The UMAX Ultimate RV Project

U M A X - RV ATW Conversion Project - October - 2017

Many FWD RVs get bogged on wet grass, what if you wanted to drive along the beach etc.?

You'll need a 4X4 RV so you may as well have one that's comfortable, that will take a bit more than a chair!

The start..
Empty 4X4 Bus = The starting point.

RV Internal shots

..Knowing RVs, we wanted to improve some things to make our RV project just like home.

UMAX ultimate RV

No toilet in the stairwell for us, nor do we want to have to man handle black water,
we're creating a
 rare combination of luxury and serious 4x4 capabilities.

Ignore signs like this!

Seep my ass

The electrical system is the heart of the RV in terms of comfort and having all the luxuries of home so we've put a lot of thought and testing into this.

Electrical System

The electrical system is based around a 4KW inverter (8KW peak) powered by a 150AH 48V battery bank. (Yes like a house..)


4000 MW

This system has the power to supply 15A which can heat water on the go for the shower etc.

A 2000W 12V backup inverter (white box control box below) is available for emergency 240V power.

The output can be routed to a point inside the RV. The engine should be running for higher loads as 10A @ 240V would draw around 160A at 12V this is the reason its connected directly to the main truck battery, however you could flatten the battery if you draw too much without the engine running. The trucks alternator can supply up to 200A.

Also check out "faster idle for charging".

Switches and gauges  Top switch (above gauges) turns on backup 2KW inverter, bottom switch will turn on/off both gauges (too bright when sleeping)..

Depending on the load it's safer to have the motor running before turning on the backup inverter, and leave on for a few minutes afterwards just to top up the 12V systems.

Charging 48V bank via Truck Motor & 56V generator mounted on engine

While it may seem wasteful running the engine to top up batteries, it's not if you consider the cost and messing around with a generator and the fact the more you cycle batteries the quicker they will need replacement. Most people don't seem to mind a "car engine" running (or don't notice) but they do tend to get miffed over generators. We suggest that you start the engine to use the 3.3KW instant hot water service (or High Power Microwave for extended periods) without stressing the 48V batteries. This also means you can run the engine for relatively short periods to get a massive charge into the 48V batteries, especially helpful if camping with little sunshine. While the 48V batteries can cope with big current drains, it extends their life if you avoid this as much as possible. Not hitting the batteries hard if you don't need to saves money in the long run.

Faster Idle Speed for Charging

Both the 12V and 56V alternators perform a lot better at a higher RPM than idle.

To get the RPM to the optimum for the 48/56V system (just under 1,000 RPM) simply turn on the truck's AC system. There is an override button so you won't actually be using AC, it tricks the trucks computer increasing the RPM. We found this to be the easiest way to get the RPM needed.

Sunny or Driving a lot?

You may not need the 56V generator so there is an isolator switch to the left of the main inverter. There is no point "generator" charging if there is a lot of sun. The advise to start to motor for very heavy loads still applies regardless (the generator can supply several thousand watts to save the battery cycles). You may be thinking how come 48V and 56V? You need more than 48V to charge a 48V bank the peak or bulk charge voltage can reach 58V for a short time then drop back to the float voltage of 54V. Under no load around 51.9V is 100% charged. 

Electrical System

The system is designed with redundancy in mind, so if one inverter/solar or alternator system fails you can get by on the other one.

If you've forgotten to turn off the 2KW inverter and flattened the cab/truck main battery (2KW inverter needs the motor running if your using it under heavy load) then you should be able to recover by pressing the button on the "Projecta" 150A switch and effectively jump start from the main 150AH house battery.

If you've flattened the lot we have a plan for that too, you can wait for some sun to charge the batteries or use the Anderson jumper leads.


Water System

100L and 65L fresh water tanks (main and reserve, both fill via single keyed inlet cap)

3 tanks Fresh, fresh, gray..

55L Grey plus 55L black water tanks (gray can be pumped to black to increase gray water (100L max) capacity & flush black water)

Water temperature and black water level Shower temperature control (using 10L HWS) & Black water level


  • Gray water used to flush Full Sized marine toilet.
  • Black water (Toilet) tank emptied via electric pump. (Just put the hose into the drop point and press a button!)

    HWS and Black Water pump

-- Suggest pump some Gray water into tank then empty that out to flush the black water tank.
-- Gray water emptied by porting to black water tank, (switch above HWS) then emptying black water or using dump tap.
-- Suggest flush black with gray water after empting black water via Gray > Black "port" swich (which powers a small pump).

  • 10L Storage heater HWS (1KW) 240V or 12V @ 25A. This will run at max temp if using 240V which we recommend.
  • Bulk drain tap for grey water is fitted in case you have more than you can use in the toilet.

