Engineer9860
Eagle Scout dad
Senior Member
Joined: 08/10/2003
View Profile
|
Caddywhompus wrote:
As I've said before, there are lies, damn lies and tow ratings.
You should change that to "there are lies, damn lies, tow ratings, and fuel mileage".
 
The Queen of the Skies
|
blt2ski
Kirkland, Wa
Moderator
Joined: 03/15/2001
View Profile
 Offline
|
Jimmy, you better add the MPG part! I like it!
In the mean time, Larry still needs to knock some 2000-4000 lbs off his total he says he can tow, as his van is basicly the same on shown on the poster in 1992 that I saw, and his trailer is over the 60# amount used for ratings, so something needs to give.
I still say a 75-150 HP to pull a 15000 lb load, bases on frontal area and windage, still accounts for a bunch of HP needed! I got 2 mpg more pulling my equipment trailer from seattle to ellensburg and back vs my TT, same wts, just 20# of FA difference. Along with needing 1 less gear, and 5-10 mph more on the grades with the ET than my TT! Frontal area and windage is useless at time......hmmmmmmmm.........
any way, off to bed, for another nights sleep, then off to work, you all probably know the song, "I owe I owe, so off to work I go!"
05 Chev CC D/A LS Dooley
92 Navistar dump truck, 7.3L 7 sp, 4.33 gears with a Detroit no spin
00 Chev C2500, V5700, 4L80E, 4.10, base truck, no options!
92 Red-e-haul 12K equipment trailer
3 Single axle utility trailers
Check RV.Net Blogs at: blog.rv.net
|
David_in_TX
Grand Prairie, Texas
Senior Member
Joined: 11/27/2007
View Profile
Offline
|
These weight numbers are not "marketing hocus pocus". Every engineer must calculate stress and subsequently size components to meet the requirements. This is a function of our jobs, and I assure you every engineer follows this practice. Every product has been through stress analysis, from the chair you are sitting on to the airplane you fly on.
I am a degreed mechanical engineer, I am not a stress engineer by trade, but I work closely with them and learned stress analysis as a part of my engineering degree. I am a design engineer, I work for a major defense contractor and have designed many things ranging from Supersonic Stealth Fighter Jets to Unmanned Combat ground vehicles. I am presently designing a truck (missile launcher) that weighs 53,000 pounds. I am not trying to brag, but I just wanted you to know what my qualifications are.
Now, let's break this issue down:
We use the term "load paths". Below is the simplified load path the weight of a truck and it's cargo will follow until it meets the earth:
Frame
Springs
Axles
Wheels
Tires
The frame strength is usually found on the manufacturer's website for upfitters (companies that fit ambulance bodies, etc.).
The springs are tuned for ride, one could add airbags or helper springs to increase the capacity. If truck manufacturers made springs with enough capacity to handle the loads we wish to carry, these trucks would ride like unloaded dump trucks. So, we need adjustable spring rates (air bags).
Axles; these weight capacities are also published, on the manufacturer's website for upfitters. As an example, the 2008 F-150 has a 5,300 lb. weight rating with the optional Heavy Duty Payload Package per Ford's fleet web page 2008 F-150 specification (page 6):
https://www.fleet.ford.com/truckbbas/non-html/2008/vs_pdf/f150_08bb.pdf
Wheels have published weight capacity in the same above referenced document, 2,400 lb. x 2 tires = 4,800 lb. These are the 7 lug steel wheels included in the above referenced Heavy Duty Payload Package.
The tires are (usually) the weakest link. These are rated at 2,460 lb., which in this case are actually higher than the wheels. 2,640 lb. x 2 wheels = 5,280 lb.
In this case the wheels are the weakest link at 4,800 lb.
Now we know the GVWR of the F-150 with the Heavy Duty Payload Package is 8,200 lb. On page 3, we can see the base curb weight of a regular cab F-150 with the Heavy Duty Payload Package is 5,097 lb. 8,200 lb - 5,097 = 3,103 lb. Ford lists the max. payload at 3,050 lb. I don't know why they do this but 53 lb. is nothing to worry about.
