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Need some information on frame re-enforcing by Tweeder
Started on: 02-01-2015 10:27 PM
Replies: 14 (478 views)
Last post by: Bloozberry on 02-03-2015 09:26 AM
Tweeder
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Report this Post02-01-2015 10:27 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
My convertible has a la machines kit and was braced according to specs. I have noticed if lifting from the rear coolant tube lifting point I cannot open the door, whatever no biggie. I did notice that the gap is quite wide at the top of the door when up in the air like that. So the cars bending like a banana. Where would I need to add some re-enforcing to stop that?

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Report this Post02-01-2015 10:50 PM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Is this something that just started happening?
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Tweeder
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Report this Post02-01-2015 10:52 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
The doors not opening has been like that as long as I've had the car but the car doing the banana thing, I've never paid attention. I'm assuming it's always been here. The car drives fine and what not, I just don't like it now that I notice it.

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86 SE Convertible 3800sc 4t65e HD(2002), Gen V, 3.3 pulley, SD headers

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Csjag
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Report this Post02-02-2015 08:13 AM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
I remember a few years back a bodyman telling me that the 80's Mustang convertibles did the same thing. I would guess that the car would have to have a roll bar spanning across the top behind the seats but I am no engineer.
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jaskispyder
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Report this Post02-02-2015 01:28 PM Click Here to See the Profile for jaskispyderSend a Private Message to jaskispyderEdit/Delete MessageReply w/QuoteDirect Link to This Post
I had a different conversion (Holland Pontiac) and I didn't have a problem opening the door, or any sagging when jacked up, like that.

I am thinking that may need more steel in there. Just think about if you got into an accident....
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fierosound
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Report this Post02-02-2015 01:41 PM Click Here to See the Profile for fierosoundClick Here to visit fierosound's HomePageClick Here to Email fierosoundSend a Private Message to fierosoundEdit/Delete MessageReply w/QuoteDirect Link to This Post
Pics of reinforcing Archie did on his cars (yellow Finale) here:
http://www.fiero.nl/forum/Forum1/HTML/089478.html

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jaskispyder
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Report this Post02-02-2015 01:54 PM Click Here to See the Profile for jaskispyderSend a Private Message to jaskispyderEdit/Delete MessageReply w/QuoteDirect Link to This Post
http://www.fiero.nl/cgi-bin...ad=20090219-2-079153

[This message has been edited by jaskispyder (edited 02-02-2015).]

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theogre
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Report this Post02-02-2015 02:13 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Make sure door hinges isn't the problem...

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Taijiguy
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Report this Post02-02-2015 04:02 PM Click Here to See the Profile for TaijiguyClick Here to Email TaijiguySend a Private Message to TaijiguyEdit/Delete MessageReply w/QuoteDirect Link to This Post
I don't know that there isn't a bit of flex inherent in the Fiero. My 85 GT did the same thing, and it hasn't been cut on, nor is there any rust to speak of. I actually noticed that when I park on a particularly uneven surface I would see the windshield pop out at the top corner a bit. Granted, there's little to no give in my suspension which would exacerbate the situation in cootraast to a nice squishy suspension setup which would compensate for the un-evenness.

[This message has been edited by Taijiguy (edited 02-02-2015).]

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jaskispyder
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Report this Post02-02-2015 04:04 PM Click Here to See the Profile for jaskispyderSend a Private Message to jaskispyderEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Taijiguy:

I don't know that their isn't a bit of flex inherent in the Fiero. My 85 GT did the same thing, and it hasn't been cut on, nor is there any rust to speak of. I actually noticed that when I park on a particularly uneven surface I would see the windshield pop out at the top corner a bit. Granted, there's little to no give in my suspension which would exacerbate the situation in cootraast to a nice squishy suspension setup which would compensate for the un-evenness.


