Metal roof rather than glass on the Cybertruck

[firsttruck]

I see no evidence of metal being heavier.

A) 305 stainless steel is 7.99 g/cm^3 while ALON is 3.696 g/cm^3

Those numbers are not weight of steel vs ALON armor glass
Those numbers above are rates (mass density, weight per volume).

** the bottom line is 3mm steel weighs a LOT LESS than 12mm Alon armor glass **
** 95.9 kg for 3mm stainless steel vs 187 kg for 12mm armor glass roof & support frame
** You can not use 3mm/6mm or 8mm of armor glass at a size of 2-meter by 2-meter **
** see below for detailed calculations **

There are two issues with the numbers you gave:

1. The numbers are mass density, only the weight for a cube of 1cm x 1cm x 1cm.
Basically the numbers are the density.
The "cm^3" part is volume.

2. The volume of material need to do approximately the same job or protection is vastly different.

To get close to 3mm 30x cold-rolled stainless steel you need approx. 12mm-15mm of aluminum oxynitride. Before aluminum oxynitride the best glass material would have required a thickness of 20mm and much heavier. Aluminum oxynitride 12mm thick is still less protection than 3mm SS metal.

aluminum oxynitride 1cm (10mm) x 200cm x 200cm
Size of window 200 cm (6.56 ft) x 200 cm (6.56 ft)
Area 40,000 cm^2 = 200 cm x 200cm (43.0336 ft2)
thickness of glass roof: 1.2 cm ( 12 mm)
total volume: 48,000 cm^3
density of aluminum oxynitride 3.696 g/cm^3
weight: 177,408 g ( 177.4 kg - 391.1 lbs)

You can not weld armor glass to 3mm steel. You also can not just glue heavy piece of armor glass to sides of hole in a 3mm sheet of steel.

You need like a L shaped metal frame for the glass to rest on.
You have to weld this frame to the other roof or side walls
then put glue/sealant on the support frame, then position the glass in the hole and frame and finally finish with more glue/sealant.

Well this support frame for the glass adds extra weight too.

Stainless 300 series L strip bracket .3 cm (3mm) x 800cm x 5cm
volume 1,200 cm^3
weight: 9,588 g ( 9.6 kg ( 21.2 lbs )

187 kg (412.3 lbs) total weight for armor glass roof & support frame

Making the frame and attaching the frame is extra the fabrication I mentioned before.
All this takes time and is more steps that need to be done. And the sealant/glue needs time to set too so more slowdowns.

Even if metal roof was an option not the default putting in a 2x2 metal piece is much easier because you do not need the frame to support the metal piece. You can just directly weld the metal roof piece to the other parts of wall or roof and no waiting after welding is done.

Metal roof
Cold-rolled Stainless 30x series sheet .3cm (3mm) 200cm x 200cm
Size of window 200cm (6.56 ft) x 2cm (6.56 ft)
Area 40,000 cm^2 = 200 cm x 200cm (43.0336 ft2)
thickness of glass roof: .3 cm ( 3 mm)
total volume: 12,000 cm^3
density of 305 stainless steel is 7.99 g/cm^3
weight: 95.9 kg ( 211.4 lbs)

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[firsttruck]

No evidence for that. A glass roof is a single panel that glues in place. That is very, very simple. Simpler than the folds, welds, and structure required to support a metal roof.

Sorry but you do no just glue 187 kg, 2-meter x 2-meter piece of 12mm armor glass to 3mm steel.

You want people to sit under a 187 kg (412.3 lbs) armor glass held only by glue as the truck bounces over bumps in the road or an off-road !!!!

The armor glass joint to 3mm steel does not have enough contact area for glue to hold the weight.

It is the 187 kg armor glass that needs the folds (steel supports), welds (steel supports), structure to support all that weight and hold it in position (you do not want it shifting around).

Yes, the 3mm 2mx2m steel metal roof is the simple & fast thing to do because you CAN just weld steel to steel to the other pieces of the exoskeleton without any additional permanent support.

The robot arms makes welds around all sides of the metal piece to make it a part of the exoskeleton body. The robot welders will complete the metal roof piece in less time than step 1 of 8 of armor glass process.

 

[firsttruck]

The side (door) panel was able to take more impact (from hammer) because it has a heavy metal structure that can flex further. It flexed so far that it broke the edge of the glass!

Yes, when the door was struck by the dead blow hammer, the entire door structure flexed to soften the blows.
But that flexing really was not that important as far as saving the 3mm steel from damage.

3mm cold rolled stainless is so strong in regards to impacts that no human could have really damaged it with a dead blow hammer.

But it is still the armor glass that failed.

Even with the excuse from Elon that the glass corners had been broken earlier is enough that we should disregard the failure.

So this ultra expensive bullet resistant armor glass is so fragile that if the corners get damaged the whole glass will completely fail in a permanent way (cracking ) and need replacing at a cost of $1,000 or more.

