dang!

If you get GM ones try snap a pic of the GM and Howks ones.

I SUSPECT the GM ones wil lhave a slight curved mounting for the glass.

 

Will do. I found on Ebay a pair of old OEM hinges. The link is on this thread: https://www.thirdgen.org/forums/body...-breakage.html
Posted 7/14/21 at 12:05PM. Don't want to keep posting Ebay and risk the wrath of the admins. The pics on Ebay are good and the hinges appear to be flat.

 

As I look at it,

1. the hinges themselves (the middle pivoting part) is angled slightl to compemsate for the glass…. So if i look directly at it the hinge part that touches the glass is partly angled even if it is / may be flat each hinge will be higher towards the middle of the car and the opposite side lower. Not wasy to tell in the pics BUT there is def an angle

2. if the 2 hinges were put on the wrong side i can definetley see how they would be different etc..

try check the hawks hinges for identifying marks for Left / Right pics are from a 87 Formula

 

Do you see that long piece of metal that is part of that metal strip that goes around the edge of the glass? It's more than twice the width of the hinge plate. I think that piece of metal may have some sort of padding between it and the glass to (not sure yet).

The Hawks hinges are marked L and R and they are slightly angled at the hinge pin like you mentioned, I presume to accommodate the curvature of the glass.

What I don't get, is if the hinge plate (the flat metal that actually touches the glass) was flat on my old hinges and the new hinge plate is also flat, how that could then result in a shattering. Since it was a total instantaneous explosion, it would have to be the top (hinges) and the rear deck (latched down by the retractable catch) literally compressing towards the middle of the glass. But, if all the new, unbent hinges did was basically scoot the whole hatch back up to its factory position and not sticking out over the back of the car, then what would cause that stress? The distance between the holes in the top of the glass and the rear deck didn't suddenly change.

I did send an email to Trans Am Specialties of FL (Miami) but they said that they rarely work on Gen III's and don't know anything about these hatch explosions.

So I'm still left in the dark on this one. If I can find an old set (the shop tossed my old hinges) I could do some comparisons to the Hawks hinges. There simply has to be something cause pressure either along the length of the glass from roof line to rear deck, or the hinges have to be creating enough stress at the glass to cause the entire glass to shatter all at once. Darn I wish I had kept those old hinges!!! By the way, your TA looks really nice. I'd actually like to get rid of the 1990 steering wheel and airbag, and go with the 3 spoke like yours.

 

You can't tell from this picture as any curvature is hidden by the metal strip.



The curve, from what I've seen, are more like "pads". There would no contact with the glass between the pads or mounting points.
If the hinge surface was flat, there would be a stress riser between the bolt holes because the glass is most definitely curved.
And further to that, look at how complex the mounting pad is on the OEM hinge.




GM didn't do that for ***** and giggles. That's a complex form and it's there for a reason.

One thing needs to be determined though is how did those with successful Hawks hinges go about their business. Luck?

 

Agree there must be some reason GM made the contact side so complex. I would think it would be more expensive to make that way as compared to just a flat piece of metal. And yes, why are some like me having their hatches explode while others are not after installing the new billet hinges.

 

haha thanks! Its a 87 Formula..i really like the wheel. akes it easy to steer etc..I think its slightly smaller than the regular wheels too?


Im at a loss for words to oon what it could be. If you do get a set of GM ones definitely compare.. suspect its is the flat surface of the hawks units…..

 

Looking at the picture, the right "circle pad" seems to be angled quite a bit angled down vs. the left circle and I don't think it's the camera angle....


If you look at my hinge, the middle part of the "hinging" area, there appears to be more of an angle than other photos of the Hawk's hinge??? Does the hawks one have the same angle etc?




@sklearman have you contacted hawk's about this? Also, did you take a look at the thread where the other member re--did his hatch? I asked him and he said he used Hawk's hinges as well but he JUST did his recently.....

