Cabin pressurization system to prevent dust infiltration.

[John E Davies]

Teaser:

 

 

I am sure dust is leaking into lots of places I haven't seen yet, like all the scupper drains and the roof vent. For sure I see it around the door seal near the hinges and the bottom, the aft outside storage door near the shower, and I am getting serious leakage under the fridge ... but that one is most probably a bad seal behind the flanges of the unit that I can fix:

 

 

The Aussies do this all the time to deal with "bull dust". The basic idea is that you add positive pressure (clean, highly filtered air) to the cabin, shut all vents and openings, and the air leaks out any places dust would normally enter. As tight as the ollie is, it would not take a lot of airflow to be effective - 100 cfm should be more than plenty.:

 

[attachment file=Aussi Dust syatem.JPG]

 

I mocked up a system on Mouse and think I could duplicate that one for less than $300, using a smaller filter assembly.

 

[attachment file=Donaldson FRG filter screen cap 03.png]

 

That unit will fit behind the street side propane bottle, I already have side access doors. It will be easy to remove the end cap for filter replacement, and the dirt purge valve will point down to exit around the frame members. Excuse the poor graphics:

 

[attachment file=IMG_4920 Labled.jpg]

 

The inlet can go into the cabin here, I think. Does anyone know what is behind the X? I am almost, sort-of, sure that it is clear under the bathroom vanity.

 

[attachment file=IMG_4916 Labled.jpg]

 

An inexpensive 3 inch bilge blower will fit here:

 

[attachment file=IMG_4838 Labled.jpg]

 

Because there is lots of room on the faucet side of that cavity:

 

[attachment file=IMG_4841 Labled.jpg]

 

Getting the pipe in would be simpler if the X location were available, if not it could be brought in from higher up but that would complicate the plumbing. Power is there at the water pump switch (the fan motor draws less than 4 amps) and I could add another waterproof switch. Air entering the vanity would diffuse throughout the floor and enter the cabin through the heater grill and other openings.

 

The inlet pipe from the air filter would go straight up between the two bottles, 90 degree elbow to the street side and then 90 degree elbow up to a snorkel tube:

 

[attachment file=IMG_4927 Labled.jpg]

 

If you wanted a totally stealth installation you could elbow down and install a washable pleated filter but that would be maintenance intensive, and the air under the doghouse is not too clean. Here is the snorkel:

 

[attachment file=IMG_4933 Labled.jpg]

 

Side view, it would fit pretty close to the front hull seam. You would have to notch the doghouse cover to clear it.:

 

 

Thoughts? Am I insane? I think it would look totally cool.....

 

John Davies

 

Spokane WA

 

 

 

 

 

 

 

 

[BackofBeyond]

John,

Probably not insane, just an absolute tinkerer, who is rarely content with the status quo. I am similar, but in a recover program....

[Foy_Mirna]

John,

 

Let's just start off with WOW!  The ability of Oliver Owners to think through problems, come up with solutions and share them with others is amazing.  I for one consider this the NUMBER ONE benefit of owning an Oliver.

 

With great admiration and appreciation,

[John E Davies]

Well, I do love projects. Thanks for the kind words.

 

I am truly a little worried about poorly sealed circuit boards, in the outside areas mostly, but also inside the hull. Normal dust is not a real issue. But the red rock dust in most of southern Utah is .... it is up to a few percent iron oxide, and it becomes conductive when moist. If an unsealed board or electrical connexion (which most are in RV appliances) gets heavily coated in red dust, and then is exposed to moisture, it can cause corrosion and board or connector failure. I have experienced this directly after a 4wd vacation in Canyonlands.

 

Inside the trailer, the completely exposed boards for the water heater, water tank level monitors, inverter, etc etc, as well as every single wire connection and unsealed switch are at risk.

 

Besides this special concern about “Moab corrosion”, regular dust inside is a general nuisance and an eyesore.

 

Why not just keep it out? I like a clean interior....

 

The outside components are still at risk tho.

 

I would really like to hear from long time owners if they have dealt with dust inside the trailer, and how they did it. I realize that only a few ever get off pavement, and fewer still are like me who might drive for three or more hours on really dusty ones.

 

BTW, I did consider cracking the roof vent and running the fan on high in reverse, but that would bring in unfiltered air. You could add a filter under the fan, but changing it would dump dust all over you and the interior. Keeping the filter mechanism outside is best.

 

Also, I had been thinking about this since well before I ordered Mouse. I started a thread 15 months ago and got minimal response...

 

John Davies

 

Spokane WA

[Rumline]

John, I love the detailed work that you do. I have nothing to contribute other than to say thank you. I may not ever install a positive pressure system but I agree with Foy and Mirna, stuff like this enriches the community and I appreciate it.

