Prototype 3.1 wrapup
May. 24th, 2022 01:54 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
solarbirdSo we have finally - much later than usual! - reached the end of heating season, and I've pulled prototype 3.1 out of service. I was expecting to be lucky if we could run it through March, but we made it halfway through May!
Functionally, it's worked out exactly as well as I'd hoped. It continued providing small but meaningful heat recovery throughout the operating period - enough to feel, and because of the way airflow works in our house, enough to detect upstairs at times - without overloading the house with humidity.
Based on observations from this single turnover period, I'm pleased (and somewhat surprised) to see that we don't in fact get humidity overages while the unit is still worth using for heat, even given a very wet end of heating cycle. (We've had a very wet May.) I did have to turn on a small secondary fan to push warm air out of the laundry room occasionally to prevent condensation on the window, but that's the worst it got, and we're obviously still coming out overwhelmingly ahead on cost even with that.
Also, the metal door retainer worked fine, preventing the filter from bulging much (it did a little, but a very little) and coming out of fit, a concern I had after Prototype 2. The primary filter overall shows very little sign of change of any kind, which is exactly what one would hope to see.
Structurally, the HTPLA held up very well, and the PLA feet also appear to have held up similarly well, and the plastic material I bought for the sidewalls also held up fine. But there's been one disappointment: while I used two kinds of specifically plastic-friendly adhesives, neither of them maintained a good grip on the sidewall plastics. I had to do emergency repairs on two of the four major side joints, and at the very end, a third side joint started to fail as well.
Because of this, I've only got one weekend so far of closed-face testing out of Prototype 3.1 - the weekend of May 21st-22nd. With the front face is closed off - something which in and of itself worked perfectly, no issues with the HTPLA front frame made themselves visible - the additional air pressure inside the unit made the third side joint failure visibly worse in a very short time, with an air leak forming fairly quickly. I was able to tape it together, but obviously, that's unacceptable.
Within the side-frames themselves, I'm entirely confident I can address this simply by screwing all sides together, as I did with the emergency repairs a couple of months ago. While the plastic in question is not capable of gluing adequately for long-term structural survival, the areas where no such load was placed on the object maintained their air seals perfectly well, so I think that will be a reasonable solution.
I also intend to improve the leg attachments a bit, despite the fact they held up just fine as they are. There's some unnecessary gapping that I can address, so I will, for long-term stability.
I'm more concerned about the HTPLA backplane's stability, given that it is also glued into place. Should I decide to build a prototype 4, I think I would find some way to router out a groove in the side components for structural support, given that one corner of that has adhesion issues now too. (Same cause, of course.)
Alternatively, I could just go with a different plastic for the frame, something that takes plastics glue properly. But it's quite unlikely I'll do that, given that there are summer tests I want to run with the basic design in place as it is.
So my immediate plan is a third iteration of Prototype 3, a Prototype 3.2. It will be a repaired and slightly-upgraded Prototype 3.1, using the same components. The primary changes will involve simple strengthening. It will then be reinstalled for a summer of leak, pressure, and lint collection tests.
And then we'll see what happens.
Functionally, it's worked out exactly as well as I'd hoped. It continued providing small but meaningful heat recovery throughout the operating period - enough to feel, and because of the way airflow works in our house, enough to detect upstairs at times - without overloading the house with humidity.
Based on observations from this single turnover period, I'm pleased (and somewhat surprised) to see that we don't in fact get humidity overages while the unit is still worth using for heat, even given a very wet end of heating cycle. (We've had a very wet May.) I did have to turn on a small secondary fan to push warm air out of the laundry room occasionally to prevent condensation on the window, but that's the worst it got, and we're obviously still coming out overwhelmingly ahead on cost even with that.
Also, the metal door retainer worked fine, preventing the filter from bulging much (it did a little, but a very little) and coming out of fit, a concern I had after Prototype 2. The primary filter overall shows very little sign of change of any kind, which is exactly what one would hope to see.
Structurally, the HTPLA held up very well, and the PLA feet also appear to have held up similarly well, and the plastic material I bought for the sidewalls also held up fine. But there's been one disappointment: while I used two kinds of specifically plastic-friendly adhesives, neither of them maintained a good grip on the sidewall plastics. I had to do emergency repairs on two of the four major side joints, and at the very end, a third side joint started to fail as well.
Because of this, I've only got one weekend so far of closed-face testing out of Prototype 3.1 - the weekend of May 21st-22nd. With the front face is closed off - something which in and of itself worked perfectly, no issues with the HTPLA front frame made themselves visible - the additional air pressure inside the unit made the third side joint failure visibly worse in a very short time, with an air leak forming fairly quickly. I was able to tape it together, but obviously, that's unacceptable.
Within the side-frames themselves, I'm entirely confident I can address this simply by screwing all sides together, as I did with the emergency repairs a couple of months ago. While the plastic in question is not capable of gluing adequately for long-term structural survival, the areas where no such load was placed on the object maintained their air seals perfectly well, so I think that will be a reasonable solution.
I also intend to improve the leg attachments a bit, despite the fact they held up just fine as they are. There's some unnecessary gapping that I can address, so I will, for long-term stability.
I'm more concerned about the HTPLA backplane's stability, given that it is also glued into place. Should I decide to build a prototype 4, I think I would find some way to router out a groove in the side components for structural support, given that one corner of that has adhesion issues now too. (Same cause, of course.)
Alternatively, I could just go with a different plastic for the frame, something that takes plastics glue properly. But it's quite unlikely I'll do that, given that there are summer tests I want to run with the basic design in place as it is.
So my immediate plan is a third iteration of Prototype 3, a Prototype 3.2. It will be a repaired and slightly-upgraded Prototype 3.1, using the same components. The primary changes will involve simple strengthening. It will then be reinstalled for a summer of leak, pressure, and lint collection tests.
And then we'll see what happens.