 

I'm wondering that too, but I'm not a mechanical engineer. But if it was the flatness of the plate against the glass, I would think it would just crack around the hinge. It would seem to cause that explosion, there would have to be incredible pressure towards the middle of the hatch, from both the hinge area and rear deck area. I don't know for sure. But what's odd, a friend's (he's not on thirdgen) Formula hatch literally exploded as it was just sitting in the driveway. It was all original too. I don't get it.

 

I still have to contact Hawks. Got this, a Jeep project, and a couple other projects going. I'm quite the busy bee in retirement! I noticed those round honeycombs at the bolt holes. I would think that that elaborate honeycomb design was more expensive to make, and therefore, made with an engineering purpose....but it's GM and they use plastic head gaskets to save a buck instead of the normal compressed paper type (not sure if I'm using the right term). I might have seen that other post on the Chronic Hatch Glass thread which I've also been posting under. Just like with the reason for the sag and projection over the back end (bent hinges vs rear deck sliding back from the glass due to lifter pressure) there seems no definite answer.

 

so that shattered with the original GM hinges? aka never touched before??

 

Yes. It was all original. Which is really weird. It's a one owner car, my buddy has had it since he was a kid and it's pristine.

 

here's one.....

 

I'm curious as to why it would bend there of all places...… and how this happens with the glass being on it.


Ddi you have luck with the Hawk's hinges?

 

bc the hatch is a thick, heavy, complex curve of glass, there will certainly be different origins for the failures. the hinges were cast bc it saved weight and MONEY, and cast had to have all the gusseting and ridging to achieve the same strength level that a flat piece of metal would have. there is no other reasons for the way the hinges are shaped or engineered. the flat spring steel that is part of the glass frame is also sized and shaped to cushion the stress that has to be handled by the hinge. because of it's size and shape it spreads the load over a large area on the hinge end of the glass, and bc it's springy, it can accommodate the weight and the curves. over time, both heat cycles and the weight of the glass AND the pressure of the fasteners warps this metal, and if there is any departure from square, the hinges should be replaced.

the hawks part has the advantage of being very light and very strong, not a cast piece, but of course they have not been around long enough to be able to see how they will handle the heat cycling and stress. i will be watching them.

the bottom line is that even when you're not changing anything, there will be movement in the parts, the rear hatch has many parts, and alot of weight. make sure they are always kept in alignment, and when making changes everything has to be checked. these are old cars that have been around a long time, heat cycles, torquey engines with relatively flexi bodies, and roadways that send shudders through those ever aging parts ensure that ever increasing care is needed.

 

i have not used the hawks hinges with glass, just polycarbonate

 

427Seven: Ok, to make sure I understand, when GM designed these original hinges with all that honeycomb on the hinge plate (that contacts the glass) it had nothing to do with preventing breaking? Just making them in a particular way? So then, why are so many experiencing hatch glass explosions (like I did) right after installing the new aluminum billet hinges? On mine, I'm not sure yet if the shop installed the rubber gaskets I made (still cleaning up the glass) but I don't think the original hinges had them either. I know for sure the through-bolts in the glass were only hand tight, so that's not likely an issue. If all that new hinges do is move the entire hatch back up towards the roof line, like original from factory, why are hatches exploding? I am considering a polycarbonate replacement because they flex and will not break...but the MFR I talked to recommended not using them because they don't do well exposed to elements (I am in S. FL and the sun is always hot and intense, but I do garage the TA). The only reason (explanation of stress factors) I can see is a compression from both the hinge location and rear deck location, basically squeezing the glass along it's long axis until it literally explodes all at once. I don't see how changing hinges would create that stress.

 

I wonder if the aluminum having differen heat absorption and disspation properties at a much faster rate than the metal GM units has wnything to do with it??

 

I don't know. My Jeep was in the shop, so I had taken the TA to a quick dr. appt at 08:00AM. Wasn't gone that long, and the sun wasn't high in the sky yet. I don't recall anything from the Navy about aluminum expanding under heat. Might have to do an internet search. I know concrete expands which is why bridges have expansion joints.

 

https://www.engineeringtoolbox.com/t...als-d_859.html Now......this said, I really don't understand what the table means. Keeping in mind, the temp variance from garage, say 80F to sitting in the sun for an hour say 110F isn't really that much. It's not like being superheated.

