Broken windshield after roll cage install |
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Broken windshield after roll cage install |
Bill's Racing 914 |
Jul 3 2015, 08:45 PM
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#1
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Member Group: Members Posts: 61 Joined: 2-March 14 From: Southern California Member No.: 17,064 Region Association: None |
Is it common for a windshield to break when driving a 914 after installing the roll cage?
I just drove the car around the neighborhood after tuning the Webers. I now have a diagonal crack running from the upper front corner of the passenger side window down to the lower center of the window. I rebuilt this 1970 914 after pulling it out of the desert two years ago. It has non adjustable KYB shocks in the rear and Bilstein struts in the front. I installed a stock front and rear swaybar. Both are non adjustable. I have the front end lowered as far as it can go. The rear is still near stock height. I will drop it when I get coil overs. I also put in a 6 point cage kit from Tangerine. My welder followed the installation instructions to the letter. Very happy with the roll cage kit. The car does ride really rough and hard. There is zero body roll. I did notice deflection between the upper frame of the windshield and the top front bar of the roll cage when I would go over rough sections of road. Is it that after stiffening up the frame by adding the roll cage and stiffening up the suspension that the 1970 windshield finally broke after I hit a few bumps in the road? Is this common? Is this why most racers just cut the front windshield off? (IMG:style_emoticons/default/confused24.gif) |
campbellcj |
Jul 3 2015, 10:20 PM
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#2
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I can't Re Member Group: Members Posts: 4,543 Joined: 26-December 02 From: Agoura, CA Member No.: 21 Region Association: Southern California |
I don't think this is really common but it also does not surprise me. I broke a windshield last year when I put a wheel off-track and it bottomed really hard. My cage is welded-in at 10 points and the suspension is pretty much all bearings and heim joints (no rubber). The combination of a very stiff suspension and having everything tied together with the cage must transmit the shock all thru the car. With a stock car there is more chassis flex and rubber to absorb such things.
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ThePaintedMan |
Jul 4 2015, 07:32 AM
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#3
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Advanced Member Group: Members Posts: 3,885 Joined: 6-September 11 From: St. Petersburg, FL Member No.: 13,527 Region Association: South East States |
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Glass does "age"... but very slowly. Combine that with a stiff suspension and possibly old butyl rubber holding the glass in, and the weak link becomes the glass itself. What spring rate are you running? Is anything binding? Perhaps from lowering the front too much, you're actually bottoming the front a-arms on the frame? Have you replaced the windshield before? |
Krieger |
Jul 4 2015, 08:24 AM
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#4
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Advanced Member Group: Members Posts: 4,705 Joined: 24-May 04 From: Santa Rosa CA Member No.: 2,104 Region Association: None |
I put in Chris's cage too and added to it. I also welded a tab on each side of the windsheild frame (near the top) to the cage. I used butyl to install windshield. No problems with cracked glass after many autocross and timetrials.
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Bill's Racing 914 |
Jul 4 2015, 11:05 AM
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#5
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Member Group: Members Posts: 61 Joined: 2-March 14 From: Southern California Member No.: 17,064 Region Association: None |
(IMG:style_emoticons/default/agree.gif) Glass does "age"... but very slowly. Combine that with a stiff suspension and possibly old butyl rubber holding the glass in, and the weak link becomes the glass itself. What spring rate are you running? Is anything binding? Perhaps from lowering the front too much, you're actually bottoming the front a-arms on the frame? Have you replaced the windshield before? No, this is the original windshield. I am running stock torsion bars in the front and don't know the spring rates in the rear. They came with the car. This happened after I lowered the front end. Could be bottoming out. |
Bill's Racing 914 |
Jul 4 2015, 11:12 AM
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#6
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Member Group: Members Posts: 61 Joined: 2-March 14 From: Southern California Member No.: 17,064 Region Association: None |
I put in Chris's cage too and added to it. I also welded a tab on each side of the windsheild frame (near the top) to the cage. I used butyl to install windshield. No problems with cracked glass after many autocross and timetrials. I was planning on adding the tabs too. I am an aerospace structural engineer. The cage is good enough to pass the tech inspectors, but there is no lateral stiffness in the front of the cage. There should be a bar under the dash going from the left front pillar to the right front pillar. Also a diagonal is needed from the center of that bar down to the point where the passenger side front pillar attaches to the frame. I also need to add struts between the front pillars through the firewall to the top of the shock towers. I am debating as to whether to just cut the windshield off or not. This car had rust int he hell hole so it will never be a concourse car. |
ThePaintedMan |
Jul 4 2015, 05:51 PM
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#7
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Advanced Member Group: Members Posts: 3,885 Joined: 6-September 11 From: St. Petersburg, FL Member No.: 13,527 Region Association: South East States |
IMHO, cutting the windshield off should be left as a final solution to a very specific goal of making the car competitive in certain classes. Otherwise, it's really going to make it hard to be able to sell to someone else in the future (it will always need to be stored inside).
From the way you're describing ZERO roll/no complacency in the front end, I'm betting on it's bottoming out. Jack it up and look for rub marks. (IMG:style_emoticons/default/beerchug.gif) |
EdwardBlume |
Jul 7 2015, 08:29 AM
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#8
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914 Wizard Group: Members Posts: 12,338 Joined: 2-January 03 From: SLO Member No.: 81 Region Association: Central California |
Sorry to tell you, but YES.
