30 replies to this topic

[Nathan]

I am curious how much the cargo box on a truck adds to the frames rigidity. I would imagine any effect is minimal, but at the same time surely it must add some strength? Most boxes are typical fastened to the frame via eight bolts. I can't find anything on Google and I'm hoping the folks here can help me out. Thank you!

Box
http://4.bp.blogspot...kbox2_large.jpg


No box
http://gallery.wiese...g2_itemId=15135

[McGuire]

I am curious how much the cargo box on a truck adds to the frames rigidity. I would imagine any effect is minimal, but at the same time surely it must add some strength? Most boxes are typical fastened to the frame via eight bolts. I can't find anything on Google and I'm hoping the folks here can help me out. Thank you!

Box
http://4.bp.blogspot...kbox2_large.jpg


No box
http://gallery.wiese...g2_itemId=15135

Not much at all. Real trucks from pickups on up (not utes, El Caminos, etc) are designed so they can be offered as chassis/cabs without cargo box so various types of third-party specialty beds and boxes can be installed at point-of-sale. The rigidity of this prospective box is unknown to the truck manufacturer. If you look at the chassis in the photo above you will note several healthy rear crossmembers not found on passenger cars.

A typical cargo box -- say a 12 foot enclosed van box -- has almost no rigidity of its own. Just sheetmetal ribs with plywood or fiberglass panels. Removed from the chassis it's like a big cardboard box. A couple of large boys could collapse it if they knew where to attack.

[Greg Locock]

An open tray is just about invisible so far as torsional stiffness goes - take the inner out of a matchbox, cut one end off, twist it. Having said that the torsional stiffness of the ladder chassis on a light truck is nothing to write home about, you'd be lucky to see 2000-3000 ft lb/deg (WAG). As an example, the vertical loads in the leaf spring are impossible to calculate correctly unless you make allowance for the stiffness (or lack thereof) of the chassis.

You see the same thing in wagons, the tailgate wrecks the torsional stiffness unless you fit a big perimeter frame. That's why you see those great fat D and E pillars these days.

[McGuire]

How do they get away with it on tonners... or do they? Do they back-half them with perimeter rails or something?

[Greg Locock]

I don't think they do anything much to reinforce the door aperture beyond what is necessary for durability. Are the big boxes mounted via compliant mounts or bolted directly to the chassis?

[McGuire]

Generally, large van boxes are built/mounted on steel C-section rails, which are then clamp-bolted or u-bolted to the truck's frame rails. (Often with a hardwood, steel, or tubing "crush pipe" in between as lath.) Saves welding on the frame and allows boxes to be easily transferred from one truck to another, etc.

Folks might find this interesting:

http://www.gmupfitte...cat/chassis.pdf

[Engineguy]

... Having said that the torsional stiffness of the ladder chassis on a light truck is nothing to write home about, you'd be lucky to see 2000-3000 ft lb/deg (WAG)....

They're writing home about it! (... well, writing a press release anywho...)

2011 GM HD pickups: doesn't give a figure, but it's five times what it was prior model. Of course it isn't the lightest truck they make.

"Starting with the front suspension, the 2011 Silverado HD receives beefier upper and lower control arms along with larger torsion bars and steering gear. The front axle can now handle up to 6,000 pounds of gross weight, which means that every HD model can bear the weight of a snow plow. Moving through the rest of the display, you can see the all new frame that utilizes 11 fully boxed assemblies that make sure of higher strength steel. The result is that the new chassis has five times more torsional strength than it did before and 92 percent better bending resistance." ... via http://www.autoblog....ween-old-and-n/

From press release:
1. New frames

In the quest to comprehensively redesign the Silverado HD chassis to improve durability and ride, while also supporting increased capability, engineers developed 11 all-new, fully boxed frame assemblies. The frames have increased cross sections and use more high-strength steel for greater durability, higher towing capacity and improved ride and handling; the front sections are hydroformed.

The bending and beaming stiffness of the frames is increased 92 percent and 20 percent, respectively, with the fully boxed sections enhancing torsional stiffness by a factor of five. Also, larger engine and transmission mounts, coupled with a 125-percent-stiffer front frame structure, provide greater vibration control, while hydraulic body mounts are incorporated under the cab section on extended and crew cab models for a more isolated feel inside.

Engineers addressed common customer and aftermarket uses when designing the new frames, including adding access holes to the rear frame section to enable easier installation of fifth-wheel/gooseneck-style hitches. Also, the frame-mounted hitch for conventional trailering is stronger, with a box-tube design. It supports up to 16,000 pounds (7,257 kg).