You can also run the HWS in 12V mode (70 deg is the auto max) by turning on the 12V breaker located near the heater.
HWS uses say 1,000W for 10min of every hour to stay full hot. This adds up so it's better to turn on say 1HR before you need it, then off when done. Even off, some hot water will last for hours for dishes. If the 10L HWS is set to max temperature, a set amount of cold water is mixed (adjustable via blue value with pliers, see image above) so as to maximise the shower time. You'll have long enough shower or 2 shorter showers on the one tank before needing to re-heat.

The easier and more echnomical way is to set the HWS temp to your acceptable shower temp then you don't have to adjust anything else.

For 240V operation, there is a switch behind the microwave so you don't need to go outside.


10L HWS should be powered off and the water output valve (near HWS) also off. 

In this case you can use the 3.3KW instant HWS as you're not feeding it hot water (the output temp would be too high).

This heater would be best if plugged into mains power. Naturally it uses a lot of electricity and is hard on the batteries so if you're not at a caravan park and using their power then you'd run the engine at the same time to save the batteries. This is why we added a 5KW 56V alternator, just run the RV's motor and there will be no stress on the 48V batteries even when drawing 3.3KW. You can also run the motor just for a fast bulk 48V charge.

  • 3.4KW intatant HWS for shower if not using storage heater above. (Great for when plugged into mains, will also work via 4KW inverter with truck motor running)

3.5KW HWS Instant HWS

--Not to be used if the 10L system is hot and connected (turn off the water out) this would be pre-heating the water making the shower temperature hard to control.

The temperature regulation is more flow = lower temperature, as set via the Off/MAX tap in the image above. WARNING always check water temperature before use.

  • Normal or Filtered water via sink tap is (electric) switch selectable (no need for 2 taps)
    -- Red indicator to remind you that pump should be off while traveling in case a pipe or fitting fails.

    Pump switch

    Sink area

  • Toilet slides into shower area when required.
  • 1.95m H x 800mm D x 900mm W (Aprox.)

-- This doubles the space as you effectively have both a shower area and toilet area of the same size.

See also Climate System for emergency water source. 


Climate System

Diesel Heater

  • 4KW diesel heater with 7 day timer, can be used as ventilation fan
  • -- Using a fraction of L/HR very economical and extremely effective heating
  • Reverse cycle AC modified to provide emergency water supply (up to 30L / Day)
  • Caframo Sirocco Fan



Recovery System

  • 1750 lb - 7938KG (24v) Winch rear mounted so you can back out of further trouble

    Fitting Winch Fitting the new Winch with custom mounting cradle..

  • -- After use suggest allow some time for 48V system to automatically re-balance before charging at high currents
  • -- Using some pulleys you could winch forwards too
  • Permanently mounted 4 X Treads and shovel

    Treads We got bogged on purpose just to try them and they work a treat!

  • Front winch point
  • 2 X spare wheels
  • Portable air compressor that can actually get to the pressure you need
  • Various ropes, pulleys, snatch strap etc.


Fuel System - Diesel

  • 220L total over 2 tanks

100L main tank is supplemented by a 2nd 120L** (reserve) tank on the other side of vehicle = 220L. 
The range is approximately 1,100km to 1,500km depending on your rush (80km/h speed is much closer to 1,500km range from our testing)

  • The 100L (main) tank can be topped up on the fly from the reserve tank.

An electric pump will pump approx 1/3 of a tank in 3 min. This pump has a key safety interlock so you can remove this key so nobody can cross pump fuel (say you have children staying).

It would be possible to overflow the main tank (just as you could at a petrol station) which is the reason it's key protected. While the pump is operating there is a large RED light on the dashboard.

If using the petrol gauge to estimate how much fuel you've cross filled remember there is a lag (unless you turn ign off then on) so we suggest you don't fill to more than 3/4 without either turning ign off/on or allowing 10 min for the gauge to average its reading. The same switch that turns on the cross pump also allows the main fuel gauge to read the reserve tank. If the switch is in this position a yellow indicator will be on to remind you that your not looking at the tank that's running the engine, thus if left in that position you could run out of fuel and stall the engine.

When the fuel gauge is reading the reserve tank it's 1/4 of a tank pessimistic so you have a fuel margin.

Note the 2nd tank supplies the diesel heater and this should be taken into account in your calculations.
** This tank was purchased used (in perfect condition) as that's the only way we could source one. 


