avatar_Weaver

HELP! Urgent advice needed re bending clear styrene!

Started by Weaver, March 16, 2011, 11:35:19 AM

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Weaver

I'm trying to make an aftermarket windscreen for a model motorbike. The real thing is a curved sheet of thick plastic, so I thought I'd use hot water to bend a smaller one from clear stylene:

Attempt 1: screen taped to a former to give it a "forced" curve, dropped in boiling water for a few minutes, then plunged into cold water. Result had "set" fingerprints and tape marks that wouldn't polish out at any price.

Attempt 2: screen polished, then covered with masking film on both sides. Taped to former with waterproof tape, dropped into boiling water and left in to cool naturally. Result: screen has correct curve and no fingerprints, but is misted by what I suspect are micro-cracks inside it's structure, which no amount of polishing will remove.

So, how do I put a permanent bend in a piece of clear styrene without either spoiling it's surface or misting it internally?

This model MUST be ready by Saturday at the latest (completely non-negotiable), so I need to know ASAP whether or not to persevere or give up.

Any and all advice gratefully received.
"Things need not have happened to be true. Tales and dreams are the shadow-truths that will endure when mere facts are dust and ashes, and forgot."
 - Sandman: A Midsummer Night's Dream, by Neil Gaiman

"I dunno, I'm making this up as I go."
 - Indiana Jones

jcf

Hi Harold,

previously formed clear styrene is notoriously a bugger to work with as it is basically 'pure' styrene with little or none
of the plasticizing compounds that make the coloured versions relatively easy to work, as a result it is brittle and easily
cracks.

Clear acetate, or PETE would be a more workable choice. Do you have any leftover clamshell packaging around the
house? This is generally PETE (recycle number 1) and it can be hot-formed and cut with scissors, the edges will take
gentle sanding/polishing. Use CA to attach it to the fairing.

HTH

Weaver

Cheers Jon.  :thumbsup:

I'm looking at other plastics at the moment.

The bike doesn't have a fairing: it's an aftermarket screen attached to the handlebars by two long, thin brackets which are incredibly fragile in 1/12th scale. This is why the curve has to be pre-formed: if I used the brackets to hold it in a curve then it's "spring effect" would just break them, because they're glued onto plastic, not clamped onto steel.
"Things need not have happened to be true. Tales and dreams are the shadow-truths that will endure when mere facts are dust and ashes, and forgot."
 - Sandman: A Midsummer Night's Dream, by Neil Gaiman

"I dunno, I'm making this up as I go."
 - Indiana Jones

deathjester

Do you have any soft drinks bottles at home?  Cut a 6''x6'' square, mount your former on a pole in a clamp/vice.  Using a candle, soften the middle of the plastic by holding 4'' - 6'' above the top of the flame, then quickly pull it down over the former.  Hold for about 3 secs.

frank2056

Quote from: deathjester on March 16, 2011, 12:40:08 PM
Do you have any soft drinks bottles at home?  Cut a 6''x6'' square, mount your former on a pole in a clamp/vice.  Using a candle, soften the middle of the plastic by holding 4'' - 6'' above the top of the flame, then quickly pull it down over the former.  Hold for about 3 secs.

Without a doubt, do ^^^this^^^. It's a lot easier and quicker than you'd think, and if you start with a soft drink bottle, it'll be "precurved". Just pick one big enough to have a curvature similar to the windscreen. If you screw up on the first (or forth) try, try again.

Weaver

Solved it!  :party:

I found some of those plastic stiffeners that come in the collar of new shirts: same thickness as the styrene but softer, and it took the hot water forming without a mark.

Thanks guys - much appreciate all the help.  :thumbsup:
"Things need not have happened to be true. Tales and dreams are the shadow-truths that will endure when mere facts are dust and ashes, and forgot."
 - Sandman: A Midsummer Night's Dream, by Neil Gaiman

"I dunno, I'm making this up as I go."
 - Indiana Jones

rickshaw

Thats good.  I'd have warned against using a candle 'cause it would more than likely leave smoke/soot on the plastic, embedding it in the softened plastic.   I've seen a small burner made from a jar, filled with cotton wool and part filled with Methylated Spirits and a wick made from cotton string soaking in it, poked through a hole in the jar lid, used for heating plastic.  It burns with a relatively low temperature, clean flame without smoke or soot.
How to reduce carbon emissions - Tip #1 - Walk to the Bar for drinks.

deathjester

That's why you hold the plastic clear of the flame - then it doesn't get burnt or smoky.  I do like the idea of that sootless burner though!

dragon

Hopefully you did dip those "failed" attempts in FUTURE (or local equivalent) prior to discarding them, right?
"As long as people are going to call you a lunatic anyway, why not get the benefits of it?  It liberates you from convention."- from the novel WICKED by Gregory Maguire.
  
"I must really be crazy to be in a looney bin like this" - Jack Nicholson in the movie ONE FLEW OVER THE CUCKOO'S NEST

Weaver

Quote from: dragon on March 17, 2011, 10:36:12 AM
Hopefully you did dip those "failed" attempts in FUTURE (or local equivalent) prior to discarding them, right?


Yep - thought the micro cracks might be on the surface in which case Future would help. They wern't and it didn't....

I tried bending a piece of the styrene with the help of a hairdryer, but it tended to set so fast when the heat was off it that it ended up wavy. Didn't help that my ideal-shape former was a plastic (polyethylene? Thick, greasy stuff...) paint brush holder, so I didn't want to heat the styrene on there in case it distorted as well.


Currently trying to make a 1/12th scale fake carbon fibre tank protector look right..... :rolleyes:
"Things need not have happened to be true. Tales and dreams are the shadow-truths that will endure when mere facts are dust and ashes, and forgot."
 - Sandman: A Midsummer Night's Dream, by Neil Gaiman

"I dunno, I'm making this up as I go."
 - Indiana Jones