M116A3 Build

[lfhoward]

Well, I won a military surplus auction this morning, so I will officially be building an offroad camping trailer!

Here are the details:

M116A3 1-ton trailer chassis, running on 37's! In a former life, it transported a diesel generator for the Marines. This thing is about 750 lbs empty, and beefy! It would probably be somewhere in the neighborhood of 1200-1500 lbs once I'm done modding it.




Here is a sketch of my plan to make it into an offroad camper. It's not really a teardrop camper, but it would be about the same size. It would be large enough to hold a queen sized mattress! (Yay, no more sleeping on the ground for me and my wife!) I definitely took some inspiration from the ROAM camper build, over on ih8mud.com: http://forum.ih8mud.com/threads/roam-camper-build.379001/. I also found their build journal right here! http://www.tnttt.com/viewtopic.php?f=39&t=42096


Hopefully I can get it finished by the time summer rolls around. In my free time the last couple of days I drafted plans using SketchUp. These blueprints don't show the exterior walls or the back doors, so you can see the interior construction. It will be insulated between the beams so it will be an all-season camper. I am hoping to skin it with aluminum when it's done.





And here is the tow vehicle:


I would be open to any helpful suggestions!

[lfhoward]

I plan to keep the military trailer chassis as stock as possible for now. I'm picking up a pintle hitch to be able to tow with the trailer's lunette ring. Because my Jeep is lifted, I only need a 4-inch rise to level out the trailer. The military trailer has surge brakes and a 1-ton axle, which I'll leave in place for now. Later I may decide to swap them out for an axle that will run rims and tires that match the Jeep, with electric brakes, but that would be a later project.

In terms of electrical, I bought a military 12-pin adaptor plate for the vehicle side, and found instructions for wiring it up to my 4-pin civilian trailer adaptor. Even though the M116A3 has a 24-volt electrical system, it will run at 12 volts by just swapping in the appropriate bulbs.

Instructions for building a 24-volt NATO plug to 12-volt 4-pin adaptor:
http://www.fjcruiserforums.com/forums/trailers-towing-tech/118774-military-civilian-trailer-adapter.html

Another helpful thread:
http://www.steelsoldiers.com/showthread.php?73639-Making-M101A2-street-legal

[Vedette]

Cool Project if you can keep it retro.
But, a half track be a more appropriate tow vehicle???
I don't know much about Military stuff????
Don't even know if we have an army here in Canada??
Good Roads
Brian & Sandi

[lfhoward]

Here is a link to the users manual for the M116 and the more common M101 trailers used by the military (US, Canada and other NATO allies as well, I presume). It should be a helpful reference for doing preventative maintenance and repairs.
http://www.hummerknowledgebase.com/acc/m101a.pdf

Thanks for the good send-off, Vedette! A half track would probably work, as would an army truck or Hummer. I have no plans to acquire one of those though! But they are for sale at government auction, believe it or not. Check out http://www.govplanet.com and be shocked and amazed at what you can buy!

[lfhoward]

The trailer is in pretty good shape for having a diesel generator mounted on its back for 24 years, but there are some holes left in the deck from its former life.


What do you all think is a good method for filling and waterproofing those holes? I won't know for sure if the deck is aluminum or steel (but I suspect aluminum) until I pick the trailer up next week. I would like to seal the floor before building on it, so water doesn't splash up through the holes and ruin the floor insulation and wood frame of the camper.

Also, is it better to post a question like this in my build thread, or as a stand alone topic in one of the other forums? I haven't been on ttnttt long enough to know the sop. Thanks!

[KCStudly]

Welcome. That thing is going to have more ground clearance than you will know what to do with! Make sure to pack a step stool or maybe a folding ladder!

Re: sealing the holes in the deck, I see tell-tale signs of rust around at least one of those bolt holes and my gut tells me that a heavy military trailer is most likely built from steel, not aluminum. In either case the best solution would be to fit some plugs made from similar thickness sheet metal and butt weld them in.