[Greg Locock]

There's a mildly amusing video of some trucks running over special surfaces. One has a you-beaut box section chassis, and the other one of interest is an old unimproved C section chassis. The difference in deflection is obvious. Incidentally the design of the cross member to ladder joints is also very important.

[gruntguru]

There's a mildly amusing video of some trucks running over special surfaces. One has a you-beaut box section chassis, and the other one of interest is an old unimproved C section chassis. The difference in deflection is obvious.

I imagine the difference between vehicles would be less obvious at most other excitation frequencies.

Incidentally the design of the cross member to ladder joints is also very important.

Watching that video, they would need to be spherical joints to have any sort of life expectancy.

[Todd]

They're writing home about it! (... well, writing a press release anywho...)

2011 GM HD pickups: doesn't give a figure, but it's five times what it was prior model. Of course it isn't the lightest truck they make.

Moving through the rest of the display, you can see the all new frame that utilizes 11 fully boxed assemblies that make sure of higher strength steel. ... via http://www.autoblog....ween-old-and-n/

Why does the type and number of assemblies determine that the steel used is any different than before?

[imaginesix]

The guys working the oils sands in Alberta stayed away from GM trucks because they knew that their frames would break apart very quickly compared to Ford / Chrysler. They never keep any truck for more than a year but they still can't replace them fast enough.

[Engineguy]

Why does the type and number of assemblies determine that the steel used is any different than before?

From the context, I think the word "sure" was supposed to be "use." Must have a lexdisic proofreader.

"Moving through the rest of the display, you can see the all new frame that utilizes 11 fully boxed assemblies that make use of higher strength steel."

[McGuire]

http://www.gmupfitte...cat/chassis.pdf

Forgot to mention there are some interesting notes in the above regarding welding and drilling on channel and box-section frame rails.

[Ray Bell]

If it's of any interest, the lightest of pickup 'frames' was the Peugeot 404...

It was endowed with some nice light box sections that were an extension of the station wagon-based frontal part of the body and the rear springs were long leaves to enable the load to be spread widely.

I remember many years ago seeing one carrying orange juice as its daily chore. About two tons of orange juice. For some reason some butcher with no appreciation of engineering practices had clamped heavy U-bolts around the lightweight rails, I don't remember why. But the thing still stood up.

[Greg Locock]

It was endowed with some nice light box sections that were an extension of the station wagon-based frontal part of the body and the rear springs were long leaves to enable the load to be spread widely.

That's pretty much the architecture of the Falcon Ute. At one point (AU) we had leafpsirings, coil spring beam axle and coil sprng IRS all in production at the same time on the same chassis rails (sort of). The only one missing is a leafspring IRS, but we don't make Corvettes, grins.

The following model we dropped the beam axle/coil spring and picked up the improved leaf spring (Crane Simplex links for the RTV). I think we've developed as many new suspensions in the last 10 years as the rest of Ford worldwide.

[Canuck]

At one point (AU) we had leafpsirings

Is that pronounced Leef-piss-rings or leef-pisser-rings? I wonder if they'd work on my trailer...

<so says the site's worst typist>

[Grumbles]

Is that pronounced Leef-piss-rings or leef-pisser-rings? I wonder if they'd work on my trailer...

<so says the site's worst typist>

If you think that's funny you should hear him try to say hopspital, I mean hopistal, hospspital HOSPITAL DAMMIT!

[McGuire]

Getting back to the original poster's question... if/when the cargo body is sufficiently rigid and there is some need for it (ambulance/EMT bodies are one example, patient comfort and stability being an issue) the cargo body may be installed using the same compliant biscuit mountings traditionally used to bolt the cab in place. Rigorous engineering seldom employed by the body supplier; often they will just use the same part number as the cab to keep things simple.

Yesterday morning on North Carolina Route 1 (driving back to the Raleigh-Durham airport from the Maxton Mile) I saw an interesting rig... a new Ford pickup cab/chassis with a sort-of handmade fiberglass camper body-type thing mounted to the chassis in the manner above. Looked like it might contain surveying or environmental test gear. Or maybe medical equipment. Going blatantly OT, at Maxton Sunday a Suzuki Hayabusa did 272 mph through the traps in a standing-start mile. Fairly awesome, I think. Fastest car was a Pontiac Firebird at 241 mph.

[Canuck]

272...wow that's fast to hanging out in the breeze...

[McGuire]

272...wow that's fast to hanging out in the breeze...

In a standing-start mile.

