Tesla Cybertruck’s Structure Will Be Unique, According to Sandy Munro

[MEDICALJMP]

Tesla Cybertruck’s Structure Will Be Unique, According to Sandy Munro

By Gustavo Henrique Ruffo
February 11, 2012
https://insideevs.com/news/487355/tesla-cybertrucks-structure-unique-sandy-munro/





He told InsideEVs the pickup truck could resemble the BMW i3 in that sense.
When the BMW i3 was first presented, it had a Life Module and a Drive Module. The former was the cabin and the latter was the rolling chassis of the electric car. Sandy Munro recently discussed Tesla Cybertruck’s mega casting with InsideEVs to clarify how it may match an exoskeleton and told us the i3 and the electric pickup truck could have a lot in common when it comes to their structure. In that respect, the Cybertruck will be unique, as Munro stressed.
Elon Musk said at Tesla’s Q4 2020 Earnings Call that the electric pickup truck would require a high-pressure die casting machine with a clamping force of 8,000 tons to create the rear body of the pickup truck because “you’ve got a long truck bed that’s going to support a lot of load.”

That would fit perfectly in a unibody vehicle such as the Model Y, which already uses mega castings. However, a stressed-skin structure vehicle was not supposed to need that due to how much stronger it is compared to a unibody vehicle. Theoretically, its own structures could handle everything and a rear casting would not be necessary.

Tesla was supposed use an exoskeleton to make the Cybertruck as tough as a body-on-frame vehicle without the weight penalty. Musk said this at the electric pickup truck's presentation:

“We moved the mass to the outside. We’ve created an exoskeleton. The way that trucks are normally designed, you have a body-on-frame, a bed-on-frame. And the body and the bed don’t do anything useful. They are carried like cargo, like a sack of potatoes. It was the way that aircraft used to be designed when we had biplanes, basically. The key to creating an effective monoplane was a stressed-skin design. You move the stress to the outside skin. Allows you to do things you can’t do with body-on-frame.”

He also told Munro personally that electric vehicles currently carry their battery pack as a sack of potatoes. The exoskeleton design would allow Tesla to put all of the Cybertruck's body to work structurally, avoiding carrying the body, the bed, and the battery pack as useless cargo. The rear mega casting, however, indicates that design could not deliver on all of Tesla's goals.

Munro told us more about the benefits the stressed-skin design could bring to the Cybertruck.

“What the exoskeleton does is to get rid of the requirements for internal longitudinals, stiffening ribs, and things like that because the structural skin would be doing all the work. What you are really doing is getting rid of roof bows, door surrounds, and things like that. They may still need an extra structure for where the hinges are. At the end of the day, you’re looking at a product that will still be self-supporting.”

Yet, it will have a massive single-piece rear casting, which does not fit the pure stressed-skin design definition. We asked Munro what role the mega aluminum rear part would play in the Cybertruck.

“The general premise would be to have the body just drop over the top of a rolling chassis. If I was doing it, I would drop a fully skinned body over the top of a rolling chassis like in the olden days. We used to do that all the time.”

He even had a suggestion about how Tesla could do that. It is here that the Cybertruck could share a lesson with the BMW i3.

“If I wanted to be really clever, I’d use the BMW way because they had the same sort of a deal. They put a body basically on top of a rolling chassis. They had two locating pins and a very, very strong urethane glue that we normally use for windshields and things like that.”

Summing up, what Munro believes will happen is this:

“It’s going to be slightly lighter than if I would have done a body-on-frame and slightly heavier than a monocoque design. The structural element of the outside skin is going to save quite a bit of weight. Having the frame made out of aluminum – instead of the steel it is normally made of – that’s also going to make it a little bit lighter and a little more nimble. It’s a little bit better than what you’d find with a body-on-frame and maybe a smidge heavier but a lot more rigid than if you have a monocoque design.”

In other words, the rear casting will be part of a frame for the exoskeleton body on the Cybertruck. If Tesla put a monocoque over a frame, that would be redundant in terms of strength and heavier than a regular body-on-frame pickup truck.

Considering the battery pack weight will already be a disadvantage for any electric pickup truck, Munro believes Tesla has solved for this with the exoskeleton for the body and a lighter frame made with mega castings.

It is not as revolutionary as a vehicle made solely with a stressed-skin design, as Musk's remarks made us believe. However, Munro thinks it will still be good enough for customers.

“With the frame the way it is, made out of cast aluminum, that will be a very, very strong product and that’s what you want when you’re going off-road. What you find is that when you have something less than that structure that you need for the carriage, for supporting the vehicle, it doesn’t work the way you want if you’re an off-roader. I believe that they’re probably going to have a cast structure underneath it and will drop the stainless steel body on top. I’ll be a happy camper when I buy one of those.”

