Re: 1:1 Landspeeder Project...NEW PICS 10/5/07!!!
I could use some help with the windscreen. I'm going to attempt a droop mold
heating up acrylic over an oval mold. The oval hole will be over a giant metal box 4x4x8. In the box there will be heat from something to be determined.
If anyone has messed with acrylic or has a better clear plastic to work with could you let me know. Temps techniques ECT. :eek
XREB
HI- This is do-able but I would allow a few sheets for trial and error.:rolleyes
http://www.lucitel.com/literature.asp
will give you a pdf of temp ranges. in 'Fabrication Guide'
http://www.crclarke.co.uk/Support/dataSheets.htm
will give you some cool ideas and more info too!
Once lucite/perspex sags, it sags- so you need to make sure that the weight of the perspex (lucite to you i think) doesnt pull it down right to the bottom of the 'tank' before you have a chance to introduce cooling.But this method would ensure pretty even curves -so long as your choice of heating is even all round.Remember to make a ruler/depth guage up to use from the top down- the reflections you will see on the plastic make it impossible to visually see how deep your dish is becoming. Plastic stays hot for a while so make sure you can remove the heartsource asap.............
Othewrwise, What I think will work is if you made up a large frame to clamp/screw a sheet of your plastic to.Allow 12 inches all round extra - or more the better really- to allow for the stretching (and will result in less forcing to shape).
Use/borrow/hire a garage jet/Parrafin space heater to heat the plastic up till saggy (not the BBQ patio type- the jet engine looking ones on wheels)- you will prob have to move it around a bit to even the heat out, and make sure you dont blister the plastic by being too close etc.(This is probably dodgy to say the least :eek) Once the plastic is saggy/bouncy, you have about a minute to:
plunge the frame/plastic over a solid/strong mould of the shape you want, + let the plastic sag to the floor over your former.
if needed- then use a second frame- with a cut out of the outside shape in it, so a heavy sheet of 25mm MDF or such like with an oval hole in it-to then press it over the heated plastic/ former and it'll help pull down the excess plastic around the sides, if this makes sense.:wacko. (The hole needs to be to size plus an inch all around or so, to allow for the thickness of plastic.).Your mould should be taller than needed unless you are happy with a flange/lip.
If you put LOADS of release agent over the mould- vaseline works a treat here- you can normally keep the plastic protection sheet on the plastic during the process. This will ensure you still have a glass clear finish to the plastic, although your former has to be very smooth to not pick up textures.
I'd avoid using any kind of painting/filler on the mould as it can react with the heat (over time).
Lucite is quite brittle and if you want a thick screen, it will be quite 'stiff' to work with- even at the pliable stage itll be like softish rubber- but very springy
Styrene or PETG are much easier to shape with thermoforming, but I think you might struggle to find something more than 3mm thick- but I cant say for the US market.
Hope this helps:love