If you took the glass window out and put in a 3mm cold-rolled stainless steel piece in the window opening, then threw the ball at the 3mm steel piece in the window opening, the only damage you would get is a dent and maybe a little bending. That is it. The steel plate would still be usable.

For scratch resistance the armor glass might have a surface hardness to scratches better than cold-rolled stainless steel. But for impact resistance to hammers, falling metal balls, rocks & bricks, the cold-rolled stainless steel is much better than armor glass.

If you make that a (metal) roof panel, you need all those sides to work together to handle the increased load that it will transmit.

Otherwise, your fancy metal roof will just total all your windows and perhaps the frame of the truck - when a glass panel would have just broken and absorbed some of the energy as it flexed and then didn't flex back.

Oh, and NO, the normal exoskeleton structure is NOT so weak that these falling objects on a metal roof is going to collapse the sides and total the car.

Also as I showed in my previous post the metal roof is almost half the weight of the armor glass roof. Metal roof saves 200 lbs. More range.

 

[Crissa]

The glass on the Cybertruck is not going to be 12mm.

I don't know what it will be, but I know that for sure.

I'm done. I really tried to help you, but your assumptions are just that: unfounded assumptions. And in several cases, straight up wrong. I gave you actual numbers and engineering basics that need to be considered and you ignored it for your fantasies.

-Crissa

And yes, the glass is just held in by glue. There's also a gasket but that only makes sure it remains sealed as the car changes temperatures and pressures, This is why a small mistake at the factory can send it flying: https://www.glassbytes.com/2020/10/you-cant-look-out-the-back-of-these-cars-recalls-issued/

 

[firsttruck]

I'm done. I really tried to help you, but your assumptions are just that: unfounded assumptions. And in several cases, straight up wrong. I gave you actual numbers and engineering basics that need to be considered and you ignored it for your fantasies.

You are the one who posted flatly incorrect info. Comparing mass density without considering volume.
You do not seem to know how to read & use basic material science info & physics.

Mass Density is not the same as weight. You have to multiply by volume.

For a glass roof of 2m x2m sheet, you need at least 12mm-15mm of Aluminium oxynitride (ALON) to stop objects impacts from steel balls or rocks and the armor glass is very likely to crack.
While you only need 3mm of steel.

Elon is smart guy but not perfect.
The Cybertruck reveal & broken armor glass is mentioned by every ICE car owner I try to convince to look at Tesla EVs. They doubt everything because Tesla "bulletproof" armor glass could not stop a simple steel ball without cracking up. How is it going to be bulletproof!

** 95.9 kg for 3mm stainless steel vs 187 kg for 12mm armor glass roof & support frame
** You can not use 3mm/6mm or 8mm of armor glass at a size of 2-meter by 2-meter **
** see previous post for detailed calculations **

Density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its mass per unit volume. The symbol most often used for density is ρ (the lower case Greek letter rho), although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume:
ρ = m / V
https://en.wikipedia.org/wiki/Density

cubic centimetre (or cubic centimeter in US English) (SI unit symbol: cm3; non-SI abbreviations: cc and ccm) is a commonly used unit of volume that corresponds to the volume of a cube that measures 1 cm x 1 cm × 1 cm.
https://en.wikipedia.org/wiki/Cubic_centimetre

To get weight you have to multiply ρ (density) by V (volume) to get m (weight)

Anyone can calculate the approx thickness and weight of based on info on two wikipedia pages (I did cross correlated accuracy with other sources).


Aluminium oxynitride
Density 3.691–3.696 g/cm3
Melting point ~2150 °C
Bulletproof glass Aluminium oxynitride
As a transparent armor material, ALON provides a bulletproof product with far less weight and thickness than traditional bulletproof glass.
41 mm thick (density 150.1) of ALON armor is capable of stopping .50 BMG armor-piercing rounds, which can penetrate 3.7 inches (94 mm) of traditional glass laminate.[12]
The weight reduction over traditional glass-clad polycarbonate is 35%.
https://en.wikipedia.org/wiki/Aluminium_oxynitride

Aluminium
Density (near r.t.) 2.70 g/cm3 when liquid (at m.p.) 2.375 g/cm3
https://en.wikipedia.org/wiki/Aluminium

Bulletproof_glass Glass-Clad Polycarbonate vs Aluminum oxynitride (ALON)
Table of Sample thickness and densities for bullet-resistant glass materials
https://en.wikipedia.org/wiki/Bulletproof_glass

 

[MEDICALJMP]

You are the one who posted flatly incorrect info. Comparing mass density without considering volume.
You do not seem to know how to read & use basic material science info & physics.

Mass Density is not the same as weight. You have to multiply by volume.

