Bear Prints Offroad - Build Thread
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aernan
Observer
Why we are starting with this truck?
We both really enjoy going and exploring new areas and we want a vehicle we can take anywhere. After having a few 4x4 vehicles we considered up armor and adding over landing capabilities. Upgrades (metal bumper, rock sliders, bash plate, suspension lift, bigger tires, winch) add a lot of weight and make the vehicle perform much worse on road. In addition it cuts into the total weight budget of the vehicle so you can carry less. At the end of the day you end up camping in a tent which has no AC. You cook on camping stoves and have no bathroom per-say. So you are effected by the elements a great deal. This limits what seasons and regions you can travel into.
I then started looking at any truck that had good out of the box 4x4 capabilities that I would not need to dramatically up fit. Of course the Unimog looks like a dream vehicle because of it's capabilities but TBH they are quite expensive. After more research into pinzgaur, volvo, tatra, man, unicat, steyr, puch I discovered the US military surplus S&S trucks. Much to my surprise they can be had very cheap.
Stewart & Stevenson, BAE and now Oshkosh Trucks
The M1078 is one of a dozen trucks all sharing common design and 85% parts interchangeability. The design is based on the Steyr 12M18. Steyr is now owned by Mercedes Benz. Due to USA munitions laws 95% of the truck must be domestically manufactured so in time of war we can continue producing munitions of war. This truck was designed to replace the "Duece and Half" named because it has 2.5 ton in bed capacity.
https://en.wikipedia.org/wiki/M35_series_2½-ton_6x6_cargo_truck
The truck is designed to be easy to drive by someone with no heavy equipment experience. So it has power steering and an automatic transmission.
Through the years the truck was constantly upgraded as newer parts/designs were available. I have an A0 (original) model but there are A1 and soon A2 models.
Engine:
Caterpillar 3116 6.6 liter Diesel. 250 Hp 750 ft lbs torque.
Gets 6.5 MPG under max load. I'm getting 8 mpg.
Transmission:
Allison 3400 series automatic
has 7 gears. Under highway use starts in 2nd gear. Pressing mode button unlocks 1st and then limits range to first 5 gears. Designed for off road use. There is some kind of 70:30 split rear:front on highway. Mode makes power 50:50.
There is no transfer case. No high/lode mode.
Based on Military spec the top speed of the vehicle is 55 mph and is governed.
Axles:
Meritor solid axles. Axles feed gears in the hubs that do final reduction. This greatly reduces the drive shaft and differential size. To get higher highway speed people are putting in 3.02 differentials which pushes top speed to 63 mph. The front differential has 22" inches of ground clearance. So it does not trip stop light turn sensors. It is 1.5" higher then the ground clearance of a Unimog with portal axles.
Some other interesting stuff:
Central Tire Inflation System (CTIS)
Being a large commercial truck the engine generates air for the air brakes which operate just like any big truck. The air is also used to air up/down the tires. The controller is in the cab and allows you go from 45 psi (highway) to 25 cross country or 15 offroad/sand. Tires are giant 46" ZXL or XZL tires which can only be had as military surplus. The rims are bead locked split rim design which allow for very low air pressure and field repair. A run flat insert is available which is a aluminum ring. With run flat the wheels weigh 350lbs otherwise only 250lbs from what I'm told.
The air box sits on top of the frame rails and has a snorkel that extends above the top of the cab. The only computers are the transmission control unit which is in the dash and the CTIS. There is an air operated fan disconnect to allow for deep water fording. To see that in action watch:
We both really enjoy going and exploring new areas and we want a vehicle we can take anywhere. After having a few 4x4 vehicles we considered up armor and adding over landing capabilities. Upgrades (metal bumper, rock sliders, bash plate, suspension lift, bigger tires, winch) add a lot of weight and make the vehicle perform much worse on road. In addition it cuts into the total weight budget of the vehicle so you can carry less. At the end of the day you end up camping in a tent which has no AC. You cook on camping stoves and have no bathroom per-say. So you are effected by the elements a great deal. This limits what seasons and regions you can travel into.