 

I forgot about the metal trim part that the glass is on....so I am thi9nking that any irregular heat things...unless extreme, won't affect it much as the metal will help dissipate it?

Also it dosnl;t touch the glass............ Looking at the 2, there isn't much of a curvature difference if any and the metal tab on the trim I think would make up for any variances?





So...whats up with the Hawk's bolts?? Is the bottom part that touches the glass any different from the GM ones? I think they are aluminum if I recall.

 

Possibly. It does seem aluminums (and alloys) have greater expansion than common steels, but it's above my pay grade to understand! The Hawks bolts that go through the glass are the same aluminum alloy as the hinges I think. So they would expand. I don't know if that means the diameter of the bolt would increase a bit, or the length. But I think the holes in the glass would allow a mm or 2 of expansion anyway. One thing I forgot about....bi-metallic corrosion. Whenever two different metal are in contact this can occur. But, that's a rust issue not an expansion issue. Surely someone from GM is around who knows why things were designed the way they were????

 

Well, basically the design thought process is "it needs to work during the warranty period and it needs to be cheap!!" But for a part like the hinge I don;t think they'd really amke al lthat design just to cheap out ? Maybe fir support vs a flat piece or some kind of other reason....

I don;t want to beat a dead horse but i think its important to observe EVERYTHING....
If you look at the GM ones closely, the contact points are ever so slightly raised.....and would be the "quarter sized round areas" where the bolts go through...unless its the angle... Thus there in theory is less contact points than the hawk flat units....

Also, a quick google question provided this:

:"Glass expands and contracts with changes in temperature and deflects due to wind, so almost all modern glass is set on resilient blocks at the bottom and with space for expansion at the sides and top. The gaskets holding the glass in the frame are also usually resilient to cushion the glass against wind buffeting."

 

I see the difference you're talking about. So would adding a quarter sized, 1/16th inch rubber washer between the Hawks hinge and the glass make a difference? If I get the design right, the Hawks hinge plate actually contacts that long metal strip that is part of the frame strip. Still, the more surface area the less PSI on an object. A woman in stiletto heels puts a lot more pressure on the floor surface than if she's wearing running shoes. Maybe polycarbonate is the way to go??? Where does one get the wax they put on fighter plane canopies????

 

-They look nothing like factory! It boils my blood when companies can't make something EXACTLY like factory. Cheap slotted holes, flat plate for glass rest, no flexibility. The factory hinges are actually soft and will curve with the glass. The glass is not flat anywhere! When you place a flat piece of metal against the glass and try to tighten down each side, you are pulling the glass to the metal. BOOM! The beauty bolts have a hexagonal stem that fits in the hexagonal slots on the factory hinge. The hinge pin is not in the same location as the factory one in relation to the mounting holes. I wouldn't even attempt using those Hawk's hinges from what I see in the pictures at least.


-427seven:howd you come to the conclusion that they were bent in the first place? if there was some event forcefull enough to bend the hinge, than it could also have bent the mounting surface and just putting new hinges in wont fix it. make sure it's all square before you re-install, or - as mentioned earlier - it will bind and something has to give

The above statement hit me right between the eyes! How indeed?

Question, are your factory hinges curved like this? It seems to me that the flat area on the Hawks might be a problem?

The one pictured has two contact points separated by an arch. The contact pads sit flush on the glass. It makes sense that that arch allows for window curvature where the Hawks piece does not. There are no hard edges on the factory piece, and there is a rubberized coating that must help. I'm going to put the originals back in. I'm following recommendations from a few places, their comments edited & pasted below;





I found these PICS and the comments in the other thread interesting........although others stil lsay the hinges work fine......


I dunno if it is due to age / wear, but the Hawks hinges are flat and have 0 curve at the edges......, but the GM ones on the edges are NOT touching one another indicating some kind of curve




__________________

 

The Hawks hinges, the side that goes to the glass, not the body, is somewhat tapered or rounded off. The plate that attaches to the metal body is squared off, but that doesn't affect the glass. I'm not sure at this point.

