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Aluminum is not an overall good metal to entirely make standard road vehicles. While it can be used quite successfully for sheeting, and casting flaws have largely been solved, it makes poor under-frames that tend to crack unless greatly oversized and nearly flexless.
The aluminum metal is inherently quite soft and has to be alloyed pretty brittle to harden it enough to provide springiness to retain shape. Much of the weight savings is therefore lost, and expense is up, when used for channel frames. Fortunately Ford is keeping steel in important places, like the frame and box. Open boxes flex quite a bit and I would guess testing revealed too much cracking. Closed cabs are stiffer and can be "tri-pod" float mounted if necessary. Since the cab is visible, I assume it will be aluminum as per
above-linked story?
Aluminum falls in between steel and wood for stiffness per unit weight. As an example, a ten pound 4' x4' wood sheet is quite thick. The same size aluminum is thinner and 4' x 4' steel thinnest of all. The wood sheet is stiffest, slightly denser aluminum next and finally high density steel most flexing. A little realized fact is that strength is about equal per pound for most common building materials, with carbon fiber composite the notable exception.
We used aluminum sided coal hoppers on a railroad that I worked for. The aluminum sheet sides were about a half inch thick compared to 3/8-7/16 inch steel car box sides. Including aluminum side beams, they saved tare weight, but occasionaly broke. I felt the final run-in that broke an aluminum hopper car on my train, and could observe the bulging side after the fact in my mirror. The car was intact enough to continue to the next repair station. Mitigating the failure, the cars were typically overloaded. The under-carriage was still steel.
I think my old 2000 Excursion has an aluminum hood and tail doors, no big dents yet. The tail doors are surprisingly light, not easily latching from momentum only. They don't slam well, but it's not a problem.
The stop-and-go city driving from a lighter F-150 will benefit. One of the reasons hybrids such as the Prius gets such great city mpg is the fact that the dynamic braking regenerates the effort used to initially accelerate. Normally it is totally wasted in brake heat, so sans regeneration, the lighter the vehicle, the better. Most F-150's are used as daily drivers.
I think that Ford may also be trying to take advantage of popular beliefs that since aluminum works well for aircraft, it must also be superior for trucks. Not necessarily so, but I admire their innovation.
A lot of folks still disdain government EPA mandates, but we wouldn't have gotten the great vehicles we eventually have today, were it not for the fact that all manufacturers were forced to play by the same rules. A mixed blessing I guess.
Wes
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Days spent camping are not subtracted from one's total.
- 2019 Leprechaun 311FS Class C
- Linda, Wes and Quincy the Standard Brown Poodle
