Rigidity and the role of the windshield

Redliner

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I don't drive, I fly.
We all know removing the roof of a car compromises the structural rigidity, but what about the windshield?
If I were to get an MX-5 for example, and remove it's windshield for weight saving purposes, would I be fucking up the rigidity as well?
Would a rollcage take the rigidity back to normal?
 
Where do I begin...

-Glass doesn't add much rigidity, if any.
-You really don't want a roll cage in a street car - not unless you're getting bucket seats, harnesses, and you never drive without a helmet.
-A roll bar adds a lot of chassis rigidity - I speak from experience.
-Why on earth would you want to remove the windshield???? If you really feel that a 2300lbs car is too heavy, there are better ways to save weight, I would think.
-What are your plans for this car? Street? Autocross? Track? Rally?
 
I can't comment about my 24 year old NA, but on any modern convertible the windshield frame plays a non-insignificant structural role. Personally, I wouldn't recommend it; you won't be saving much weight and really fucking up the dynamics of the car.
 
I don't know guys, I kind of like playing these "what ifs". Keeps the mind going.

I can imagine that a windshield can provide a little in the way structure to a convertible. However, it can't be much. The goop they hold the windshield in with must have some flex, but I also imagine that just like if you build a square out of 2x4s and then cover it with a thin plywood it adds a lot of stiffness.

However, if you are removing the windshield with the intent of saving weight, but then adding a roll bar. I'd think the roll bar would weigh more than the windshield.
 
The 2x4 frame is not supported and the windshield frame is. There is very little that a windshield adds to the rigidness of the chassis. I am sure there is a plexiglass kit you can get for an MX5, but unless you are using only for the track, I don't recommend it.
 
when a monocoque chassis vehicle is flexed too much, the windscreen breaks apart - there goes the rigidity provided by the windscreen... :p the windscreen needs a rigid frame to sit in comfortably with all the PU and rubbers around it for some flexibility not the other way around :D
 
Where do I begin...

-Glass doesn't add much rigidity, if any.
-You really don't want a roll cage in a street car - not unless you're getting bucket seats, harnesses, and you never drive without a helmet.
-A roll bar adds a lot of chassis rigidity - I speak from experience.
-Why on earth would you want to remove the windshield???? If you really feel that a 2300lbs car is too heavy, there are better ways to save weight, I would think.
-What are your plans for this car? Street? Autocross? Track? Rally?

-You're an engineer, I expected more. :p :lol:
-Yeah, I was thinking roll cage because it would be a hardcore, as light as possible track day toy.
-Could a roll bar substitute the windshield for rollover protection? (Assuming the windshield frame provided any)
-Don't get too focused on a Miata, it was just an example. Could be any other car, even non-convertibles ones. Also, it would be an extreme project, stopping short of removing body panels.
-Track, I guess? I don't have a specific plan, I was just walking and thinking about cars and the stuff people remove to make them lighter.

After thinking and Googling a bit, I got reminded of this:
mazda-mx-5-superligh_600x0w.jpg


I really like the looks of it. It is mostly my desire of owning a Caterham Super 7. :lol:

I don't know guys, I kind of like playing these "what ifs". Keeps the mind going.

I can imagine that a windshield can provide a little in the way structure to a convertible. However, it can't be much. The goop they hold the windshield in with must have some flex, but I also imagine that just like if you build a square out of 2x4s and then cover it with a thin plywood it adds a lot of stiffness.

However, if you are removing the windshield with the intent of saving weight, but then adding a roll bar. I'd think the roll bar would weigh more than the windshield.

That's what this thread is: a big "what if".
The trade-off between roll bar and windshield also crossed my mind: would I be trading rigidity for more weight? Would I be ending with the same weight but more rigidity? I was just curious. :D

I can't comment about my 24 year old NA, but on any modern convertible the windshield frame plays a non-insignificant structural role. Personally, I wouldn't recommend it; you won't be saving much weight and really fucking up the dynamics of the car.

See above: roll bar. Better or worse compared to a windshield?

The 2x4 frame is not supported and the windshield frame is. There is very little that a windshield adds to the rigidness of the chassis. I am sure there is a plexiglass kit you can get for an MX5, but unless you are using only for the track, I don't recommend it.

Fair point, but I liked the experience of riding on a Caterham without a windshield. :lol:
 
The glass portion aka the ACTUAL windshield itself provides pretty much no structural rigidity, the metal frame that holds it in on the other hand is pretty important.
 
I know I said "don't think Miata", but this is just too good-looking:
mazda-mx5-speedster-chicago-livepics-2.jpg


This, on the other hand, isn't:
06wsdu20012.jpg

:|
 
The 2x4 frame is not supported and the windshield frame is. There is very little that a windshield adds to the rigidness of the chassis. I am sure there is a plexiglass kit you can get for an MX5, but unless you are using only for the track, I don't recommend it.

Plexiglass sucks. Lexan is better, but Lexan with Marguard is the best. Doesn't scratch as easy as the other two.


That's what this thread is: a big "what if".
The trade-off between roll bar and windshield also crossed my mind: would I be trading rigidity for more weight? Would I be ending with the same weight but more rigidity? I was just curious. :D

I remember seeing a roadster Miata at an autocross I went to a couple years ago. Beyond the roll bar/cage everything else had been stripped out. Nothing was left. I think the doors had even been gutted and welded in place.


This, on the other hand, isn't:
06wsdu20012.jpg

:|

I think almost anything can look good as a roadster. In drag racing they are fairly common in the Super Gas (9.90 index) class. Heck there's a local that his dad built a Henry J roadster.

 
-You're an engineer, I expected more. :p :lol:
Just because I'm Russian I have to be an engineer or a computer programmer?!? I'm neither :tease:

And no, the Miata's windshield provides zero rollover protection. It folds like butter.
 
Just because I'm Russian I have to be an engineer or a computer programmer?!? I'm neither :tease:

And no, the Miata's windshield provides zero rollover protection. It folds like butter.

Why did I had in my mind you were an engineer? :unsure: Sorry!
So, you're telling me the NA Miata without a roll bar is a tad unsafe in case of a rollover?
 
There's a bunch of different ways to design a convertible. My Viper for example has a box frame and there's no subframes or anything. I highly doubt the windshield does anything at all.

[video=youtube;KBdg-mDx1tM]https://www.youtube.com/watch?v=KBdg-mDx1tM[/video]


However with a unibody, I suspect it might matter more. It's probably helping some with rigidity. A strut bar would probably suffice in its place though.
 

Damn.:|

There's a bunch of different ways to design a convertible. My Viper for example has a box frame and there's no subframes or anything. I highly doubt the windshield does anything at all.

[video=youtube;KBdg-mDx1tM]https://www.youtube.com/watch?v=KBdg-mDx1tM[/video]


However with a unibody, I suspect it might matter more. It's probably helping some with rigidity. A strut bar would probably suffice in its place though.

Interesting, I haven't thought of that.
 
There's a bunch of different ways to design a convertible. My Viper for example has a box frame and there's no subframes or anything. I highly doubt the windshield does anything at all.

[video=youtube;KBdg-mDx1tM]https://www.youtube.com/watch?v=KBdg-mDx1tM[/video]


However with a unibody, I suspect it might matter more. It's probably helping some with rigidity. A strut bar would probably suffice in its place though.
Interesting video from Sweden. I wonder if they managed to put that Saab body over it as they planned.

Edit:
Apparantly they did, sort of
 
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