Interesting guy who did it... Bill Warner, a marine biologist. Got into the scene with a Yamaha VMax street bike. At one point he decided he wanted to go 200 on his VMax, naked (no fairing). Of course, the people selling him parts (the experts) laughed so he put together a combination and did it. Then figured he may as well see what he could do with a Hayabusa. He went 255 naked at the Texas Mile a few weeks ago so everyone knew it was there if he could put it together. Says he is making around 650-700 hp with his boost somewhere in the 30s.

The car that went 241 mph is driven on the street. Run by Eric Yost, fabricator at Michael Waltrip Racing. 23-degree Chevy, 400ci, two turbos, air/water charge cooler.

[Canuck]

Crazy...I don't know how you stay on.

I wonder if he's the Yost of the "Yost Power Tube" product for Keihen CV carbs.

[Canuck]

WORLD’S FASTEST WHEELS:
BST CARBON-FIBER WHEELS SET RECORD ON MAXTON MILE

Claiming the title of “World’s Fastest Streetbike,”Brock’s Performance-sponsored Bill Warner rode into the record books at the East Coast Timing Association’s Maxton Mile on April 11 with an astounding 272.340 mph pass in the standing mile.

In preparation for Maxton, Warner, 41, a tropical fish farmer and marine biologist from Tampa Bay, Florida, went to a Texas Mile event two weeks earlier, stripped the bodywork off his turbocharged, 1298cc Suzuki Hayabusa and made two 255 mph passes—the fastest unfaired, naked-bike runs ever recorded—at one point data logging a rear-wheel speed over 308 mph as the tire spun trying to harness more than 600 horsepower.

Setup dialed in, Warner and his team arrived at the all-concrete, one-mile course on a former air base in Maxton, North Carolina, planning his weekend record assault using the 253 mph MPS/BF-1650/4 class record as his target. Warner’s third run on Saturday, a 257.604 mph pass, did the trick, but there was more to come. On Sunday, he posted a pair of 256 mph test runs in the morning with stock body panels before Shane Stubbs upped the ante, and the nearly five-year-old fastest-streetbike record previously held by Lee Shierts at 260.288 in the MPS/BF-3000/4 class, with a 264.375 mph blast.

“I was excited for him,” says Wild Bill, “but Shane went a bunch faster than I expected him to go, so I reached in my bag of tricks.” Warner pulled out three key ingredients to a better run: a leaner air-fuel mixture (“Because leaner is meaner in turbo racing,” he insists), two pounds more turbo boost in top gear and a set of top-secret, custom bodywork.

“I figured that one of two things were gonna happen, either I would have to shut it down early or I’d put in a really good run,” Warner continued. “You get really motivated in these situations. I stayed in the throttle and kept the bike straight up, charging forward.” This little bit of inspiration is all he needed to post his 272.340 mph run—obliterating the class and track records, making this ‘Busa the fastest vehicle ever run at Maxton.

Warner was so motivated and charging forward so quickly that he failed to get the bike slowed down in time for a corner halfway through Maxton’s shut-down zone: “My timing was off because I was traveling so much faster, it caught me a little off guard. I went in at the wrong angle and hit the third traffic cone at 167 mph.” This ripped off the front fender and damaged his hand-built bodywork, which took 300 man-hours to perfect, but didn’t wipe the smile off his face.

Fellow land-speed-record-holder Paul Livingston was blown away by Warner’s accomplishments: “I was shocked and excited to hear about Bill going 272 mph,” says Livingston, “but what knocked us on our asses were the 255 mph naked runs. This makes him a hero—even among the hard-core land-speed guys.”

Brock’s Performance President Brock Davidson put a lot of homework into finding the right land-speed team to sponsor. “We can design, create and supply the greatest parts we know how to produce,” he says, “but we have to provide them to people who know how to set up a motorcycle, do the proper testing, read the data and move forward intelligently. Bill’s drive, determination and ability—on and off the bike—are the reasons we chose Wild Bros Racing. And he killed it.”

In addition to supporting such land-speed efforts, Brock’s Performance is reaching out to AMA Dragbike, MIROCK Superbike dragrace and WERA Motorcycle Roadracing series competitors with nearly $118,000 worth of contingency awards in 2010. Racers using various Brock’s Performance exhaust systems and BST carbon-fiber wheels are eligible.

For more information on BST wheels, Brock’s Performance exhaust pipes, other sportbike performance parts and the company’s contingency programs, go to BrocksPerformance.com.

