Sandy Munro talks about the teardown of the Model 3

[moridin2002]

I don't understand why you guys are hanging on his every word. This is amazing to me.

We're not the ones attacking his character because he said something with facts to back it up.

"IF" its true?

Haven't you guys already concluded that it is true? For goodness sake...they guy said it was true.

The 'if' refers to it being a deliberate design choice in making the chassis structurally independent of the battery pack. The may have not been deliberate, but possibly a result of poor management/communications in during the design process.

 

[voip-ninja]

Common sense says if the battery pack absorbs some of the crash energy it has a higher chance of being damaged. To deny that is silly.

You don't do this in a vacuum. It should be pretty easy to calculate how much force you can apply to the battery from any given direction and make sure it counts towards the vehicle structural integrity without unnecessarily putting the battery at risk.

You say "common sense" and I'd say that you are just pulling things out of thin air to hold up this supposition that Munro is an idiot who doesn't understand Tesla brilliance.

Common sense says that if the battery pack is not a stressed member of the chassis that protection of the battery pack was a design goal.

I'm amazed at the lack of critical thinking that passes as analysis here.

Something is amazing to be sure.

 

[StealthP3D]

Except Siemens actually tested the chassis for Munro and can back up the argument.

What argument can Siemens back up? That the Model 3 chassis in incredibly strong? That it could have been made weaker and still received a 4-5 star crash rating? Remember in Spinal Tap the stereo whose volume didn't stop at "10" but went all the way to "11"?

Maybe some car buyers want a car that goes all the way to 6-star crash rating. Even if the rating organizations don't rate that high. Is the car going to contain your loved ones or not?

 

[voip-ninja]

Name something that you think he said that was wrong. I'll wait......

………


……..

More goal post moving.

Munro was overly harsh in his criticism of Tesla's panel gap problems but, frankly, Tesla needed to hear it. When Munro compared early Model 3 build quality to circa 90's KIA that was a serious jab at Tesla... probably unnecessarily so.

I honestly doubt you've even listened to these interviews. Even in his initial criticism of the car Munro had a lot of positive things to say about it.

 

[mongo]

Munro's comment that "the whole thing is blue, there are no stress point" means that Tesla either intentionally made a wastefully overbuilt design or they got it wrong.

That's not the way FEA outputs work (unless they purposely messed with the scale). It auto scales to the min and max stresses on a linear or log scale. It was not blue somewhere, and I'd guess that somewhere is where the torque happy motors connect. The loading there will be very high and make the rest of the car look overbuilt. If they didn't model the motor loads, then the analysis is really lacking.

 

[voip-ninja]

That's not the way FEA outputs work (unless they purposely messed with the scale). It auto scales to the min and max stresses on a linear or log scale. It was not blue somewhere, and I'd guess that somewhere is where the torque happy motors connect. The loading there will be very high and make the rest of the car look overbuilt. If they didn't model the motor loads, then the analysis is really lacking.

I don't claim to understand anything about the software or analysis that was done, I just know that Munro has used the reference that there are no stress points on the unibody... the only way to find out what he's objecting to is to buy his report or invite him to a conversation about it here or elsewhere.

I do find it hard to believe that Munro has pushed this hard on the body design, involved Siemens in the analysis, conveyed the results of this Analysis in a very expensive report and gotten it completely wrong. If Munro was as wrong as some here think and the Model 3 body was intentionally overbuilt to protect the occupants and battery then it seems that instead of telling Munro he'd fired the engineer Musk would have defended the product.

The reduction of 300 spot welds on a "finished" design that had been in production for many months is the strongest evidence we have to date that Tesla "got it wrong" and overbuilt the unibody.

 

[moridin2002]

What argument can Siemens back up? That the Model 3 chassis in incredibly strong? That it could have been made weaker and still received a 4-5 star crash rating? Remember in Spinal Tap the stereo whose volume didn't stop at "10" but went all the way to "11"?

Maybe some car buyers want a car that goes all the way to 6-star crash rating. Even if the rating organizations don't rate that high. Is the car going to contain your loved ones or not?

They can back up BIW testing for:
- global modal frequencies and mode shapes
- global static stiffness for both torsion and vertical bending
- body attachment point stiffness.

All those were done both with and without the battery.

https://leandesign.com/pdf/Tesla-3-Analysis-Sales-Information.pdf

There is such a thing as making a chassis to stiff for its intended usage. Its possible to direct too much force to an occupant because structures are too stiff to properly absorb energy and decelerate the vehicle (and its occupants) in a controlled manner with the lowest possible peak gs.