Re: your cabin design, it looks like you intend to use 2x4's, and a lot of them. 1x2's or even 1x3's, and a lot less of them would be more than adequate and will help you meet your overall weight goal (you may be in for a surprise on just how heavy that thing is... is the 750 lb est. a published spec. or just a guess?). Unless you have specific items/features in mind that need to have some place to attach, you probably don't need so many vertical studs, or any of the horizontal blocking. If you fully glue your skins, wall frames and foam board insulation you will be amazed at how strong the "composite strength" of the assembly becomes.

Only the most extreme rock crawlers and hardcore wheelers would ever need anything more than this, and IMO at that stage should be looking at a steel frame or exo-cage design. Unless you have big big plans to build up your TV (full roll cage, 3/4 ton axles, 35+ inch tires, recovery winch, etc.), I just don't see that being an issue for you. For forest service roads, the occasional 2 track off road excursion, and the like, you will get plenty of strength from the standard techniques proven by so many people here.

If you are concerned about tree branch puncture resistance or impacts along the top edges of your walls, then maybe consider using a slightly thicker outside skin (like 1/4 or 3/8 instead of 1/8 or 5 mm) and reinforce the wall to roof join with some 2x2 cleats. But, again IMO and from reading so many of the experiences expressed by many others that have gone before (many of whom have multiple builds under their belts and the camping experiences to back them up), there is no reason to build heavy. You will just end up with a heavy camper wishing that you had built lighter.

I would focus on protecting against water intrusion/rot, and against stone chips and other debris kicked up from the TV.

Not intended to be discouraging, just a reality check.

[lfhoward]

KCStudly, you bring up some very good points. Thank you for sharing your experience with building trailers, and explaining how strong does not need to mean heavy. I am very open to redesigning the cabin structure, as long as I can keep the basic shape, have it be strong enough to hold together in off-camber situations on rutty jeep trails, resist being punctured by trees as you suggest, and maybe support 150 lbs of roof rack or a solar panel on top. Lighter weight means less gas consumed and less wear and tear, both of which would be good.

Re: ladder or stool... Yes!

Re: sealing holes: thanks. I'll see when I pick the trailer up next week which metal it is made of. A magnet should do the trick. The rust we see could be from the generator feet if the deck is made of aluminum. I was hoping to avoid having to get it welded. Are there other good methods that would stand up to time, or do I really need to bite the bullet and get it professionally sealed by welding?

Re: trailer weight: you are right, 750 was low balling it. Here is a data plate from a similar trailer that I found using Google. Hard to see, but it looks like the dry weight of the M116A3 is 960 lbs.


Thanks again for your suggestions. They are not discouraging. I am learning as I read your responses and research other threads. Thanks for having the patience to help the noobs! If this were the LostJeeps forum, where I chat about my Jeep Liberty, I think you just kept me from the equivalent of installing a spacer lift kit (a bad idea that looks good on the surface).

Let me dig deeper. Please let me know if this sounds right, or what you would change:
A composite shell for the cabin could be a sandwich of 1/4 inch plywood on the interior and exterior, with 3/4 ply in the middle, with sections cut out of it (skeletonized) for foam insulation using a jig saw.
- The inner 1/4 ply could be a nice interior grade birch, whereas the outer 1/4 could be rougher, since I would cover it with aluminum.
- Does the outside ply need to be marine grade to resist rot (whether under aluminum or not)?
- 1x2's or 1x3's (both are actually 3/4 inch wide) could stand in for the 3/4 inch plywood in the wall sandwich, right? What kind of spacing would do the trick (a vertical beam every foot, 2 feet, etc.)? I do want the trailer to be insulated.
- Does polyurethane glue or carpenter's wood glue work better to hold it all together?

Thanks for answering my questions. Apologies if these things have been answered a lot already. I am in the process of doing my research, and I want to create a high quality trailer even though this is my first build.

Have a good night. --Lauren

[lfhoward]

The pintle hitch came from eTrailer today. This thing is HEAVY. It has a 10,000 lb capacity, which is 2x the towing capacity of my Jeep! (But it is small for pintle hitches in general, based on what was available for sale.)

[skinnedknuckles]

Cool idea Make sure that when building that you keep in mind of getting your tongue weight correct. With the axle in the center older style rims and of your building structure you will find out just how quickly you can loose tongue weight. I have m101's ( with the older style rims and only parking brakes set up for my m37B1 3/4 ton Dodge) and m105's and you have to be careful when loading. I have a m105 carpenters trailer that's set up for a large radial arm saw with a tailgate and it has no tongue weight at all ( I can easily pick up the front with 1 hand ). Good that you are ready to build some weight into it to make those springs work, they are pretty stiff. Make sure that the override lock latch works on the surge brakes or you may have some trouble backing up an incline ( and keep the master cylinder full of brake fluid- check to make sure of the type of brake fluid some military things use silicone brake fluid I believe DOT 5 ). I am thinking about when I get my teardrop trailer done for my rat rod ( its going to be nice looking and not rusty like my ratrod ) I have an extra m105 trailer that I would like to build into a larger teardrop to pull behind one of my larger army trucks. It's going to be an interesting build for you You have a great base to start building an off-road trailer. There is a wealth of information on this website and a lot of great people here to help
Paul, still building my teardrop in Wisconsin

[KCStudly]

... Let me dig deeper. Please let me know if this sounds right, or what you would change:
A composite shell for the cabin could be a sandwich of 1/4 inch plywood on the interior and exterior, with 3/4 ply in the middle, with sections cut out of it (skeletonized) for foam insulation using a jig saw.
- The inner 1/4 ply could be a nice interior grade birch, whereas the outer 1/4 could be rougher, since I would cover it with aluminum.
- Does the outside ply need to be marine grade to resist rot (whether under aluminum or not)?
- 1x2's or 1x3's (both are actually 3/4 inch wide) could stand in for the 3/4 inch plywood in the wall sandwich, right? What kind of spacing would do the trick (a vertical beam every foot, 2 feet, etc.)? I do want the trailer to be insulated.
- Does polyurethane glue or carpenter's wood glue work better to hold it all together?
<snip>
. --Lauren

'Skeletonizing' is a perfectly legit method, IMO, but some people have complained about the amount of waste and cost of the ply. The up side is that it can be quicker and more stable than a stick built frame. Depending on the species and grade of wood used, I think the cost could go either way.

With aluminum outer skin and good sealing techniques (my gold standard reference is Aggie79/Tom's Silver Beatle build... search for it), IMO you do not need to use marine grade ply, but exterior grades are always a good idea. Water has a way. On my build I have selected marine grade ply and cedar for both water resistance and lighter weight, but I am kind of building in a non-traditional way with just glued and painted canvas outer skin. Not very puncture resistant, but light weight, "easy"/thrifty build techniques compared to skinning with AL and trimming (if I could stay out of my own way, so to speak )

I prefer TB2 wood glue for fitted wood to wood joints; PL Premium for less precise construction joints (such as wall to floor); and still haven't hit on "the best" product or technique for foam to wood. GG or GS work for foam to foam. GG is strong but dries harder and expands, so you have to weigh or clamp carefully, and it is harder to fair. GS dries softer, but can have larger bubbles and voids under the skin when used as a filler. I tried some expensive 3M green water based contact adhesive for bonding ply panels to foam, but had mixed results; didn't seem to be worth the extra cost. If you get the application right, TB2 can make a good bond between wood and foam, but it works better on smaller panels with good clamping and a thin application (rolled on fairly thin). Lots more details about my experience spread throughout my build thread.

I think my next attempts at bonding foam to ply (my roof foam) will us PL and a notched trowel.

