Model 3 glass roof question

[Gorilapaws]

Can someone explain the logic behind the all-glass roof to me? I realize that it helps with headroom and the feeling of "spaciousness" in the back, but aren't the 2 main goals with the Model 3 range and cost reduction (of course both are related to each other)? Glass is heavy and expensive, so having all of that glass should decrease range and increase cost right? It just seems like a strange design choice from an economics perspective (from an aesthetics perspective, it makes a lot of sense).

Tesla engineers are very smart people, so obviously there's probably something I'm not understanding. Anyone care to explain it to me?

 

[zenmaster]

Glass roof is a more expensive option, paid for by customer. Weight difference will be nominal for range consideration. Remember, due to heavy batteries, the car will weigh over 4000lbs. A glass roof weighs perhaps, at most, 30lbs more than a stainless steel roof?

 

[Zoomit]

The two key, opposing design constraints were a low coefficient of drag (Cd) and rear seat headroom. The low Cd was needed to meet their highway range requirement. The available rear seat headroom is unique in the segment and was apparently a significant design driver. Most (probably all) compact sedans do not have generous rear headroom. To make this a comfortable rear seat for taller people they needed to raise the roof, but that requires a vehicle shape that challenges the Cd goals. The glass allows tall heads to get very close to the roof while also being transparent for proper visibility out the back for the driver.

There are a few penalties of this configuration. The glass weight and cost are two, but not a major consideration. Another somewhat minor one is the chassis stiffness. Putting the upper crossmember further aft would probably make meeting their stiffness criteria easier. The big penalty is of course the inability to have a liftback like the Model S. ...and there are many threads showcasing people's emotional reaction to this conclusion.

So basically, the higher priorities for the Model 3 were high-speed range and rear seat headroom. Access to the cargo area was a lower priority. The Model Y will have a more squared off rear roof and yield high-speed range for a larger cargo area that is easier to access via a hatchback.

 

[Gorilapaws]

This will be an option thought right? How do you think the metal roof will handle the headroom issue? Also, is the weight difference really that negligible?

 

[ZAKEEUS]

The rear piece of glass is large and will cover the entire back seat. I don't think that is an option.

 

[Gorilapaws]

The rear piece of glass is large and will cover the entire back seat. I don't think that is an option.

In this clip at 2:11 the Tesla driver says you can get a "fixed roof, glass panel like this, or a sunroof." Maybe I'm confused about what part of the car would be metal. Obviously there will be SOME glass in the rear so you can see.

 

[Zaphod]

There are 3 pieces total. The windshield obviously, the rear glass, and the center part. The center section can be either metal like traditional roof, a fixed glass piece, or a retracting piece like the panoramic roof on the S. Metal will get standard, with both glass versions optional.

 

[PaulJB]

In this clip at 2:11 the Tesla driver says you can get a "fixed roof, glass panel like this, or a sunroof." Maybe I'm confused about what part of the car would be metal. Obviously there will be SOME glass in the rear so you can see.

The dead horse has been beaten many times. The rear glass panel (from behind the front seats all the way to the back) will NOT be an option but will be standard. The discussion in that video pertains to the section of roof above the front seats between the A and B pillars, which will be metal standard with glass options.

The two key, opposing design constraints were a low coefficient of drag (Cd) and rear seat headroom. The low Cd was needed to meet their highway range requirement. The available rear seat headroom is unique in the segment and was apparently a significant design driver. Most (probably all) compact sedans do not have generous rear headroom. To make this a comfortable rear seat for taller people they needed to raise the roof, but that requires a vehicle shape that challenges the Cd goals. The glass allows tall heads to get very close to the roof while also being transparent for proper visibility out the back for the driver.

There are a few penalties of this configuration. The glass weight and cost are two, but not a major consideration. Another somewhat minor one is the chassis stiffness. Putting the upper crossmember further aft would probably make meeting their stiffness criteria easier. The big penalty is of course the inability to have a liftback like the Model S. ...and there are many threads showcasing people's emotional reaction to this conclusion.

So basically, the higher priorities for the Model 3 were high-speed range and rear seat headroom. Access to the cargo area was a lower priority. The Model Y will have a more squared off rear roof and yield high-speed range for a larger cargo area that is easier to access via a hatchback.

