blow-up

[richard bachert]

And let's emphasize the 100 POUNDS PER SQUARE INCH! Anyone want to do the
math? Assuming a total loaded coach weight of 12K, we can probably put 8K
of that on the rear (that's why, after all, there are 4 tires back there).
In a satic condition, each cone is handling a minimum of 2K (ONE TON!) And
under way the load is anything but static, the cone loading to more than 2K
(as the rear of the coach tries to bottom) and less as the coash rises.
Although the cushioning effect of the air bags minimizes or eliminates any
sharp impacts, any imperfections, stress fractures at manufacturing or post
production injury (or loss of elasticity due to aging) to the cone COULD
easily become the site of the start of a violent and -- if your head were
actually IN the wheelwell at the time -- VERY dramatic failure. It would
give new meaning to the expression "Cone Head."
Very funny -- NOT!
Still checking, but a preliminary inspection of the cones on this 75 PB
indicates that they are either plastic or molded fiberglass -- not aluminum
or iron. If so, mine are outta there when I change the bags.
Glad we started this thread.
Dick 75 PB in soggy Hotlanta. Looks like you guys will be heading out of MB
just about in time cause it's comin' your way.



>
>> Dear gmc gang: How does a piece of solid plastic blow up? What pressures
>> are being exerted. Does the air bag blow? I'm concerned, I'm a 73 with
>> plastic!
>
>Arden,
> The force involved is whatever force the plastic cone is trying to transfer
>to the bogie arm. Or. to look at it another way, the ~100 psi air pressure on
>the inside of the cone, PLUS the force transferred from the bag to the cone.
> Fwiw, the GMCMI newsletter (vol. 50, 1995, IIRC) stated that the "black
>plastic cones" were "dangerous". From the confirmations we've received here,
>I tend to agree. I, for one, would never reuse a plastic cone when replacing
>an air bag, and would seriously consider replacing said cones in any case.
> My .02.
>
>Rick Staples
>'75 Eleganza
>Louisville, CO
>

 

[thomas g. warner]

Lets be careful or we will start another myth that will become impossible to
stamp out, and Arch doesn't seem to be monitoring the net to kill it.

I remember in college I took a class that included testing concrete core
samples(even though I was an electical Engineer) and was scared to death
when testing the first one. Professor got us ready for a terrible
explosion, hid behind a wall etc only to be disappointed later. As the
pressure on the sample built up I expected a large explosion and flying
pieces every where. Not to be however. A pop and the concrete split and
broke. No big deal. If someone has an old plastic one, put it in a
hydraulic press and load it up and see what happens. bet you will be
disappointed.

>And let's emphasize the 100 POUNDS PER SQUARE INCH! Anyone want to do the
>math? Assuming a total loaded coach weight of 12K, we can probably put 8K
>of that on the rear (that's why, after all, there are 4 tires back there).
>In a satic condition, each cone is handling a minimum of 2K (ONE TON!) And
>under way the load is anything but static, the cone loading to more than 2K
>(as the rear of the coach tries to bottom) and less as the coash rises.
>Although the cushioning effect of the air bags minimizes or eliminates any
>sharp impacts, any imperfections, stress fractures at manufacturing or post
>production injury (or loss of elasticity due to aging) to the cone COULD
>easily become the site of the start of a violent and -- if your head were
>actually IN the wheelwell at the time -- VERY dramatic failure. It would
>give new meaning to the expression "Cone Head."
>Very funny -- NOT!
>Still checking, but a preliminary inspection of the cones on this 75 PB
>indicates that they are either plastic or molded fiberglass -- not aluminum
>or iron. If so, mine are outta there when I change the bags.
>Glad we started this thread.
>Dick 75 PB in soggy Hotlanta. Looks like you guys will be heading out of MB
>just about in time cause it's comin' your way.
>
>
>
>

>>
>>> Dear gmc gang: How does a piece of solid plastic blow up? What pressures
>>> are being exerted. Does the air bag blow? I'm concerned, I'm a 73 with
>>> plastic!
>>
>>Arden,
>> The force involved is whatever force the plastic cone is trying to transfer
>>to the bogie arm. Or. to look at it another way, the ~100 psi air pressure on
>>the inside of the cone, PLUS the force transferred from the bag to the cone.
>> Fwiw, the GMCMI newsletter (vol. 50, 1995, IIRC) stated that the "black
>>plastic cones" were "dangerous". From the confirmations we've received here,
>>I tend to agree. I, for one, would never reuse a plastic cone when replacing
>>an air bag, and would seriously consider replacing said cones in any case.
>> My .02.
>>
>>Rick Staples
>>'75 Eleganza
>>Louisville, CO
>>
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach

 

[thomas g. warner]

Rick is this all theory or has someone on the net actually witnessed an
explosion of the cone? Not first, second or third hand but actually
witnessed it? Remember if the cone fails, the bogie arm is still there to
restrain the bag. When the cone fails does it explode the bag also? I can
understand the cone failing, and maybe even rupturing the bag, but have
never heard of one actually exploding.

Inspected my cones tonight and still cannot tell if they are aluminum or
plastic. they are black but I really don't want to scrape them for fear of
losing the protection of the covering if they are aluminum.

>
>> .........
>..............................................................................
>.......As the
>> pressure on the sample built up I expected a large explosion and flying
>> pieces every where. Not to be however. A pop and the concrete split and
>> broke. No big deal. If someone has an old plastic one, put it in a
>> hydraulic press and load it up and see what happens. bet you will be
>> disappointed.
>
>All,
> There is a tremendous difference between loading a part with a hydraulic
>ram and loading it the same amount with compressed air. When the part under
>the hydraulic (or mechanical) ram fails, that's it. The ram stops where it
>is, and the only forces released are those built up within the part.
> When the part being loaded by compressed air fails, the air keeps right on
>pushing, hard, until its pressure is totallly relieved. This continuing force
>can accelerate pieces of the sample to very high velocity. A common example
>is the retaining ring on split-rim truck wheels, whose violent expulsion has
>killed hundreds of mechanics, so many that OSHA mandates use of a safety cage
>when inflating new truck tires.
> Another common example involves removing brake caliper pistons for
>overhaul. The smart mechanic leaves the caliper connected to the vehicle, and
>uses hydraulic pressure to safely expel the piston. Even though this may
>approach several hundred PSI to budge a siezed piston, the piston doesn't fly
>out, it gently falls out. OTOH, those who use compressed air for the same
>task, are cautioned (rightfully) to place padding or wood blocks to catch the
>flying piston, to keep fingers away, etc, even though they never exceed 150
>PSI.
> Bottom line: shattered plastic air bag cones can and do send pieces flying
>violently. A material-testing ram is not analogous.
>
>Rick Staples
>'75 Eleganza
>Louisville, CO
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach