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saltfever
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« on: April 17, 2009, 02:00:23 AM » |
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There are many Plexiglass windscreens in LSR. That material is always at risk of cracking when drilling! To lower the risk you never drill it cold, always ensure it is warm first. The video shows why a drill causes a cracking problem and how to modify it to lower the risk. Enjoy  http://www.eaa.org/video/homebuilders.html?videoId=19802261001 |
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« Last Edit: April 17, 2009, 04:19:56 AM by saltfever »
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Peter Jack
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« Reply #1 on: April 17, 2009, 03:48:54 AM » |
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Take a look down the list of videos. There are a bunch more that are applicable to race cars, for example safety wiring and jig building.
Pete
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My avatar shows Tok, a 100# Alaskan Malamute.
He's the one who runs everything around here.
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RichFox
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« Reply #2 on: April 17, 2009, 08:40:25 AM » |
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I still say Lexan and Center drills.
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Peter Jack
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« Reply #3 on: April 17, 2009, 01:56:01 PM » |
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I definitely prefer Lexan. It doesn't shatter and form nasty pointed objects like plexiglass and offers much better protection in the case of an object or bird striking it. If you pay the extra for the marguard it resists scratching as well.
Pete
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My avatar shows Tok, a 100# Alaskan Malamute.
He's the one who runs everything around here.
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dick elliott
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« Reply #4 on: April 17, 2009, 03:31:20 PM » |
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And you can bend it too!
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Its better to be a has been, than a never was.
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mojomann
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« Reply #5 on: April 17, 2009, 03:50:52 PM » |
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 Everything that the video shows will work for plexiglass and Polycarbonate sheet, as well. From the safety standpoint, the polycarbonate (LEXAN) isfar and away the choice. If you don't care to chamfer the flutes on some bits, just chuck it up in your cordless and gently touch the concrete floor with it. That will dull it enough so it won't grab the edge as it breaks through, provided that you are not trying to horse the bit through the plastic. Easy does it and you will be fine. When you get to the last size hole, you can clean up all that melt snot just by using a bigger bit or a countersink to touch the edges of the hole and stop any hairline cracks from developing into something worse.
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hotschue
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« Reply #6 on: April 17, 2009, 05:31:08 PM » |
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Hello all, Reverse drill, run bit backwards. Makes a nice clean hole definitely won't grab material and shatter.
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Udo Horn
221.559 D/CGC '03
178.835 G/GMS '10
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RichFox
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« Reply #7 on: April 17, 2009, 05:49:40 PM » |
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Since we are all going to be using a Polycarbonate and not a cast acrylic, what difference does it make how you drill it?
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dick elliott
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« Reply #8 on: April 17, 2009, 06:05:16 PM » |
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If your going to drill lexan for pop rivets, make the holes .050 or so oversize to allow room for the rivet to expand.
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Its better to be a has been, than a never was.
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manta22
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What, me worry?
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« Reply #9 on: April 17, 2009, 06:12:08 PM » |
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The oversized hole is needed to allow the plastic to expand & contract with temperature-- o/s holes are needed for screws, too.
Regards, Neil Tucson, AZ
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Regards, Neil Tucson, AZ
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Dakin Engineering
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« Reply #10 on: April 17, 2009, 06:31:15 PM » |
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I prefer a hot soldering iron to drilling.
Sam
#6062
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Turbo Sportsters
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saltfever
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« Reply #11 on: April 19, 2009, 01:42:34 AM » |
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As the video showed plexiglas is used in general aviation. However, due to it physical properties, it is not suitable in an LSR environment. I was intent on sharing what I thought was a fabrication technique but forgot that plexiglas was not shatter proof. Thanks for all of the other great ideas that were posted.  |
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Jonny Hotnuts
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« Reply #12 on: April 19, 2009, 12:28:52 PM » |
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I prefer a hot soldering iron to drilling. My only issue with this is the fumes generated by melting polycarb are f-ing crazy poisonous. I have tried doing this, even outside but still get a nasty headache afterwards. They make drills for plexi-lexan and these may work better, but I have always had good luck using regular drill bits with high motor speed and ultra slow feed speed. Still not one of my fave things to do. |
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"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
(when Im not working on the car, I am ususally playing classical guitar)
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Rex Schimmer
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Only time and money prevent completion!
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« Reply #13 on: April 19, 2009, 12:35:16 PM » |
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Lexan (polycarbonate) is extremely difficult to have formed in compound curves, such as for a lakester or streamliner , I heard that GM spent $50,000 getting the one made for the SO CAL lakester. If the wind screen shape is not compound then Lexan is a good choice but for anything else you will have a very difficult time finding anyone that can form Lexan and not have it be wavy. All of the ex permental airplane guys use a type of ballistic Plexiglas that is strong, clear and affordable.
Rex
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Rex
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1194
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« Reply #14 on: April 19, 2009, 12:41:15 PM » |
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Use a Dremel at high speed, with a diamond tip cutter................................................................................
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