For a glass roof of 2m x2m sheet, you need at least 12mm-15mm of Aluminium oxynitride (ALON) to stop objects impacts from steel balls or rocks and the armor glass is very likely to crack.
While you only need 3mm of steel.

Elon is smart guy but not perfect.
The Cybertruck reveal & broken armor glass is mentioned by every ICE car owner I try to convince to look at Tesla EVs. They doubt everything because Tesla "bulletproof" armor glass could not stop a simple steel ball without cracking up. How is it going to be bulletproof!

** 95.9 kg for 3mm stainless steel vs 187 kg for 12mm armor glass roof & support frame
** You can not use 3mm/6mm or 8mm of armor glass at a size of 2-meter by 2-meter **
** see previous post for detailed calculations **

Density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its mass per unit volume. The symbol most often used for density is ρ (the lower case Greek letter rho), although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume:
ρ = m / V
https://en.wikipedia.org/wiki/Density

cubic centimetre (or cubic centimeter in US English) (SI unit symbol: cm3; non-SI abbreviations: cc and ccm) is a commonly used unit of volume that corresponds to the volume of a cube that measures 1 cm x 1 cm × 1 cm.
https://en.wikipedia.org/wiki/Cubic_centimetre

To get weight you have to multiply ρ (density) by V (volume) to get m (weight)

Anyone can calculate the approx thickness and weight of based on info on two wikipedia pages (I did cross correlated accuracy with other sources).


Aluminium oxynitride
Density 3.691–3.696 g/cm3
Melting point ~2150 °C
Bulletproof glass Aluminium oxynitride
As a transparent armor material, ALON provides a bulletproof product with far less weight and thickness than traditional bulletproof glass.
41 mm thick (density 150.1) of ALON armor is capable of stopping .50 BMG armor-piercing rounds, which can penetrate 3.7 inches (94 mm) of traditional glass laminate.[12]
The weight reduction over traditional glass-clad polycarbonate is 35%.
https://en.wikipedia.org/wiki/Aluminium_oxynitride

Aluminium
Density (near r.t.) 2.70 g/cm3 when liquid (at m.p.) 2.375 g/cm3
https://en.wikipedia.org/wiki/Aluminium

Bulletproof_glass Glass-Clad Polycarbonate vs Aluminum oxynitride (ALON)
Table of Sample thickness and densities for bullet-resistant glass materials
https://en.wikipedia.org/wiki/Bulletproof_glass

Elon never said the CTs Armor Glass would be bulletproof. Nor did he say that the Cybertruck is bulletproof. He said the skin — that 3mm stainless steel used for the body — would resist 9mm rounds fired from 10 meters. These were 115 grain full metal jacket rounds. Go back to the reveal video and listen to what he said, watch the graphics displayed to the audience. The armor glass on Cybertruck is not, nor is it intended to be, bulletproof. Many FMJ rifle rounds, especially with the newer steel cores, will pierce that at 10 meters. I’ve personally shot 5mm tread plate at twice that distance and it went through cleanly.

 

[firsttruck]

Elon never said the CTs Armor Glass would be bulletproof. Nor did he say that the Cybertruck is bulletproof. He said the skin — that 3mm stainless steel used for the body — would resist 9mm rounds fired from 10 meters. These were 115 grain full metal jacket rounds. Go back to the reveal video and listen to what he said, watch the graphics displayed to the audience. The armor glass on Cybertruck is not, nor is it intended to be, bulletproof. Many FMJ rifle rounds, especially with the newer steel cores, will pierce that at 10 meters. I’ve personally shot 5mm tread plate at twice that distance and it went through cleanly.

Yes, you are right. I know that I should not say bulletproof but it slips in some times.

This is why Elon & Tesla should not have even used guns & bullets in the demo.
Why use them when there are plenty real world examples of rocks, bricks, hammer, birds.

Same with waterproof. In most cases should say water resistant.

Maybe need terms like
metal ball resistant
rock resistant
Canada Goose resistant
chicken gun resistant

The first chicken gun was created in the 1950s at de Havilland Aircraft in Hatfield, Hertfordshire
By Rosie Gizauskas
9 Jan 2019
https://www.thesun.co.uk/travel/8158069/plane-safety-frozen-chicken-bird-gun/

 

[T3slaDad]

Chicken guns are a critical testing mechanism for testing aircraft safety and durability, specifically for the windshields. It's amazing how creative inventions can be!

 

[firsttruck]

... I had to chime in as liking the option. Other stuff comes up as well. Where do you hang the radios inside the vehicle so you can use them? It appears there will be space in the CT. The F150 with a 40/20/40 seat allows you to toss out the center seat and mount a console. Up until the 2021, the options I wanted (blind spot, all round camera, adaptive cruise) precluded this seating configuration. I can get it on the new 2021, so it is back into contention.

Metal roof makes it a lot easier to mount equipment to the cab ceiling (like single/multiple radios, ceiling center consoles, LCD monitors/TVs, storage).

