Planning on cutting out my spare tire area to frame it in and make a better mounting space / tank cage for my lpg tanks.

any reason this is a bad idea? I plan on bolting the frame into the chassis rails, nothing will be welded to the car, the frame will be welded.

obviously, i need to reinforce it properly, anything i do across the back is stronger than the flimsy metal there. i plan on having the top have several cross pieces to brace the box.

I know the top will meed to be covered and sealed when done.

My thinking is also, this frame can be the start of a cage for the car.

I havn't started really, I plan on figuring out a few things once i open it up and see what makes sense.

seems like the part of the frame that bolts to the car won't be tube, but the part that protects the tank will be, the top will have to be perhaps L rotated, it needs to be strong against force from the bottom, and resistant to compressing when hit from behind...

i think one of the things to keep in mind is nothing can be done to make something impervious.

just by using 1/8" mild steel it's already stronger than the chassis it bolts to.

hehe more being stupid.


( yes these are not welded, i know the bar near the latch is tilted, it's not clamped, it fits nicely. )
so i'm committed. what we have here is a big hole in the floor, and the top part of the frame taking shape. Gonna tack weld this shape together and take it out and weld it up good, then put it back in there and figure out where to bolt into the chassis rails.

Chose a trapezoidal shape, 1 because it's the shape od the rails back there, and it allows lots of overlap for the welding. gonna be doubling things up and making it real strong. where does the tank go? don't know yet. need to do something that allows me to bolt in a bigger tank without redoing lots of work.

the front and back are 1/8"X1" mild steel square tube stock, the sides are 1/8"X2" L stock flat part UP.

I still think this is stronger than the frame or the tank straps.

any advice or warnings yet

;)

If you are bolting anything throught the rear "chassis rails" be sure to use crush tubes to prevent the rails being crushed. (Kinda like what is used when fitting towbars.

good idea. I'll have to make something like that up. that will help with the no good frame spots near by to bolt to.

got my crappy welder out and tacked it together and got it out of the car to work on, since we're expecting rain, then rechecked fit, fits perfectly, so tomorrow i'll get an earlier start on welding, and maybe some help.

I'll post a pic in a bit, gotta go prewash the wifes car.
no pics till tomorrow...

falling asleep i had a concept.

once the frame is completed. I think the parts that attach the tank will be bolted to the frame, so what i'm specifically thinking is the cross pieces that it hangs from will be bolt in, basically the tank will be detachable, but still provide a strong attachment point.

I think that leaves me with figuring out where to bolt the frame to still.

lol need to figure out how it attaches to the car...

managed to get the frame welded up, started thinking about mounting the tanks, realized that if i flip the frame so the L flange is at the bottom, it's more mounting friendly, and fits just as well.

if i mount the tank this way...
/---\
/{ }\
/-------\
then i can fit 1 of the current tank, or something bigger that would be the perferred direction.

if i turn the tank 90 deg, i can fit 2 tanks that size.

=D

the idea was to make it upgradable. so that's working well.

had to put a blower on my welder to keep it from overheating as it's a piece of crap.

discovered that the 1/2" channel i was thinking of using bends too easily, gonna use 2" square tube like the front and back bits.

learning about crush tubes.

looks like i might need the help of someone with a good welder... mine will destroy sheet metal.

I've got a question.
You may have thought about this already so I'm just going to throw it out...
what happens if you get rear ended??
Will there be enough room, if the back caved in? or will the tank(s) get smashed between the rearend(axle) and the dick that hits you?
Didn't the Pinto have some minor flaw that punctured the gas tank on the axle when rearended?
I'm not a gastank mounting expert. It's just that this was the first thing that came to mind when I saw your axle in that gapping hole.
angelo

the same thing that happens if i had a petrol tank, i die.

I already recognize the fact that nothing is bullet proof, the intention of this is to: 1. Allow the tank to be strapped securely to the vehicle. 2. Reinforce what is a pretty flimsy rear end section.

The tank should remain in the vehicle ideally handle 20G in the direction of travel and 8G perpendicular to the direction of travel.

The pinto and other fords have had problems with bolts under the car poking holes in the tank, this continued until recently in the crown vic line that the police use.

the lpg tank is made of 3/8" cold rolled steel, pressure tested to 6x working pressure.

a petrol tank will burst in those conditions whether or not it's still attached to the vehicle.

The hole is going to be closed and sealed once i'm done. the tank is going to be about center of the hole in this version.

You ask good questions.

The answers are complex, I've though a lot about these things. I'm more worried about the speeding SUV's bumper going right above mine, as my wifes explorer does and the thing plowing right over the top of the car.

One of my plans is to perhaps have some sort of tube steel cage bumper made to protect the tank itself.

these cars aren't good to be hit from behind in period. so I'm also working on 3'd stop light high up in the hatch.

kicking around the idea of some sort of kill switch that kills power to the vehicle or shuts stuff down it the tank moves more than a few mm.

seriously considering a Co2 system or something for the tank area.

I've considered the failure possibilities for parts here. The thin sheet metal of the chassis is the weakest part, followed by the straps going around the tank, followed by the brackets for the straps, then the 1 1/2" square tube stock, then the 2"L then finally the 8.9 grade bolts.

Thinking about that has made me consider using the sort of straps found on diesel truck's fuel tanks, they and straps of that type would be more reliable, and easier to work on the tank.




you know your petrol tank is covering the whole floor back there, not much clearance to anything. I have room for a N20 tank and a CO2 tank with room to spare.