A Question on Pick-up Trucks

Well, C&D drives them pretty hard, so you’d probably get better mpgs with one of the new ones. But they drive them equally hard, so there’s not much apparent real difference, seems to me.

Aluminium does not rust because rust is iron oxide but it does corrode and form aluminum oxide. Around here steel wheels hold up better than aluminum, Sometime between 5-7 years aluminum wheels start losing air due to salt eating away at the bead area.I don’t know why this doesn’t become a problem with the steel wheels but it doesn’t. The wheels get rusty but don’t leak.

“aluminum does have problems with repeated stress causing failure (remember the Hawaiian Airlines 737…?”

Yes, and as an interesting(?) aside, this is an issue for those people who are really, really into bicycling. 7000-series Al is used to make light, strong frames…but it is admittedly more fatigue-prone than steel. So there’s a whole “steel is real” ethos about steel frames vs “throwaway” Al. (Of course, fatigue failure is a very infrequent cause wrecks on any bicycle. More likely, the fact that Al lends itself to mass-production, and lugged-frame steel is an “artisan” design (these days) leads to a smear campaign to justify the higher cost/value…but that’s just my opinion.)

For cars, the whole Carbon Fiber Bandwagon makes me uneasy, for similar reasons. High strength/weight, sure, but fatigue failure issues, no “plastic deformation” dissipating energy in crashes, and the whole “the warmer it is out, the weaker the structure is…hope you like the color white!” are concerns that will need to be addressed.

As for the strength of body parts, I recall removing the front bumper fascia on late model cars to access mechanical repairs and it’s amazing how little structure there is. Many cars have styrafoam molded to fit the fascia and is attached to a front sub frame extension which never seemed to look very substantial. Even a strip of 1/2 plywood accross the front between the foam and fascia and another reiforcing the sub frame would seem to greatly improve the crash worthiness of the vehicle. I guess some highly trained engineers with million dollar computers have it figured out though. I see small sedans totalled out and everyone walks away.

Both aluminum and steel (iron, actually) are highly reactive metals. They will oxidize quickly. Aluminum does form an oxide coating quickly, but it is very thin; much less than a micrometer in thickness (about 200 Angstroms). That is not much protection for anything outside. Unpainted aluminum is usually has an anoxic coating on it. Anodizing provides a thick aluminum oxide, but it is a manufactured coating. Take a look at aluminum rims that have been scraped. There is an unsightly oxide bloom in addition to the scratches where the anoxic coating was scraped off.

I think the glaring difference between aluminum use in cars and aircraft is that no car owner will ever stand still for the costs if their ride was subjected to the type and frequency of maintenance required by aircraft.

At the base near me some of the instructor pilots grab some extra solo stick time on the weekends so to speak.
On Monday morning the maintenance guys are cursing the popped rivets… :wink:

Imagine if those cars were also used in the same mission capable rate as the planes. It’s doubtful many people would be thrilled to have their cars in the hangar for 40% of the time.

Other than weight and while aluminum is more costly than steel, machine tooling (which is $$$$$) used to manufacture the parts also has a longer life so the end result could be lower cost as compared to machining and stamping steel. That’s just an opinion on my part.

wish those composite beds would have worked out.

Yeah…heck with putting a plastic bedliner on top of your bed…make the dang bed OUT of plastic in the first place!

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To be completely accurate, the DeHavilland Comets did suffer from stress cracking, and a few did crash because of it. What they discovered was that the shape of the orginal windows is what was causing the problems. WIth repeated cycles (one takeoff, and one landing makes one cycle) the cracks formed from the square corners of the windows, which is why you will always see round corners on aircraft windows. They changed the square windows to oval ones, problem solved. But since the public never really trusted the aircraft, the type died an early death. A shame, because by all accounts, once that problem was solved, it was a superb airliner.

Texases writes …

Recently Car and Driver did a comparison test, and the Ford and Chevy pickups tied in performance, the Ford was all of 80 pounds lighter, and they both managed 16 mpg overall. So the aluminum + Ecoboost on the Ford had about zero impact

That’s interesting. It’s sort of a parallel development that what was learned in mt bicycles. They switched from steel to aluminum to save weight, but then the riders complained of the stiff ride, so they had to add suspension, which brought the weight back up to what it was with steel …lol .