Regarding everything else, THIS ^^^

 

[Raindog1]

I'm guessing the cost of building another cross member (of which the glass is replacing) and head liner would just be more $$ & parts to create. Simplicity of building one single part which acts multiple parts.... as a structural member and replaces a headliner... and provides more room is a no brainer. My hope is that they add a photo-chromatic layer.

 

[baoconnor]

Personally I don't really care about headroom in the back seat. I'll always be in the drivers seat! I'll be getting the sunroof option.

 

[Jersey Shore Tom]

Perhaps I am an incurable optimist, but I think the fixed all glass roof will be standard (base model) and the metal roof and the glass roof that opens will be options. Elon made the all glass roof sound like it was important to meet basic design criteria that has been set for the car. I see nothing on the Tesla website or in official statements that even imply it won't be standard.

 

[Zoomit]

Perhaps I am an incurable optimist, but I think the fixed all glass roof will be standard (base model) and the metal roof and the glass roof that opens will be options. Elon made the all glass roof sound like it was important to meet basic design criteria that has been set for the car. I see nothing on the Tesla website or in official statements that even imply it won't be standard.

I think you're confusing the glass panels. On the Model 3's shown at the reveal, they each had three pieces of glass: the windshield, the roof, and the backlight.

The backlight is what's being discussed in this thread as necessary for rear seat headroom and what Elon referenced as necessary for the car's design. It extends from the trunk to ahead of the rear seat passengers.

The roof, as shown at the reveal in all three cars, was fixed glass. This is about a 2 feet long directly above the driver. It's this roof that will be the option of metal, fixed glass, or a sunroof (tilting and/or sliding glass). The metal roof is likely to be standard, in my opinion, and the fixed glass and sunroof will be options.

We should really start calling the rear window the "backlight", not the "roof", to avoid this confusion.

 

[Zoomit]

Personally I don't really care about headroom in the back seat. I'll always be in the drivers seat!

But I bet you do care about rearward visibility. Have you driven a Model S? The view through the liftback is both short and narrow. The Model 3 backlight will open up the view considerably.

 

[Zoomit]

Here's a 360 video from the reveal that shows what these three windows look like from the inside:

Don't forget to scroll around!

 

[Jersey Shore Tom]

I think you're confusing the glass panels. On the Model 3's shown at the reveal, they each had three pieces of glass: the windshield, the roof, and the backlight.

No, I'm not confused (dazed maybe, but not currently confused) . I know it is three pieces. I believe that the center piece of glass contributes to the comfort level of tall rear seat passengers so they are not looking directly into the headliner. While I am short and don't have to worry about it, I can see my taller friends finding the metal roof somewhat claustrophobic.

 

[Zoomit]

Ah, I was confused then! I hadn't thought about tall rear passengers looking into the headliner. I suspect the rear crossmember may block the view somewhat. It definitely will be a unique experience, especially for tall folk. Based on the above spherical YouTube video, it looks like tall people may be blocked from viewing sideways due to the location of the upper longeron, or whatever they call the side structure that holds the window. I'm not too worried about a metal roof panel causing claustrophobia though.

The rear passengers might get an experience similar to a rumble seat, where the view forward is limited but the view up and back is open...

 

[baoconnor]

But I bet you do care about rearward visibility. Have you driven a Model S? The view through the liftback is both short and narrow. The Model 3 backlight will open up the view considerably.

Good point. Too bad we won't know what the rearward visibility is like until it's sitting in our driveway!

 

[Jason Bourne]

Perhaps I am an incurable optimist, but I think the fixed all glass roof will be standard (base model) and the metal roof and the glass roof that opens will be options. Elon made the all glass roof sound like it was important to meet basic design criteria that has been set for the car. I see nothing on the Tesla website or in official statements that even imply it won't be standard.

I disagree. I think the metal roof will be standard and the two options will be fixed glass or a sunroof. I don't see why a metal roof would be an upgrade option, nobody would choose it.

 

[Jersey Shore Tom]

I disagree. I think the metal roof will be standard and the two options will be fixed glass or a sunroof. I don't see why a metal roof would be an upgrade option, nobody would choose it.

Considering the number of people above who appear to be opposed to all glass, I would assume there is a market for metal as an option.

 

[geoffreak]

I remember someone saying that although an all glass back is slightly more expensive, it simplifies production. It's much easier to slap on pieces of glass than to weld on more pieces of metal. This is why I think the all-glass roof will be default with an optional metal or panoramic roof.