Here we take a detour away from politics to look at a high profile product from Tesla.
Self-inflicted wound #2: The frame of the Cybertruck and over-hyped performance
The appearance of the Cybertruck is polarizing. Most either hate it or love it. The number of “meh” responses is low. I already pointed out that you’re only supposed to look at it from the side. Straight-on at the front or back and you could be looking at a 2D drawing on a wall, which I then created in Microsoft Paint.
There are other problems with it that will be covered separately. This is going to look at an issue of durability with the frame of the Cybertruck and how Musk’s own words boasting about it would come back to bite him later on as a self-inflicted wound.
At the presentation of the Cybertruck, Musk asked, “You want a truck that’s tough? You want a truck that’s really tough, not fake tough?” Infamously, the supposedly unbreakable “armor glass” for the windows wasn’t. Four years later, Musk says let’s try it again. He has Franz (same guy as last time) throw another ball and the window doesn’t break. Except, the ball this time isn’t metal. It’s a baseball. Musk changed the conditions of the test in more than just an improved window design. It takes other people recording their own videos to show the new windows can stand up to metal impacts, though one uses a marble-sized metal ball. And haven’t people already said that you don’t want unbreakable windows on a car or truck so that emergency personnel can get you out of them after a crash?
Regardless, the frame has its own set of problems that are due to it being made from cast aluminum instead of steel. Videos started being posted showing it having catastrophic failures while towing and under other situations like pulling out another truck that was stuck. Two newer videos help pinpoint the problems.
The first video is “Should you tow with a Cybertruck?! - (catastrophic failure test)”, hosted by Zack. Here’s info on the frame:
- Tesla uses the Giga Press, an aluminum injection molding machine that can make a Cybertruck frame in minutes. It’s an aluminum frame instead of steel.
- Casted aluminum is more porous than than extruded aluminum or steel.
- The Cybertruck is rated for 11,000 pounds of towing capacity and a maximum of 1100 pounds on the tongue of the hitch. (May have been said in the video as “1500” pounds by mistake.)
The test was set up so a Caterpillar excavator would apply downward force on the hitch to see when it would break. The attached crane scale shows 6000 pounds is when something could be heard to start happening and a twist was visible. First crack was heard at 6700, the alarm system went off at 7000, truck is creaking at 8000, and at 9000, there is obvious movement of the parts. Failure occurred at 10,400 pounds.
Sounds good so far. The hitch took 10 times the downward force it was rated for.
But when Zack and the rest of the team looked at the failure, that’s when they found out about adhesive being used to attach the steel hitch to the aluminum frame. That makes sense because it’s very difficult to weld aluminum to other metals and requires specialized processes.
The glue lasted to the 10,400 pounds of force point, but all of the force was being transmitted to the frame through that adhesive. That means the aluminum frame started having problems at 6000 pounds.
Still, that’s over five times what it’s rated for. As long as the trailer carries 90% of the weight, it should be good. But there are times when more weight will transfer onto the hitch, like when cresting a hill or going up a steep driveway, pulling another vehicle out of a mud pit while off-roading, or if the trailer comes off the ball of the hitch and the trailer jerks down on the safety chains. Pot holes could also cause weight to go onto the ball.
The team also wasn’t impressed with seeing the frame was only 3/16" at the point of breakage.
As a control, they repeated the test with a 2004 Dodge 2500 that has a steel frame. It had been in an accident so the hitch area was slightly bent already. At 5000 pounds, something moved on the truck, but by the time the Cat was applying 10,500 pounds, they had to switch to bouncing the load to try and simulate a higher weight.
Even with all that, the frame of the Dodge never reached a failure point and the hitch area stopped moving after a while. This was addressed in the second video.
Jason Fenske at Engineering Explained decided to look at the hitch issue in a more real-world and logical manner in his “Does The Tesla Cybertruck Have A Problem? Broken Tow Hitch!” video. He has five questions:
- What do regulations require? (for the 11,000 pound tow rating)
- Could a real world scenario load the hitch to 11,000 pound? (Vertical load, heavy braking or pothole.)
- What are the industry standards for other OEMs?
- Are there any fatigue life concerns? (Specifically from the hitch being attached to an aluminum frame.)
- Should customers worry about towing at rated capacity?
I’ll try to condense this even more. The hitch has to be designed to take 47% of the weight of the trailer as a vertical load on the hitch, plus 480 pounds, for at least five seconds. Cybertruck is rated for 11,000 pounds towing, so it has to meet 5650 pounds. It does, at 184% when the failure point occurred.
The coupler on the trailer that docks with the ball is mounted on the hitch has to be able to take 1.3 times the tow rating, which is 14,300 pounds of vertical load in this case. That would 138% of the observed failure point.
To address his second question, Jason asked, “Can you do everything right and still fall into a situation where you’d exceed that vertical load?” This is not deliberately over-stressing the truck by a load with more than 10% on the hitch, jumping the truck while towing, and/or excessive speed.
The answer is yes. When you brake, weight on the trailer gets shifted into force on the hitch, even more so during a panic stop. Same goes with going down a hill. Hitting a pothole becomes a force multiplier and you can end up with 100% of the towed weight being put on the ball of the hitch.
In comparison, engineers at Ram Trucks (formerly Dodge Ram before it was spun off) use a steel frame and test for 15% of the weight on the hitch over 120,000 miles of real-world tow testing, using rough roads with bumps, potholes, inclines/declines and starts/stops for the truck. They use steel because it’s 3x stiffer and 5x tougher than aluminum, and resists bending and deformation better under load.
Steel also has an Endurance Limit where it stops bending and would break, so as long as you design it to withstand stress below that point, it will never break. Aluminum doesn’t have an Endurance Limit. As times goes on, the point where the amount of stress needed to fracture it gets lower and lower.
What this means is the core of the Cybertruck, its frame, has a weakness if it’s actually used for what it’s advertised and promoted as being capable of. If you tow anything with it, even if you keep it well below the limits, the stresses and forces that come with towing are being passed through the steel hitch into the aluminum frame the hitch is glued to. Use the Cybertruck for towing on a regular basis or even a somewhat frequent basis and you’re weakening its frame.
Commercial and military aircraft use aluminum alloy in their airframes. The airframes have published lifespans, such as 30,000 cycles and 70,000 flight hours. “Cycles” refers to how many times the aircraft is pressurized and depressurized for takeoff and landing.
While towing, the hitch experiences multiple cycles per minute as the trailer bounces and is jostled by the road you’re driving on. Take it on a washboard dirt or gravel road and it’s worse. Jason says this at the end of his video: ""If I could ask Tesla just one question, it would be ‘How many miles towing at rated capacity is the Cybertruck’s rear aluminum casting designed to handle?’
The decision to use aluminum may have come with the advantages of speed in manufacturing a lighter-weight frame in the than steel could provide, which would then decrease the costs of operating the truck (longer range per battery charge).
But the bad publicity that’s come from the failures of the frame and what appears to be the reduced lifespan of such a core part of its construction is a self-inflicted wound that may appear in the not too distant future. Is it feasible to take an otherwise working Cybertruck and move the components to a new frame like you can with a steel frame-based vehicle? Or will this end up being essentially a disposable vehicle if you tow with it?
There are more self-inflicted wounds surrounding the Cybertruck and other Tesla vehicles, and it’s not the only wound inflicted upon them by Musk’s words and deeds.