On page 3 Ford lists the rear axle weight of a base F-150 at 2,139 lb.
Take 4,800 lb. for the wheel rating (weakest link) - 2,139 lb. = 2,661 lb. for the max. rear axle load.
Now if you add options, this will be reduced by the weight of the options. See pages 12-13 for this.
Stress engineers have come to the above ratings through extensive calculations. There is a safety margin built into all of these numbers because nothing is perfect, all materials and manufacturing processes have defects. Engineers call these tolerances. Crash loads are also included in these safety margins. It is important to know if you go over these safety margins, there will be failures. Statistics can show this. If you choose to ignore the statistics and go over the GVWR of the weakest link in the load path, you are basically rolling the dice with your safety (and others). There is no disputing this commonly accepted engineering practice, it is a requirement that engineers have been using for decades. If you have ever watched the History Channel show Modern Marvels - Engineering Disasters, you can see the consequences. This show chronicles the history of engineering errors, manufacturing defects, etc. and the resultant loss of life they create. The SAE standardization is welcome, but the manufacturers have been doing this all along.
As far as Truck Trend magazine, I have had issues with them in the past:
http://www.trailerlife.com/cforum/index.........d/21389272/gotomsg/21390419.cfm#21390419
While I don't have first hand knowledge of the interviews they did with the quoted engineers, I suspect there is a lot more to the story than what is printed. The press has a tendency to edit for their advantage (in this case magazine sales).
Flame me if you wish, call me a weight police, but unless you have experience in engineering and can dispute this with facts and firsthand experience in engineering, I will stand behind my analysis. The fact is: it is foolish to go over the manufacturers GVWR and GCVWR.
http://www.linkedin.com/in/davidnicholstx
|
Caddywhompus
Southeast WI
Senior Member
Joined: 06/27/2001
View Profile
Offline
|
David_in_TX wrote:Flame me if you wish, call me a weight police, but unless you have experience in engineering and can dispute this with facts and firsthand experience in engineering, I will stand behind my analysis. The fact is: it is foolish to go over the manufacturers GVWR and GCVWR. You and I have similiar backgrounds, and I understand where you are coming from. In fact, I agree with you 100% that all the things you mentioned are definitely handled in the typical design phase of an object. If, and here's the catch, engineering departments across the land set the final specifications of our most-loved objects, then I would be 100% behind the ratings.
What is happening more often than not, is that engineering has less and less to say about what is ultimately published to the public. Take Ben's earlier statements regarding engineering signing off on designs. It just doesn't happen that way anymore, because as Ben noted, engineering can disagree and refuse to sign off, which just buys you a ticket to the unemployment line so your replacement can sign off on what you refused too.
The automotive marketplace is driven by sales and advertising. This feeds the need to be the biggest, baddest out there (for trucks) and the constant one-upping of each other's tow ratings. That said, go try and buy an MDT (Medium Duty Truck) and you will experience a completely different environment. Trucks that are sold on merit and capability. Salesmen who will sit down, go over your intended use and recommend an appropriate vehicle. They KNOW what can/can't be done and aren't afraid to tell you. Go to your local big 3 dealership and tell them you need a truck for towing, and you will probably know more than the salesman about the vehicles he's selling you.
'04 Ford Freestar (Primary tow vehicle)
'05 Subaru Forester (Backup tow vehicle)
'65 Bethany popup (best popups ever made!)
Looking for a tow vehicle
Minivan towing
|
David_in_TX
Grand Prairie, Texas
Senior Member
Joined: 11/27/2007
View Profile
Offline
|
The manufacturers will not allow the marketing department to set the weight limits and override the engineering department for many reasons, the biggest one being the liability. The legal department would never allow that kind of exposure to class action lawsuits. I do agree that when it gets filtered down to the consumer, either thru misleading articles written by Truck Trend magazine, or an overzealous salesperson trying to make money, the weight limits have errors (misunderstanding). Ford is guilty of a nationwide television commercial for the F-150 towing 11,000 lbs., however that rating is for a specific F-150 with a specific configuration of options, and the public is guilty of being gullible enough to translate that to any F-150 made. The data is out there (Ford's lawyers made sure of that), as I have shown you on their upfitters website. It is the consumer's personal responsibility (something we need more of in our country) to find the data and do the simple calculations as I have done here to find their own trucks limits.
