Mounting method - 100litre LPG tank on 110 wheelbox

In message <[email protected]>, EMB <[email protected]> writes
>Simon Birkby wrote:
>
>> 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 ****ing 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.
--
hugh
Reply to address is valid at the time of posting

hugh wrote:
> In message <[email protected]>, EMB <[email protected]> writes
>
>> Simon Birkby wrote:
>>
>>> 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 ****ing 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.

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.

--
EMB

In article <[email protected]>, hugh@[127.0.0.1]
says...
> In message <[email protected]>, EMB <[email protected]> writes
> >Simon Birkby wrote:
> >
> >> 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 ****ing 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.
>

Sheesh! It's not going to go <anywhere> - I'm gonna put gaffer tape all
over it :0)

In message <[email protected]>, Badger
<[email protected]> writes

[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?

--
Jonathan

Between the optimist and the pessimist,
the difference is droll
The optimist sees the doughnut;
the pessimist the hole.
Mclandburgh Wilson

"Jonathan Spencer" <[email protected]> wrote in message
news:[email protected]...
> In message <[email protected]>, Badger
> <[email protected]> writes
>
> [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?

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 ****-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
<[email protected]>
[email protected] "Badger" wrote:

> "Jonathan Spencer" <[email protected]> wrote in message
> news:[email protected]...
> > In message <[email protected]>, Badger
> > <[email protected]> writes
> >
> > [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?
>
> 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 ****-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.

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.


--
David G. Bell -- SF Fan, Filker, and Punslinger.

"I am Number Two," said Penfold. "You are Number Six."

Badger wrote:
> "Jonathan Spencer" <[email protected]> wrote in message
> news:[email protected]...
>
>>In message <[email protected]>, Badger
>><[email protected]> writes
>>
>>[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?
>
>
> 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 ****-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.

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.

In article <[email protected]>,
[email protected] says...
> On Thursday, in article
> <[email protected]>
> [email protected] "Badger" wrote:
>
> > "Jonathan Spencer" <[email protected]> wrote in message
> > news:[email protected]...
> > > In message <[email protected]>, Badger
> > > <[email protected]> writes
> > >
> > > [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?
> >
> > 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 ****-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.
>
> 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.
>
>
>

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

On Fri, 12 May 2006 14:46:08 +0100, Simon Birkby
<[email protected]> wrote:

>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