As you can see, being redundant in terms of strength would be more than welcome if it does not increase weight. The Cybertruck's new structure may have achieved just that. Munro just warned that aluminum and stainless steel are not the best friends, something that Tesla should really take into consideration.

“You’d have to isolate the aluminum frame from the stainless steel body because aluminum and stainless steel do not get along with each other. They cause galvanic action and they do it rather quickly. However, the actual marriage should not be that big a deal.”

Instead of the classic definition for car body designs, Tesla’s solution would be something we have never seen. Jokingly, we asked Munro if we could define that as a hybrid of an exoskeleton with a body-on-frame – it would be Tesla’s first official hybrid. The Obrist Mark II was an independent creation.

“You can say that it has an exoskeleton and that it is unique. Whenever I hear hybrid I think of an engine, a motor, and a battery. I’d skip that and just go say it is unique. Nobody’s got anything quite like it. It is a perfect combination of what someone who wants to drive off-road would want.”

More Articles On Stressed-Skin Structure:

⠀

Tesla Cybertruck Engineering Analysis Explains Exoskeleton’s Edges


⠀

Sandy Munro Thinks Cybertruck Will Be A Cash Cow For Tesla


Interestingly, Munro does not classify the Cybertruck as a pickup truck.

“I look at it as something that could fulfill some pickup truck needs, more like a utility truck, similar to my existing Jeep (Wrangler Rubicon). The difference is that I can get my quads and my bikes in it, but I don’t think I would be hauling two-by-fours or material for building a house. If I wanted something like that, then I’d move toward the Rivian.”

The engineer is also enthusiastic about the stainless steel body, but we'll tell you more about that in a future article from our 50-minute conversation with Sandy Munro. Don't miss it!

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[Revoltlution]

Sandy is a smart fellar, but the last comment about "hauling 2x4s or building materials, he'd use a Rivian" is just so wrong, on every level.
I'll give Sandy a mulligan on this one, since I don't want to go researching if he really said that.
Yikes.

 

[firsttruck]

Tesla Cybertruck’s Structure Will Be Unique, According to Sandy Munro

By Gustavo Henrique Ruffo
February 11, 2012
https://insideevs.com/news/487355/tesla-cybertrucks-structure-unique-sandy-munro/


Interestingly, Munro does not classify the Cybertruck as a pickup truck.

Sandy comment about Cybertruck
“ I don’t think I would be hauling two-by-fours or material for building a house. If I wanted something like that, then I’d move toward the Rivian.”

Sandy has made this comment before about Rivian being better work truck.

I wish Sandy would explain in more detail.

The Rivian truck bed (4.5 ft) is significantly shorter than Cybertruck (6.5 ft).
I think the shortest F-150 bed is 5.5 ft. Standard bed 6.5 ft and long bed 8 ft.


KBB review - 2021 Rivian R1T
Dimensions, Weights & Capacities
Wheel Base 135.8 inches
Bed Length 4.50 feet
https://www.kbb.com/rivian/r1t/


Rivian Support
Are there bed size options on the R1T?
We are not offering additional bed sizes at this time. Our bed is optimized for the outdoors — which means it’s the perfect size for bikes, kayaks and gear.
https://rivian.com/support/article/are-there-bed-size-options-on-the-r1t

So maybe no quads or motorcycles?

Even Rivian does not claim the R1T is a work truck.

 

[Crissa]

The bed on the Cybertruck is bigger, wouldn't it be better for moving building materials?

This article is... so flawed 'supposed to' this and 'supposed to' that.

What do they think the suspension and motors were going to be mounted to on the exoskeleton? Air? There has to be an inside (and underside) to mount these things to.

-Crissa.

 

[rodmacpherson]

Sandy has made this comment before about Rivian being better work truck.

I wish Sandy would explain in more detail.

The Rivian truck bed (4.5 ft) is significantly shorter than Cybertruck (6.5 ft).
I think the shortest F-150 bed is 5.5 ft. Standard bed 6.5 ft and long bed 8 ft.


KBB review - 2021 Rivian R1T
Dimensions, Weights & Capacities
Wheel Base 135.8 inches
Bed Length 4.50 feet
https://www.kbb.com/rivian/r1t/


Rivian Support
Are there bed size options on the R1T?
We are not offering additional bed sizes at this time. Our bed is optimized for the outdoors — which means it’s the perfect size for bikes, kayaks and gear.
https://rivian.com/support/article/are-there-bed-size-options-on-the-r1t

So maybe no quads or motorcycles?

Even Rivian does not claim the R1T is a work truck.