Nope, not in any stock fiero.. including t-top and convertible, my experience.
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Bloozberry
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Report this Post02-02-2015 09:58 PM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
Forgive me if I'm explaining something you already know, but here are the basics. To know where you need to strengthen the frame, you need to understand the Fiero's structure. Essentially, the frame is comprised of three boxes: the front, the cabin, and the engine compartment. Three things span between the front compartment and the engine compartment: the door sills, the fuel tank tunnel, and the horizontal roof members. Here's a schematic of the Fiero frame with those three components highlighted:



The roof and fuel tank tunnel provide the lion's share of resistance against bending. When you cut the roof off, it leaves the door sills and the fuel tank tunnel. The door sills weren't designed with enough strength to resist bending without the roof. With the weight of the car on the wheels, the car sags in the middle, and when the car is lifted with an X-style hydraulic lift, the two ends sag in relation to the middle. The whole car acts like a giant slinky when the front wheels hit a bump, followed by the back wheels. That bending pinches the door in the frame:



There are several ways to reduce bending. As shown in Archie's thread above you can stiffen the fuel tank tunnel, but that alone isn't the best solution. By far the best way is to beef up the rocker panels (door sills) and connect them securely to the front and rear frame rails. Yarmouth Fiero has a great thread in the Construction Zone showing how he did this: www.fiero.nl/forum/Forum3/HTML/000137-3.html



The combination of the two door sills at the outer extreme edges of the car along with the fuel tank tunnel should stiffen the frame remarkably. Earlier builders were under the mistaken impression that an X-frame welded to the bottom of the car would do the trick, but there isn't enough ground clearance to make that X-frame strong enough (read: thick enough) to be useful in bending.

There's another mode of flexibility as well... that of torsion. That's where the front end might twist with the left side up and the rear with the left side down. An X-frame would help counteract torsion but again, much would depend on the mounting points of the frame and the thickness of it.

A convertible usually needs to have the frame strengthened before the roof is cut off and before the body gets put back on. Trying to do it afterwards is much more complicated because it's difficult to ensure the frame is straight once it's been chopped. If you posted more details about how your car was strengthened, I or someone else might be able to suggest several methods of varying complexity to regain at least some of the lost rigidity in your car.

Edit to add link.

[This message has been edited by Bloozberry (edited 02-02-2015).]

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Tweeder
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Report this Post02-02-2015 10:41 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
Blooze, my car looks to be doing what your diagram number 2 is showing. The po re-enforced the frame according to the la machines specs shown in post number 7 by jaskispyder here
http://www.fiero.nl/cgi-bin...d=20090219-2-079153.

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[This message has been edited by Tweeder (edited 02-03-2015).]

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Bloozberry
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Report this Post02-03-2015 08:17 AM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have no idea what you mean by "a la machine's method" even after having gone through that linked thread twice. Do you mean an X-frame welded to the bottom of the car?
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Tweeder
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Report this Post02-03-2015 08:45 AM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Bloozberry:

I have no idea what you mean by "a la machine's method" even after having gone through that linked thread twice. Do you mean an X-frame welded to the bottom of the car?


Yeah there was a drawing right under the metal x frame, that's how the undercarriage was re-enforced.

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86 SE Convertible 3800sc 4t65e HD(2002), Gen V, 3.3 pulley, SD headers

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Bloozberry
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Report this Post02-03-2015 09:26 AM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you mean this:



...I can't see that frame contributing much to chassis stiffness either in bending or torsion. 1" x 2" x 0.125 wall mild steel tubing is easily bent in the orientation it's laid out. Then there are the attachment points. For it to be effective, the sub-frame would have to be attached to something substantial and has to be in the right plane. The proof of the pudding that it doesn't meet those criteria is that you've got lots of chassis flex.

Unfortunately I'm not sure what you'll be able to do at this point short of removing the lower body panels, having the frame set straight on a jig, and fabricating new beefier rocker panels that are interconnected to the front and rear frame rails. You can take comfort in knowing that you're not alone... I'd easily say 90% of the convertible Fiero's I've seen photos of, have been poorly reinforced.

So what's the risk of doing nothing? Not much in the short term other than compromised handling. In the medium to long term you have to be aware of the potential for fatigue cracks to develop in the steel rockers in the corners where they transition from horizontal to vertical. The other place to keep an eye on is the area where the fuel tank tunnel attaches to the front and rear firewalls. The cracks would likely start at the outer edges of a hole such as a fastener or drain hole. Once they start, they will progress quite fast. As a temporary measure you can try to slow crack propagation by locating the end of it and drilling a small hole. That slows the crack progression by spreading out the loads to a larger surface area, but only if you've drilled in the right place. Normally the end of a crack can't be seen without some form of dye penetrant.
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