Hmm, good points, but but the bottom line is strength
and ease of application vs welding.
--- Trevor Boicey <tboicey@brit.ca> wrote:
> Carter Shore wrote:
> >
> > Epoxy, and (stainless pop) rivets.
> >
> > Hey, it's what holds airliners together.
>
> Too many differences between airliners and
> cars for this to hold water.
>
> Airliners are made of thin aluminum.
Airframes have thin aluminum skin, but there are many
other components that are substantial. The stringers,
ribs, headers, doublers, etc, that hold the skin in
the proper shape to maintain it's strength, to
distribute point loads, and interface to other
components. These are typically extrusions, forgings
or weldments.
>
> Cars are made out of thick(er) steel.
>
Any idea what guage the floorpan on a Spitfire is?
Maybe .032 - .062". The body panels are probably
similar. I chopped up a rusty old Spitfire hulk with a
small hand hatchet (to take to the dump) It was easy.
>
> Airliners have few if any tight curves or
> especially
> stressed areas made this way. Wing leading edges are
> an example, control surfaces, and so on. It's the
> long
> flat sections that are done this way.
The structural adhesives are used in conjunction with
rivets to bond the skin to the stringers and ribs.
This helps to avoid the point loading associated with
rivet holes by spreading the load accross the entire
joint. Most monocouque structures are designed as
torgue boxes, such that the skin is stressed in shear
and tension. The thin materials are not very strong in
compression and bending. These forces must be taken by
auxillary structures and reinforcements.
>
> Cars have many tight curves, and the steel
> body varies between unstressed and very stressed
> areas over short distances.
>
Spitfire body does not carry any substantial load. The
outboard sections of the tub, and the brace between
the scuttle and the frame (AKA the 'radio holder')
serve to increase the torsional rigidity. The major
load that the body carries to the frame is the weight
of the passengers, via the seat frame. Examine the
size of the 4 bolts to get an idea of the stresses
here.
> Airliners only have to look pretty from afar. The
> panels can be wavy and the rivets can be visible.
>
> Cars have to be smooth, so any rivets have to
> be buried in filler. Yech. As well, the panel
> cannot wave up and down between the rivets.
>
Yes, for external panels this is true.
> Airliners have to be inspectable. Rivets are
> inspectable in-situ.
>
> Cars do not have to be inspectable, if nothing
> is showing nothing is wrong. Welds are not
> inspectable
> in situ without big dollar equipment.
>
> Airliners have to be serviceable. A panel has to
> be
> removed, refitted, and replaced, then inspected, in
> situ and in budget. Rivets work well for this.
And what about structural adhesive bonds? They are
used on airframes, but do not appear to either
inspectable or serviceable.
>
> Car bodies almost never have to be removed of
> sectioned for service. They only need to be
> disassembled
> if and when they have major problems, so being able
> to take apart a working section without distroying
> it (something you can do with rivets) is of no
> value.
>
> Airframes are large items assembled from a series
> of smaller panels. You can't take a machine like a
> spot
> welder to close a large section of airframe, the
> machine isn't portable enough and the surfaces are
> not always accessible.
>
I believe that the Russians built several supersonic
aircraft entirely of welded stainless steel.
> Cars are small items that can be stamped out in a
> short number of operations and can be moved to
> welding machines on assembly lines where specific
> joining welds can be made quickly and easily.
>
> Basing what is BEST for you car based on what is
> "Industry Standard" for airframes is illogical.
>
> --
> Trevor Boicey, P. Eng.
> Ottawa, Canada, tboicey@brit.ca
> ICQ #17432933 http://www.brit.ca/~tboicey/
> Any part can be removed with the careful application
> of too much force.
Not saying it was BEST, just pointing out that it can
be an effective alternative to welding, that has been
used safely and effectively in an application where
failure must be avoided at all costs.
If I repair my rusty floor board by cutting out the
old one, leaving an overlap seam for the new one,
using epoxy and stainless rivets on the joint, it will
be just as strong, just as durable, and just as
appropriate as welding.
It's a repair that I can accomplish without the
equipment, skill, and training that welding requires.
It's a more forgiving technnology. It takes just one
slip to make a bad weld. Grind it out, patch it up,
start over. With epoxy, I've got time before it sets.
I can mate/unmate the joint several times, make
adjustments, get it postioned just so. Drill a bad
hole, fudge up a pop rivet? Easy to fix, or just make
a new one right beside the old one.
So, it's not just what may be best for the car. It's
also about choosing what's best for me (or you).
Thanks,
Carter Shore
__________________________________________________
Yahoo! Mail - Free email you can access from anywhere!
|