Has anyone cut a passthrough from an M109 box to a hardtop cab?

[Bantha RV]

Greetings guys and gals,

I recently bought a 1971 M109A3 with the intentions of converting it to an Overlander RV. I have gathered most of the guts and am starting on the cabinetry, plumbing, and electrical now. One thing I'm considering and leaving room for is to cut a flexible passthrough from the box to the cab, has anyone already done this? Any structural integrity issues I should be concerned with? I'm thinking of making the cut directly below the front window and approximately the same width....guessing there's already framing there that I can work between without cutting, and there doesn't appear to be any electrical I'd sever either. I've looked online for the blueprints of the box, but can't find any, even in Jatonka. Does anyone have any blueprint or elevation drawings that show the framing of an M109 box?

The guts include:
1. EcoFlow Delta Pro 3600kWh batt/inverter + spare batt (3600kWh) = 7200kWh total
2. EcoFlow Delta Pro Smart Generator (1800W
3. EcoFlow Smart Solar Panels 2x 400W (800W total)
4. Stiebel Eltron 6 gallon water heater (120v 11.3amp max)
5. Sterling Store+ 34"x48" shower kit.
6. Lordear stainless 30"x22"10" drop in sink
7. Vevor - generic 8kw diesel heater
8. Frigidaire EnergyStar dorm fridges x2 (one as fridge, one as freezer)
9. 55 gallon drum potable water tank
10. IH - 2400w (1200w + 1200w) dual element induction cooktop.
11. Deco Chef - Convection/Air Fryer/Rotisserie oven.
12. Thetford 5.1 gallon cassette toilet.
13. 24v to 12v converter x2
14. LED indirect and direct cabin lighting.
15. Shurflo on-demand pump with recirculating circuit for freeze protection.

Thanks in advance. I'm really enjoying, and learning a lot, reading about all of your builds.

 

[WillWagner]

I'd do propane for your water heater, fridge...use a 2 or 3 way....cooktop/oven and comfort heating. I can go apx 3 weeks on a 10 gallon tank using all of the above daily in cold weather, hot even longer due to no heater and not using the oven as much.

As for the passthrough, it will need to be a flexible type because the cab and body will move independently.

 

[Bantha RV]

I'd do propane for your water heater, fridge...use a 2 or 3 way....cooktop/oven and comfort heating. I can go apx 3 weeks on a 10 gallon tank using all of the above daily in cold weather, hot even longer due to no heater and not using the oven as much.

As for the passthrough, it will need to be a flexible type because the cab and body will move independently.

I think I've got the flexible seal between the cab and box all figured out. Mainly concerned with the structure/wiring of the box and where is safe to cut. Should I be ok cutting an inch or two below the front window and keeping the width of my cut the same or less than the window width on center?

 

[Bantha RV]

I'd do propane for your water heater, fridge...use a 2 or 3 way....cooktop/oven and comfort heating. I can go apx 3 weeks on a 10 gallon tank using all of the above daily in cold weather, hot even longer due to no heater and not using the oven as much.

As for the passthrough, it will need to be a flexible type because the cab and body will move independently.

I thought about LPG.....but I didn't want to punch a bunch of holes in the rig for ventilation and exhaust (says the guy who wants to put a great big hole to the cab in it....). I'm going with electric so that the only fuel I need to carry (or acquire) on the vehicle is diesel, the only penetrations I need to put in it are through the floor, and all summer long the living space could be 100% off grid/100% renewable energy. Also, I live in Wyoming and plan to hit every ski hill near me on the weekends this winter, but I don't want to have to winterize it every Sunday night and refill everything every Friday afternoon. During the week, I can just plug it in and open my recirculating circuit in my plumbing to constantly recirculate the freshwater tank through the water heater (in freeze protection mode), run a space heater set to 50* or so, and rest easy until the next weekend. The induction range means no open flames or ignition sources while cooking, no potential LPG leaks, and (with the exception of the diesel heater) no CO2 sources.

Right now everything on the truck could be on and running at normal output (except the range) and the solar would handle it all by itself without even using the 7200kWh of battery I've got onboard.

 

[cbrTodd]

You asked about structure below that window. Here is a picture of mine when I had everything torn out. As long as you stay below that 1/4" thick cross bar right below the window, you should be OK. There is no wiring or extra structure in that area.

With that being said, the mounts from the van body to the truck frame are set up to be rigid at the rear and have the flex at the front. It's the opposite of what you would want to minimize relative motion from the cab to the box. It might be worth attempting to reverse the order to have less motion to deal with. It would be a lot of work though. FYI I did not incorporate a pass through into my build.

 

[Bantha RV]

You asked about structure below that window. Here is a picture of mine when I had everything torn out. As long as you stay below that 1/4" thick cross bar right below the window, you should be OK. There is no wiring or extra structure in that area.

With that being said, the mounts from the van body to the truck frame are set up to be rigid at the rear and have the flex at the front. It's the opposite of what you would want to minimize relative motion from the cab to the box. It might be worth attempting to reverse the order to have less motion to deal with. It would be a lot of work though. FYI I did not incorporate a pass through into my build.
View attachment 850021

This is exactly what I was hoping to find! Thank you. I'm still contemplating the cost/benefit of a pass-through. There's definitely a lot of potential down sides: insulation compromised; weather-proofing the gap; flexibility in the gap....may outweigh the benefits of being able to wake up and crawl right into the drivers seat in my jammies, and the dog having more space to roam on the road.