Caddywhompus wrote:David_in_TX wrote:Flame me if you wish, call me a weight police, but unless you have experience in engineering and can dispute this with facts and firsthand experience in engineering, I will stand behind my analysis. The fact is: it is foolish to go over the manufacturers GVWR and GCVWR. You and I have similiar backgrounds, and I understand where you are coming from. In fact, I agree with you 100% that all the things you mentioned are definitely handled in the typical design phase of an object. If, and here's the catch, engineering departments across the land set the final specifications of our most-loved objects, then I would be 100% behind the ratings.
What is happening more often than not, is that engineering has less and less to say about what is ultimately published to the public. Take Ben's earlier statements regarding engineering signing off on designs. It just doesn't happen that way anymore, because as Ben noted, engineering can disagree and refuse to sign off, which just buys you a ticket to the unemployment line so your replacement can sign off on what you refused too.
The automotive marketplace is driven by sales and advertising. This feeds the need to be the biggest, baddest out there (for trucks) and the constant one-upping of each other's tow ratings. That said, go try and buy an MDT (Medium Duty Truck) and you will experience a completely different environment. Trucks that are sold on merit and capability. Salesmen who will sit down, go over your intended use and recommend an appropriate vehicle. They KNOW what can/can't be done and aren't afraid to tell you. Go to your local big 3 dealership and tell them you need a truck for towing, and you will probably know more than the salesman about the vehicles he's selling you.
|
|
|
smkettner
Southern California
Senior Member
Joined: 03/21/2005
View Profile
Good Sam RV Club Member
|
So does marketing tell the engineers to build a truck to tow 10,000 or do the engineers produce a truck and marketing determines it can tow 10,000?
I think each year marketing says they want more power, payload, increased towing, better air conditioner, larger wheels that look better, layout the dash better, more leg room, better mileage, better stereo, navigation, stability control, the list is endless. If accounting approves then the engineers design and build it.
2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
|
BenK
SF BayArea
Senior Member
Joined: 04/18/2002
View Profile
|
You guys are smack on one of my biggest hot buttons...bean counter
management and how they have ruined our society...and...that it really
is 'us' who drive or allow this.
Our whole economy is driven by this and what we have today...Medoff,
Lay, Enron, etc.
After leaving engineering to take a position in the M&A group as their
technologist & Sr Program Manager, one of the most rewarding and
frustrating things I've ever done. Also why got laid off in 2001...my
mouth on this type of subject.
I became a 'suite' for a major corporation, but assigned to CTO's staff
and his Labs.
Saying this to give reference to my point that you guys are both
right and wrong at the same time. I've been there done that from
all sides of that issue.
Posted before and here it is again, as it is timely to the discussion
MotorTrend Angus MacKinzie "The Big Picture: Street Smarts"
It is automotive based, but applies to any large corporation in the USA
today.
These bean counters have no clue of their product specifications and
really don't care. The bottom line and their bonuses are supreme
The public is really to blame, as 'our hero worship' is based on these
types and their money.
Geez, give the CEO a golden parachute of a tens to hundreds of millions
for screwing up, and the life time membership to the country club with
life time benefits....where as....in old Japan, their CEO would resign
in disgrace and some times, often times commit suicide.
Was in industrial controls and all industries my customer. They all
had this metric. Last one was one of the top 3 computer companies
in the world and can say they all ditto.