Even just by looking at that photo comparison you can tell the Rivian bed is at least a foot shorter. I don't know how that is a better truck for hauling lumber. At least with the Cybertruck or standard F150 you can drop the tailgate and a 4x8 sheet of plywood or average 2x4 wouldn't hang out past the end of the tailgate. You can put racks on if you need to carry long lumber, but with the Rivian I think you would need racks for any kind of lumber. My LEAF is just about as good for a home depot run as it seems the Rivian would be.

 

[johnm6875]

I'm fascinated to find out how the "not-a-skateboard" aluminum underpinnings are married to the upper folded and stamped Stainless. Bolted and sealed would be my preference.

 

[Revoltlution]

I'm assuming one could, literally,

• load a CT by throwing the lumber in the back
• dump 1.5 tons of gravel or
• fork lift a pallet of bricks/lumber in the back
• let the suspension do it's thing
• Pressure wash it out
• no dings, no dents, no paint scratches, (just added patina)

No - freaking - competition.

 

[shocker]

Who'd have guessed body on frame is the best way to build a pickup truck?
Since the terafactory has a paintshop needed to build the Y, they might as well ditch the expensive SS and go high strength steel with paint. Line-X the bed for durability and Bob's your uncle.
Just having some fun here on a cold Friday afternoon.

 

[Crissa]

I'm assuming one could, literally,

• load a CT by throwing the lumber in the back
• dump 1.5 tons of gravel or
• fork lift a pallet of bricks/lumber in the back
• let the suspension do it's thing
• Pressure wash it out
• no dings, no dents, no paint scratches, (just added patina)

No - freaking - competition.

I'm counting on this. I don't mind if there's rubber weather stripping in the T-track, either. Being able to mount a bike directly to the floor and sides will be awesome.

-Crissa

 

[rr6013]

Who'd have guessed body on frame is the best way to build a pickup truck?
Since the terafactory has a paintshop needed to build the Y, they might as well ditch the expensive SS and go high strength steel with paint. Line-X the bed for durability and Bob's your uncle.
Just having some fun here on a cold Friday afternoon.

Sandy Munro‘s word of choice “unique” will stand the test of time. Cybertruck dependent on stressed skin exo-skeleton was a non-starter. Seen too many twisted door openings body-on-frame from offroad, heavy haul and accidents. Castings are going to pickup torque axel loads, cargo and blunt wheel impacts. Exo would have transferred all into the body - something has to give; usually door openings are the weakest. 2x maybe but 4x==no way. Structurals had to find mass and those casting-battery-casting tie-in keeps it all below CG. Awesomely unique easily better than frame if the casting||batterybox bond is stronger than steel weld.

 

[Crissa]

Sandy Munro‘s word of choice “unique” will stand the test of time. Cybertruck dependent on stressed skin exo-skeleton was a non-starter. Seen too many twisted door openings body-on-frame from ...

....That's not how that works. It's twisted because the skin isn't structural, not because it is. The ladder frame doesn't have the stiffness to make a truck move as a single unit, but a stressed skin would have that leverage and stiffness.

You are right, the casting will support the torque of the motors and the jolt of the shocks: But that's because the Cybertruck is built like a truss bridge and a ladder frame truck is like a beam. The castings are the piers the truck sits upon; the stressed skin provides leverage and stiffness that an internal ladder never could.

-Crissa

 

[Mr.Dee]

People who argue against the exoskeleton/stressed skin design must not be aware of an invention called the airplane.
It's the lightest and stiffest possible way to transfer loads through a structure. The reason you don't see exoskeletons on other trucks is not because cab-on-frame is "better" but because cab-on-frame is the simplest and easiest way to make a truck that's just "good" enough.
Plus, you don't need world-class engineers to design a cab-on-frame vehicle. Otherwise, airplanes would be cabin-on-frame.

 

[Mr.Dee]

Another thing to keep in mind, as I often see the argument that, "the switch to using castings means the exo is not strong enough" which is incorrect. From an engineering perspective, I can tell you that the casting was planned from day one.

The motors and suspension and all other vehicle systems in that area need to attach to a repeatable structure, ie: a casting. The casting transfers 100% of the loads into the exo in a predictable manner. Without the casting, you would need many brackets and supports and braces, likely requiring dozens of fasteners, various metals, and sealants. This all equals time and cost that is no longer needed with the casting.

Also, one thing that people don't realize about the manufacturing world, nothing is perfect. It would be product suicide to try and bolt the motors and systems to the steel exo. There will never be 2 Cybertruck bodies that are identical. Which means every single part of every truck would have to be custom drilled, even if off by only 0.010". Every bracket, brace, motor, everything. This adds significant time and cost.
Instead, the most likely scenario is that the casting will mount to the exo in as few as 4 locations that will be match-drilled on assembly. Everything else then attaches to the casting, which is essentially identical from part to part and requires no alterations or repairs.

 

[Revoltlution]

... leverage

-Crissa

This is the key ?️