I was in the bike store a couple weeks ago, and the better-quality aluminum mt bikes, some are full suspension front and back, some are suspension on the front fork only (hard-tails), the better quality mt bikes they have for sale there weigh between 28 to 32 pounds. You have to pay quite a bit more to get the 28 pound bike vs the 32 pounder. My 25+ year old cro-moly steel mt bike weighs 27 1/2 pounds.

So maybe aluminum for trucks isn’t the panacea it is thought to be.

Better make sure,they were actually comparable models,a note on these so called tests,my take is,most of the testers seem to be throttle jockeys and most of the time,they like to rate the worthiness of a vehicle,by the G-force generated on takeoff,most careful or at least average drivers can usually hit the EPA numbers.

A number of years ago I did a shock project on a Ford Expedition, their big SUV. Got weights on it and compared it to GM’s Tahoe, a similar sized vehicle. The Ford was about 600 lbs heavier but equipped virtually the same in all respects. I asked a Ford engineer friend of mine why this thing was so much heavier than the Tahoe. His reply; “We don’t know, If you figure it out, let us know”

You can always step back and point to the big stuff, like the engine or the body and decide to make that out of lightweight aluminum but if you don’t take care of the details, you are doomed when it comes to weight reduction. The Mazda MX-5 guys designed their new model with a theme, “gram light” - take care of the grams and the kilogram reductions will come. So the new car is as light as the original, some 25+ years ago.

So what I’m hearing here is that Ford had a weight problem, 600 pounds heavier than the competition. They would need a complete redesign to lose that weight, and instead chose to us an Al body to lose that weight and become competitive.

I worked with a fellow who owned a 1936 Avon, British car. It had an all aluminum body. He used to carry a small magnet to show that off. It looked pretty much like the MG-TC etcetera.

keith F-14s are made by Grumman Iron Works. I did 6 years in Grumman OV-1 Mohawks. When we did airshow displays people would ask why the landing gear struts were so big? The answer. Everything Grumman makes is stressed for carrier operations. Aircraft aluminum and magnesium is vulnerable to salt water corrosion and requires diligent maintenance and inspection.

texases Thank you. I thought galvanic reaction was the correct term but was not sure. I have seen some ugly corrosion with bare aluminum and ferrous metals being in contact.

Mustangman Mazda used the “gram light” concept when designing the Generation 2 RX-7 in 1985. It was a contest where all employees were encouraged to send their gram saving ideas to the engineers. It worked.

irlandes Both of my MGAs were composite. Steel body and fenders with aluminum hood, doors, and trunk lid. The 1960 roadster was an Oregon car and the 1962 coupe was purchased when I lived in California so neither one had any rust or corrosion. The roadster did have a bit of minor dry rot in the floorboards which were actual boards.

Guys . . .

We have Tahoes AND Expeditions in our fleet

I can tell you that the Expedition is quite a bit bigger than the Tahoe

I’m talking physical dimensions

So I think a 600 pound difference is about right

An Expedition is bigger than a Tahoe, but smaller than a Suburban

If you want gargantuan, look at the Excursion. However, I don’t it’s being built anymore

I saw an “Expedition XL” recently. Can I assume it’s just a stretched Expedition? To me, it looked that way. While the Excursion was more akin to the F250 Superduty, at least as far as mechanicals goes

Well if you get underneath a Silverado,you can see some of the weight saving things GM did,some of it made a quite a bit of sense,GM has been aware for a long time that dead weight is not cost effective,now when you get to the big guys,there are some things that look over engineered,I was amazed when chevy did their redesign around 2000,how thin the metal looked on the frames(think import guage) the driveshafts are very light weight too along with the aluminum block engines,ad nauseum.

Chevrolet used higher strength alloys and that allowed them to shrink the size and weight without sacrificing strength. Of course this makes the truck cost more.