Well, bugger!

Today I gave my ventilation unit a thorough test. I connected it to a 12v battery and put the unit on a box outside then set it going, with a ventilation tube running into the bus.

It seems that I need to pump more outside air into the bus than that is capable of. The beauty of my design is that everything was filtered and it didn't take up a window unlike my previous design. That design worked but definitely could have stood some redesign and improvement. I'd still like an underfloor design and I still want to avoid air conditioning.

I think the problem with my system (built strongly and over a couple of months) is threefold.

• The Honda lawnmower engine filter just isn't big enough. Even with a CPU fan, it restricts the airflow. 
• The 1.5 inch tubing used is not big enough (shown).
• The CPU fan though blowing gallantly cannot override the other two issues.

After putting the newly built system away, I pulled out my old window based unit that I'd built from cheap battery fans and plywood. Although it's funky about which windows it'll fit into, it brought the temperature down from 95F to 91F fairly quickly.

It's not a unit I much care for but it does actually work. It's just two O2 cool fans from Walmart that I bought on sale a year or two back. The batteries had festered (Dollar General brand) but with some fresh Harbor Freight batteries it was up and running.

So, where now? Let's look at the list of options.

• I don't want to use massive batteries, solar arrays or a generator.
• I don't want an air conditioner of any variety.
• I want filtered air blown in from underneath. 
• I need air flow rather than cooling.
• I have two solar setups to draw from totaling 35W. 
• I did mentally design a ventilation system using a separate blower and filter unit.

Sitting here by my window unit I feel far cooler than I was before despite the temperature being only two degrees lower. The humidity has plummeted from 67% to 55% just in a few minutes. Clearly I need to push greater volumes of air through. 

I had been thinking of making filter changes easy by having filter access on the side of the vehicle. That, however, comes with other issues, the main one being the weight of the unit. Moving on from there, it should be possible given the steel just lying around nearby to build a big filter box or to obtain something similar from a scrap merchant. What I need is a 12v turbo fan to power it all.