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Car Forum / Land Rover Cars / May 2006Mounting method - 100litre LPG tank on 110 wheelbox
I've got a 100-litre LPG tank that I want to mount on the RH wheelbox, inside the back of a 110. Couple of issues: (i) the wheelbox looks flimsy, considering the wet weight of the tank: it took two of us to lift it in (bought it 2/3 full). I don't want it going anywhere in an accident (ii) the tank is wider than the wheelbox, meaning the mounting cradle will partly over-hang the edge. So I'm thinking of making a plate to mount the tank cradle to and brace the wheelbox, plus some supporting legs braced on the loadspace floor, to suppport the over-hang. Steel would be nice and strong, but heavy too and I guess will rust the aluminium of the wheelbox if I'm not careful. I'm assuming 1/4" aluminium plate will be expensive, so I'm thinking of a piece of 20mm ply. Is this safe/legal/sensible? Anyone done this before/got all the answers? [sorry if this has been covered before; I checked for previous posts on Google Groups but didn't find anyhting] /Simon > I've got a 100-litre LPG tank that I want to mount on the RH wheelbox, > inside the back of a 110. [quoted text clipped - 4 lines] > it took two of us to lift it in (bought it 2/3 full). I don't want it > going anywhere in an accident No sh.t sherlock! :-) > (ii) the tank is wider than the wheelbox, meaning the mounting cradle > will partly over-hang the edge. [quoted text clipped - 5 lines] > I'm assuming 1/4" aluminium plate will be expensive, so I'm thinking of > a piece of 20mm ply. Is this safe/legal/sensible? No, not in the eyes of the LPGA, and no. > Anyone done this before/got all the answers? 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 www.bhengineering.co.uk > > I've got a 100-litre LPG tank that I want to mount on the RH wheelbox, > > inside the back of a 110. [quoted text clipped - 24 lines] > 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 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 ... > 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 [quoted text clipped - 6 lines] > Badger > www.bhengineering.co.uk >> What I'd do, personally, is manufacture a proper steel cradle for the >> tank [quoted text clipped - 6 lines] > 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. > >> What I'd do, personally, is manufacture a proper steel cradle for the > >> tank [quoted text clipped - 18 lines] > afraid, and unless the tank is properly secured, it's unsafe. > badger. 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 [sniperoo] >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? Out of curiosity, any takers on how many g is developed by our friend's half-full 100-litre LPG tank when his LR is in a head-on collision with, say, a Mondeo sized car, with each vehicle doing 20mph? More than 7g?  SignatureJonathan Between the optimist and the pessimist, the difference is droll The optimist sees the doughnut; the pessimist the hole. Mclandburgh Wilson > [sniperoo] > [quoted text clipped - 7 lines] > half-full 100-litre LPG tank when his LR is in a head-on collision with, > say, a Mondeo sized car, with each vehicle doing 20mph? More than 7g? Well, a lot of cars can reach 100% braking efficiency when doing a decelerometer test for an MOT, and that's done at 20mph, 100% efficiency for a given vehicle mass being equivalent to 1g I assume?? (assumption, the mother of all f.ck-ups!). Highest reading I've seen recently was a P38 rangie which achieved a decel rate of 155% (1), but that's emergency stop stuff, not head-on collision. I'd imagine the impacting of a Mundane might add another 2g, possibly, bringing the total to approx 3.5g?? Badger. (1). Most vehicles will give considerably higher brake force on the road than on the test rollers, due to weight transfer under braking. On Thursday, in article <MZqdnaaqw5-nev_ZnZ2dnUVZ8s2dnZ2d@bt.com> > > [sniperoo] > > [quoted text clipped - 19 lines] > (1). Most vehicles will give considerably higher brake force on the road > than on the test rollers, due to weight transfer under braking. 1g is an acceleration of 32 feet per second per second (approximate round figure) and 20mph is just short of 30 feet per second. So we're not going to be far wrong if we say 32 feet per second for the vehicle speed, which simplifies the arithmetic slightly. v**2 = 2*a*s v=32 a=32 s=distance. Re-arrange and we get: v*v/a = 2*s which means v/2 = s So 1g at 20mph is a stopping distance of 16 feet, plus thinking. Doubling the acceleration halves the distance. Follow this through, and a 7g limit on those tank fittings gives you a distance of 28 inches, which is about what you might expect for a car's crumple zone. Fortunately, there is an answer to this apparent safety problem. And if I knew who was driving over that crest into a crossroads at 60mph I'd tell them to take their bloody foot off the accelerator too. SignatureDavid G. Bell -- SF Fan, Filker, and Punslinger. "I am Number Two," said Penfold. "You are Number Six." > On Thursday, in article > <MZqdnaaqw5-nev_ZnZ2dnUVZ8s2dnZ2d@bt.com> [quoted text clipped - 46 lines] > And if I knew who was driving over that crest into a crossroads at 60mph > I'd tell them to take their bloody foot off the accelerator too. Hmm. So I need to fabricate a mount to survive +7g (extra for safety margin) longitudinal deceleration and, say half that for the inverse and the same for lateral and vertical. It's going to take some intelligent triangulation back to the chassis to do that - considering that the extremities of the mount will be 18" above and outboard of the chassis rail ... It just so happens that while I was sitting on the porcelain recliner in the 'library' at home this morning (on the bog), I saw something interesting in the LRM November 2003 issue. On