 

[TT97]

The man changed his mind.

His first analysis was asinine. They he did a second one and it was better and closer to actual facts than opinion.

I'm waiting for the third that is closer to reality.

Until then....you can call me as many names as you like. LOL.

How did he change his mind? His first video was before he did a teardown. His initial impressions were just based on visual inspection of the car and had a lot of issues with the build quality. He also did not like the frunk operations as well as the handles to open the doors.

From the very beginning he was impressed with the handling and acceleration of the car.

He has never changed his mind on any of that. Since the first videos, he has done a tear down of the vehicle and is very impressed with the electronics, batteries, harnesses, motor, etc. and states Tesla is years beyond every other competitor in those aspects but he still has issues with the build quality of the vehicle.

 

[moridin2002]

That's not the way FEA outputs work (unless they purposely messed with the scale). It auto scales to the min and max stresses on a linear or log scale. It was not blue somewhere, and I'd guess that somewhere is where the torque happy motors connect. The loading there will be very high and make the rest of the car look overbuilt. If they didn't model the motor loads, then the analysis is really lacking.

You can globally change the scale to match other tested BIWs. I would never make design decisions solely based on FEA with an auto scaled output. Only way to properly compare across BIWs from various vehicles is to place them on the same scale and compare.

 

[StealthP3D]

BIW testing for:
- global modal frequencies and mode shapes
- global static stiffness for both torsion and vertical bending
- body attachment point stiffness.

All those were done both with and without the battery.

https://leandesign.com/pdf/Tesla-3-Analysis-Sales-Information.pdf

So, if I spend $31,000 I can learn it's the strongest chassis in its class? I think we already know that.

 

[mongo]

I don't claim to understand anything about the software or analysis that was done, I just know that Munro has used the reference that there are no stress points on the unibody... the only way to find out what he's objecting to is to buy his report or invite him to a conversation about it here or elsewhere.

I do find it hard to believe that Munro has pushed this hard on the body design, involved Siemens in the analysis, conveyed the results of this Analysis in a very expensive report and gotten it completely wrong. If Munro was as wrong as some here think and the Model 3 body was intentionally overbuilt to protect the occupants and battery then it seems that instead of telling Munro he'd fired the engineer Musk would have defended the product.

The reduction of 300 spot welds on a "finished" design that had been in production for many months is the strongest evidence we have to date that Tesla "got it wrong" and overbuilt the unibody.

Sorry for the confusion, I was addressing Munro's comment, not your quoting of the quote
As to the welds, easier to start out with too many and back off, that to have too few then scrap bodies and retool the assembly line.

You can global change the scale to match other tested BIWs. I would never make design decisions solely based on FEA with an auto scaled output. Only way to properly compare across BIWs from various vehicles is to place them on the same scale and compare.

Yar, if you manually mess with scale. It does seems though a mostly glass frame would have different stiffness requirements than a conventional vehicle. Esp in torsional rigidity.

 

[moridin2002]

So, if I spend $31,000 I can learn it's the strongest chassis in its class? I think we already know that.

Nope, you can learn that the battery adds zero stiffness when it should.

And, its $5k.

 

[mongo]

Nope, you can learn that the battery adds zero stiffness when it should.

I'd say could, not should. And really, it can't add zero stiffness (unless it is on gooey isolators), that is shorthand for "it was already too stiff IMHO, and now it's just silly".

 

[ℬête Noire]

He is clearly astonished by what they are doing. Sometimes I wonder if we are missing something -- he is confirming a lot of what folks on TMC have known/speculated on for some time. The competition is screeeewed.

Sure lots of people are missing that. I thought it was pretty obvious from the very first Munro-Tesla video, even as Munro was lighting his hair on fire over some things he was already impressed about a few others. Yet over and over I've run into people that know about Munro doing the teardown and his findings. But they sound like they heard about it filtered through clueless fools like Welch here. Over and over in this video Welch tries floating a heavily distorted version, a Tesla is Doomed version, of what Munro is saying and when Munro pushes back on that Welch will say something like "well that's what the market has question about" or try flip to something else (usually re-imagined too).

P.S. At least a couple of times Welch talks about the Model X being a failure and nobody buying it like the Model S. Yet the right-hand host (balding, glasses) explicitly mentioned that the Model X had slightly higher sales than the Model S in 2018. Welch is clearly running on a script from a FUD script some in the past. Maliciously or just is having a hard time coming to grips with being so damn wrong? ¯\_(ツ)_/¯

 

[StealthP3D]

Nope, you can learn that the battery adds zero stiffness when it should.