Kitchen - Cooking

  • Smeg Convection Microwave
  • Engel 95L Compressor Refrigerator (they work in hot conditions unlike the others)
  • Electric induction hotplates (removable) supplied
  • Dometic Rangehood
  • Dometic Sink
  • Kitchen drawers / Overhead Storage / Push to open draws and cupboards (excludes overhead they open upwards)
  • Soft close duel garbage containers (one or both can be used for storage)
  • Soft close pan rack
  • Wine Glass Holders
  • Outside - Slide out BBQ




Other Items

  • Electric Awning with inbuilt LED lights
  • Ranger Roof Hatch with LED lights
  • 2 x Side skylights either side of Main Roof Hatch

    Fitting Sky Lights and Hatch Installing Sky Lights and main Hatch

  • Full sized windows (4 x 800mm x 1.4m, Rear 600mm x 1.8m, Bathroom 700mm x 1.2m, Door 540mm x 750mm)

    Full Sized Windows

    Full Sized Windows

  • Rear Glass - Upgraded to incorporate a sliding window 1400 x 320mm. Lockable with fly screen for better ventilation flow through 
  • Entry to Cab from Cabin (Great for starting engine, use in emergency to gain access) 
  • Aluminium blinds
  • LED lights to number plate
  • Auto Electric Steps into RV
  • CB Radio
  • CD / MP3 player in cab
  • GPS in cab in place of rear view mirror
  • Registered to seat 5 (Currently only 3 seat belts installed in cab, would require installing 2 to rear seat inside RV)
  • TV antenna (high gain with adjustable amplifier next to TV)
  • Yamaha Soundbar (Top of range very good sound) - Review

    Drivers: 2 x 19mm dome tweeters, 2 x 55mm midrange, 2 x 75mm woofers Quoted soundbar power: 30W x 2, 60W Subwoofer: 200W (no specs) Inputs/outputs: 1 x optical digital, 1 x coaxial digital, 1 x analogue (RCA phono pair), Ethernet, USB (service only), Bluetooth, AirPlay, MusicCast MusicCast file type support: MP3, WMA, AAC, FLAC, WAV, ALAC, AIFF Streaming services: Spotify Connect, Pandora, internet radio, others via AirPlay/Bluetooth Dimensions (bench): 950mm x 72mm x 131mm Dimensions (wallmount): 950 x 131 x 80mm Weight : 4.9kg.

    Sound and Vision

  • Spotlight (Marine, remote controlled at front)
  • Emergency light (Yellow, flashing at rear of RV powered on with spotlight can be overridden to always off)
  • Driving lights (2 X high powered LED) 

    LED Driving lights

  • Laptop Table (removable, magnetic & latch secured)
  • Magnetic locks on cupboards & draws (all that would open can be magnetically locked by simply turning on running running lights or main lights (i.e. you are driving)
  • Colour coded aluminium side protection to match powder coated wheels

    Colour Coded Siding Protection
    Colour Coded Powder Coated

  • High power USB charger (next to bed)
  • Reading light and all lights can be controlled from the bed
  • Reupholster drivers and passenger seats (plus matching seat covers) to math couch/bed
  • Fit new carpet (Genuine, you would not believe the price..) in place of vinyl. Fit extra second layer of sound proofing underneath carpet
  • 4 Cupboards (Push to open, 2 x 400mm x 540mm x 680mm H, 1 x 400mm x 200mm x 680mm H, 1 x 540mm x 170mm x 680mm H)
  • 4 Draws (Push to open, 400mm x 500mm x 100mm D)
  • 7 Overhead aircraft style storage lockers (150mm x 850mm x 300mm aprox)
  • 1 Sealed "Coffee, Sugar" storage unit under sink (130mm x 270mm x 160mm)
  • Boot storage (850mm W x 350mm H x 1.5m W Approx. usable) The boot also contains the batteries etc.
  • Long item hanging area 
  • Full width couch turns into bed 1.1 W x 2.3m L
  • 56V - 90A Alternator (5KW) Approximate total cost $3,200.00 (Completed)
  • Overhaul Gearbox & Changeover Transfer Box
  • The gearbox was in very good condition given the low KMs. However the synchros were starting to wear, there was one gear with a mark on it (Replaced = $1500) and a few bearings that were not 100%. FG Transfer boxes are known for problems, in particular alignment. The box was replaced with one that's been overhauled and had alignment problems sorted. Total cost for both in the order of $16k. The reason this investigations started as because of a high pinch whine noticeable over 80KM/h. It did not matter what gear you were in the pitch was about the same. We ruled out the engine by turning it off at 100KMh, also in neutral the noise went. It was not the front diff or back as both were virtually silent. That leaved only the gearbox or transfer box, as the syncro in 3rd was not working as well as the other gears the thought was to do everything (replace the set and anything else not 100%) for peace of mind. We'd already done the clutch.

