'THE 2017 GMC Acadia sport utility vehicle that is just starting to
arrive in dealerships around the country is 700 pounds lighter than
the version it replaces, and can go 23 miles on a gallon of gasoline,
up from 18 m.p.g., a 28 percent improvement.
'One of the secrets to the big weight loss? Glue.
‘Many of the steel parts of the Acadia’s underbody are held together
not by rivets or welds but by advanced adhesives similar to those used
in modern airplanes’
I finally found a use for the skill I developed building models when I was a kid.
Colin Chapman would have loved these adhesives. He was famous for asking his engineers to ‘add more lightness,’ to the point in his race cars where they were dangerously flimsy. It is suspected that this philosophy at least contributed to HJim Clark’s death in an F1 crash of a Lotus.
Maybe that’s why there is now a minimum mass requirement of 702 Kg in F-1. (I was going to say “minimum weight” but the kilogram is a unit of mass, not weight.)
Automotive engineers have been moving toward bonding for many applications for decades. Most all the supercars are now bonded carbon fiber components now.
“England and other Germanic-speaking countries of northern Europe formerly used various standardized “stones” for trade, with their values ranging from about 5 to 40 local pounds (roughly 3 to 15 kg) depending on the location and objects weighed. The United Kingdom’s imperial system adopted the wool stone of 14 pounds in 1835. With the advent of metrication, Europe’s various “stones” were superseded by or adapted to the kilogram from the mid-19th century on. The stone continues in customary use in Britain and Ireland for measuring body weight, but was prohibited for commercial use in the UK by the Weights and Measures Act of 1985”
NOTE: I copied this from Wikipedia bout cannot link it in. My software has developed a glitch.
I suppose it helps top realize that all measuring systems are really arbitrary systems devised to communicate some measure of something, and many originated using the weight of a stone, or the length of the king’s thumb, or something like that. Except perhaps atomic weights.
One thing I don’t understand if weight is supposedly the sole reason for a 5 MPG gain.
I can load my Lincoln down with 700 pounds of passengers and cargo and the fuel mileage is the same as when I’m in it solo.
By that logic shouldn’t my Lincoln get a little better mileage with a solo driver?
OK4450, are you suggesting that someone in the marketing department was exaggerating?? How can you suggest that? Don’t you know that only the most honest and trustworthy people become salespeople?
No, I would never accuse anyone in the automotive industry of lying, exaggerating, or fudging any fact…
(Speaking of unicorns and pots of gold at the end of the rainbow…)
I’m having a hard time seeing how they’re coming up with 700 pounds of rivets and welds on one vehicle. I wonder if the glue will degrade over time and the vehicle will start shedding parts while tooling down the expressway…
Speaking of glue, ,many years go my aircraft instructor traded his Piper off and bought a new at the time hot rod Grumman Yankee which he used to take me up in and try to teach me to fly.
The first time up we’re at 3000 feet and cruising at about a 100 and he said, “Did you know this plane is epoxied together?:”.
The rest of that flight I kept looking down at the right side wing root expecting to see it start separating…
Back on the ground he told me the motor mount was epoxied to the firewall. A look showed there were 4 globs of epoxy on each mounting point. Whether there were bolts buried in the glue I do not know.
It was only many years later I found out that epoxy wasn’t the weak point on the early Yankees. They were prone to flat spins and quick stalls which bumped both the lethal factor and fatality count up. There was a few times I thought I was going to be part of the body count and it would take about 5 minutes for my heart to drop back to where it belongs.
All said though, still a blast.
The new lighter Acadia is available with a 2.5 L four cylinder engine, the former came with the 3.6 L engine exclusively.
The use of adhesives allows for greater use of dissimilar metals. GM has been using aluminum front structural panels joined to steel in late model vehicles, although I don’t know the specific method of joining the two.
If 700 pounds of extra weight doesn’t affect your fuel economy you must not live in an area where the traffic lights are a quarter of a mile apart.
The Kinks also seem to have a passing familiarity with the stone as a unit of weight or mass.
