I'm trying to understand your motivation quite frankly. I was joking when I said you were trying to justify driving a rustbucket, but is that really what you're doing here? Rust is not structural. Anywhere you see rust, the strength of the original iron has been reduced. You are now more susceptible to any damage that may be caused through movement (or elimination) of that member. Keep reducing the structural integrity enough, and eventually the structure will collapse under its own weight. Q.E.D. This can happen to any car. The C3 is no exception. And once rust has started, it doesn't stop until the surface is cleaned and sealed off from oxygen. You're ok with allowing your car to rust away. Most of the rest of us are not.

I asked you to define a catastrophic failure, and you did not. Multiple people have now related stories of inexplicable windshield breakage due to a rust compromised frame. That sounds pretty catastrophic to me. What more would you like to know?

 

That speaker looks like new!

 

A man's gotta have priorities.

 

It is pretty amazing how that speaker can look so good, when half the upper birdcage is lace!

 

Well that's easy. The speaker is galvanized, the bird cage barely has a coat of paint on it. Just over spray to a half a coat. No mystery there.

 

Plus, I am sure all those good vibrations help to shake off the water and keep the speaker dry!!

 

It depends on where the rust is. For example you can punch a hole in the center of a beam and it still retains 90+% of its original strength. Punch a hole in the edge of a beam and its toast. Most of the common holes i see are in the very thinnest middle areas of the supports and not on the edges. This looks very ugly; however, it does not have a great impact on overall strength of the member.

I'm not OK with it but i'm not going to go to the extremes most here do. I wanted to get a discussion going to get ideas on some easy stopgap measures that can be taken for those of us who will never attempt to separate the frame from the body.

1. What is a fair, simple test of the structural rigidity of the windshield frame and door mounting? My feeling is that if the corner of the windshield can withstand 100 pounds force in each direction it's structurally sound. If an open door can support 100 pounds without failure that's a fair test in my opinion.

2. How to easily treat the rust without tearing the interior completely apart. I've had the interior trim around the windshield off for years and there are definitely cracks and holes by which a small tube could be inserted to apply some spray product.

3. What kind of products to use. Most of the rust will not be reachable with a paint brush so i'm thinking it needs to be a spray product. I've applied Vasoline to the body mount areas around 7 years ago and that's actually looking like it is stopping further rusting in that area.

4. When the windshield is replaced it should be replaced with the thicker one rather than the thinner one. I've always heard the 80s models had a thin windshield to save weight.

 

You may be forgetting about one point. A hundred pounds may sound like a lot, but if, God forbid, you get into an accident and hit a large stationary object at 50 or 60 MPH what will the force be. I like driving my car, and I don't think I will ever get into an accident, but there is a reason they don't call them on purposes. Stuff happens, and when it happens to me at 50 or 60 mph I want all the metal around me to be as strong as possible.
Just sayin'

Kelley

 

yep

My dad (an old naval mech/hydraulic engineer) used to throw around terms like "5x standard". Which is to say if you're going to support something that weighs X, then you need to build the support strong enough for 5x+. E.g. you want to hoist a 200 lbs load, you use a rope tested for 1000 lbs or more. It's just a heuristic, but it's a good one.

Take a 5 lbs hand weight and drop it on a scale from 6 feet up. How far did that needle swing? Quite a bit more than 5 lbs, right?

Are you kidding me? I could have every interior piece including the carpet yanked out of my C3 in under an hour. screws and clips ... that's it.

Grind off and seal up what you can see. If you have penetrations then you'll have to make the call to either seal them off or cut and replace sections of the frame. I've heard of people using any number of spraying methods to coat/fog a cavity with rust preventor/convertor, but realistically if you can seal the cavity and keep anymore air and water from getting to it then corrosion will only procede at a snail's pace until that cavity is compromised again.

dunno