page 67, there's a picture of a wheelbox mounted tank in the back of what looks like a Series from the side windows? Or maybe a panel with aftermarket side- windows. Anyhoo, (million-to-one shot) anyone know anything about it? /Simon >Hmm. So I need to fabricate a mount to survive +7g I'd think you needed more than this, humans survive much more than this http://hypertextbook.com/facts/1998/PhillipAndriyevsky.shtml So it'd be a shame if they were then crushed by a heavy object. AJH >>[sniperoo] >> [quoted text clipped - 19 lines] > (1). Most vehicles will give considerably higher brake force on the road > than on the test rollers, due to weight transfer under braking. If I've done the sums correctly, a 7g stop is the result of stopping from 30 mph in around 4.3 ft. That doesn't seem too improbable for a head on into a standard collapsible car. > I've got a 100-litre LPG tank that I want to mount on the RH wheelbox, > inside the back of a 110. [quoted text clipped - 21 lines] > > /Simon 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 got a 100-litre LPG tank that I want to mount on the RH wheelbox, > > inside the back of a 110. [quoted text clipped - 24 lines] > You can buy cradles/saddles for round tanks which have the mounting > legs and the straps to hold the tank in place. 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. > 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 I agree, with the cradle just bolted to it. Hence the idea of a full- surface 'plate' > 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 I see what you mean > 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. 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 > > > I've got a 100-litre LPG tank that I want to mount on the RH wheelbox, > > > inside the back of a 110. [quoted text clipped - 53 lines] > 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. > > > > I've got a 100-litre LPG tank that I want to mount on the RH wheelbox, > > > > inside the back of a 110. [quoted text clipped - 63 lines] > designed places. Too much flex will cause either the chassis to crack or > the mouting brackets to crack - both unpleasant. 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! > 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. 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? > 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 [quoted text clipped - 8 lines] > the underside of the wheelbox reduces the contact area of the > re-enforcement - you need contact area. Hope this helps. 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 ... > > 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. [quoted text clipped - 4 lines] > the Iwema kit. I'm assuming it's so nothing can find an electrical > ground through the tank? 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. >Couple of issues: 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. >>Couple of issues: > [quoted text clipped - 5 lines] > 4. > 5. It's a bomb. ZZzzz Pain! > >Couple of issues: > [quoted text clipped - 5 lines] > 4. You may need a certificate after fitting. > 5. It's a bomb. It's a <lot> safer than the average petrol tank ... Insurance/Certification in hand. > It's a <lot> safer than the average petrol tank ... 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. SignatureEMB > > It's a <lot> safer than the average petrol tank ... > > 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? >>>It's a <lot> safer than the average petrol tank ... >> [quoted text clipped - 3 lines] > > Errr, should n't the tank be fitted with excess flow valves? Yes.... but in several years as a firefighter (mostly attending vehicle accidents) I've seen more than enough that just piss gas everywhere regardless. SignatureEMB >> > It's a <lot> safer than the average petrol tank ... >> [quoted text clipped - 3 lines] >> >Errr, should n't the tank be fitted with excess flow valves? First rule of safety - never *rely* on the safety device. Signaturehugh Reply to address is valid at the time of posting In message <e3lr4h$drt$1@lust.ihug.co.nz>, EMB <embtwo@gmail.com> writes >> It's a <lot> safer than the average petrol tank ... > >Unless its torn itself off it's mounts and just clouted you in the back >of the head. By which stage it's also normally torn itself free of the >gas lines and is pissing gas everywhere just to add to your problems. When it will propel around itself around the interior at a great rate of knots, like a rocket. Signaturehugh Reply to address is valid at the time of posting > In message <e3lr4h$drt$1@lust.ihug.co.nz>, EMB <embtwo@gmail.com> writes > [quoted text clipped - 7 lines] > When it will propel around itself around the interior at a great rate of > knots, like a rocket. LPG cylinders don't actuall do a lot of propelling (the pressures a bit low), but if they're emitting liquid LPG they do a lovely line in cryogenic burns. SignatureEMB > In message <e3lr4h$drt$1@lust.ihug.co.nz>, EMB <embtwo@gmail.com> writes > > [quoted text clipped - 6 lines] > When it will propel around itself around the interior at a great rate of > knots, like a rocket. Sheesh! It's not going to go <anywhere> - I'm gonna put gaffer tape all over it :0) >> >Couple of issues: >> [quoted text clipped - 9 lines] > >Insurance/Certification in hand. Not if it's just bolted to a wheel box it's not. Signaturehugh Reply to address is valid at the time of posting >Thoughts: > [quoted text clipped - 3 lines] >4. You may need a certificate after fitting. >5. It's a bomb. says he who chops up gas bottles for fun... :) >>Couple of issues: > [quoted text clipped - 5 lines] >4. You may need a certificate after fitting. >5. It's a bomb. And it's a bloody heavy bomb too. Signaturehugh Reply to address is valid at the time of posting |
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