From “(I Want to Fly Like) Superman”
“Woke up this morning, started to sneeze
Had a cigarette and a cup of tea
I looked in the mirror, what did I see
A nine stone weakling with knobbly knees”
Weight has little effect on a car’s gas mileage on the highway, maybe a little extra rolling resistance from the tires, but it kills your gas mileage in stop and go driving. On airplanes it’s a whole 'nother story, increasing the induced drag of the wings. Induced drag is essentially the kinetic energy imparted to the air from the wing’s downwash.
Funny how tires are measured with a mix of metric and imperial units. The rest of the world is not as completely metric as a lot of people think. Aircraft and ships still use nautical miles the world around, the Europeans still shoot “12 gauge” shotguns at the Olympic trap and skeet events, and I’m pretty sure that precious metals are still traded in troy ounces and pounds over there.
I liive out in the sticks. It’s 25 miles to town so most of my driving is open road. Over the past 15-20 years I’ve made many open road trips by myself or with a light load to my daughter’s house in TX and multiple trips to CO and NM.
The TX trips were pretty much solo or with my wife only. The ones to CO and NM always had both my wife and I along with the car being stuffed full of debris including fishing/camping gear.
The mileage has always been the same. As a matter of fact, the mileage always improves by about 1.5 MPG in the mountains compared to the flats where I live.
So the 4 banger is the reason for the improvement in MPG; not the glue.
Speaking of weighs and measures, I remember this question on an 8th grade math quiz: “Which is heavier, a pound of feathers or a pound of gold?”.This was a trick question with the answer being a pound of feathers since gold is measured in troy weight with 12. ounces to a pound. On the use of joining parts with adhesives, certain years of Ford Windstars including the 2000 models were recalled for a rear suspension problem. Ford bought back some of these minivans and repaired the rest with some sort of adhesive. Our son had a 2000 Windstar he was trying to sell that was in the recall. He hoped Ford would buy it back, but his was.glued back together and he had to sell it. Perhaps this repair wasn’t as bad as I thought.
Yeah, B.L.E., that thing about tires has always puzzled me too. The section width is metric, the sidewall is expressed as a ratio, and the wheel size is in inches. I’ve never been able to find out how that came to be. Makes no sense to me that it should be that way, and I can think of nothing else that uses such an odd mix of measuring systems.
The inch wheel size is a concession to standardization, I think. That got adopted so long ago, and would require such a major cost to change, that the industry has just decided to live with it. Michelin tried to change that with the ‘TRX’ line of tires that required metric sized wheels (you could get them on a Mustang at one point), but failed because of the non-standard wheel size, with only them supplying replacement tires. Here’s more info on it:
It’s a little more complicated than just the weight, as many simple answers are. If a given model has metrics that include “must do 0 to 60 in less than 9 seconds” and/or “must be able to pull a 40% grade at 15% over gross weight,” the weight savings alone would allow the model to exceed these metrics. So, the logical thing to do, is put in a taller final drive to reduce the new-found performance back to just meet the metric AND get a little better MPG’s in the process. So while 700 lbs itself might give 3 mpg, the gear change adds 2 more. Not only does it all add up, each change feeds other areas.
But all that is waaay too complicated for the marketing department and the media they entertain.
The Troy system uses a heavier ounce though, so an ounce of gold would be heavier than an ounce of feathers, but the pound of gold would be lighter than a pound of feathers.
The Avoirdupois pound weighs 7000 grains, and is divided into 16 Avoirdupois ounces of 437.5 grains and the ounce is divided into 16 drams of 27.34 grains.
The Troy pound weighs 5760 grains and is divided into 12 Troy ounces of 480 grains, which is divided into 20 pennyweights of 24 grains.
Speaking of gold, did you know that it is heavier than uranium, in fact, along with gold, tungsten, platinum, and osmium are all heavier than uranium metal, in spite of the fact that people who play scientists on TV kid’s shows say that uranium is the heaviest naturally occurring element.
So the ratio of pounds to kilograms varies with the gravitational field? In other words a pound of something on the moon woul tip the scales more than a kilogram of something? Interesting, I never knew that.
