Hey Norval,

How much structural support do you suppose the bird cage lends to the body? Would it be feasible to swiss cheese it? There has got to be something weighing down our cars. I have a hunch it may be the steel that's reinforcing the fiberglass.

 

It provides pretty much all of the strength in the passenger compartment incase of roll over or side impact.

Swiss cheesing that would cause major structural issues even before an accident--sagging doors, cracked windshields from the twisting of the birdcage during launches, sepAeration of the bonds that hold birdcage to the body.

Please thank me for removing all of my sarcasm from this post. The more I read the more scared I was that you are actually thinking of doing it.

DON"T ever do this. Is the weight lost worth your life?

The thing weighing down our cars is the Fiberglass..... it ain't as light as you think!


[Modified by MikeC, 11:42 PM 12/7/2003]

 

Another way to look at it is that GM installed heavier springs as more options were ordered...spring rates went from something like 283 lb/in per spring all the way to 550 lb/in for HD.

So, remove pumps and options and you would save a bunch. The late model C3 rubber bumber system added considerable weight as well...go back to chrome bumpers.

 

MikeC-
Side impact? Maybe. Though I would think the frame would do serve in that capacity better. Roll over? Nah. First off, that metal is not thick enough to do anything other than weight the car down up top. Second, if it were that crucial for safety the general woouldn't have hacked it off himself for the convertable models.

Sagging doors- Not if the metal removed was from the seats to the back

Body flex during launch- A more rigid frame should do more to fight the body flex than any birdcage could.

Separation of the bonds- How do you figure? One would probably have to remove the entire thing to do this any how. So when re-bonding the piece back in wouldn't the glue go through the holes and then act like an anchor when dry?

Fiberglass- I agree, the fiberglass could be worked on a bit.


hunt4cleanair-
The old trick of deleting options is a good onek. But a 1969 four door Nova weighs a tad over 3 grand.

I want to explore other places that can be trimmed down.


This question may send a few off, but stick with me here. Do our cars have a steel firewall?

 

No
My 73 and 74 both have fiberglass firewalls.
If you don't believe that the doors will sag if you drill the birdcage full of holes your welcome to have a look at what a little rust has done to my 74.

Steve :steering:

 

you can drill holes and keep the rigidity if you flare the holes. Lotsa work though for a minimal weight savings.

Here's some inspiration, of course the rigidity here relies on the rollcage and not so much on the birdcage.


This is the greenwood "swiss cheeze car"..if mr. swiss cheeze himself Norval sees this he will break out the drill :) ....

 

Stpman-
Where is the rust on your birdcage located? I'm not sure of the lingo, so... the part of the birdcage surounding the windshield and the part running directly under would be left alone.

Twin_Turbo-
Flare the holes?

Gotta love that car.


I wonder if one could fabricate a carbon fiber birdcage. Only the windshield part would need a mold. The rest you could just lie the sheets down into.


[Modified by applevette, 7:20 PM 12/8/2003]

 

the holes can be flared with a big flare tool. The GS vettes had aluminium bird cages.

 

1) side impact--- Have you recently seen the bumper heights of fullsize trucks? Your frame won't help in that situation too much. As for the thickness of the metal.... it is mostly inconsequential... its the geometric shape that the steel is formed into that provides most of the strength. AS for the convertible issue, I believe that the convertible body has been reinforced in different ways. This rear bar is equivilent to a small roll bar on a vehicle.... It is the factory designed rollover protection. If you can't see this maybe we can get a forum member near you to help you get your head out of your butt.:D

2) Sagging doors--- you aren't going to save much weight doing that.... Pluss all of you roll over protection is gone.

3)Body flex- Stiffening up the frame adds weight. Isn't that what you are trying to get rid of?

4) Separation of bonds will happen due to the stress created during the flex. A less rigid chassis twists more and stresses get higher causing the bonds between the fiberglass and the steel bird cage to weaken and/or the fiberglass to crack.

5)AS for the firewall they are fiberglass and maybe weigh 40-50lbs bare. if you relaced it with sheetmetal, the heat transfer woul dbe greater so you would have to insulate this area more, probably negating any weight savings.

Applevette, I would suggest learning more about engineering before you start tearing me apart, I went to school for this stuff. I'm all about loosing weight on our vehicles but a holesaw is a dangerous thing to have when you don't have the knowledge or the engineering abilities to determine where to drill.

