how structural is the windshield?

[1990heepxj]

if the flex is breaking the seal that tells you right there it doesnt provide much strength if its bond breaks off instead of the force of hard flexing just cracking the glass and keeping the glue intact. so this is how i look at if the factory glue breaks flexing anyway then silicone will atleast allow it to move in the body and not start leaking

 

[joe_peters]

if the flex is breaking the seal that tells you right there it doesnt provide much strength if its bond breaks off instead of the force of hard flexing just cracking the glass and keeping the glue intact

Unless its an age-thing with the urethane/sealer. Gets old, hard, and then we flex it doing fun things? I honestly don't know.

After JJacobs started whacking me on the head ( ) I Googled and found a little information in the 1973 roof crush standards: http://www.nhtsa.dot.gov/cars/rules/crashworthy/RoofCrResist/FMVSS216Notice.html which are really simplistic.

 

[96XJ_4.0]

Unless its an age-thing with the urethane/sealer. Gets old, hard, and then we flex it doing fun things? I honestly don't know.

After JJacobs started whacking me on the head ( ) I Googled and found a little information in the 1973 roof crush standards: http://www.nhtsa.dot.gov/cars/rules/crashworthy/RoofCrResist/FMVSS216Notice.html which are really simplistic.

Yea.

.gov pages are a good chuckle too.

" Further, 89 percent of roof-injured drivers received their most serious injuries from the roof."


Wait, so is the other 11% driving verts?

LoL:guitar:

 

[winterbeater]

OP is driving an '89 XJ. Weren't those just held in with a rubber gasket? Even my 2000 has the rubber gasket, but I believe they had advanced to a combination glue/gasket deal. Not anything like most of the newer cars and trucks (even my old 93 F150) where they are only glued to the body with no rubber gasket.

 

[1990heepxj]

id bet they purposely make it able to move a little on the XJs since they probly knew frame flex would cause it to crack otherwise. and with a full frame the body is more rigid

 

[RedChuck]

its not that it supports any weight it keeps the metal from tweaking like a cross brace. i was in my buddies evo and when he hit the curb (Dumba$$)the shock cracked the window at an angle from lower right corner to the upper left. but i don't see how it could be 40%.

tempered glass is a pretty strong material though.

 

[89Daytona]

If the jeep only sees off highway use the plexi/lexan and rivet it in and add a cross brace if you want to. You could add a protective layer to the plexi to prevent scratching, something like http://www.raysandsglass.com/Product-Services/windshield-protection-film.htm or use a ready made polycarb windshield like http://www.polyshields.com/main.html


Silicone caulk/sealant only has a tensile strength around 220 psi, where as Urathane adhesive has a tensile strength around 1000 psi.
Marine grade silicone sealant specs
Automotive Glass Urethane specs

Read the "bonding experience" section of this: http://www.automedia.com/Professional_Windshield_Install/ccr20050801wi/1

http://www.carlite.com/whycarlite.html

If you roll the jeep the windshield is the most likely place for the roof to fold, even more likely if you use an adhesive that was not designed to hold the windshield in place...

 

[Kevinma255]

Decided to go with plan C for now. Just use some clear tape on the inside of the window and use it. If it shatters the rest of the way the tape will hold everything somewhat together. Just have to carry a couple of garbage bags to pick up the pieces if that happens. Thanks for the input everyone.

 

[srimes]

do you plan on running with no glass windshield from here on out, or are you talking about a temporary patch?

 

[heyhar]

OP is driving an '89 XJ. Weren't those just held in with a rubber gasket? Even my 2000 has the rubber gasket, but I believe they had advanced to a combination glue/gasket deal. Not anything like most of the newer cars and trucks (even my old 93 F150) where they are only glued to the body with no rubber gasket.

The earlier models <94 have the bright, and later matte black stainless trim around the glass, held on by plastic clips on little studs. Later models have the black plastic trim applied to the perimeter of the glass. Either way, both types are glued in with the urethane sealant/adhesive. When I had the windshield replaced on my '92, the installer had prepped a later one. When I said I had the metal trim, he asked if I would like the later one with the plastic, he'd just grind off the studs, apparently the only difference. I opted to keep the earlier style, as I'd gotten new trim to replace the old stuff that had been chewed up by floppy wipers.

On a unit-body vehicle, the glued-in windows add torsional stiffness, and the windshield is working alone in a wagon-type body.