[Mainiac]

This talk of pressuring the interior makes me think of the bathroom fan. I left that fan on once. When I went back in and opened the door, you could hear the exhaust fan relax. It was getting air from the main cabin and was not having to work so hard. The thought is to put a small pass through vent high up by the left of the door that was always open. Evidently there is not enough air allowed into the room from the narrow gap around the door. This should also allow the heat to circulate better when running the furnace as it doesn't run into a pressure situation, and can circulate freely.

This said, wouldn't a small exhaust type fan, maybe installed backward and high up, pressurize the whole cabin? It could draw air through an easily changed filter(s). This would eliminate the need for the snorkle and associated plumbing. Probably pick up the needed power from the existing fan? Maybe swap out the existing fan?

[John E Davies]

Well, this is disappointing but not at all unexpected. I raised up the rear blinds and found the window channel, and the back of the blinds, choked with dust.

 

 

However, it is very possible that I did this when I blew the dust off the outside with my leafblower, has anyone else seen this happen naturally, without power assistance?

 

John Davies

 

Spokane WA

 

 

 

 

[Overland]

John, I like this project but I'm surprised at the amount of dust you're getting inside. We've had the outside of our truck and trailer caked in dust but never anything inside. Not even a film of dust on the counters, and even between the hull our trailer has stayed remarkably clean so far. We track all sorts of things into the trailer while camped of course, but that's a different issue. I'm wondering if the difference is our lack of fridge vents? I can't think of anything else different except I know at one point Oliver changed windows but I think that was before yours.

[John E Davies]

Found more dust, I had not looked under the streetside bed in a while, this is dust accumulating under the floor from driving on gravel roads. I am convinced it comes in the dozen half inch drain holes and maybe around the septic drain area. I can seal the latter, but can’t plug up those drains. I hope to build this filtration/ pressurization system over the winter. It should not be difficult or costly and I hope it will stop this infiltration in its tracks.

 

 

John Davies

 

Spokane WA

[John E Davies]

Well, I thought I would post an update, I found the two really BIG dirt entry points .... the waste drain pipe grommet was hanging free about two inches away from its location. That was letting in vast amounts of dust into the cabin and electronics.

 

The rear exit hatch was missing about nine inches of rubber seal along the bottom. That was an easy fix..

 

Both those locations are at the low pressure area behind the trailer, so at speed on dusty roads dust is highly concentrated there. Since fixing those two areas dust has not been so bad.

 

In regards to the filtration intake.....  up near the roof is still the best spot for a stock Ollie, but it is vulnerable to damage from a tree branch or passing bird and it requires some stout mounting brackets bolted through the fiberglass hull, not good. With my Stone Stomper, 95% of the dust is channelled below the A frame, so a much lower inlet would be practical, and it would look a little less exotic. It might even be possible to hide everything within the doghouse, but that would mean eliminating the cyclone pre-filter. I don’t think the pre-filtration would be needed in this case.

 

John Davies

 

Spokane WA

 

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[Raspy]

John,

 

I don't know where it is, but someone posted a picture of a system that was simply a 1960's style automotive air cleaner from a big V8, from a Chevy or something, that was mounted to the side of their trailer. I think there was a fan behind it. These are very low profile and have an easily replaceable filter with lots of surface area. They re made of durable steel, light weight, easy to get, and have a nice air horn on the front. Easily adaptable to this purpose. One might be mounted on the roof, with a fan below in a cabinet or some place out of the way. Or maybe the forward facing horn would be enough to make it work.

 

Simpler is better! Lots of exterior plumbing running around is definitely out of the question in a clean design.

[John E Davies]

John,

I don’t know where it is, but someone posted a picture of a system that was simply a 1960’s style automotive air cleaner from a big V8, from a Chevy or something, that was mounted to the side of their trailer. I think there was a fan behind it. These are very low profile and have an easily replaceable filter with lots of surface area. They re made of durable steel, light weight, easy to get, and have a nice air horn on the front. Easily adaptable to this purpose. One might be mounted on the roof, with a fan below in a cabinet or some place out of the way. Or maybe the forward facing horn would be enough to make it work.

Simpler is better! Lots of exterior plumbing running around is definitely out of the question in a clean design.

 

Thanks for the comments, I had thought about an automotive airbox and filter, but mounted inside the closet. It would take up a lot of room there but would be out of sight and away from water. It would be nasty changing the filter there! One like on my old Series 80 would work great - it had a monster paper filter and a swirl design, and a rubber duckbill on the bottom for grit to be dumped manually. It was rather large though.

 

The problem with hanging a paper filter outside is water damage - a rainstorm would destroy the filter element and wash mud inside. External snorkels on trucks use a water separating design in the horn, that could help.

 

The Donaldson unit is ideal because it is reasonably compact and centrifugally separates and dumps most of the dirt before it ever reaches the filter element.

 

John Davies

Spokane WA