 

Oh I mean like if you compare the two pictures, when you put the GM ones side by side they don't sit flush against one another. Could be bent / age but i dunno....But at the ends there is some gap between the surfaces that sit against glass. area (i know its really the metal part on the trim) ...the gap is slight but there indicating they are slightly curved.... Kinda like this ----- > )(


But if you look at the hawks ones, there is absolutely no gap and they sit flush against one another like two completely flat straight edge surfaces . Like this ---> II

 

Basically going back to the whole, is the mounting are straight or curved thing

 

Yes, definitely. But also I noticed that long metal strip that is part of the side trim metal that goes around the glass, seems to be molded and has padding on it. I wonder if that part is what allows the curved glass to meet the flat hinge plate w/o damage. I'm having no luck finding salvage glass either. Even tried Glass Finders. No luck.

 

oh man


its best to find WHAT probably occured...you don;t want the same thing to happen again

 

its best to find WHAT probably occured...........YES! That is the important thing, the Holy Grail. And yet, I have no answers

 

Im leaning towards some kind of angle diference in the hawk hinges...wether they be the angle of the mounting surface...or the angle the hinge part is at???

 

I'm pretty much stumped. A crack around the bolt holes I could see, but the whole glass shattering in one giant boom?? I found a FB group which might be of help for Gen III enthusiasts. https://www.facebook.com/groups/1746480845598056

 

mmmm I believe the hatch is what's called "tempered" glass like side door windows, so if it damaged, rather than just crack like a windshield, the whole thing "explodes" much like side glass on any car to prevent shards etc....

So that means SOMETHING...an impact, imperfection, stress point etc.... caused the breakage.

 

Yes the glass is tempered and made to shatter into tiny pebbles. I have been told, the "tempering" continues through the life of the glass so the more hot and more cold the glass gets over the years, the more it tempers and become fragile. The pinch point would surely have to be either the through-holes in the top of the glass, or under that point where the hinges put pressure on, or a combo of the hinges pushing towards the rear, and the deck lid (held by the hatch pulldown motor) pushing towards the roofline. I may have found a brand new glass but it's way up in NH and I'm trying to get bids on shipping costs. It never just falls into place!

 

BRAND new????

As in nOS?? thats gonna be a pretty penny!!!

 

Item cost isn't the issue. It's in NH. I'm in FL. UPS store can't ship it. Put out bid request on UShip....zilch so far. I can't even get an outrageous price estimate. It's always something.

 

Depending on cost, I'd be thinking about Optic Armor. I can't imagine going through all of the hassle, not to mention the expense and risk having another one blow up. Regardless of the hinges you use.

By the way, here's a little engineering paper on tempered glass and how and why it might break.

There are many potential causes for spontaneous breakage of tempered glass. The most common is damage to the edges of glass as it is being pre-cut into panels, or nicks or chips to the edges that occur when the glass is being packaged, shipped, or installed onsite.

While such damage may not be readily apparent, stress concentrations around these imperfections can occur as the glass expands and contracts in response to in-service temperature changes, wind load, building movement, and other environmental factors. Ultimately, when those stresses cause the glass to break, the action may appear to have been spontaneous when, in fact, the circumstances for failure had been put in place months or even years earlier.

So, any damage, anywhere on the hatch can result in exploding as it does. Doesn't have to be the bolt holes. Just a nick along the edge could do it.

I'm not sure about the glass continuing to "temper" over time. The process to temper the glass involves temperatures over 600F. And then rapid cooling.

 

I understand that with the optic armor polycarbonate the way it goes in basically locks the hatch down permanently...you can't open/close it. Do you know about that at all? Also, when I talked to the rep he said polycarbonate doesn't hold up well in elements. My car is garaged, and only comes out for short drives a couple times a month. Once fully restored, I'll just take it to car shows. I know the Navy uses a wax of some sort to protect aircraft canopies when sitting idle and they're made of similar material, so that could be an option if I can find it.

