Copying a windshield

[beerbaron]

Hi, I have a cracked windshield and been wanting to copy it so that I would have a new one.

I tried to mold plexiglass over it with a heat gun... very hard work and always ugly.

I tried to make a ciment mold that would be raised to high temp and then mold the fiberglass with a heat gun on it... very hard work and still ugly.

I'm thinking about making my next windshield with fiberglass (I don't care if it's painted).

In an ideal world I would have one of those machines that heats the fiberglass and then mold it, but I don't. Any ideas ?

BeerBaron

 

[evelrod]

I have made medium sized polycarbonate canopies for my quarter scale radio controlled sailplanes using a home made vacuum forming mold. It would take a lot more work to make a motorcycle windscreen...but still doable.
Any modeler magazine, Google, etc. will yield a variety of plans. A trip to a hobby shop to look over the commercially available ones (too small) should give you an idea how to uprate their design.
If the windscreen is that bad, why not buy a new one. It will be a whole bunch cheaper than making your own.

Rod

 

[beerbaron]

I know, but the principle of making my own mold will be quite usefull for some other projects I have. Making a windshield is kinda my road test.

BeerBaron

 

[beerbaron]

By the way evelrod, how did you mold polycarbonate, I was told polycarbonate needed a 12 hour drying phase to get rid of the moisture? Is polycarbonate's flashpoint as high as acrylique ?

Thanks
BeerBaron

 

[evelrod]

The parts I made were from very thin sheets of Lexan and I did not know there was a problem until just now! Ignorance is bliss. ;-)

Rod

 

[GoKarts]

Perhaps you could heat a sheet of acrylic in a pizza oven. Know a buddy who works in a pizza place?

 

[MikeHalloran]

The trick to molding and forming plastic sheet, whether acrylic or polycarbonate, is close control of the temperature, and patience.

It takes a loooong time to heat all the way through a sheet of plastic because its thermal conductivity is very poor. If you want to drape form it, you need to ramp the temperature up to near the softening temperature over a period of hours. Tens of hours are better. If you want the plastic to come out without locked in stresses that can cause cracking and optical effects, the temperature should also be ramped down, over tens of hours. Vacuum assist can make the forming happen faster and at a lower temperature, but you stll need a ramping temperature controller for best results.

Heat guns and pizza ovens are way too crude.



Mike Halloran
Pembroke Pines, FL, USA