Screen (weight) saver

In case anyone is considering buying an Enfield 8000ECC, take note: If the windscreen is broken the car is almost certainly worthless. Why? Because although the car cleverly used many other car’s parts from the era (Hillman door handles, Reliant rear axle to name a few), the designers decided to furnish it with a bespoke ultra-aerodynamic windscreen. A heated one at that.

My Enfield’s screen was completely crack-free. Was. During the strip down, restoration and repaint Tim at Roadhouse Retro spent hours ensuring it was removed and refitted unscathed. Then I come along and accidentally tweak the corner trying to rush fit the dash cover around the roll cage one morning before it went to an exhibition for npower.

Crack. Bye-bye lovely glass original windscreen. Bye-bye hopes of passing the MoT test. Tragedy. Tears. Anger. Panic.

So, I was in a bit of a pickle. No secondhand windscreens exist, because not enough cars were built in the first place. It’s at this point I sincerely thought the project would have to be shelved. My own fault for using such a rare vehicle I s’pose.

But the good thing about Britain is that there’s always a talented person with a fantastic cottage industry somewhere. Recommended by my mate Andy Frost (he with the 3000bhp street legal Vauxhall Victor) was a company in Bolton called Plastics4Performance.

These guys specialise in making Lexan polycarbonate windows for all kinds of cars. Turns out they relish the challenge of moulding rare stuff too. Not to put a finer point on it, but Plastics4Performance saved the Flux Capacitor’s life. 

Too frightened to trust myself to remove the cracked windscreen intact (which is kinda important to make a master mould), I trailered the whole car to the Plastics4Performance base in Belmont, near Bolton.

Boss man Paul Davenport put the kettle on and gave me a tour of this spectacular hive of innovation. We shoved a Subaru BRZ race car out the way (which was also in to have new template windows moulded) and pushed the Enfield into the P4P HQ. 

“We did a Bizzarrini once” Paul says. “Didn’t think we’d do another and I’ve had orders for 2 since. We make screens and windows for WRC, British Touring Car, WTCC, GT Championship cars, classic rally, historic racing, you name it. We also do work for manufacturers like Aston Martin and Bentley. It’s all mail order. No one ever really visits us!”

Many of you will be asking why bother with Lexan? Simple really. It is lighter, safer and stronger (i.e more flexible) than glass. Contrary to belief it is MoT friendly too. Lexan’s molecular density is half that of glass. About a third of the weight. So in the case of my Enfield’s huge goldfish bowl screen, that’s a lot of bulk lopped off the kerbweight – handy for a race car.

If you’re still not convinced watch this video

“Lexan is immensely strong” says Paul. “We’ve run over screens with our fork lift and they were absolutely fine!” Blimey.

Here is how Plastics4Performance custom made a new windscreen for my Enfield. And the best bit is that anyone else out there can now have a new windscreen for their Enfield. Not that there’s many of you…

1) Firstly, the windscreen has to be removed from the car. Luckily the P4P guys removed my screen without turning it into cubes. I was too scared.

2) First thing is to make a flat paper pattern of it for 3D CAD data. In my case they did the old school way – by making a paper template pattern – the traditional method before computers were invented.

3) From the paper pattern P4P put it onto a digitising table, which digitises the outside the silouhette into the CAD system. P4P makes sure it is nice smooth shape (removing any jagged edges). From the CAD data they turn it into ‘machining code’ for the CNC machines, going from a drawing to a programme for the cutter.

4) Next process is to take the sheet of polycarbonate – which in their industry is optical grade of Lexan – and put onto the CNC machine. Then the flat windscreeny sheet is cut required.

5) Time to make the tooling. Says Paul “We make a high temperature forming tool from ceramic paste with a woven glass cloth inside. Think of it as a workable plaster that sets in 2-3 days. Then it can be broken away from the original glass screen.”

I returned to help with this part. Careful Jonny…

Don’t drop the master mould.

The other side of this plaster mould is all smooth. Obviously.

6) Once dry P4P rechecks all dimensions and give the mating surfaces a check for smoothness and dust/debris pollution. Then it’s ready for forming. This pic shows my Enfield windscreen sharing a work bench with a Koenigsegg screen. Am I delusional, or do they share a similar shape?

7) So now the whole process goes into the thermo forming department. A bloke called Andy usually. The mould and the polycarbonate sheet go into a heat cycle in the oven, where the sheet of Lexan gets hot, loses tension, becomes elastic and sags neatly into the mould. This part is hard to photograph without getting badly burnt.

“The oven baking process can take between 7 to 10 hours. The slower you heat it and the longer you leave it in defines the optical quality and strength. What you DON’T want to do is shock it by rushing it and speeding up the temperature change.” Says Paul.

From what I could see, it’s basically like slow cooking a joint of meat, or some specialist Bake Off bake.

Once heated it then goes through a cooling cycle. Polycarbonate tends to have a ‘memory’ and wants to return to a flat sheet (original state) so by doing slow cooling this avoids. Usually left overnight to cool. Again, difficult to photograph inside a hot oven.

Paul: “You’ve only got a window of 1 or 2 degrees between getting it right and it becoming liquid and turning to scrap – literally only good to be granulated and turned into CDs! That’s why this is a specialist business.”

8) In the case of my Enfield’s screen, once out of the oven it is checked for its optical qualities. Then it’s ready for a hard surface coating…

…to protect it from scratches. Windscreen wiper abrasion, chemical attack, stone chips. A liquid silicone coating which is thermally coated in the oven on a long low temp cycle. All this is done in a class 1 laboratory clean room.

P4P also now has the ability to make heated Lexan screens, which is basically sandwiching two screens together with a heater matrix between. Clever. My Enfield originally had a heated windscreen, but for racing it wasn’t high on my agenda.

Once back from the hard coating P4P hand finishes the edges to remove any burrs. Then it’s ready to post out.

Just before Christmas I received this parcel. It didn’t say FRAGILE on it. I couldn’t believe it was the windscreen…

…but it was. I was so excited I unwrapped it on the kitchen floor and left it there to admire, much to my wife’s glee

So you now know how brilliant and perfect Lexan windows are for performance and race cars. You probably think they cost a absolute fortune. Actually, not. I was pleasantly surprised to discover that screens start from about £325 for a simple (or flat) off the shelf item, like an old Beetle, classic Mini or Escort.

About £500 for really curvy panoramic screens, like Ferraris and some Japanese cars. And my Enfield.

That Koenigsegg screen is about £1200.

And here’s the best bit. Plastics4Performance doesn’t usually charge for tooling up, because that would prohibitively expensive. Instead they use new moulds as an opportunity to build up an archive of car window templates. You should see their workshop with racks of screens – it’s like a glass library.

In some cases Lexan can be cheaper than original glass windscreens. Paul said: “We’ve done screens for the 458 Italia – I used a friend’s crashed race car for the mould, because a new glass screen from Ferrari costs £9k!”

If you want to have a screen custom moulded, the typical turn around is 8-10 weeks. These guys are busy. Because they’re bloody good.

My new screen is fitted, I’ve just got to insert the original chrome strip (which is right knuckle skinner in cold weather). I will weigh it and let you know how much flab has been sliced off the Flux Capacitor’s kerbweight.