Right from the beginning of this project I made the decision to mount my primary fuel tank between the chassis rails and to do away with the OEM fuel tank that was mounted on the side of the chassis rail. Well… I thought this was technically a good idea, as it moves more of the weight into the centre, but the implementation has proven to be quite challenging.

 

To recap a little about my how I initially did my new fuel system setup…

• A sturdy bracket was made for the fuel tank out of 75mm structural C channel and this was bolted directly to the chassis rails of the truck.
• I had a local fabricator manufacture a custom 200 litre fuel tank out of 1.5mm stainless steel.
• Stainless steel fuel lines were made, along with some custom brackets, and these were secured to the chassis rails.
• A water separator was added into the fuel system as an insurance policy against crappy diesel fuel, of which Australia has an abundance.

 If you are interested in reading that article first, click here!

 

Unfortunately, not until everything had been installed and setup did I realise that there was a real problem with the initial fuel tank bracket.
The nuts on the bolts that secured the tank bracket to the chassis rails were virtually inaccessible when the tank was fitted. This meant that if I ever needed to remove the tank, it would be a challenge. Well, that’s a bit of an understatement… it would have been virtually impossible.

The only solution here was to modify the fuel tank bracket. This involved draining then removing the fuel tank, so that I could get the tank bracket off. I utilised most of the existing bracket, modifying the rear portion into a three part system; two side rails and the main section that bolted to these rails. This allowed for the side rails bolted to the chassis to stay in place while giving very easy access to the bolts that secured the main tank bracket.
The modified tank bracket was repainted and refitted into the truck. The fuel tank was reinstalled, the fuel lines were all hooked up then the system was bled. Problem solved… right? Well, maybe not.

 

This modified fuel tank bracket definitely resolved the initial removal problem, but I had started to question myself about whether or not this fuel tank bracket would adequately withstand the rigours of off road use. After hearing from someone else that had encountered issues with his centrally mounted fuel tank I decided that a different design was probably warranted.
One factor that I did not really pay enough attention to when designing the first to iterations of the fuel tank bracket was the chassis flex that occurs when the truck is undergoing articulation. With a solidly mounted fuel tank bracket, like the first two that I built, any torsional stresses that develop would be transferred directly into the fuel tank. This would likely result in one or more of the welds in the tank fracturing.
As is too often the case, Murphy’s Law would probably have this happen at the most inopportune time, so it was back to the drawing board.
I cannot really understand why I did not factor the chassis twist into my original fuel tank bracket designs, but I definitely didn’t.

 

I tested a few different designs, finally settling on a three point mount system. So, a third version of the fuel tank bracket was built.

With this design the front “legs” of the fuel tank bracket are the same as the previous two incarnations, but at the rear I removed all of the pieces that used to attach the bracket directly to the chassis rails. The rear of the fuel tank bracket is now attached to a heavy duty central mount via a single 16mm heim joint (spherical plain bearing rod end). The mount is bolted directly to the chassis cross member, both horizontally and vertically, which gives it more strength. The heim joint I have chosen to use is maintenance free and features a high strength chrome molybdenum body, chrome plated hardened ball and PTFE/kevlar high performance liner. This heim joint design will cater for any chassis twist that may occur during articulation.

The fuel tank bracket, now only being secured in three locations, is not as torsionally strong as it was previously. I was concerned initially that there was too much flex in the bracket itself, but then I realised that when the fuel tank is strapped to the bracket that the tank will add quite a bit of additional strength, making the fuel tank and bracket setup quite rigid. This is mandatory, as I don’t have a large amount of clearance between the fuel tank and the insides of the chassis rails; enough clearance to allow for chassis flex, but not a lot more.

 

This new fuel tank bracket seems to do the job, but I will do some articulation tests in order to confirm that.