Are there any production cars with double curvature glass?

[Blue Angel]

Originally Posted by Shepherd777

If you want to buy 10,000, they'll talk to you.

This is no surprise!

Do they use a hard coating "waterfall" process? We supplied the side door appliques for the Buick LaCrosse and Chevy Impala in the Oshawa plant, and they were injection molded Polypropylene with a liquid hard coat. I never did see the process in person, but was told the parts were loaded into fixtures on a conveyor and passed through a flowing sheet of fluid (like a waterfall). They were then cured while dripping any excess coating material.

The finish on these parts was excellent... glass smooth and apparently very hard and scratch resistant. I was told a similar process was used on some headlight lenses also, but nobody was doing production glass with this method 6-7 years ago that I was aware of.

[HydroJim]

it's not hard. You just need a big oven and a big mold. We made clocks in shop class one time and we made the cover for the clock face out of acrylic. We just put the pieces in a toaster oven and then took them out and put a little weight on them over the mold and had a perfect dome shaped piece. I'd imagine the same principle applies to windshields.

[Shepherd777]

Originally Posted by HydroJim

it's not hard. You just need a big oven and a big mold. We made clocks in shop class one time and we made the cover for the clock face out of acrylic. We just put the pieces in a toaster oven and then took them out and put a little weight on them over the mold and had a perfect dome shaped piece. I'd imagine the same principle applies to windshields.

Hi HydroJim -

The basic physical technique of heating and molding the Lexan for automotive-type windshields is as you describe, but with two additional and complicated steps.

One, I believe it would have to be a vacuum mold, so the warm Lexan is actually pulled into the mold for the best optical clarity.

Secondly, AFAIK, raw Lexan is not DOT approved for automotive glass. So even if one had a perfectly shaped Lexan windshield for their project, it would still have to be hard coated. And a DOT emblem would have to be added to the lower passengers side corner to certify the approval to the authorities. I could never get my truck registered without a DOT approved windshield and that little emblem. I know, as the State of CT DMV Truck Squad checked my OEM windshield for the DOT marking before they approved my composite vehicle build.

[Blue Angel]

Originally Posted by Shepherd777

I believe it would have to be a vacuum mold, so the warm Lexan is actually pulled into the mold for the best optical clarity.

This is how tempered glass parts are done. It gives greater control over the shape of the part.

Originally Posted by Shepherd777

Secondly, AFAIK, raw Lexan is not DOT approved for automotive glass. So even if one had a perfectly shaped Lexan windshield for their project, it would still have to be hard coated. And a DOT emblem would have to be added to the lower passengers side corner to certify the approval to the authorities.

So does this render it impossible to build your own truck?

I'm not sure whether the DOT has different windshield rules for trucks than they do for cars, but as far as I know if you are building a "kit car" for personal use and not selling it to anyone the rules get pretty soft.

Now if you want to start selling your truck to others at a profit, I think that might be another story.

Based on the look of your scale model, that windshield is HUGE with a very deep profile... I wouldn't be surprised if it wouldn't fit in a traditional windshield production line. For production you may find you need to make it in two pieces, with a seam in the middle. If there's any aero benefit to styling the truck with a sharp leading edge instead of a fully rounded profile, a split windshield would work well.

If you are not thinking ahead to volume production then keeping the single piece design might be possible.

[Vekke]

Shepherd I think you will have better chances if you search your glass outside US. I am pretty sure that OEMs don`t like any bit what you are trying to build and can even pay glass manufacturers not to make you any glass...



Citycab glasses were just free formed so only heating in a oven it its frame. It took many test pieces before that rear glass got perfect shape because there was not that tooling under it. I think those had E marks needed in Europe, but the price is very expensive if they are willing to manufacture them.

Those glasses were made at Pilkington Laitila factory:
Toimipisteet


In Finland you are able to legal permit in some cases to use something that is not sertified / verified glasses. Specially if the case is good and it project has clear purpose.

[Blue Angel]

Shepherd, a stupid idea just popped into my head... what if you were to use an ordinary DOT approved windshield BEHIND your custom aero windshield? Would the DOT be satisfied from a driver/passenger safety standpoint? Instead of calling the aero-piece a "windshield" you could call it a "deflector" instead? Just a thought... it might help you at least get a prototype rolling.