I had NEW glass on my gray AX car which had just a welded in bar with a forward bar to the pass long. Jacking the car up by the front donut cracked my new windshield. I replaced it and only jacked the car by the rear donut from that point on. The whole car raised nicely from the rear. |
stugray |
Jul 7 2015, 10:47 PM
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#9
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Advanced Member Group: Members Posts: 3,824 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
I broke a 40 year old windshield the first time on track when I got a little "air time" after cutting a corner a little too tight.
Replaced it with lexan my self (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436330845.1.jpg) (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436330845.2.jpg) (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436330845.3.jpg) (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436330845.4.jpg) |
Randal |
Jul 8 2015, 09:46 AM
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#10
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Advanced Member Group: Members Posts: 4,446 Joined: 29-May 03 From: Los Altos, CA Member No.: 750 |
I broke a 40 year old windshield the first time on track when I got a little "air time" after cutting a corner a little too tight. Replaced it with lexan my self (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436330845.1.jpg) (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436330845.2.jpg) (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436330845.3.jpg) (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436330845.4.jpg) Did you make a pattern first or how did you get that fit so nice? |
stugray |
Jul 8 2015, 06:08 PM
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#11
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Advanced Member Group: Members Posts: 3,824 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
Did you make a pattern first or how did you get that fit so nice? I made a template from hard board and routed it: (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436400519.1.jpg) |
carr914 |
Jul 8 2015, 07:28 PM
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#12
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Racer from Birth Group: Members Posts: 118,356 Joined: 2-February 04 From: Tampa,FL Member No.: 1,623 Region Association: South East States |
No it is very common for this to happen. When you Track a 914 with Rubber it was never intended for, the Lateral G's exceed the car's Torsional Limits. Putting a Cage in can put different forces within the car. Especially if the cage was done in correctly.
The Factory knew there were problems with windshields cracking & Windshield A-Pillars flexing. Here is the Factory Fix on a Factory GT |
Bill's Racing 914 |
Jul 9 2015, 10:33 AM
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#13
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Member Group: Members Posts: 61 Joined: 2-March 14 From: Southern California Member No.: 17,064 Region Association: None |
I broke a 40 year old windshield the first time on track when I got a little "air time" after cutting a corner a little too tight. Replaced it with lexan my self (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436330845.1.jpg) (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436330845.2.jpg) (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436330845.3.jpg) (IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1436330845.4.jpg) What thickness lexan did you use and did yo have to do any heat forming? thx, Bill |
brant |
Jul 9 2015, 10:38 AM
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#14
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914 Wizard Group: Members Posts: 11,618 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
different racing clubs have different thickness requirements.
my memory is that 1/4 often works... but verify that |
Bill's Racing 914 |
Jul 9 2015, 10:54 AM
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#15
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Member Group: Members Posts: 61 Joined: 2-March 14 From: Southern California Member No.: 17,064 Region Association: None |
(IMG:style_emoticons/default/WTF.gif)
Here's why the windshield broke.....the original glue had dry rotten and the windshield came loose. Again this is a California car I pulled out of the desert. Every piece of rubber on the car had dry rotted and has been removed. I stripped the chassis down to bare metal...This car is strictly for vintage racing and will never be returned to street condition. In previous test drives, I heard something rattling. I could not tell what it was. Now I know. It was the loose windshield banging against the frame...it finally broke. On close inspection, the metal trim around the windshield had finally come loose and I could see gap between the windshield and the frame(see photos). Word to the wise: Have your OEM glass windshield removed and professionally reinstalled if you plan on racing the car. Without safety tabs, this windshield could have popped out on the track. That would have REALLY sucked..... I will look to make a lexan windshield like Stu Gray. Thank you everyone for your kind words of wisdom and help with this problem. Thanks 914World.... Attached thumbnail(s) |
ThePaintedMan |
Jul 9 2015, 11:46 AM
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#16
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Advanced Member Group: Members Posts: 3,885 Joined: 6-September 11 From: St. Petersburg, FL Member No.: 13,527 Region Association: South East States |
That's why I made my comment about the butyl rubber drying out. By now, all of these cars need the original glass reinstalled, regardless of whether they're racing or not.
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Bill's Racing 914 |
Jul 9 2015, 11:51 AM
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#17
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Member Group: Members Posts: 61 Joined: 2-March 14 From: Southern California Member No.: 17,064 Region Association: None |
That's why I made my comment about the butyl rubber drying out. By now, all of these cars need the original glass reinstalled, regardless of whether they're racing or not. yep...this one will sneak up and bite you. I would have never know had the chrome trim not come loose. |
stugray |
Jul 9 2015, 08:36 PM
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#18
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Advanced Member Group: Members Posts: 3,824 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
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Eddie914 |
Jul 19 2015, 08:00 PM
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#19
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Unregistered |
Stu
How much for the flat sheet lexan? Thanks Eddie |
Eddie914 |
Jul 19 2015, 08:06 PM
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#20
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Unregistered |
Bills Racing ...
The front glass on my teener had a big diagonal crack. IIRC it was after the cage. I suppose it can be expected ... Big 3.2 six Big torsion bars, 225lb springs, big front sway bars, Big 235/255/17 R tires Big Wilwood Superlite II brakes. Something has to give ... Mine has been replaced with cheap glass, foam tape, universal rubber trim and racing clips. |
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