    Bed / Couch

  • Front seats can be used as bed via insert that fits between driver and passenger seats
  • Headroom for 6' 2" (Approx 1.9m)
  • Full sized shower / Toilet (1.95m H x 800mm D x 900mm W)

    ShowerToilet slide out

  • Cabin internal area approx 18 m2 volume (4m L x 1.9m H x 2.4m W)

    Cabin area



Extra Service Items Done

Even though the Fuso only had around 47,000kms when we started the project we've seen to:
(While working on it may as well "do the lot")

  • New clutch
  • Overhaul Gearbox and Transfer case
    -- To be honest they thought we were mad the problems were that minor
  • New shockers all round
  • Full safety check & service
  • New windscreen (even though the old one passed the roadworthy)
  • Various other small mechanical items such as suspension bushes 

Upgrades by ATW 

Super Single Wheels, Parabolic Suspension etc.

Super Single Wheel Conversion

As all wheels are the same having 2 spares makes this RV virtually unstoppable.



Bull Bar



Unless we mention otherwise every item (we fitted) mentioned on this page is new

Case in point Winch (never used apart from to pre-tension the line so you don't burn it).



Errors & Omissions Exempted (E&O.E.)

 Parts list (not complete list)

  • GME AE4018K2 UHF CB Antenna Kit High Gain 6.6dBi
  • CCD Reversing Camera 4Pin Waterproof + 7" LCD Monitor
  • Gleamous DSK-45EP 3.3 kw Portable Instant Hot Water Heater with Shower
  • PROJECTA DBC150 12V 150A DUAL BATTERY SYSTEM ISOLATOR (To charge house battery from engine or jump start flat starting batter)
  • Bio 4in1 AIR CONDITIONER Reverse Cycle Fan Heater DEHUMIDIFIER (modified to supply emergency water) - 16000 BTU
  • 200A 12V Car Audio Inline Circuit Breaker Fuse Replace Reset for Vehicle MA692
  • 60A Amp DC Circuit Breaker Car Auto Vehicle Marine Stereo Audio Fuse (Behind fiidge to distribute 12V, this should never blow because there is a breaker before it)
  • 12V MA782 Panel Mount IP67 Waterproof Circuit Breaker 50A
  • Philips HD4992 Electric Single Induction Cooker Digital Display HotPlate Cook top
  • 2 x 130W 12V Solar Panels (for 12V system)- 2 x 200W 24V Solar Panels (for 48V system) total 660W
  • Caframo Sirocco Fan

    Solar Fitting  In the process of fitting the high gain TV antenna

  • 4 x 10m Extension Cable Wire MC4 Connectors for PV from Solar Panel to regulato 220-240V
  • Temperature Controller Control Temp Thermostat Switch 1 Relay w/ Sensor (used to pressurise battery / electronics bay when hot to keep dust out)
  • Access Hatch with Storage Box for Caravan/ Boat/RV White Lid storage Box R2333 (Houses HWS, Hose, Black water pump)
  • Milenco Power 900L Digital Caravan Antenna TV Aerial
  • Navman EZY 350 GPS with lifetime free maps

    Navman GPS

  • Battery Capacity Volt Meter 48V DC Lead Acid LED Indicator
  • Battery Capacity Volt Meter 12V DC Lead Acid LED Indicator
  • Battery equaliser / balancer for 9.6v- 48v lead acid, LiFePO4 and NiMh.
  • Esmart 40A LCD MPPT Solar Charge Controller Battery Auto 12V 24V 48V Regulator
  • Pure Sine Wave Power Inverter 2000W (4000W Max)12V-240V 2.1Amp USB
  • Dometic Rangehood CK155 Surface Mounted with 2 speed fan
  • 4 x Push To Open Beetles Drawer Cabinet Latch Catch
  • 4 x RV Seat Magazine Storage Pocket - Netting - Black - 400-00658
  • 6 x 12V 60KG Small Magnetic Locks
  • Gear Oil Pump Fuel Diesel Bio-diesel Transfer Scavenge 12v DC
  • 2X 4LED License Number Plate Light Tail Rear Lamp
  • 8MM 5/16" Aluminium One Way Non Return Fuel Line Check Valve Petrol Diesel Water
  • H3Y-2 DC12V Delay Timer Time Relay 0-10 Minute w/ H3Y-2 Base Contact Capacity 5A
  • Caravan Access Door 2 Locking Black 415 x 681 mm - 600-00022
  • 1 x Pro Power 12V Volt 150AH AGM Deep Cycle Battery
  • 4 x 150AH AGM Deep Cycle Battery - Giant Power
  • SSB LH51913 High Performance Lithium battery CCA 580 (Cold cranking amps, 10 year design life)
    - Aux 12V battery in parrellel with main truck battery for amazing starting performance
  • 1 x 200-38110 - CAREFREE Freedom 12v Box Awning - 3.0m - Silver Shale Fade
  • 4 X Monroe 16-0342 Gas-Magnum TDT is a super duty gas charged shock absorbers
    Made for Australian conditions, Monroe's exclusive Twin Disc Technology (TDT) has delivered a tough, durable shock
    absorber that can keep you comfortable and safe on virtually any type of surface.
  • Runva Winch (1750 lb/7938KG) EWN17500 24V with Dyneema
  • 1400 x 320 sliding window with fly screen (rear, AU made)
  • Anderson connection for jump starting with Anderson connection jumper leads
  • Truck power isolation switch (hidden, great extra security feature if leaving unattended for long periods)