I then started looking at any truck that had good out of the box 4x4 capabilities that I would not need to dramatically up fit. Of course the Unimog looks like a dream vehicle because of it's capabilities but TBH they are quite expensive. After more research into pinzgaur, volvo, tatra, man, unicat, steyr, puch I discovered the US military surplus S&S trucks. Much to my surprise they can be had very cheap.
Stewart & Stevenson, BAE and now Oshkosh Trucks
The M1078 is one of a dozen trucks all sharing common design and 85% parts interchangeability. The design is based on the Steyr 12M18. Steyr is now owned by Mercedes Benz. Due to USA munitions laws 95% of the truck must be domestically manufactured so in time of war we can continue producing munitions of war. This truck was designed to replace the "Duece and Half" named because it has 2.5 ton in bed capacity.
https://en.wikipedia.org/wiki/M35_series_2½-ton_6x6_cargo_truck
The truck is designed to be easy to drive by someone with no heavy equipment experience. So it has power steering and an automatic transmission.
Through the years the truck was constantly upgraded as newer parts/designs were available. I have an A0 (original) model but there are A1 and soon A2 models.
Engine:
Caterpillar 3116 6.6 liter Diesel. 250 Hp 750 ft lbs torque.
Gets 6.5 MPG under max load. I'm getting 8 mpg.
Transmission:
Allison 3400 series automatic
has 7 gears. Under highway use starts in 2nd gear. Pressing mode button unlocks 1st and then limits range to first 5 gears. Designed for off road use. There is some kind of 70:30 split rear:front on highway. Mode makes power 50:50.
There is no transfer case. No high/lode mode.
Based on Military spec the top speed of the vehicle is 55 mph and is governed.
Axles:
Meritor solid axles. Axles feed gears in the hubs that do final reduction. This greatly reduces the drive shaft and differential size. To get higher highway speed people are putting in 3.02 differentials which pushes top speed to 63 mph. The front differential has 22" inches of ground clearance. So it does not trip stop light turn sensors. It is 1.5" higher then the ground clearance of a Unimog with portal axles.
Some other interesting stuff:
Central Tire Inflation System (CTIS)
Being a large commercial truck the engine generates air for the air brakes which operate just like any big truck. The air is also used to air up/down the tires. The controller is in the cab and allows you go from 45 psi (highway) to 25 cross country or 15 offroad/sand. Tires are giant 46" ZXL or XZL tires which can only be had as military surplus. The rims are bead locked split rim design which allow for very low air pressure and field repair. A run flat insert is available which is a aluminum ring. With run flat the wheels weigh 350lbs otherwise only 250lbs from what I'm told.
The air box sits on top of the frame rails and has a snorkel that extends above the top of the cab. The only computers are the transmission control unit which is in the dash and the CTIS. There is an air operated fan disconnect to allow for deep water fording. To see that in action watch:
aernan
Observer
If you are considering buying one of these trucks here are some pro/con considerations:
Pro
Size:
The truck is small enough to fit in a normal parking spot so that means it's also short enough to fit on many roads and trails. Any longer and wheeling the truck would be impossible. That also leads to a giant con. The bed give you 12.2' of space to build a box. You can relocate the spare tire and air box and expand that to 14.4'. If you don't mind an overhang you can easily put a 15' box on the bed.
Parts:
Since it's all American made the parts are not specific to a military truck and with some skill you can actually source everything for the truck. You must learn to convert the NSN into a vendor part number and then you need to hunt the part but it does exist. For those of you embarking on a global journey my advice is to make the truck 100% before the trip and have friends in the states that can help source parts. I am totally surprised to find that I can buy regular grade 8 bolts from a local hardware store. The con about this is anything made from rubber in a vehicle that is 24 years old is going bad so you do have some up front replacements in store to fix leaks and replace hoses before they burst. Don't fear there is a large community of private owners who can help you find what you need.
