Military S-250 Shelter Conversion

rlrenz

Explorer
Yep, I'm guilty! And the bad thing was, I made three laps around the yard before I realized it.

Apparently, the price was right or you wouldn't have sold it, but just think how much more time and space you'll have to work on your ambulance now.

The price was derived based on the original cost, the money I had sunk into it, and the fact that I needed it gone SOON. If you assume that my time is worth the customary 5 cents per hour, I probably came close to breaking even.

I didn't start the project for any reason - it just kinda happened. It was something to fiddle with when I felt like it - and when my arthritis became more apparent than it had been, I needed something that was more accessible and easier to work with. Somehow, that logic turned into a 20,000 Lb ambulance - go figure....
 

Gatsma

Adventurer
Ohhh, that sounds PERFECTLY logical to me.... because of the enjoyment you are and will be having with it!
 

rlrenz

Explorer
Ohhh, that sounds PERFECTLY logical to me.... because of the enjoyment you are and will be having with it!

Actually, it is very useful - I drove it to a place we rented in northern WI for a week - everything fit perfectly, and it swallowed 2 kayaks without a burp. This morning, it made a panic run to Home Depot to pick up some Masonite to protect the patio pavers from a skid steer tractor turning while holding my Bridgeport. It has made trips to pick up bags of wood mulch - lots of space for bags of anything in fact. And, it's fun to drive--- A Freightliner, air ride seats, a Cummins diesel, and stutter air horns - what more could anyone want??

Plus, it's something I can work on (or in) from a stool. My knees and hip have started talking to me - and the conversations don't start with "Good Morning!"...
 

Gatsma

Adventurer
Man, you're living a trucker's dream!
Ahh yes, knees and hips; I know of which you speak, compadre!
 

rlrenz

Explorer
Man, you're living a trucker's dream!
Ahh yes, knees and hips; I know of which you speak, compadre!

I finally figured out that your body remembers everything you do to it, and very little of what you do for it....
 

rlrenz

Explorer
Well, I loaded 'er up this morning. I used my gantry crane for the front, and a die lift for the rear. The whole process probably took about 1/2 hour. She went complete with a 120 VAC power cord, the boarding ladder, the lifting / tie down cables - the whole works.

Now I can concentrate on my new project - a medium ambulance.
 

rlrenz

Explorer
I drove it to one of the largest ambulance dealers in the US yesterday. They regularly remount (new truck, rebuilt ambulance module) ambulances, and their customers nearly always want new air conditioning. They had just removed the 120 VAC (a Hoseline unit) from a module they were rebuilding, and I was able to buy it for a whale of a lot less than new.

It will have a front-of-module condenser, a compressor probably mounted under the module, and a dual evaporator to handle both the engine AC, and the 120 VAC AC. It needs a control module to get the two systems to cooperate with each other, and an 80 amp 12 volt supply to run the condenser fans and the AC blower. The end result is about 12,000 BTU.

That will make it more humane for me to work in the module in the summer, and I can also plug 'er in somewhere else. A 4000 watt generator is also in the works.
 

NEPolarbear

Observer
What generators are you looking at?
May be going with a Honda.
Is it worth looking at used generators and if so, what do you look for?

Your threads have been a big help.
 

rlrenz

Explorer
I'm looking at the Onan Microlite 4 KW, running on propane. Diesel costs too much, and a diesel likes to be loaded to about 70-75%, but propane can live off the propane tank I have to have for the cooktop - I can easily fit a 100# tank on board. Propane has the advantage that once I close the valve, it's all winterized, and propane doesn't degrade in the tank like gasoline does. The Microlites are shorter than the older Onan Emerald generators, and weigh less than 200 Lbs - the old Emeralds come in at nearly 400 Lbs, plus the 2-cylinder engines they use used to fight with me when I had one in an arc welder, so I'm a bit prejudiced against the Emeralds. I have a perfect space that can hold either unit, but the Microlite is winning the argument right now.

The Microlites show up on CL for about $1000-$1500, with many of them already being set up for propane since they were used on trailers that had propane for the kitchen. I can do a propane conversion, but I'd prefer to buy one already set up for propane. I'm planning on a good used generator versus new.

The generator may wind up on a set of slides to make service easier.

A Honda would do the job, but I want to build in a generator so I can use it anytime, anywhere. A Honda would have to be set up next to the ambulance.
 

aernan

Observer
Sorry to resurrect such an old thread. There a bunch of military vehicles being auctioned off and some come with the shelters attached so I'm sure there will be renewed interest in this build.

I was wondering if anyone knows how they build the S-250? Are the internal aluminum beams welded/glued/riveted together? Is the skin welded from the inside or glued on?
 

rlrenz

Explorer
The S-250 panels are built a bit like a refrigerator. There is a thin outer skin (about 1/32"), then foam filling around some internal "C" channel frame elements, then another layer of 1/32" aluminum. Where the interior skin meets the channel framing, there is a 1/8" thick piece of wood between the inner skin and the channel. The whole thing is bonded by the foam filling.

As I recall, the channels all run vertically. No welding is used - only bonding or rivets.

If you chase down the MIL manuals for the shelters, the manuals show the construction, and how to repair them. The most common damage is someone using a forklift to move them, and harpooning through the side of the shelter.

The shelters make a decent all-weather enclosure - due to their construction, they can be heated with a lightbulb. Air conditioning is a lot easier if a standard room air conditioner is adapted to the shelters in place of the military air conditioner - the MIL model used R22 refrigerant, and has so many components that are piped with flare fittings that they always tend to leak refrigerant. I had one of the MIL air conditioners (from Coleman Surplus) that I bought new in the box, and I could never get it to hold a refrigerant charge for more than a few months. Friends of mine who used the shelters in the military told me that the mechanics were always adding refrigerant, so that was probably normal.

If you buy one, it may or may not have been de-militarized. Sometimes the de-mil was done neatly, but more often, it was done with a sledge hammer or an axe. I have seen some shelters that were surplused in ready-to-use condition, though.

Have fun!
 
Heat transfer coefficient
U-factor = 0.50 .
http://www.ramims.com/index.aspx?id=4166

With a U-factor of 0.50 the R factor is only 2. The 55mm of urethane foam in my camper is R 13 which is comparable to a house with 4" fiberglass batts. IMHO the shelters have not very good insulation; maybe better than Class C campers but that isn't saying much.

Charlie
 

rlrenz

Explorer
The shelters were based on shelters used in WWII, so their designs were probably some of the first military products to use foam insulation. Considering that earlier versions used fiberglass insulation, they were definitely an innovation.

The military wasn't reaching for superior design, but adequate design that was durable, reliable, and repairable. The shelters used a gasolene fueled heater, and a 6000 BTU air conditioner. The air conditioner was sized for the waste heat from the radio gear.

Friends of mine who worked with shelters in the far east have universally grumbled to me that the air conditioned shelters always seemed to go to Korea, while shelters in Vietnam never seemed to have AC.

The two louvered vents on the side of the shelter could be connected to a free-standing air conditioner. This AC package may have been developed to serve as a field upgrade/retrofit to avoid the time and labor that would be required to add an AC module to a shelter since the ground based package could be designed and purchased state-side for deployment to the field.
 

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