  • Engel 95 Litre Upright Freestanding Refrigerator (ID: 137626, STR100F, 9334660025938)
  • 1 x RV MEDIA: 28 Inch HD LED TV & DVD Combo - 12v / 24v / 240v (CC-043524) Actual image below:

    Features  D DVB-T digital TV tuner Inbuilt DVD/CD/VCD player USB multimedia playback & PVR function Quick Tune auto tune button on remote Sleep timer Multi-language Parental controls LED TV Resolution: 1366 x 768 Dimensions: 643x80x390mm (without stand), 643x179x434mm (with stand) Net Weight: 6kg Aspect Ratio: 16:9, Contract Ratio: 3000:1 Brightness: 200 cd/m2, Viewing Angle: 160(H) x 170(V) Response Time: 8ms Inputs: 1 x HDMI, 1 x USB 2.0, 1 x VGA (PC), 1 x PC audio, 1 x antenna, 1 x composite, 1 x component Outputs: 1 x component, 1 x co-axial digital.

  • Yamaha Sound Bar AIR SURROUND XTREME (YAS-306)
  • Giant Power 48V 4000W Integrated Power System
  • Duoetto Mk2 Dual Voltage (12v/240v) Electric 10l Storage
  • Kaboodle kitchen cabinets - 10 year structural warranty - Tested to Australian standards - Solid 16mm construction
  • Marine grade carpet
  • Recessed Toilet Paper Holder & Wash sink
  • TMC Electric Luxury Marine Toilet 89669N
  • 12V Remote Macerator Pump (45031)
  • SearchLight Remote LED (RWB1658)
  • 4 x Water tanks (100L / 65L / 55L / 55L) Fresh/fresh/gray/black
  • 2 x Water pumps 12V (Fresh/cross pump gray to black) - 2 X Water gauges
  • 2 x Bathroom taps - Sink - Shower base - Custom Sliing Shower Door
  • Set of Mudflaps with stainless steel trimmings
  • Alternator Prestolite 48V 90Amp Internal Reg Mod To 56V R240105470S
  • 150A Breaker - 200A Cable 20M



This project is based on the 4000 series mining bus made by ATW


ATW – Manufacturer of 4x4 buses and other specialized 4x4 vehicles for Eco-Tourism operators; commercial drilling, mining and mineral exploration companies. Our 4x4 buses are renowned worldwide for their safe operation, sturdy and long lasting construction, operating in extreme terrains and highly corrosive environments. All vehicles are based on Japanese or European 4x4 truck chassis that are commonly available through existing dealer networks and incorporate specially developed passenger modules by ATW.

ATW INCLUSIONS: • Duragal Frame built to ADR 59 ROPS. • 19.5” super single wheel conversion. • OH&S compliant, IP66 automatic electric step. • Low maintenance, tough and corrosion proof inner/ outer fiberglass body shell. • Offload body mounting system. • Reverse beeper & rotating beacons roof-mounted front and rear of vehicle. • “White noise” cancelling squawker. • All appropriate mine safety signage and Class-1 reflective side tape. •All metal access / egress steps and handles. • Water proof interior. • Sealed rear boot with LED lighting and wheel changing tools securely mounted. • Rotating beacon rear with all ADR signal lighting molded into body. • Sock ring pass-through between cab and passenger module. • Driver and passenger SRS air bags in cab.

We are not associated with ATW.

PDF Brochure for information only. Several items are different from our project 4X4 RV.

  • We understand the price for a new 4000 series bus is around $260,000 AUD.

Basic Truck Specifications before any alterations by ATW (many vary) PDF

This project will be for sale late 2017. ($240K)