Offroad Capabilities:
With 22" of clearance under the differential. 40 degree approach and departure angles. The truck is very capable. It has parabolic leaf sprung suspension.
https://olive-drab.com/idphoto/id_photos_m1078.php
http://www.military-today.com/trucks/m1078_lmtv.htm
I have taken mine to a local terrain park called Hollister Hills SVRA and gotten it stuck a couple of times. It performed well and I have confidence taking it on fire roads and very technical roads. I'm certain even with the box on the back it will go mostly anywhere it will fit.
The ground clearance is exceptional and in 1st gear it crawls great. 46" tires with CTIS make setting the air pressure easy which is a big help.
The truck is massively heavy so once stuck it's hard to pull free. The articulation appears excellent and it remains planted well in slippery and soft terrain. Now the Con. The truck is very tall and you will hit branches and trees. The paint is CARC and you won't be scraping it off so branches are actually not a problem. Most of the weight is up front with a cab over engine layout. Once in a concrete lined mud put I could not get the front end to climb out and I needed help. I believe if there was weight in the rear it would have been easier. There is no locking differential. You can get a posi for the rear but there are no lockers available. This could be a big deal breaker for those considering serous off road action.
My truck has an optional Self Recovery Winch (SRW). It's a hydraulically operated 11k lb pulling capacity with 300' of line on the drum. The winch is frame mounted mid body and can be deployed front or rear through a set of guides and roller fair leads built into the bumpers. Basic math you will realize the truck weighs 17k lb so if your wheels are locked that 11k won't even budge it. For pulling power you will need to double the line through a pulley/snatch block or triple it to get enough power to move the truck. The other terrible problem is the SRW can only be operated with the truck in neutral because the PTO comes off the transmission.
CON
The truck is quite heavy and the fuel economy is terrible. Going international finding parts could be harder then domestic but it is easy enough to repair at the side of the road. The truck is very tall and you will hit branches when off roading. The cab and engine are very loud. This can be helped with cetane booster and insulating the cab better but it will never be quiet like a modern vehicle.
All your friend will decide you are a prepper and make endless zombie apocalypse jokes.
Pro
Size:
The truck is small enough to fit in a normal parking spot so that means it's also short enough to fit on many roads and trails. Any longer and wheeling the truck would be impossible. That also leads to a giant con. The bed give you 12.2' of space to build a box. You can relocate the spare tire and air box and expand that to 14.4'. If you don't mind an overhang you can easily put a 15' box on the bed.
Parts:
Since it's all American made the parts are not specific to a military truck and with some skill you can actually source everything for the truck. You must learn to convert the NSN into a vendor part number and then you need to hunt the part but it does exist. For those of you embarking on a global journey my advice is to make the truck 100% before the trip and have friends in the states that can help source parts. I am totally surprised to find that I can buy regular grade 8 bolts from a local hardware store. The con about this is anything made from rubber in a vehicle that is 24 years old is going bad so you do have some up front replacements in store to fix leaks and replace hoses before they burst. Don't fear there is a large community of private owners who can help you find what you need.
Offroad Capabilities:
With 22" of clearance under the differential. 40 degree approach and departure angles. The truck is very capable. It has parabolic leaf sprung suspension.
https://olive-drab.com/idphoto/id_photos_m1078.php
http://www.military-today.com/trucks/m1078_lmtv.htm
I have taken mine to a local terrain park called Hollister Hills SVRA and gotten it stuck a couple of times. It performed well and I have confidence taking it on fire roads and very technical roads. I'm certain even with the box on the back it will go mostly anywhere it will fit.
The ground clearance is exceptional and in 1st gear it crawls great. 46" tires with CTIS make setting the air pressure easy which is a big help.