You could even have it hinged, like the visor on a bike helmet, so you could raise it and have them put their stickers on the DOT glass beneath.

[aerohead]

Originally Posted by Shepherd777

Are you able to post a link to this firm?

I learned of them in AUTOWEEK Magazine and kept the article.
Metalcrafters is the name of the outfit.I'll bring the info next time.They may have a website.Don't know.

[Shepherd777]

Originally Posted by Blue Angel

This is how tempered glass parts are done. It gives greater control over the shape of the part.



So does this render it impossible to build your own truck?

I'm not sure whether the DOT has different windshield rules for trucks than they do for cars, but as far as I know if you are building a "kit car" for personal use and not selling it to anyone the rules get pretty soft.

Now if you want to start selling your truck to others at a profit, I think that might be another story.

Based on the look of your scale model, that windshield is HUGE with a very deep profile... I wouldn't be surprised if it wouldn't fit in a traditional windshield production line. For production you may find you need to make it in two pieces, with a seam in the middle. If there's any aero benefit to styling the truck with a sharp leading edge instead of a fully rounded profile, a split windshield would work well.

If you are not thinking ahead to volume production then keeping the single piece design might be possible.

So does this render it impossible to build your own truck?

No not at all. It just makes it more difficult. But nobody told me it would be easy.

I'm not sure whether the DOT has different windshield rules for trucks than they do for cars, but as far as I know if you are building a "kit car" for personal use and not selling it to anyone the rules get pretty soft.

The BulletTruck was considered a personal "composite vehicle" in the State of CT. And again, the Inspector was looking for that little DOT etched-in emblem, before he approved the build.

Now if you want to start selling your truck to others at a profit, I think that might be another story.

That's exactly what we aspire to do. So we might as well figure out how to have certified windshields with the next-generation prototype.

Based on the look of your scale model, that windshield is HUGE with a very deep profile... I wouldn't be surprised if it wouldn't fit in a traditional windshield production line. For production you may find you need to make it in two pieces, with a seam in the middle. If there's any aero benefit to styling the truck with a sharp leading edge instead of a fully rounded profile, a split windshield would work well.

Agreed. I always figured it would be two piece with a vertical seam down the middle.

[Shepherd777]

Originally Posted by Vekke

Shepherd I think you will have better chances if you search your glass outside US. I am pretty sure that OEMs don`t like any bit what you are trying to build and can even pay glass manufacturers not to make you any glass...



Citycab glasses were just free formed so only heating in a oven it its frame. It took many test pieces before that rear glass got perfect shape because there was not that tooling under it. I think those had E marks needed in Europe, but the price is very expensive if they are willing to manufacture them.

Those glasses were made at Pilkington Laitila factory:
Toimipisteet


In Finland you are able to legal permit in some cases to use something that is not sertified / verified glasses. Specially if the case is good and it project has clear purpose.

Hi Vekke -

Thanks for the info and the link!

[Shepherd777]

Originally Posted by Blue Angel

Shepherd, a stupid idea just popped into my head... what if you were to use an ordinary DOT approved windshield BEHIND your custom aero windshield? Would the DOT be satisfied from a driver/passenger safety standpoint? Instead of calling the aero-piece a "windshield" you could call it a "deflector" instead? Just a thought... it might help you at least get a prototype rolling.

You could even have it hinged, like the visor on a bike helmet, so you could raise it and have them put their stickers on the DOT glass beneath.

We were thinking of initially doing exactly what you describe on the BulletTruck. Having a Lexan "deflector" in front of the OEM windshield. The OEM windshield has a 65 degree slant backward. The Lexan deflector, built into the rear of the hood, would of had a much shallower angle.

We decided instead to make the fiberglass front end of the truck so it diverted air around the sides of the truck from about 5' off the pavement and lower. This somewhat mitigated that 65 degree windshield, aerodynamically, as there was much less air trying to go over the cab. And obviously, with our MPG figures, this, along with many other concepts and features, worked.