Removal of accesories is an easy way to remove weight. using aluminum rims is a great way too. JUST think before you remove safety factors built into our cars. I don't want to see anyone die because of lack of knowledge or stupidity.

:cheers:

 

Hold on a sec... TEAR you apart? I don't think I was doing that. If anything I wrote could be interpretted as such I do apologize.

 

1a) side impact- How does the bird cage aid in protection againt a side collision since I obviously misunderstood what you meant.

1b) thickness- did i mention anything about the thickness of the steel?

1c) convertible issue- I still do not see how any kind of bar that lies at a height below the head gives any rollover protection.

head in butt... that was uncalled for.

2) ???

3) By constructing a well triangulated backbone for the existing frame one could probably get away with trimming a little from parts of the frame that will no longer hold much weight or endure much stress. The goal is a much less flexible chassis that weighs in around 400lbs. I can live with my frame weighing a bit more than it does right now, but it can't be as flexible as it currently is.

4) If the chassis is more rigid then the separation of bonds shouldn't be a problem.

5) Please explain to me what the exact purpose of the firewall is. I am being serious, and yes there is a point.

 

While I am a firm believer is holes and have more holes drilled in my car then anyone on this forum I would NOT drill the bird cage.
Twin turbo posted a great picture but that car has a full rollcage. Look at how he also drilled the frame. I drill holes in alot of things but the frame is also out for me.
Leave the birdcage and frame alone.

 

What would be so wrong with holes in 3 and holes in the inner most part of 2 and 4?

As for the frame, I don't want to get into that one yet.

No, I do not want the number of nor the size of the holes in the greenwood car.

 

I wouldn't do it. The metal is very thin to begin with so the weight saving is less. I would try removing weight elsewhere where holes are more effective. Even my 4 rotors lost 12 pounds through holes . They have stood up over 14 years so far with the holes.
I like drilling things but not my birdcage.

 

Sorry Twin_Turbo, I overlooked your earlier post about the grant sports. I really like the idea. The only thing about that one is I wouldn't have the first clue how to start fabricating a birdcage from aluminum. Do you?

 

Come on Norval spot 3, at least give me that :cry

 

First the head up the butt was a bit of joke a bit of frustration, sorry for that.

a) The door bolts to the dorr pillars in the front, and to the rollover bar in the rear. This makes the door an intergral part of side impact protection and the birdcage also since the door is bolted to it. any weakness in the bridcage caused by holes will allow the birdcage to bend in easier, thus have parts of the door intrude into the passenger compartment and possibly yourself.

b)"First off, that metal is not thick enough to do anything other than weight the car down up top" taken directly from your post

C) it helps in conjunction with the windshield frame strength. Definitely not as good as the coupe, I will agree, but your car will not have that reinforcing.

5) the purpose of the firwall is to not allow fumes, engine heat into the compartment as well as be a little bit of a fire break incase of engine fire. Like I said there is little to gain from removing it and or replacing it with steel.

Carbon fiber would be the way to go for light weight and big $, you must have engineering background to understand where the material needs to be.

Honestly from a lot of this conversation, I think some engineering courses- I think statics/dynamics course and mechanicas of materials would be beneficial before you enter into the world of speed holes.

AS for twin turbo's pic, that is really scary but it is a race car. The only thing helping that car is the rollcage. A roll cage will add significant strength to the chassis..... but also adds weight.

I think your best bet is more HP to overcome the weight. Its one of the easiest solutions to the problem. Holes can come later after you have learned more about engineering and chaassis design.




[Modified by MikeC, 3:14 PM 12/8/2003]

 

scary? I'm not that scared by the holes, look at all the holes the general put in there, one being in a very bad spot (access hole for steering power ram bracket on drivers side).

 

to add 2 cents worth

back in 1980 FORD in an atempt to lose weight on the frames of the F150 filled it full of holes. Well I crash tested one (not on purpose), hit a pole dead on the right frame rail at 15 MPH. The frame rail accordianed(sp?) and the right side ended up a foot shorter than stock. they made it lighter but it didn't survive a low speed impact. oh yea the truck was only 4 years old not a rust bucket.

Steve :steering:

 

That steel has no fiberglass behind it. if you open that up you will have a hole to the outside

FYI te whole bircage of a corvette maybe... maybe weighs 100LB.... figure if you remove 10% of the material you'll only loose 10lbs..... is your life worth 10lbs?

BTW what year is your car? removing material from #2 in a 77 or earlier car is downright impossible as the cage is sandwiched in fibreglass. in a 78 or neweer it is open for holing.