4wd Interiors - ROOF CONSOLES
USA Sales centers in Florida & Washingron State. Shipping available to other states
https://www.4wdinteriors.com/products/roof-console

REI Universal Roof-Mount Radio Kit AM/FM/WB/AUX/USB with Bluetooth — 2 Speakers, 2 Power Ports, Model# REC24W
https://www.northerntool.com/shop/tools/product_200715889_200715889

Heavy Duty Radios - Overhead radio system
https://www.heavydutyradios.com/jensen_overhead.html

https://www.consoles.com.au/Images/Console Designs Page Images/Across_Screen_Full_Facia_Roof_Large.jpg

https://www.consoles.com.au/Images/Roof/PatrolGU_low.jpg

https://www.consoles.com.au/Images/Roof/Pajero_NM_low_4.jpg

https://www.consoles.com.au/Images/Main Index Page Images/Across_Windscreen_Full_Facia_Roof_Large.jpg

Car Console Supplies Pty Ltd - Department of the Interior
https://www.consoles.com.au/

 

[Crissa]

I know I said I wasn't going to butt back in, but...

...Do you even know where the roof panel is and how inconvenient it would be to mount any of those things to the underside of it would be?

-Crissa

 

[firsttruck]

I know I said I wasn't going to butt back in, but...

...Do you even know where the roof panel is and how inconvenient it would be to mount any of those things to the underside of it would be?

forum member ThomasG asked about those kinds of products.
I used my time to find some examples for him.

Why is that a problem?

 

[ldjessee]

The ridge or peak of the roof is behind the driver’s head, so the ‘roof’ panel is only above the second row of seats.

 

[firsttruck]

The ridge or peak of the roof is behind the driver’s head, so the ‘roof’ panel is only above the second row of seats.

So, I still do not see the problem.

Tesla is not the only company that has engineers. Maybe those other companies do not have rocket engineers like Tesla has but those other engineers managed to design most of the devices & accessories we use today.

Clamped to the edge of my desk is a two-foot vertical steel pole and on that pole are four (4) 2-foot arms that support a total of four (4) heavy (48 lbs total) medium-size LCD displays .

Humanscale M/Flex for M2.1 Multi-Monitor Arm System
Weight Capacity: Supports up to 100 lbs
Maximum Arm Reach: Up to 28"
https://www.ergodirect.com/images/H....1-Multi-Monitor-Arm-System_lg_1593782375.jpg

Even the cheap $1 store down the street has a simple 1-monitor version at the cashier stand.

When sitting at my computer there is a wall on the left side of my desk. I can not touch the wall when I am sitting down but fortunately the local hardware store had a cheap kit of a steel bracket and piece of wood. Now I have a shelf attached to the wall. The shelf extends out 18" and I can reach out and pickup many items on that shelf without having to get up.

One two-way CB radios only weighs total of 3.5 lbs. I would not mount that on truck's glass.
Two two-way CB radios only weighs total of 7 lbs

Many of the ceiling console makers I linked to also do custom consoles.
If the engineers knew they had a sturdy metal roof to mount to the engineers could design a console that extends forward without hitting the windshield but be reachable by driver or front seat passenger.

 

[ThomasG]

Have you considered using starlink? If glass roof is transparent to starlink it might be beneficial since the antenna is rather large and might do better inside the vehicle.
Actually Elon said at an investor day that lower bandwidth 20-30mb antenna could be smaller

The USAF will be a Starlink customer, but it is not likely to replace two-way radios for SAR in my little part of USAF. Starlink is wireless Internet and something I am keenly awaiting, but one of our goals is to be able to operate independently from the Internet and grid if necessary. Running VOIP over the Internet won't handle that. There are some neat cellular apps that emulate two-way radio, but they don't work without a cellular or Internet connection.

One question. How many of the people seem offended by folks who would like a metal roof for whatever reason use trucks for work, SAR, or public safety? I can understand Tesla deciding not to serve that market. It is Tesla's privilege and they can probably live without the sales. I don't get why folks here don't accept that some customers know what they need and sadly, what we need may turn out not to be a Tesla. Personally, I really want to see one and determine if there are work arounds, but I suspect there won't be. That won't keep it from being the perfect truck for the rest of you.

 

[ThomasG]

Metal roof makes it a lot easier to mount equipment to the cab ceiling (like single/multiple radios, ceiling center consoles, LCD monitors/TVs, storage).

4wd Interiors - ROOF CONSOLES
USA Sales centers in Florida & Washingron State. Shipping available to other states
https://www.4wdinteriors.com/products/roof-console

......

Thanks for the links. Havis, Troy, Jotto and Gamber Johnson are the big suppliers of consoles for public safety vehicles in the US. Some of the overhead ones look useful for a vehicle with a lot of headroom.