The truck is massively heavy so once stuck it's hard to pull free. The articulation appears excellent and it remains planted well in slippery and soft terrain. Now the Con. The truck is very tall and you will hit branches and trees. The paint is CARC and you won't be scraping it off so branches are actually not a problem. Most of the weight is up front with a cab over engine layout. Once in a concrete lined mud put I could not get the front end to climb out and I needed help. I believe if there was weight in the rear it would have been easier. There is no locking differential. You can get a posi for the rear but there are no lockers available. This could be a big deal breaker for those considering serous off road action.
My truck has an optional Self Recovery Winch (SRW). It's a hydraulically operated 11k lb pulling capacity with 300' of line on the drum. The winch is frame mounted mid body and can be deployed front or rear through a set of guides and roller fair leads built into the bumpers. Basic math you will realize the truck weighs 17k lb so if your wheels are locked that 11k won't even budge it. For pulling power you will need to double the line through a pulley/snatch block or triple it to get enough power to move the truck. The other terrible problem is the SRW can only be operated with the truck in neutral because the PTO comes off the transmission.
CON
The truck is quite heavy and the fuel economy is terrible. Going international finding parts could be harder then domestic but it is easy enough to repair at the side of the road. The truck is very tall and you will hit branches when off roading. The cab and engine are very loud. This can be helped with cetane booster and insulating the cab better but it will never be quiet like a modern vehicle.
All your friend will decide you are a prepper and make endless zombie apocalypse jokes.
aernan
Observer
Vision
The long term vision is to build up to a global capable expedition vehicle with redundant systems and a single fuel (diesel).
Design Goals
- Be in 110 F heat and have 60 F interrior so we can enjoy moab and other deserts in the summer. And go to cold frozen place too.
- don't use a generator at all. Run from engine/alternator and solar exclusively. No plugging into the grid if possible
- 1000 mile fuel range.
- 1 week of off grid living
- Capacity for 2 people and a dog with space for 3rd
- Act as base station for activities
- Act as off road recovery vehicle for expeditions
The long term vision is to build up to a global capable expedition vehicle with redundant systems and a single fuel (diesel).
Design Goals
- Be in 110 F heat and have 60 F interrior so we can enjoy moab and other deserts in the summer. And go to cold frozen place too.
- don't use a generator at all. Run from engine/alternator and solar exclusively. No plugging into the grid if possible
- 1000 mile fuel range.
- 1 week of off grid living
- Capacity for 2 people and a dog with space for 3rd
- Act as base station for activities
- Act as off road recovery vehicle for expeditions
aernan
Observer
Current Design - Cabin
After doing a bunch of research it looks like a composit box is both strong light and well insulated. Based on projected cost and lack of experience working with composite construction we are going to opt for riveted aluminum sheet metal construction with residential spray foam insulation.
Current design floor truss will be "hat" profile bent from aluminum sheet with a top sheet to make a single rigid beam. The void will be filled with XPS/EPS from a local hardware store so it's not hollow. Corners will be C channel and have box beams riveted in place. Walls have identical construction with thiner hat profile. The exterior skin will be glued in place on the ribs with a sikaflex glue. The perimeter will be riveted for mechanical sheer strength. A cosmetic corner cornice will be put over the riveted areas. This seals the area and hides the rivets. Roof will be identical to floor. The idea is to avoid welding which would melt the foam insulation and warp the structure. All interior areas of the walls/floors will be covered in foam.
It looks like to get great insulation the spray foam is an R value of 8 at the best so we will be doing 2.3-2.5 inches to get a target R value of 18.4 for the walls. The number of windows will be minimal and double pane.
Securing the Cabin to the Frame
In many overland vehicles the frame twists a great deal during articulation. It is advised to have a 3/4 point connection to a sub frame. I believe the LMTV is unique in it's frame design and it has minimal or almost no frame flex under full load. The bed that is currently affixed is connected in six places and hard riveted in place. I am told the "van" body is hard connected with eight bolts. I will be inspecting the design this weekend.
