Mounting method - 100litre LPG tank on 110 wheelbox

No shit sherlock! :-)

No, not in the eyes of the LPGA, and no.

NO-ONE has ALL the answers, and it's a dangerous fool that claims to! What I'd do, personally, is manufacture a proper steel cradle for the tank to mount to, a steel support framework to bolt/weld to the chassis, with the bolts going through the two sandwiching the ally in the middle, but I'd insulate the ally from the steel by cutting up an old inner tube into suitable sized strips and punching the bolt holes through it with a suitable punch. As you rightly point out, a full gas tank is 'kin heavy, the LPGA (Bless 'em!) rulebook gives a "G" value for the security of any mounts but I can't remember it at the moment. I think it's something ridiculous like 7g or thereabouts? Badger

You can buy cradles/saddles for round tanks which have the mounting legs and the straps to hold the tank in place.

As for the likelyhood of the Birmabright holding a gas tank down in the back of a LR - hmmmm I doubt it without some serious re-enforcing of the underside of the wheelbox. The problem with all retro fits is that if you do any serious off road stuff the gas tank stiffens the body too much and you end up with cracks around the mounting holes in the Birmabright. Have a look at the seat belt mountings and you'll get an idea of what would be required to hold an 90kg adult without pulling the bolts through the floors, bear in mind that seat belts are usually mounted close to pressed/curved parts to give extra strength..

Plywood is a non event other than as an "insulator" between steel and alloy.

I've already got a very sturdy cradle and four 30mm wide steel straps to secure the tank to the cradle. The problem is that the wheelbox top where I want to put it is weak and the top of it is laterally and vertically some distance from the chassis member; otherwise it would have been an obvious choice to put a steel frame underneath ...

But in all honesty mate, it needs to be anchored somehow to the chassis, it's the only safe way to do it, even if it's only 2 rise brackets made of, say, 40mm box welded to the side of the chassis in an inverted "L" shape. Weld the long leg of the bracket to the chassis with the short legs running across the underside of the seat box, preferably with a triangulating gusset on each one, and bolt right through the whole lot. Unless you do something along those lines, you'll never get anyone to certify the conversion should your insurers request certification either now or in the future. The one thing I would never compromise in any LPG installation is safety, I'm afraid, and unless the tank is properly secured, it's unsafe. badger.

Yep, got those bits already. Strong enough to stop it budging even a millimetre in the beat-up RR Trialler it was fitted in before and still in as new condition.

I agree, with the cradle just bolted to it. Hence the idea of a full- surface 'plate'

I see what you mean

The 20mm stuff is pretty strong ... but it's still wood.

I can see me having to fabricate a steel wheelbox with triangulated bracing down to the chassis member

No No No, never bolt through from the body to the chassis except in the designed places. Too much flex will cause either the chassis to crack or the mouting brackets to crack - both unpleasant.

Just had a look at some notes I have on fitting LPG tanks in Australia where it is highly regulated fitment of LPG tanks and LPG systems.

What you need to do is look at the amount of re-enforcing around the seatbelt mounts, double the size and then re-enforce the underside of the wheelbox. eg if the sadlles holes are 100mm apart and are 10mm bolts, then using a rule of thumb the re-enforcing plate would have to be 100mm longer and wider in all directions from each hole. The thickness of the re-enforcement will depend on the steel or alloy you can use - 7mm mild steel should be ok, with 20mm washers on the bolt head. The re-enforcing plate needs to be attached to the Birmabright by double the number of saddle bolts and the through bolts no closer than 25mm to the edge. Dont forget that ribbing on the underside of the wheelbox reduces the contact area of the re-enforcement - you need contact area. Hope this helps.

Thanks Badger,

You're right: I've got do something along those lines. I think I was just indulging myself for a moment - shying away from the idea of all that fabrication ... I'll probably enjoy it once I get stuck in

Don't worry: spent a whole week last year grinding and plating the chassis, last thing I want to do is punch any holes in it!

Brilliant - thanks! Does it say anything about tanks mounted North/South in the passenger compartment being no closer than 10cm to any bodywork? There's something to this effect in an extract from the Dutch regs in the Iwema kit. I'm assuming it's so nothing can find an electrical ground through the tank?

I see what you mean. Now I'm thinking it through, my concern is for the integrity of the wheelbox as a whole: the potential for the whole thing to come adrift rather than just point fixings. I'm starting to lean towards Badger's idea of a triangulated steel frame underneath - bolted to bracket welded to plates on the chassis ...

Thoughts:

1. It's a bomb.
2. Your insurance.
3. It's a bomb.
4. You may need a certificate after fitting.
5. It's a bomb.

ZZzzz Pain!

It's a safer than the average petrol tank ...

Insurance/Certification in hand.

says he who chops up gas bottles for fun... :)

Unless its torn itself off it's mounts and just clouted you in the back of the head. By which stage it's also normally torn itself free of the gas lines and is pissing gas everywhere just to add to your problems.

Errr, should n't the tank be fitted with excess flow valves?

Not sure what that would be about, every bloody country around the world has different regs to make it as hard as possible to have large volume production of LPG powered vehicles. The tank must be electrically bonded to the vehicle, usually through bolts or the fill hose line.

Nothing on the alignment that you want that I can find, interior fitment of tanks just refers to mounting security, excess flow valves, solenoid valves, valve protection from accidental damage. I'd be inclined to put an alloy box around the tank, a rounded surface just encourages things to fall behind the tank and rattle around.

Yes.... but in several years as a firefighter (mostly attending vehicle accidents) I've seen more than enough that just piss gas everywhere regardless.

In message , Mother writes

And it's a bloody heavy bomb too.

In message , Simon Birkby writes

Not if it's just bolted to a wheel box it's not.

When it will propel around itself around the interior at a great rate of knots, like a rocket.