Do you know why the fuel tanks in ICE vehicles are not stressed members of the chassis? Yep, because they don't want the tank to be breached in an accident. Tesla's early cars used the battery as a stressed member and they got roasted for a few battery fires. Now they fix the problem and they get roasted for wasting money.

It would be comical if it weren't so callous to the survivors of battery fires.

Gas tanks are protected by supporting them with flexible straps. Even if the frame structure is deformed the strapping holding the tank will not crush the tank. Why would you suggest the battery of a Model 3 doesn't deserve equal protection? This was obviously a conscious decision by Tesla, not an exercise in ignorance. I wonder how many EV's Munro has designed and manufactured? I would buy a Tesla over a "Munro". Especially if he used the highly flammable battery pack to absorb crash energy. Nobody wants to be in an accident but, if they are, they don't want the battery to burst into flames.

 

[voip-ninja]

Do you know why the fuel tanks in ICE vehicles are not stressed members of the chassis? Yep, because they don't want the tank to be breached in an accident. Tesla's early cars used the battery as a stressed member and they got roasted for a few battery fires. Now they fix the problem and they get roasted for wasting money.

It would be comical if it weren't so callous to the survivors of battery fires.

Gas tanks are protected by supporting them with flexible straps. Even if the frame structure is deformed the strapping holding the tank will not crush the tank. Why would you suggest the battery of a Model 3 doesn't deserve equal protection? This was obviously a conscious decision by Tesla, not an exercise in ignorance. I wonder how many EV's Munro has designed and manufactured? I would buy a Tesla over a "Munro". Especially if he used the highly flammable battery pack to absorb crash energy. Nobody wants to be in an accident but, if they are, they don't want the battery to burst into flames.

Does the BMW i3 use the battery as a stressed member of the body? Your answer will be timed.

This paper is pretty good. It talks about mitigation strategies for battery damage when they are crashed. It does not indicate that the battery should be excluded as a stress bearing member in designing the vehicle chassis.

http://www.prba.org/wp-content/uploads/Elham-MIT-Presentation-17.pdf

 

[ℬête Noire]

How did he change his mind? His first video was before he did a teardown. His initial impressions were just based on visual inspection of the car and had a lot of issues with the build quality. He also did not like the frunk operations as well as the handles to open the doors.

From the very beginning he was impressed with the handling and acceleration of the car.

He has never changed his mind on any of that. Since the first videos, he has done a tear down of the vehicle and is very impressed with the electronics, batteries, harnesses, motor, etc. and states Tesla is years beyond every other competitor in those aspects but he still has issues with the build quality of the vehicle.

On particular items, most, however he has explicitly changed his overall opinion of the car over that time. His own turn of phrase for it is "eat crow". He has even come to the realization that things like the "gap fit" don't actually matter as much for the product as they do for his own personal ideals.

What he hasn't quite grasped yet is why the things he doesn't like look the way they do. He's so close, it's right there mixed into his words but I don't think he's quite grokked it yet.

 

[ℬête Noire]

This paper is pretty good. It talks about mitigation strategies for battery damage when they are crashed. It does not indicate that the battery should be excluded as a stress bearing member in designing the vehicle chassis.

http://www.prba.org/wp-content/uploads/Elham-MIT-Presentation-17.pdf

*facepalm*

It doesn't say it explicitly, one way or the other. However it very clearly concerns itself almost exclusively with the cells themselves, I'd hazard a guess that's Esfahani's area of expertise? It's got a single throwaway bullet point about "Design of BIW, pack housing and connections" and then heads off to minutiae about the cells.

 

[SageBrush]

I trust Munro's judgement and experience when it comes to manufacturing ICE vehicles

 

[voip-ninja]

*facepalm*

It doesn't say it explicitly, one way or the other. However it very clearly concerns itself almost exclusively with the cells themselves, I'd hazard a guess that's Esfahani's area of expertise? It's got a single throwaway bullet point about "Design of BIW, pack housing and connections" and then head off to minutiae about the cells.

It is definitely primarily around cell design and what kind of tests were done on the cells to try to rupture them including squeezing them, object intrusion, etc.

I found it very interesting that most of their concern was about puncture resistance of the pack as that is the highest risk of failure compared to say being squished or compressed in an accident.

I think if the battery pack being physically distorted in an accident where it was over-relied on as a load bearing member was an issue they would have mentioned it, but would have to ask them or read more of their work.