I most likely will hard connect the box to the frame with some springs and bolts. Between the box and frame I will put a strip of high density rubber or hardwood strip to attempt to isolate the box in a small way.
After doing a bunch of research it looks like a composit box is both strong light and well insulated. Based on projected cost and lack of experience working with composite construction we are going to opt for riveted aluminum sheet metal construction with residential spray foam insulation.
Current design floor truss will be "hat" profile bent from aluminum sheet with a top sheet to make a single rigid beam. The void will be filled with XPS/EPS from a local hardware store so it's not hollow. Corners will be C channel and have box beams riveted in place. Walls have identical construction with thiner hat profile. The exterior skin will be glued in place on the ribs with a sikaflex glue. The perimeter will be riveted for mechanical sheer strength. A cosmetic corner cornice will be put over the riveted areas. This seals the area and hides the rivets. Roof will be identical to floor. The idea is to avoid welding which would melt the foam insulation and warp the structure. All interior areas of the walls/floors will be covered in foam.
It looks like to get great insulation the spray foam is an R value of 8 at the best so we will be doing 2.3-2.5 inches to get a target R value of 18.4 for the walls. The number of windows will be minimal and double pane.
Securing the Cabin to the Frame
In many overland vehicles the frame twists a great deal during articulation. It is advised to have a 3/4 point connection to a sub frame. I believe the LMTV is unique in it's frame design and it has minimal or almost no frame flex under full load. The bed that is currently affixed is connected in six places and hard riveted in place. I am told the "van" body is hard connected with eight bolts. I will be inspecting the design this weekend.
I most likely will hard connect the box to the frame with some springs and bolts. Between the box and frame I will put a strip of high density rubber or hardwood strip to attempt to isolate the box in a small way.
aernan
Observer
Amenities and systems
HVAC
We would like to avoid ever needing to be in an RV park and run a generator so we are doing everything possible to make system run off the alternator and solar panels. To this end the Air conditioner which is the largest load in the system will be run on 48V dc. So that means our battery pack must supply that voltage. We are also going the route of lithium batteries because of the high cycle count and density.
The AC unit can be run as a heat pump to warm the cabin but the main heating will be provided by a diesel fired hydronic furnace. The hot water will circulate to a hot water tank then into hydronic circuits. To get forced hot air we will use water -> air heat exchanges with fans. This same furnace will be tasked with warming up the engine prior to starting in cold climates. So it serves triple duty. The hot water tank can also be heated with electricity so we have redundancy there as well.
Refrigeration
One or two top loading electric freezer fridges will be put in the box (depending on space). No propane will be used because it's hard to fill outside our home country and most RV fires seem to be a failed fridge and propane.
Cooking
A combination microwave, oven, broiler will be installed and a single/dual cook top induction range will be used. This is based on recent advice about diesel cook tops and propane issues. We may opt for a hot water kettle (electric) due to efficiency.
Sleeping
We originally wanted to do a raising roof design to keep the camper height low and gain us a loft. After considering the complexity we are opting to have a motorized bed above the couch. Of course the couch and table turn into a bed as well so the truck could sleep 4 people.
Water Closet
We are opting for a cartridge style toilet over a black water tank. The bathroom will also be a shower. Due to limited space we might opt for a folding sink or tiny sink in bathroom.
Capacities
Fresh water: 120 gallons
Grey water: 120 gallons
Fuel: 53 standard + 100 gallon auxiliary @ 6.5 mpg 945 miles @8 mpg 1200 miles
Solar: 5x 400 watt panels = 2 kw @ 6 hours daily sun = 12 kw input peak
Battery: 22 kw (still calculating this number doing power budgets now)
HVAC
We would like to avoid ever needing to be in an RV park and run a generator so we are doing everything possible to make system run off the alternator and solar panels. To this end the Air conditioner which is the largest load in the system will be run on 48V dc. So that means our battery pack must supply that voltage. We are also going the route of lithium batteries because of the high cycle count and density.
