Polycarbonate screen

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Prof
Founder, Choppers Australia
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Joined: Sat Oct 22, 2005 3:54 pm
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Polycarbonate screen

Post by Prof » Thu Jan 02, 2014 10:10 am

A small screen on your chopper can make a big difference on long trips. Strong headwinds especially when have to wear these ridiculous modern bubble helmets can literally be a real pain in the neck! The benefits of the poor man's fairing (your sleeping bag mounted across the bars) of the 60's has not realised this time around, but even that makes a big difference, especially if your rake has been achieved with upward stretch.

To break the main blast of the wind in your face requires little more than a glove sized screen. If your steering head is high due to upward stretch and you have narrow pull backs, T or Z bars, then a screen is quite practical and not bad looking.

Only Perspex used to be available, but this discolours over time. Modern polycarbonate is excellent, stands a fair bit of ill treatment, drills safely and retains its transparency. 3mm is a good size for small screens.

Your screen will be effective with its highest point being an inch or so below your vision line. Mount it on three or four points. I use some soft rubber washers each side of the screen to reduce the chance of cracking. Top mount(s) should be low enough to allow the screen to bend forward and snap off in the event of a sudden stop (accident) so you don't lose your head! Even a bad cut is worth avoiding.

Having made a cardboard pattern, trace the outline onto the protective cover paper.

Cut it out on a bandsaw or with a jigsaw. If using a jig saw, the paper may be scratched through by the vibration of the base, so before I had a bandsaw I used to cover the bottom of the jigsaw base with a couple of layers of tape. Polycarbonate scratches very easily...
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The edges now need to be sanded to remove the sharpness and to smooth out any irregularities due to inaccurate sawing. You can go down through progressive grit sizes of 'wet & dry" paper right down to 1200 (and cut and polish if you are keen) and get a perfectly clear edge. I drill mounting holes while the screen is still flat and has its protective paper. Nothing special about drilling except don't force the bit through too quickly.
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A curve in the screen looks better, has less wind resistance and is much stronger. Use a smooth piece of clean aluminium as a former. 1.6mm is quite thick enough. To get the curve punch a small hole in each corner and use some thin wire to pull it into a curve..

The kitchen oven works the best to heat and form your screen. Around 150 degrees C (275F) will do the trick and takes about 5 minutes in a preheated oven. It will gradually sag as it reaches temperature. I usually find that once it has sagged over the former, it needs to be removed and the edges held down as they will often sit out 5mm from the former.
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Here's the cooled curved screen on its aluminium former. You'll notice that the former is a different curve at each end...
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Mounted...
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Now you can hit the highway and no matter what kind of head wind you hit, your trip will be just that bit more comfortable... and as you can see the screen though highly effective is not too obvious...
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Chopit'nrideit... Prof

steve
Posts: 66
Joined: Fri May 05, 2006 2:25 pm
Location: Ipswich

Re: Polycarbonate screen

Post by steve » Thu Jan 02, 2014 10:20 am

I have found a cheap material that is resistant to stones to make a screen out of.
It comes pre-curved as well.
It also does not discolour in the sun.

Simply take a visor from an old motorcycle helmet and cut to shape. These are available in clear or smoked finish.
I have one mounted just above my headlight and it blends in very well.

Steve

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