New WhistlinDiesel: Cybertruck vs. F-150 Frame & Hitch Video

[cyberos]

Have a look at this video, you will have a much better idea where the frame snapped. You can clearly see the hitch mounting hole at the 18 minutes mark. The frame rail section's procedure is still in development (and parts can't be order yet) but if it ever becomes available, it will be a much simplier fix then replacing the complete rear under body, which can be done too.



*Parts catalogue item #6 and frame rail procedure

How many innovations has Tesla achieved in the Cybertruck? It's more like a space program than a new vehicle program

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[TickTock]

So basically to sum it up, aluminum of the CT cracks and breaks while steel in the F150 will bend. Aluminum is light and strong, but breaks. Steel is strong and bends, but is heavy.

Each has a tradeoff. But I think that the part that snapped off should have some steel reinforcement that would prevent such a catastrophic failure. Should be simple enough, no? Especially if towing something 11 thousand pounds. Don't want a trailer that heavy breaking away and flying down the road.

Exactly. There is no issue if you abuse your truck and break it. Happens all the time. The whole issue is you may have broken the truck without realizing it (cracked it) and you then have a catastrophe waiting to happen next time you tow something. Doesn't have to be anything radical, even a couple short chains or steel bars from the receiver to the other side of the stress point would do. Just need to ensure the trailer stays with the vehicle so it can be guided off the road.

 

[Airbus350]

As strong as the stainless steel doors are taking that C4 explosion like a champ, why not make the frame out of Stainless steel? Too heavy? Too expensive ? I don’t know, I’m not an engineer, just curious!!

 

[CosmicOwl]

So basically to sum it up, aluminum of the CT cracks and breaks while steel in the F150 will bend. Aluminum is light and strong, but breaks. Steel is strong and bends, but is heavy.

Each has a tradeoff. But I think that the part that snapped off should have some steel reinforcement that would prevent such a catastrophic failure. Should be simple enough, no? Especially if towing something 11 thousand pounds. Don't want a trailer that heavy breaking away and flying down the road.

Steel isn't necessarily heavy, in fact many steels have a higher strength to weight ratio than most aluminums. However if you want it to be stiff the steel structure is probably going to be thinner and possibly more prone to local damage.

To me, the sheared off section of the CT looks really thin. I don't know if this is a limit imposed by the giga-casting process but I would have made that a lot thicker. If the bolt holes are 1/2", it looks like the webbing is around 1/8" thick and only maybe 1.5" deep where it cracked. Tesla needs to update the FEA load cases for what the real world will produce.

to Mongo:
Tesla does have a really good materials team and so it is possible they have improved on the properties of typical cast aluminum but I think it is quite unlikely they have reached wrought or forged properties and even wrought aluminum has about 1/3 the ductility of steel. I have a 10,000 lb rated wrought aluminum trailer hitch on my Colorado but it's solid aluminum... it still weights less than a steel hitch and won't rust. I wouldn't use a cast aluminum piece there.

on tractor pulls, etc.
In this case, the vehicle is providing the tension force so loading cannot exceed what can be produced with the tires given the additional weight on the truck unless you have a chain or some other element that allows you to get a big dynamic load (not what happens at tractor pulls or towing any real trailer). Maybe on dry pavement with max tongue load you can get a force around 1.0 * (vehicle weight + tongue weight) but that's 10,000 lbs. or so. To give an approximate size, for A356-T6 (cast aluminum), yield strength of 26 ksi and using 75% of that to give reasonable cycle life, you need about 0.5 in^2 of material to resist this load. In turn, if the web thickness is 0.125", this would require a width of about 4". Where the casting broke, it looks to me like it might be 6x this total area but it's in bending the way WD loaded it and there is a local section reduction (some kind of pass through hole?) so no surprise it broke. I would imagine you would be able to break it with a pretty stout chain hooked to something heavy as well.

I will say during just modest off-roading in rocks I have hit my hitch receiver pretty hard a bunch of times, seems like a reasonable use case especially for long overall length pickups although not from the WD height.

 

[CosmicOwl]

As strong as the stainless steel doors are taking that C4 explosion like a champ, why not make the frame out of Stainless steel? Too heavy? Too expensive ? I don’t know, I’m not an engineer, just curious!!

Surely more expensive but at what volume (those giga presses cost a lot I am sure)? It would be so much more durable if they just did a stainless unibody and it might not be that much heavier. Why not actually make the frame the body and just robot polish it?

Stampings, robot welding and robot polishing vs. super expensive giant press with super cheap material.

 

[Hunter71294]

Exactly. There is no issue if you abuse your truck and break it. Happens all the time. The whole issue is you may have broken the truck without realizing it (cracked it) and you then have a catastrophe waiting to happen next time you tow something. Doesn't have to be anything radical, even a couple short chains or steel bars from the receiver to the other side of the stress point would do. Just need to ensure the trailer stays with the vehicle so it can be guided off the road.

Agreed. While this probably won't happen, it should never happen. I don't think it would be too hard to fix but losing a trailer going 70mph is extremely dangerous. Seems like castings should probably be thicker and some sort of backup safety feature. Any cast metal is known to break and not bend. Not the best attribute for a frame.

 

[Darth abbott]

Not going to lie I was in the camp of "the concrete broke the hitch, this would never happen in real life". But after watching his followup video and seeing the F150 frame take that abuse... Maybe they should make the CT casting thicker. Easier said than done. Im still getting my CT

I thought the same thing too, but definitely there is a problem. He posted a real today of another one

 

[mongo]

To me, the sheared off section of the CT looks really thin. I don't know if this is a limit imposed by the giga-casting process but I would have made that a lot thicker. If the bolt holes are 1/2", it looks like the webbing is around 1/8" thick and only maybe 1.5" deep where it cracked. Tesla needs to update the FEA load cases for what the real world will produce.