 

[Tow4]

av8or put a pass through on his M916/146 box camper. He used a large flexible acordian type seal between the cab and the box. There may be a thread about it somewhere.

 

[Bantha RV]

av8or put a pass through on his M916/146 box camper. He used a large flexible acordian type seal between the cab and the box. There may be a thread about it somewhere.

Thanks! I'll try to find it.

 

[Third From Texas]

I'd do propane for your water heater, fridge...use a 2 or 3 way....cooktop/oven and comfort heating. I can go apx 3 weeks on a 10 gallon tank using all of the above daily in cold weather, hot even longer due to no heater and not using the oven as much.

As for the passthrough, it will need to be a flexible type because the cab and body will move independently.

Good info there. I recently accepted the fact that I'll use propane (since a number of the items I was given for the build can use it). I wasn't sure how much/how many tanks I would need. I have a pair of 5-gals that a neighbor tossed me after he upgraded to 30 and was looking at a pair of 30's myself. Not sure I need that much now.

 

[WillWagner]

Good info there. I recently accepted the fact that I'll use propane (since a number of the items I was given for the build can use it). I wasn't sure how much/how many tanks I would need. I have a pair of 5-gals that a neighbor tossed me after he upgraded to 30 and was looking at a pair of 30's myself. Not sure I need that much now.

If I were looking to do a home built camping rig, I would locate some, or one of the horizontal mount tanks that are 50 or so gallons. Out this way, there are a couple of RV salvage places and parts can be had for 1/3rd the cost of new. As for the OP stating not wanting to hole the box, the only things that need venting are the water heater and heater unit. Water heater vents thru the unit, heater used 1 small 2 inch hole. The range and stove vent into the living area with only a small louvered vent above the stack. The box will need to have holes in it to bring fresh water in and waste out anyway.

Venting the stove/oven into the living area has no effect......look at me, I'm normal! 5 gallon tanks last around 5 to 7 days each, don't ask me what the difference is between the 5 and 10 gallon tanks other than maybe the 5 gallon ones are not actually 5 gallons here in Ca, they are done by weight. I also have a camper with no oven, but has a heater, fridge and stove that uses a horizontal 5 gallon and it will last 6 or 7 trips, 3-4 days each and a pop up trailer that I can run around 24 days on but that only has a stove and small fridge, no water heater in the two of those. The pop up gets 2 nine day trips and 1 seven day trips a year. Also depends on the weather. Hotter makes the fridge run more. I need to re insulate that one. The camper improved by 2 trips after re insulating the area around the fridge with 1/2 inch foil covered styrofoam.

 

[Third From Texas]

If I were looking to do a home built camping rig, I would locate some, or one of the horizontal mount tanks that are 50 or so gallons. Out this way, there are a couple of RV salvage places and parts can be had for 1/3rd the cost of new. As for the OP stating not wanting to hole the box, the only things that need venting are the water heater and heater unit. Water heater vents thru the unit, heater used 1 small 2 inch hole. The range and stove vent into the living area with only a small louvered vent above the stack. The box will need to have holes in it to bring fresh water in and waste out anyway.

Venting the stove/oven into the living area has no effect......look at me, I'm normal! 5 gallon tanks last around 5 to 7 days each, don't ask me what the difference is between the 5 and 10 gallon tanks other than maybe the 5 gallon ones are not actually 5 gallons here in Ca, they are done by weight. I also have a camper with no oven, but has a heater, fridge and stove that uses a horizontal 5 gallon and it will last 6 or 7 trips, 3-4 days each and a pop up trailer that I can run around 24 days on but that only has a stove and small fridge, no water heater in the two of those. The pop up gets 2 nine day trips and 1 seven day trips a year. Also depends on the weather. Hotter makes the fridge run more. I need to re insulate that one. The camper improved by 2 trips after re insulating the area around the fridge with 1/2 inch foil covered styrofoam.

But those 3-way stoves can often be installed incorrectly especially if not a manufacture install. There's an industry standard to building the combustion box behind the fridge. Hell, the one I got from my nephew did not work on gas when he got his new RV. He had know that his family would need more fridge than the little Dometic. When he pulled it to bring down here he discovered that the gas line wasn't even connected at the factory. I recall reading somewhere that those 3-way fridges are the cause of like +90% of RV fires. *One reason I wasn't planning on having propane at all (original plan was diesel and solar only). But since the stovetop and fridge were just taking up space in my living room I had a change of heart and decided to add propane into the build. Honestly, I've cooked on a gas stove for over 40 years now and always have felt it was superior to electric. Maybe I'm just too old-school (I've never tried some of the fancy new electric cooktop tech).

 

[chucky]

Good info there. I recently accepted the fact that I'll use propane (since a number of the items I was given for the build can use it). I wasn't sure how much/how many tanks I would need. I have a pair of 5-gals that a neighbor tossed me after he upgraded to 30 and was looking at a pair of 30's myself. Not sure I need that much now.

A 20 gal unless your going to open a taco stand at the beach feeding all those starved skinny sun clad cuties you have down there lol!

 

[WillWagner]

I can't cook on electric, I can only burn