Sunday, June 25, 2017

Temperature differential

Its cloudy and midday. The temperature outside is 78.8 but inside the bus it's 86. That's a small difference though I'm sure it gets more on hotter days. At least it's not the 140 that I recorded two years ago inside.

I've rethought my ventilation unit. While I could patch what I have by increasing the tubing size or adding a second fan, what I've opted for is a radical redesign. This time I'll use a 130CFM marine bilge blower. That's a bit more powerful than my existing CPU fan. At least it's a dedicated fan!

Thinking more along those lines, because the fan I ordered is 3 inch (I should have gone for 4), I can still use my sink tailpipe as an inlet though I might want instead of using just one which is 1.25 inches in diameter, to use two. The surface area of one tailpipe is 3.927 square inches while the surface area of a 3 inch tube is 9.425 square inches. Having said that, since the whole of the tailpipe is not open, it could be worth using three or even four. That would allow me to spread my ventilation around the cabin and even into the cockpit. Alternatively I could just cut a square hole in the floor and after treating the bare edges, put a square vent with a vent cover.

The new fan which should arrive on the 30th is much more powerful at 2.5A. It might be all my front solar panel can handle. At a maximum 15W or more likely 10W, it would take about three times as long as the fan runs to charge the battery. As I found with my rear extraction fans, the best way of doing that is to use a small battery and thus increase the cycling. When the weather gets colder and the bugs have gone, I'll be able to get underneath the bus to install everything, including extra underbody cabling. I will probably connect the solar panels in order that the power can be better utilized.

As far as filtering is concerned, an increase in filter size is definitely in order. I'd been thinking solely about vehicle engine filters. Now I'm wondering whether Hepa air cleaning filters might be a better route since they're bigger and designed for faster airflow. Having said that, they do allow more garbage through and they're not as resilient. It's a toss up, to be honest. Rather than building a brand new filter holder from scratch, I'm tempted to return to my old idea of using an ammunition box to hold the filter. It wouldn't take much to cut some sheet steel, tack weld it into place and seal with silicone sealant. Nor would it take much to build a little trap to hold it in place. Suction from the fan would pull it more firmly into place. I'm tempted to make it accessible solely by going under the bus and changing it in the winter only. That way I can just have a straightforward ducted vent on the skirt with nothing heavy involved. Even the commonly available vent tubing is light weight.

Many people ask why I don't just put an air conditioning unit on and have done. Sure - I could do that. I don't want to though. I'd rather do it this way so I can avoid adding too many solar panels and or batteries. I do have a 120V plugin and I really don't want to put an AC unit in. They're big and bulky and I'm not too sure how good my structural welding is.

Speaking of welding, I started on my power supply unit today. The plan was to use an ammunition box as the base. As usual I started with complicated ideas first. The intent was to put an XLR socket plus a panel mount fuse for each of two batteries plus a switch. I was going to weld some holders to keep the batteries from slopping about in the box too. As usual though, reality sets in.

The first thing I did was to haul out my welder and weld a holder. Needless to say, the first weld was very strong but in completely the wrong place. My carefully inked line moved all by itself and the bar I'd welded was half an inch out from where it should have been. Disillusioned, I put my welder away and went with another solution.

I'd had plenty leftover plastic planking from doing the bathroom floor. They'd been lying in the yard for two years but that makes little to no difference as they don't decay or get attacked by bugs. A few minutes with my marker (this time I watched my line carefully in order that it didn't getup and move. These pesky lines are awkward like that) and then a few minutes with a hand saw and my pieces of plastic were cut.

Finding panel head screws was challenging but since I organized my screws and bolts better, it was significantly less challenging than before. If only I could say that about my tools! So, the next thing was to drill holes through the case and into my plastic pieces. That actually worked quite well.
The next stage was to connect wires, fuse holders and terminals to the batteries and the ammunition box. That actually went along quite quickly and I remembered my heat shrink sleeving. I'd never used it before but it worked remarkably well. I'm a convert! I'm not sure where I'll find heat shrink sleeving now that Radio Shack has gone under.
The fuse holders and in fact most of my useful electronics came from Radio Shacks going out of business sale. I spent $20 and got probably $50 worth of stuff though at Radio Shacks normal prices they'd probably have been $250 or thereabouts.

I've used banana plug terminals that also accept spade connectors. It's completed as it is but there are always add one that can be included. The main reason I didn't use my XLR connector was I needed to drill a one inch diameter hole and my biggest drill bit is 1/2 inch. My step drill bit committed suicide a while ago and I've not replaced it.

My next task will be to put the correct connectors onto leads from my charge controllers in order to use my new battery compartment. I've chosen an ammunition box because it's sealed with an airtight seal and is non flammable. My batteries are all sealed so they shouldn't leak or anything but a steel box should ensure safety. Any fire should rapidly smother itself. The ideal would be to install these batteries under the bus for safety, which I might do in due course.

The battery box is not currently in use but will be next weekend or even perhaps on Tuesday. Tuesday is not a normal bus day. In fact, it should be a work day but I've had to take the day off to go and visit the IRS. It seems my employer went and lost all their payroll information and thus false claims have been filed and I have to go and prove who I am. So, after that, I'll probably come home and do some bus work.

There are two batteries in the box. One is a 10ah battery that'll run my induction fan. The other is a 5ah battery that normally runs my extraction fans. Currently I've got one of my two 7ah batteries doing the job until I can put the right connectors together to connect the battery box to my charge controller.

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