Bottom line is most techniques will work well enough. Experiment enough to see what works best for you, and report your findings to help others who will follow.

p.s. I understand that the hitch is a good off road solution and is a compatibility factor to your existing trailer, but remember, every little extra pound adds up fast; and if you add them in 10's and 20's every time you do some part of your build you will quickly find that you have built a tank. As a minimum, I would consider cutting the excess plate off of the draw bar (down to the foot print of the lunette ring mounting face). If you don't need the offset you could pare a few pounds off by using a straight/one piece hook. Oh yeah, expect to hear and feel it clunking. Up side is they are easy to couple and are pretty fool proof.

[lfhoward]

I got out the soldering iron today and fabricated an adaptor to connect the military trailer's 12 pole receptacle to my Jeep's 4 pole connector. My adaptor consists of a vehicle-side military receptacle and a trailer-side 4 pin adaptor (so I can just plug it into then existing vehicle-side 4 pin on my receiver hitch).





In case anyone would like to make one:
From Texas TT on FJcruiserforums:
http://www.fjcruiserforums.com/forums/trailers-towing-tech/118774-military-civilian-trailer-adapter.html

Civilian......Military.....Function
Green........J.............RH stop and turn
Yellow.......B.............LH stop and turn
Brown........E............Tail/Running lights
White........D & L.......Ground

I verified the above using the trailer's technical manual, downloaded at:
http://www.hummerknowledgebase.com/acc/m101a.pdf
I used D for the ground, after looking at the wiring diagram in the technical manual.

[lfhoward]

@skinnedknuckles, thanks for the tip about the tongue weight. I plan to have the batteries up front, as well as stack the boards that will support the mattress up front when not in use. I can always add a tongue box full of tools if the tongue weight gets too light, too. Also, I will be sure to check to override latch when I pick up the trailer. I downloaded the trailer's technical manual, so I'll read up on how the brakes work and what kind of fluid to have on hand. Do you think there is any need to repack wheel bearings before towing it home (300 miles)? Hopefully those will not be an issue right away, if the Marines have kept up with their maintenance.

@KCStudly, thanks for the excellent reference build for skinning in aluminum and waterproofing. That will come in very handy. Also, thanks for the glue recommendations. I will check those out as well.

Another question for anyone reading:
I live in PA and read the thread about how registering trailers in PA can be an expensive hassle, and how it is pretty easy to get an out of state Maine registration. Good idea? Hopefully my paperwork will come next week, then I can register it, pick it up, and drive it home from VA with an actual plate on it. Only issue is, I have a 10 day window (from today) to pick up the trailer before it incurs storage fees.

Thanks!

[skinnedknuckles]

Ifhoward, as far as wheel bearing issues, of all of the trailers and trucks that I brought home from government surplus auctions, I have had no problems with the bearings. Once you pick it up and are heading down the road for a few miles get out and touch the hubs to see if any are hot (keep in mind that these trailers have parking brakes on them and they have to be fully released before moving) If you are concerned take some wheel bearing grease and some wrenches and a jack. These trailers sat most of their life, so as long as the grease caps are still on ,the grease should be good to transport. When you get home you should go through the bearings anyway before you put it on the road as a camper. One thing you may want to do when you pick up your trailer is to have a cheap set of magnetic mount lights to stick on the back of the trailer frame. there is no guarantee that the plug-in and or wires are going to be in good shape. I take it that you bought this from Gov Planet, I have not yet dealt with them as of yet it will be interesting how they work the title. The people over at SteelSoldiers should be able to help you with that. I always purchased through Gov liquidation and it was pretty simple, I never had any problems with the police officers here in Wisconsin. But then I do not know the laws governing trailer registration for your state. Have fun
Paul

[lfhoward]

The trailer I bought at government auction, it turns out, is parked in a highly secure installation in Virginia. That means I need security clearance to go pick it up, which puts project on pause for another week. Next step is a criminal background check!

[KCStudly]

Seems like it would be easier on the tax payers if they had someone drag it out for you. Geez.