The AC unit can be run as a heat pump to warm the cabin but the main heating will be provided by a diesel fired hydronic furnace. The hot water will circulate to a hot water tank then into hydronic circuits. To get forced hot air we will use water -> air heat exchanges with fans. This same furnace will be tasked with warming up the engine prior to starting in cold climates. So it serves triple duty. The hot water tank can also be heated with electricity so we have redundancy there as well.
Refrigeration
One or two top loading electric freezer fridges will be put in the box (depending on space). No propane will be used because it's hard to fill outside our home country and most RV fires seem to be a failed fridge and propane.
Cooking
A combination microwave, oven, broiler will be installed and a single/dual cook top induction range will be used. This is based on recent advice about diesel cook tops and propane issues. We may opt for a hot water kettle (electric) due to efficiency.
Sleeping
We originally wanted to do a raising roof design to keep the camper height low and gain us a loft. After considering the complexity we are opting to have a motorized bed above the couch. Of course the couch and table turn into a bed as well so the truck could sleep 4 people.
Water Closet
We are opting for a cartridge style toilet over a black water tank. The bathroom will also be a shower. Due to limited space we might opt for a folding sink or tiny sink in bathroom.
Capacities
Fresh water: 120 gallons
Grey water: 120 gallons
Fuel: 53 standard + 100 gallon auxiliary @ 6.5 mpg 945 miles @8 mpg 1200 miles
Solar: 5x 400 watt panels = 2 kw @ 6 hours daily sun = 12 kw input peak
Battery: 22 kw (still calculating this number doing power budgets now)
silvrzuki77
explorer
Need more build pics..... are you going to swap the gears out?
Sent from my iPhone using Tapatalk
Sent from my iPhone using Tapatalk
aernan
Observer
I am planing on high speed gears. I can get a Detroit rear locker but I'm not certain if that's necessary. I have recently located a set (I hope) and am working on doing a group buy.
aernan
Observer
I wish I had more build pictures to share. I am still in the engineering portion of the design. Here is where I am currently at.
Working on:
- I need to figure out where the doors/hatches and windows go (mostly done).
- pick an interior layout so I can figure out where vents and drains go
- do a first pass design of electrical system to figure out how many batteries and what size and locations of large components.
This will get me enough information to figure out where to put reinforcements in the walls to hang cabinets and walls.
Working on:
- I need to figure out where the doors/hatches and windows go (mostly done).
- pick an interior layout so I can figure out where vents and drains go
- do a first pass design of electrical system to figure out how many batteries and what size and locations of large components.
This will get me enough information to figure out where to put reinforcements in the walls to hang cabinets and walls.
aernan
Observer
I am opting for a very high carried water because the truck has a very high in bed capacity. I plan on using 20 gallons of water for a methanol/water or straight water injection system which I hope will reduce the exhaust gas temperature and partially offset my fuel costs. If the total weight of the water becomes a significant cost in fuel I will simply not fill the tank to capacity.
I also recently realized that my air conditioner will condense water and that could be a source of water after filtering. I do realize this could be a tiny amount.
Coachgeo
Explorer
if your going that route.. might as well consider other experiment.. Urine based HHO. Urine (which if your building a camper.... you will have anyway) inherently contains a catalyst already.. has a higher hydrogen yield than water based+ catalyst and requires less voltage to break it down than water+catalyst based systems. can supplement your meth/water experiment. Maybe replace it. will be doing something similar eventually. Meth-water though mostly just to occasionally clean combustion areas.
aernan
Observer
I'm planning on using a cassette toilet and I hope it will be easier to dump in public bathrooms so I can avoid going to dumping locations. I have heard mention of hydrogen injection in diesel vehicles. I don't really know much about it.