Cybertruck Stainless Panels are falling off ...Is this a new phenomena?

[PLC]

I don't think we've established that the carrier has a highly different coefficient of expansion. Steel vs stainless maxes out at around 6 ppm per degree C. If the piece is 2 m long and was assembled at 25C, then assuming uniform shrink at -40C we get 65*6*1*10e-6=390x10e-6m = 0.39 mm differential or 1.5x the minimum bond thickness. Note the shear strength increases at colder temps.

Differential could be worse if they heat cure at 200F (93C).

But the shear strenght of the glue is not the bottle-neck in this case. It is the deformation. The 2m piece will be about 0.2mm shorter on each side. No problem, if the thickness of the glue is for example 1mm. The glue would have to absorb 11° of dislocation. If the thickness is 0.25mm, the dislocation is 38°. I am not confident, that this glue can handle such a dislocation at those temperatures.

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[mongo]

OMG, it's a pandemic! Somebody call NHTSA

or Fauci

Our Explorer has two NHTSA recalls for the roof rail trim and A pillar trim detaching.

 

[mongo]

But the shear strenght of the glue is not the bottle-neck in this case. It is the deformation. The 2m piece will be about 0.2mm shorter on each side. No problem, if the thickness of the glue is for example 1mm. The glue would have to absorb 11° of dislocation. If the thickness is 0.25mm, the dislocation is 38°. I am not confident, that this glue can handle such a dislocation at those temperatures.

Restrained 2m steel object with delta coefficient of expansion of 6ppm, temperature swing of 65K, Young's modulus of 200, and crossection of 100mm² (1.2mm*80mm) (.0001m²) is 7800N or 1754 pounds. So a square inch of adhesive at either end would restrain it in shear. If it bulges, all bets are off (especially since I'm not a mechanical engineer).
https://www.engineeringtoolbox.com/stress-restricting-thermal-expansion-d_1756.html

 

[Mini2nut]

The adhesive seems to holding where it's applied to the steel BIW, but failing on the SS cantrail part.

It could be as simple as cantrail manufacturing oils were not removed properly from the SS before adhesive was applied.

Once a certain number of complaints get filed with NHTSA a recall kicks in.

 

[PLC]

Restrained 2m steel object with delta coefficient of expansion of 6ppm, temperature swing of 65K, Young's modulus of 200, and crossection of 100mm² (1.2mm*80mm) (.0001m²) is 7800N or 1754 pounds. So a square inch of adhesive at either end would restrain it in shear. If it bulges, all bets are off (especially since I'm not a mechanical engineer).
https://www.engineeringtoolbox.com/stress-restricting-thermal-expansion-d_1756.html

Yeah, I came to the same conclusion in the meantime, thinking about it. The adhesive just will transmit the 8000N of tension with ease between the parts, if the processing has proceeded properly. Nevertheless, a thicker layer of adhesive could significantly reduce the stress out of different expansion. But of course I admit my mistake.

 

[mongo]

Yeah, I came to the same conclusion in the meantime, thinking about it. The adhesive just will transmit the 8000N of tension with ease between the parts, if the processing has proceeded properly. Nevertheless, a thicker layer of adhesive could significantly reduce the stress out of different expansion. But of course I admit my mistake.

We're all learning here, I'd never done that calculation before. Data sheet shows lower shear strength with thicker application, but doesn't give a stress/strain plot.
Given the entire length is glued, seems strong enough with localized constraint.

 

[PLC]

We're all learning here, I'd never done that calculation before. Data sheet shows lower shear strength with thicker application, but doesn't give a stress/strain plot.
Given the entire length is glued, seems strong enough with localized constraint.

My experience with adhesives comes out of the construction industry (facades out of steel, aluminum, HPL and so on) where the cross sections of the involved materials are most of the time way bigger than the adhesive surfaces. The expansion difference is therefore unavoidable as the youngs modulus will always get its will . Thats why I learnd to design those bondings as "soft" as possible and have done well with it so far.
But in that case it should definitely be possible to show the youngs modulus its limit. I hope the reputation of the CT wont suffer too much because of this.

 

[Mini2nut]

Complaints to the National Highway Traffic Safety Administration will start a recall if enough owners complain of a safety hazard.

Here is the link to document your loose cantrail safety concerns. Just click on the “report a safety problem” box on top of the page.

https://www.nhtsa.gov/recalls

 

[ewkplymi]

Noticed a noise coming from the rear left side of my CT today. Checked for source and found the very rear of the roof rail trim on the left-hand side detached. Submitted a service request to the SC.

 

[Black306]

Noticed a noise coming from the rear left side of my CT today. Checked for source and found the very rear of the roof rail trim on the left-hand side detached. Submitted a service request to the SC.

Check to see if it wasn't pressed down properly. Might save you time from having to go to a Service location.

https://service.tesla.com/docs/Cybe...UID-36C8B01A-2C43-4272-A3C7-1811ACD4BB72.html

 

[Langestreet]

My concern, while waiting to see if this is a widespread issue (or not), is that I want to attach a Ham Radio Antenna using a Trunk Lip mount (like a Diamond K9000TM)., on these pieces. Due to air resistance on the antenna, there would be increased loads on that glue joint. Part of me says the loads S.B. pretty insignificant overall; but another part of me says that having it mounted would cloud the issue if mine came off. This kind of derails my antenna project for now...

I'm putting my antenna on a crossbar as soon. As I can figure out a good path for the feed.

 

[BannedByTMC]

Speed tape

Is speed tape a double sided adhesive? Or are you suggesting using it on top as a temporary fix?

 

[techfoamer]

My concern, while waiting to see if this is a widespread issue (or not), is that I want to attach a Ham Radio Antenna using a Trunk Lip mount (like a Diamond K9000TM)., on these pieces. Due to air resistance on the antenna, there would be increased loads on that glue joint. Part of me says the loads S.B. pretty insignificant overall; but another part of me says that having it mounted would cloud the issue if mine came off. This kind of derails my antenna project for now...

I bought the crossbars from Tesla for mounting antennas. Haven't had a chance to put any ham antennas on them, but did test an in-motion OneWeb terminal recently. Glad I had the crossbars for this.

 

[CTInProcess]

Help is on the way with these little issues. Once Elon has gone and corrected these agencies a recall will be immediately sent to correct these issues.

 

[BannedByTMC]

Good bot ?

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