What is your thought of what real world load is for a 11k lb trailer with 1,100 lb tongue weight? How many vertical (in each direction) G's can a sprung trailer and vehicle produce?

to Mongo:
Tesla does have a really good materials team and so it is possible they have improved on the properties of typical cast aluminum but I think it is quite unlikely they have reached wrought or forged properties and even wrought aluminum has about 1/3 the ductility of steel. I have a 10,000 lb rated wrought aluminum trailer hitch on my Colorado but it's solid aluminum... it still weights less than a steel hitch and won't rust. I wouldn't use a cast aluminum piece there.

Regardless of material, it should not be reaching the point where loads result in plastic deformation (when ductility matters).

I will say during just modest off-roading in rocks I have hit my hitch receiver pretty hard a bunch of times, seems like a reasonable use case especially for long overall length pickups although not from the WD height.

There is scraping while risk crawling, and then there is driving off a ledge fast enough to catch air before landing on your frame instead of tires due to having your suspension in low/ entry and catching a rock ledge on the way down.

 

[jimbobb23]

Hard to know anything based on these videos. He hit a click homer on the first so wants a second click homer. No way to know what he is doing outside the video. Is it a concern? No idea. But nothing in these videos can answer that question.

 

[greggertruck]

Did you watch this latest video? It definitely seems the casting is weak…. Especially if there was another truck that had one shear off while towing.

There's another truck with its casting damaged.... that's for sure.

As I showcased in my video, dude is entertainment. That being said. Not one of us has seen any details, nor heard anything else regarding this supposedly same issue truck.

That's highly suspicious.

 

[CosmicOwl]

What is your thought of what real world load is for a 11k lb trailer with 1,100 lb tongue weight? How many vertical (in each direction) G's can a sprung trailer and vehicle produce?


Regardless of material, it should not be reaching the point where loads result in plastic deformation (when ductility matters).


There is scraping while risk crawling, and then there is driving off a ledge fast enough to catch air before landing on your frame instead of tires due to having your suspension in low/ entry and catching a rock ledge on the way down.

I'm not sure. This is definitely some of the secret sauce that car companies build up over time to set their load cases. Laying aside things that abusive (pulling hard from a slack case with stiff chain) Just thinking of going over a big bump/pothole with a trailer maybe 2x? Or someone pressing hard on the accel pedal and taking up the small amount of slack in the trailer ball/neck combination maybe 2x? The tongue weight comes from the small lever of the load against the wheel contact point so that should just be a function of vertical bump Gs. Hard to see more than 5x there, so that's pretty small like 5,500 lbs. So vector load maybe 22,700 lbs and my napkin estimate (from squinting at a screenshot of a video) is around 66,000 to fail in fatigue. Seems in the ballpark but not as robust as would be ideal given the abuse that trucks receive.

I agree, ductility should not be used normal although in the case of parts with flaws (ie all castings), ductility is a really good quick metric for strength and life. It's really easy to go from 5% ductility with best case flaws to broken at half load with -2 sigma flaws. Also, when you are going well beyond the design case, ductility is the difference between bending 1/2" (say an overloaded a-arm or frame) and total failure.

I definitely wasn't scrapping my frame, I was dropping off rock ledges onto the bumper / receiver. Not sure the exact height but must be 12+" drop to take up the ground clearance.

 

[CosmicOwl]

I'm not sure. This is definitely some of the secret sauce that car companies build up over time to set their load cases. Laying aside things that abusive (pulling hard from a slack case with stiff chain) Just thinking of going over a big bump/pothole with a trailer maybe 2x? Or someone pressing hard on the accel pedal and taking up the small amount of slack in the trailer ball/neck combination maybe 2x? The tongue weight comes from the small lever of the load against the wheel contact point so that should just be a function of vertical bump Gs. Hard to see more than 5x there, so that's pretty small like 5,500 lbs. So vector load maybe 22,700 lbs and my napkin estimate (from squinting at a screenshot of a video) is around 66,000 to fail in fatigue. Seems in the ballpark but not as robust as would be ideal given the abuse that trucks receive.

I agree, ductility should not be used normal although in the case of parts with flaws (ie all castings), ductility is a really good quick metric for strength and life. It's really easy to go from 5% ductility with best case flaws to broken at half load with -2 sigma flaws. Also, when you are going well beyond the design case, ductility is the difference between bending 1/2" (say an overloaded a-arm or frame) and total failure.

I definitely wasn't scrapping my frame, I was dropping off rock ledges onto the bumper / receiver. Not sure the exact height but must be 12+" drop to take up the ground clearance.

Also, it would be easy for someone with access to get a coupon cut out of a totaled CT frame and get a tensile test done to find out how ductile the material really is. Less than $500 of total expense probably if you have the material. I imagine Munroe and others have already done this.

 

[CyberCatnip]

Not going to lie I was in the camp of "the concrete broke the hitch, this would never happen in real life". But after watching his followup video and seeing the F150 frame take that abuse... Maybe they should make the CT casting thicker. Easier said than done. Im still getting my CT

Yes, been driving my CT for 5 months now. The 2023 Chevy3500 I bought last year just sits in the driveway now (7mpg towing). Love my CT almost 13,000 miles already. Tows my tractor, boat and 4xjetski trailers no problem locally.

Now, I am for sure if I tried hard enough I guarantee I could break some shit on the Silverado ?

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