 

[90 waggy]

think of it as a piece of sheathing on ur house.....itll flex but not much before it breaks......windshields dont account for much rigidity in the xj's uni-body.....cant say much since mine is still original after 20 years and ive flexed the hell out of it so it cant be that much of a structural component if it hasnt broken yet. my .02 take it for what it is and slap that plexi in itll just hafta be replaced every so often

 

[XJskibum]

For those guys who don't think the windshield provides any rigidity, have you actually looked at the "piece of glass" as some have called it? That sucker isn't your little side window, it's thick stuff that will take some serious forces. Obviously flexing it just right will break it, but it's glass and that's what glass does....but most of the time the position that it's in makes it a solid component. .02

 

[96XJ_4.0]

Test:

go to junkyard

take windshield out.

Stretch string from corner to corner on winshield frame.

Tip car on roof and see if the string stretches.


LMAO

You guys are funny. It's held on by something flexible. Simple physics would *probably show us that something is only as strong as it's weakest link.

 

[Kevinma255]

Srimes, it is just a temp fix. I need the jeep in a month or two for my bachelor party and I dont want to spend the money for the cage or new glass until the wedding is paid off. Plan on putting a cage in it then bolting on a flip up windshield from an old wrangler or Mil jeep if I can make it look right.

 

[ROBZ95Xj]

i would never run plexi as a windshield, when it breaks it breaks into sharp shards

 

[joe_peters]

Skip the plexi--two pair government surplus goggles, couple of hoodies, some gloves--all set.

Bonus--you will save on wear and tear on the wipers!

 

[96XJ_4.0]

3 words Joe.

Peel away goggles.

/thread

 

[kastein]

"Automotive Grade Urethane" made me chuckle.


Did you notice the website's name....windshield EXPERTS...as in these people preform tests and develop real life results...I doubt it?

That little part up there about being strong AND flexible proves the lack of rigidity of a windshield.

I have heard this before in the past. If my memory serves me right, I believe the point of that rant you quoted was that A WINDSHIELD CAN BECOME DISLODGED IN A FRONT END COLLISION, subsequently leaving the vehicle at speeds near that of the impact. ie.: 70mph airborne windshield

Care to explain how silicone is a "far cry" from urethane? Cause I'm just not seeing it.

So that explains it. rofl

You also might want to tell NASAs JPA that they messed up. Somehow urethane is better now since they built the space shuttle. Seems they might not Know of this drastic difference.
http://findarticles.com/p/articles/mi_qa3957/is_200405/ai_n9457726/


Here is some actual facts presented by DowCorning.
http://www.dowcorning.co.kr/ko_KR/content/publishedlit/63-1015-01.pdf?DCWS=urethane&popup=true



Were talking peas and carrots here.

Test:

go to junkyard

take windshield out.

Stretch string from corner to corner on winshield frame.

Tip car on roof and see if the string stretches.


LMAO

You guys are funny. It's held on by something flexible. Simple physics would *probably show us that something is only as strong as it's weakest link.

3 words Joe.

Peel away goggles.

/thread

Nominated

You're an idiot. You also seem to think you know more than anyone else in this thread even though you're spouting blatant nonsense. Try kicking a windshield out sometime, or try cutting through the urethane - urethane adhesive is VERY stiff compared to silicone and extremely strong. I should know, because I broke a utility knife blade cutting it a while ago...

You do realize that urethane adhesives are used for everything from attaching windshields to gluing entire car frames together in some cases right?

You also seem to have no concept of something that flexes and yet is strong - yeah, the uniframe flexes too, but according to your " and say something sarcastic" logic, this means it does not provide much of the strength, right?

Auto windshields these days are an integral part of the body - they also are required for proper passenger airbag operation. Ever notice that the passenger airbag is pointed mostly upwards? If you look at a vehicle that's been in a collision that deployed the airbags you'll probably see a basketball-sized crater in the windshield right over the airbag, where it bounced off the windshield and was directed at the passenger.

 

[1990heepxj]

true but XJs dont have air bags

 

[kastein]

Incorrect. They don't have airbags till 95, when a driver airbag was added (mechanical standalone type), then in 97 electronically controlled driver and passenger airbags were added.

That was just an example anyways, the windshield still provides a large portion of the upper unibody strength either way.

Another way to look at the whole "it flexes so it's not the strongest part" argument - put a metal frame around a large piece of 18 gauge steel sheet, tack welded on every inch or two. Now try to wrack that frame - i.e. collapse it from a rectangle to a parallelogram. Pretty tough eh? But I bet you can still fold the whole thing in half over your leg.

so that 18 gauge piece of sheetmetal isn't providing any strength right? /thread etc etc

Oh wait. Welding, silicone, urethane, same thing, what am I talking about.