Don't believe? Take a look at Apple Computer. Jobs was doing fine till
the stock holder decided they needed a bean counter (MBA), so they
hired Scully to oust Jobs. Ruined the company managing to the bottom
line, while neglecting the product. Jobs came back and managed to the
product, not the bottom line and ran the company back up to one of the
most profitable companies in America.
|
lesmore49
canada
Senior Member
Joined: 11/25/2004
View Profile
|
Caddywhompus says;
"The automotive marketplace is driven by sales and advertising. "
I agree with this view. In fact I would venture that one of the factors (among many) for the group of domestic automotive manufacturers formerly known as the Big 3, encountering so much difficulty in simple survival over the past number of years, is due to emphasizing sales at any cost and marketing/advertising based on the school of smoke and mirrors.
In these tight times, I find it interesting that automotive companies that are doing not bad, continue to emphasize solid engineering, (BMW, Honda, Toyota, Subaru, etc.) as opposed to other companies who merely continue to promote the same old, same old products based on older engineering, not much newer product and little R + D to actually develop (real) new ...well engineered products are the manufacturers that are suffering the most.
The Big 3 have been foundering for the most part over the past # of years.
They have been making strong efforts to recover their past share of the market, with better products that reflect strong engineering. The problem is though, convincing the masses with money that they (Big 3) have turned it around.
The market nowadays has a grasp of what is really good and what is not. The market, it seems with the sales #'s of Toyota and Honda, for example, are willing to pay a higher price for vehicles that are perceived as having top quality...read well engineered with current or advanced technology.
As an aside, I am concerned that some of the GM vehicles that represented the pinnacle of engineering have been dropped for 2010. They include the high performance Cadillac (Corvette V8), the Impala V8...the SS, the Cobalt 4 door SS, the Pontiac G8, the Pontiac Solstice...all these cars in recent tests from a variety of sources have demonstrated that GM is more than capable of designing and building vehicles of world class performance.
What it seems we are left with are 'practical' cars that emphasize A to B transportation.
The hi-po cars that were dropped were leaders in their market segments...coupling great engineering, high performance (remember Nurburgring tests) with reasonable costs.
These were vehicles that emphasized engineering. Now that they are gone, I would think it has to have had, an affect morale with the engineering department.
Bean counters and marketing/sales are important, but should not have a final decision making powers, IMHO.
lesmore49
|
BenK
SF BayArea
Senior Member
Joined: 04/18/2002
View Profile
|
smkettner wrote:So does marketing tell the engineers to build a truck to tow 10,000 or do the engineers produce a truck and marketing determines it can tow 10,000?
I think each year marketing says they want more power, payload, increased towing, better air conditioner, larger wheels that look better, layout the dash better, more leg room, better mileage, better stereo, navigation, stability control, the list is endless. If accounting approves then the engineers design and build it.
Dependent on how the company is organized...marketing is the input for
the product team.
Marketing/sales writes the product requirements for the product team.
The product team signs up or modifies or refuses that specification.
It is a negotiated position. The product team chair runs the product
team. Some companies has the program manager engineering based, while
others marketing based.
Engineering has to design to that product team specification, as all
departments signed up to it before the program manager would allow any
money be spent on the program.
Since driven my the buying public and their beliefs in the advertising
'half ton' TVs must now have a MTWR in the 9K-10K range. Again driven
by the buyers who believe the MTWR in absolute terms.
Legal is involved throughout and those weasel words are always there
to protect the corporation.
Then forums like this where legions will advise that the MTWR is an
absolute, or that over loading is okay, or that the OEM doesn't know
what they are doing (right to a point), and the 'you are good for it'
to the "I've been doing it for decades with no problems"...
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...
|
BenK
SF BayArea
Senior Member
Joined: 04/18/2002
View Profile
|
Les, a prime example of these bean counters not knowing their product
A 'product ID' person makes some where around $500K/year PLUS
bonuses, in large corporations like GM.
Take the director of Marketing ID for the GMC Suburban who chose to to change it's
branding ID away from the worlds longest running and most known badge "Suburban". Just
about anyone world wide knows what a Suburban is. What the heck is a Yukon XL?
Then to further dilute that ID branding, they weakened it by also using 'XL' for the smaller SUV.
Again, too many examples of why the 'Big Three' had their lunches eaten by
foreign badges.
|
|
|
|
