Isuzu frame mounted water tanks

SkiFreak

Crazy Person
In my opinion, it is normally better to mount any additional tanks onto the subframe.
This is assuming that you have a kinematic subframe that disconnects the chassis from the habitat. This will reduce potential issues with flexing and twisting.
Having said that, I have tanks mounted between the chassis rails as well, but all of those have their own kinematic mounting brackets.
I have a Fuso, but I do not see any reason why it would be different on an Isuzu.
 

Ultimark

Active member
Hmmm, interesting concept.

The chassis rails on the NPS which in Australia comes with the Isuzu 3395mm medium wheelbase, flexes like a circus contortionist. If you are converting an NPR into a 4x4, or just using it as a 4x2, and if it has a longer wheelbase than the standard NPS. I would hazard a guess that the mounts may eventually stretch and/or fail with use.

I have a 140 litre water tank mounted almost directly above and forward of the rear differential, it is attached in four places to the tray, which is kinetically mounted to the chassis rails.

Having seen the distortion possible on my own little truck, I would not suggest attaching anything solid to the chassis rails as they flex like plasticine; so to speak.

Our Isuzu NPS has 600mm of articulation on both axles, in this picture you can see that the front and rear axles are basically at their diagonally opposed limits. Trust me when I say the chassis rails are twisted like anything at the moment this frame was taken. The tray, which the camper is bolted to, stays straight, otherwise the camper would have been destroyed some years back.

I have personally seen a series of three water tanks bolted to the chassis rails of an earlier NPS, 2009ish during a build in 2019, I don't know what or why, but as I understand it, those tanks have now been removed/replaced with ones that are attached to the camper subframe.

Mick.

Front_Live_Axle_003.jpg
 

Peter_n_Margaret

Adventurer
I have an OKA which is now 30 years old. It was fitted with a chassis mounted 100L OEM stainless steel water tank.
The OKA chassis is a very stiff ladder frame, but the S/S tank cracked on several occasions until I replaced it with a heavy duty HDPE rotational moulded tank of my own manufacture. That has been trouble free.

I am now building a new light weight OKA motorhome. I have made my own rotomoulding moulds for all the tanks I need for the vehicle for both water and diesel. All are mounted directly to the chassis rails.
Tanks.jpg
Cheers,
Peter
OKA196 motorhome
 

gator70

Active member
For now I will avoid the frame mounted freshwater tank. I do need more water. I also need more storage than my rig is designed for. A 2nd spare tire would be nice. And I want to carry Kayaks. I will solve all four solutions with a TOAD. And place a extra water tank behind the driver, in the rear.
 

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BigSkyBrad

Active member
If mounting to the chassis, could the tank be on a frame that is static mounted to the chassis at one end and gimbaled on the centreline of the tank at the other end (maybe a large heim/rose joint)? - essentially like a 3-point subframe is.
 

Peter_n_Margaret

Adventurer
Or use a tank material that is flexible and has no fatigue issues such as rotomoulded High Density Polyethylene.
Cheers,
Peter
OKA196 motorhome
 

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