Date: Fri, 19 Sep 2003 08:29:06 -0700
Reply-To: Alistair Bell <albell@UVIC.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Alistair Bell <albell@UVIC.CA>
Subject: Re: Headlight Crack Protection
In-Reply-To: <BB9091C5.17C3%robertmstewart@mac.com>
Content-type: text/plain; charset="ISO-8859-1"
Robert,
first of all, acrylic is often sold under the "Plexiglas" trade name and
shouldn't be confused with Lexan, which is polycarbonate.
Lexan is much, much tougher but a shade harder to work with. Both can be
formed, bent after heating, acrlyic softens around 225-250 (oven temps) and
also can be worked with after dipping in hot, just boiled (*S*) water.
Lexan can also be heat formed, but a a bit higher temps (300) but first one
has to dry the Lexan at around 200-220. Lexan absorbs water and if heated
before drying, the water forms bubbles in the sheet. This is not as much of
a problem with 1/8 or thinner sheet, but still may happen especially if you
use a heat gun to soften a localised area.
Special ground twist drills (more acute grind) are sold for drilling Plexi,
but i have found that a regular grind (but sharp) twist drill works well.
Both plastics have a tendency to melt as they are drilled, so keep the feed
rate constant and a bit on the fast side. Drill press best, I have had
unpleasant experience drilling 2" plexi with portable drill....bit getting
stuck due to plastic melting...ugh.
Plexi more prone to stress fractures around drilled holes.
Both machine well, ie table saw and routing. 72 plus table saw blade best
(plywood/melamine type blade, or even a neg rake 72 tooth aluminum cutting
blade). Router bits should be sharp, clean, pilot bearings on bits (if used)
should be free running. Light cuts and many passes the key when routing. Be
prepared for losts of "snow".
Plexi will plane with hand plane or jointer. Light cuts again.
If i were to make headlight covers I would go for thinner (less than 1/8",
maybe 1/16"?) Lexan. I would try to use screws to mount to light surround
and use blobs of silicon on edges of lights as spacers to keep lexan a
distance from the light. Writing this now makes me think that that would let
dirt in between light and cover, hard to clean....maybe best to fit then
with Lexan pressed tight to light (was originally thinking "spaced armour").
Alistair
--
'82 Westy -> diesel converted to gas in '94
albell@uvic.ca
http://members.shaw.ca/albell
on 19/9/03 7:58 am, robertmstewart wrote:
> Happy Friday to all,
>
> 2 weeks ago I had a rock or object crack my front right small headlight
> glass. This got me thinking about ways to protect it. I know they make Lexan
> covers but I figured that for the same $50 dollars I could just go to the
> plastic store and pickup some thick clear acrylic sheets, cut it to size to
> cover both the low and high beam glass.
>
> I am not sure how to adhere it to the glass, I guess I can figure someway to
> adhere it to the body grill. Maybe Clear Silicon, or a possibly 2 mounting
> screws. I am open to ideas. I just canšt see purchasing those lexan covers
> when I can make it myself. Anyone see any draw backs to this idea?
>
> Anyone know how those Lexan Lens covers adhere to the Glass?
>
> Thanks,
>
> Robert
> NYC
> 89 Carat Auto