In one of my former lives...over a period of years, I used to vacuum form
Plexiglass, Lexan, ABS, and Styrene, in sheets as large as 4' x
8'... (and w/o vacuum forming, 8' x 10' pieces!) and I made plenty of props
and set pieces using all the above materials... cutting it,
glueing it, shaping it, etc. etc...
I know what you're saying... but theory and practice are two different things.
The amount of flex across the top of the dash, where a
windshield is mounted... is not that significant... I would think... relative
to the flex across the cross section of the whole area
(floorboard, sides, to dash, etc.)
To call plexiglas "very brittle" is a little overboard... standard plate glass
is "very brittle"... You could punch plexiglass all day
long, and not get it to break... it's all a matter of type of impact...
score it and whack it on a benchtop edge... sure, it will
break... but if your windshield is experiencing that sort of impact... well...
I hope your head and neck is still attached to your
shoulder when it's all over! : )
I don't know about vinyl... How well does it deal with sunlight? scratches?
fleibility in the wind at speed? (there does have to be
some structural intregrity there)
Don't get me wrong... I'm not saying you don't have valid points... and maybe
vinyl is the way to go... I just thought you were a little
biased about Plex... as your wording and examples were, I felt, misleading...
to those that may not have experience with the material.
This thread is starting to sound like the answer is "all the above"... like
someone manufacturing a windscreen product for TR's would
have to offer all the above materials as options... as each has it's positives
and negatives... and each buyer would have his own
preferences. Bill Burroughs, for example, is probably never going to buy
Lexan again!
I do like to see the comments though... to weigh in the various opinions and
experience.
--Justin
Joe Curry wrote:
> Justin,
> In one of my former lives, I used to make guards for presses out of
>Plexiglas. I find that the stuff is very brittle and it doesn't
> take very much force to crack it. We would cut straight sections of it by
>scribing and flexing the piece against a table edge. It
> would always break in a straight line if properly scribed.
>
> The point is that Spitfires are very flexible and I assume the other Racers
>are as well. In extreme situations, I would expect enough
> body flex to crack a plexi windshield unless it was mounted with rubber
>mounts that will flex instead of transferring the flex to the
> plexiglas causing it to crack.
>
> That is why I think sheet vinyl of a thickness in the range od 3/16" might be
>the ideal material for this application.
>
> Joe
>
> jmwagner wrote:
> >
> > On this topic.... and I know there's no one simple answer... as the shape,
> > size, configuration, etc. of a windshield is going to make all the
>difference..
> > but in general...
> >
> > What thickness are people using on their TR's? 1/4" 5/16"?
> >
> > Secondly... I keep hearing about Plexiglass cracking... but overall....
> > wouldn't Plexiglass be the better choice? You can polish Plexiglass...
>Lexan,
> > on the other hand, is very unforgiving.
> >
> > While Plex might crack on an impact, it is unlikely (seems to me) to create
> > projectiles.
> >
> > What I'm getting at is... in the life of a windshield... if the impact is
>hard
> > enough to crack the plex... it's likely hard enough to damage lexan...
> > meanwhile... if you have lexan... you'll find yourself having to live with
> > scratches... during the life of the windshield.
> >
> > One of the racers mentioned to me, that after losing it in a turn, the car
> > became enveloped in dust... and a track helper reached over and whiped
>down his
> > windshield, so that he could see before returning to the track..... this
>simple
> > wipe down... scratched his Lexan beyond repair.
> >
> > So the question is... Lexan or Plex? and what thickness are people using?
> >
> > --Justin
> >
> > fredd wrote:
> >
> > > > (Lexan is what they make bullet-proof windows out of, by the way.)
> > >
> > > Lexan by itself is only used on very cheap low level armored cars, as in
> > > money transporters.
> > > Even then is has to be very thick, as 3/4" up to 1", and barely will stop
>a
> > > .38spl.
> > > So now you know that those very impressive looking Brinks trucks are, only
> > > impressive, and their protection level is typical *you get what you pay
> > > for*.
> > >
> > > The only way Lexan is decent in armored glass is when laminated between
> > > glass layers.
> > > Lexan is good for lamination on the inside of glass to stop smach and
>grab,
> > > as being used in the transit busses in the LA area.
> > >
> > > BTW, since you guys are thinking about balistic transmission covers and
> > > Lexan for your windshield, why don't we build you complete armored race
>cars
> > > ?
> > > OK, they would be a bit slower due to the weight :))
> > >
> > > I have build an armored Countach years ago for one customer.
> > >
> > > fredd
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