https://twitter.com/freebsdfrau/status/1314394563348320256

ASIDE: Spoiler alert! I didn’t cut all the way through on the outer ring. Went to go release it and it was stuck. Pulled up the board and I didn’t cut all the way through.

(below 2 images) I had to have another go at trying to release this second ring.


(below image) Making a second attempt to free the ring.

Awwww, crud. Well, you can’t make the second cut if your center point is gone. We’ll have to bring that back and nail that sucker all the way through. Thankfully there was a pin-hole mark left in the spoil board telling me exactly where to place the center puck.

(below image) Have to put the center puck back otherwise we’ve lost-center.

The final cut to free the second ring: (video) https://twitter.com/freebsdfrau/status/1315101079034458114

ASIDE: I now recognize quite clearly the sound of chattering which would have been almost eliminated if I was taking shallower passes. This thin 3/8” ply in my experience chatters.

(below 2 images) I am fairly confident that I’ve gone all the way through the top ply now. Yes, pretty certain.


I might have used a bit too much double-stick tape: (video)
https://twitter.com/freebsdfrau/status/1315102554133393408

(below image) This ring gave me a fair bit more work than the first one. But, hey, now I have my 2 duct risers.

(below 3 images) Let’s make sure that the dimensions are good and they fit the intended hardware:



I was actually off. Shoot. Had to cut a replacement for one of the two rings.

Cut 1 of replacement: (video) https://twitter.com/freebsdfrau/status/1316182664051740672
Cut 2 of replacement: (video) https://twitter.com/freebsdfrau/status/1316183311316705280
Replacement reveal: (video) https://twitter.com/freebsdfrau/status/1316183506079289344
Replacement release: (video) https://twitter.com/freebsdfrau/status/1316183900696141824

ASIDE: Used less double-stick tape this time and it was certainly easier to release.

(below) Phew, that was quite a bit of work, let’s see if it all panned out:

Looks good! No, looks great! Hmmm, but I’m not exactly digging those sharp corners on the shelf. Someone could get hurt. I struck a 30mm taper on each leading corner, clamped down a guide, and hogged off the material:
(video 1) https://twitter.com/freebsdfrau/status/1316543635693871105
(video 2) https://twitter.com/freebsdfrau/status/1316546122186252288

ASIDE: When I say hogged-off, I perhaps was a bit aggressive. If I did that over, I would probably have been a little more gentle (and done multiple passes). I now know that 3/4” on a single pass is asking for a bit much (hey, I was still learning how to use it—I keep it to no deeper than the width of the bit now).

I then threw a beveled edge on the thing:
(video) https://twitter.com/freebsdfrau/status/1316552828819664896

(below 4 images) I took everything back upstairs and did a dry fit.




ASIDE: Note how these flexible hoses are not even extended. They are 100% compressed. That’s part of the system I am creating where the supply/return are on the shortest possible run, but also note that the walls of compressed tubing is far greater than that of when fully expanded. That’s really going to eliminate the need to further insulate this ductwork.

I am really pleased so-far, it’s time to transcribe those rings onto the shelf and cut the holes out.

(below image) Using Thale’s Theorem to find the center of the transcribed circles.


(below image) So we it was time to cut the actual holes for the actual duct termination (bootless, but a termination nonetheless).

It was late into the night when I finished cutting the first hole and had to get to bed:
(video) https://twitter.com/freebsdfrau/status/1317317870443876352

(below 3 images) Once I got the second hole cut, I quickly brought it back upstairs to test drive it, once again. I just used blue painter’s tape to re-attach the rings and put things back the way they were before I cut the holes. I threw in some cheap metal vent covers that I am using for the prototype, not the nice bronzed Corinthian covers.



However, we aren’t quite done yet with the supply/return.

(below 13 images) It’s finally glue-up time for the duct risers.













(below image) Then I buttoned it all up with screws.

Here is how this step turned out:

-- Devin, SF, CA



7 comments so far

View pottz's profile

pottz

16138 posts in 2036 days


#1 posted 03-29-2021 03:02 AM

you amaze me “jilly” im totally impressed with the stuff youve presented us in just a few days,i would like more pic’s though,kinda vague-lol. the only one that competes with you on pic’s are my good friends lbd (duckie) or mafe (mads)

-- working with my hands is a joy,it gives me a sense of fulfillment,somthing so many seek and so few find.-SAM MALOOF.

View DevinT's profile (online now)

DevinT

262 posts in 18 days


#2 posted 03-29-2021 06:30 PM

Thank you pottz. I’ll keep it coming ;D

-- Devin, SF, CA

View kaerlighedsbamsen's profile

kaerlighedsbamsen

1359 posts in 2765 days


#3 posted 03-29-2021 08:04 PM

Would love to read along but see no images at all in this whole blog series. A shame as you clearly put a lot of work into it

-- "Do or Do not. There is no try." - Yoda

View DevinT's profile (online now)

DevinT

262 posts in 18 days


#4 posted 03-29-2021 08:18 PM


Would love to read along but see no images at all in this whole blog series. A shame as you clearly put a lot of work into it

- kaerlighedsbamsen

I’ve tried 10 different versions of Firefox, Safari, and Chrome on 4 different Operating Systems, and they all see images fine. What OS and browser are you using?

-- Devin, SF, CA

View pottz's profile

pottz

16138 posts in 2036 days


#5 posted 03-29-2021 09:45 PM

yeah i see the pic’s fine,lots of em.

-- working with my hands is a joy,it gives me a sense of fulfillment,somthing so many seek and so few find.-SAM MALOOF.

View kaerlighedsbamsen's profile

kaerlighedsbamsen

1359 posts in 2765 days


#6 posted 04-01-2021 06:08 PM


I ve tried 10 different versions of Firefox, Safari, and Chrome on 4 different Operating Systems, and they all see images fine. What OS and browser are you using?

- DevinT


Hmm that´ s weird. Firefox 86 on Osx 10.15.7

-- "Do or Do not. There is no try." - Yoda

View DevinT's profile (online now)

DevinT

262 posts in 18 days


#7 posted 04-01-2021 06:37 PM

One of the combinations I tested was Firefox 87 on Mac OS X 10.14.6 (Mojava). Maybe it’s a Catalina issue?

-- Devin, SF, CA

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