 

I can't see that being the case. Sounds like an internet anecdote to me.

You most definitely will have to change the hatch struts. Much like there are different specs for hatches with no spoilers, lip spoilers and the large aero wrap around wing. They all require something each their own.
If you think about it, what would prevent you from using the hatch with no struts at all? Nothing really. Other than inconvenience. So it stands to reason that the appropriate strut will do the job.
IIRC, there's a data base/catalogue that has different lengths, strokes and pressure (or lifting capacity) for these gas struts somewhere on the web.
That said, it won't have the stability of glass. Especially the 1/8" version. But the thicker units will have some integrity and should work just fine.
As for durability in the weather, in particular direct sunshine, I understand the Armor Coat coating helps in that regard.

But, I don't have any first hand experience with Optic Armor although I intend to. (just not anytime soon).

 

Looking at my hatch struts, they appear to be pretty new and may have been replaced by the previous owner (deceased, so I can't inquire). My glass seemed to be 1/4" thick and Optic Armor makes a 1/4" thick back glass. But like you said, there could be a stability issue. I can tell you from personal experience trying to force entry into a townhouse with the fire dept on a rescue run, we wore out an entire squad of cops, the pumper crew and the ambulance crew trying to break the impact windows. They were not typical hurricane impact glass.....we surmised some sort of polycarbonate. It flexed, but we could not break it. We had to gain entry by forcing our way thru the steel hurricane door. If memory serves, military (civilian?) planes use some sort of polycarbonate for canopies so it must be pretty tough.

 

Does the new one have a decklid / hinges already attached?


you COULD in theory drive there hatchless with somebody........, and install lit and drive back home! Is that legal / doable??


I dunno how far that would be.....I'm in Hawaii so like long distances etc.. .aren;t my expertise lol

 

Well the seller does own an auto glass shop! But I have no AC, the rear hatch would probably suck exhaust back into the cabin, state troopers would ticket me for some nonsense, and I've not driven the TA more than about 5 miles from home yet. Not sure on reliability. Yes, the glass is new, never installed. One less step in the fix.

 

Have you decided on hinges?

 

I think I'm going to go back to old OEM. If it shatters again (in which case a grown man is gonna cry) then I can rule out the billet hinges having any effect. Big problem right now is the glass. I actually found a guy with never-used glass, but he's in NH and I'm in FL. I can't even get a shipping company to bid on it. I might have to rent a Uhaul pickup and go to a u-wrench it salvage yard and get an old hatch. I'm just worried about putting 30 yr old glass back on the car. Tempered glass seems to weaken over the years, so it might just shatter again. Some aftermarket glass co. needs to start making this glass again. The market is clearly re-forming.

 

Doid you contact the guy in the other thread with the hatch restoration?


he seemd to do it right with no problems....he listed torque specs etc... too!

 

No, haven't gotten to that yet. I'm juggling too many things at once right now. My Jeep is down (again) third time this year. Trying to get my book rolling to the marketplace. Pulling my hair (if I had any) out trying to find a way to get that glass from NH down to me. I think the key on torque, particularly on the hinge to glass side, is just barely hand tight not to factory specs. Less pressure on the glass.

 

Hmmmmmmmmmmm



If its too loose......perhaps it created uneven pressure on the glass? Like the hatch bolts that go through the glass, maybe they were angled due to uneven tightness, created pressure on one point of the glass (under the head of the bolt) and stressed and shattered it?

 

On my S-10..... there was an annoying CUNk that would occur everytime i braked or accelerated.


Turned out to be the bolt on the fender..it was tight but not tight enough.

So there was SOME kind of movement there between the fender and bolt despite it being tight. Enough to cause a really loud clunk etc..

 

I think the 4 bolts were pretty well evenly tightened. I'm at a loss. I'm wondering if the heavy weight of that aero wing plays a part. Maybe I should go back to the 82-85 KITT Style, https://www.hawksmotorsports.com/198...-reproduction/

I looked on Hawks for weights of the reproduction aero and standard, but they don't give them. Think I'll email them.