The record-setting bike, a first-generation Hayabusa, was set up with products and technical support from the following sponsors: BST, Brock's Performance, RCC Turbos, Garrett Turbo Technologies/Honeywell, Ward Performance, R & D Motorsports Inc., Ohlins USA, Pirelli Tires, MTC Engineering, Worldwide Bearings, Knecum Performance Engines, Web Cam Inc., McIntosh Machine and Fabrication, Aerospace Lubricants, Inc., Spiegler Performance Parts, Heads Up Performance, Falicon Crankshaft Components Inc., Millennium Technologies Inc., Power-Coat, Zip Sensors, Helmet House, Larry Forstall Racing, AiM Sports LLC SE and Crower Rods.
For more on Bill Warner’s accomplishments, sponsors, bike and team, Click here: http://www.brocksper...dbrosracing.htm

[McGuire]

Warner was so motivated and charging forward so quickly that he failed to get the bike slowed down in time for a corner halfway through Maxton’s shut-down zone: “My timing was off because I was traveling so much faster, it caught me a little off guard. I went in at the wrong angle and hit the third traffic cone at 167 mph.” This ripped off the front fender and damaged his hand-built bodywork, which took 300 man-hours to perfect, but didn’t wipe the smile off his face.

That was one dead orange cone. Killed instantly, never felt a thing.

Bill's bike after the 272 run. Note the shattered bodywork underneath.



BTW, see the white Mitsu poking out behind in the background? Went 237 with stock block, head, and crank, handbuilt intake manifold.

[GeorgeTheCar]

Ihave a funny truck "low torsion rigidity" story I'll try and type out later

Taught me a lot!

I have long wondered why the truck makers didn't pin the top of the box to the cab.

IMHO it would add a lot of torsional rigidity for the cost of a couple of bolts and stiffner plates!

Edited by GeorgeTheCar, 01 May 2010 - 19:28.

[McGuire]

I have long wondered why the truck makers didn't pin the top of the box to the cab.

IMHO it would add a lot of torsional rigidity for the cost of a couple of bolts and stiffner plates!

To prevent owners from wrecking the cab when they overload the box. If the box gets twisted when Mr. truck owner hauls away two tons of large, sharp rocks, BFD. Slightly lumpy box and the tailgate closes kinda funny. Badge of honor. But if the cab gets twisted the doors no longer work properly, the windshield cracks, etc.

A separate pickup box is the basic tell between a real truck and a wannabe truck (El Camino, Honda Ridgeline, so on). Though in the early '60s, Ford made some F-100 pickups with bed and cab integrated. Ford soon switched back to conventional construction and now these trucks are minor collectors' items... if you can find a straight one.

...Some years back we had an old Isuzu Pup shop truck we used as a snow plow in the winter. In the middle of big snowstorm the frame snapped in two in an inaccessible location behind the cab. No time to tear apart the truck to weld it, so I got two pieces of 12x20-in .125 steel plate and welded the cab to the box on both sides behind the door handles. It stayed together long enough to get the snow moved.

Edited by McGuire, 01 May 2010 - 21:14.

[Canuck]

Mercury Unibody Truck

[GeorgeTheCar]

Any gain in pickup performance has been at the expense of incredible weight gain.

They have almost doubled in weight for no appreciable gain in cargo capacity

[desmo]

Maybe, but they are typically more luxurious now than the most over the top luxury cars like Rolls-Royces were not that long ago. Climb from a '70s full size PU directly into a new one. The old ones seem like stripped out Roman chariots by comparison. What was once unimaginable luxury reserved for only the wealthy few is now expected by Joe six-pack in his work truck.

[gruntguru]

I have long wondered why the truck makers didn't pin the top of the box to the cab.

IMHO it would add a lot of torsional rigidity for the cost of a couple of bolts and stiffner plates!

Real trucks have the cab rubber mounted to the chassis.

[Greg Locock]

Real trucks have the cab rubber mounted to the chassis.

Maybe. As usual the weight increase in trucks is driven by customers. If /you/ weren't prepared to pay for trucks with AC, carpets, leather seats, 6 speaker stereo, 200 hp (I used to deliver 1.5 tons of stuff in a 40 hp diesel in the hills of Northern England) etc etc, then we wouldn't build them. You are, so we do.

[Canuck]

Maybe, but they are typically more luxurious now than the most over the top luxury cars like Rolls-Royces were not that long ago. Climb from a '70s full size PU directly into a new one. The old ones seem like stripped out Roman chariots by comparison. What was once unimaginable luxury reserved for only the wealthy few is now expected by Joe six-pack in his work truck.

In all fairness, I've not spent any time in an old Rolls Royce and the next closest thing to an old RR I was in was an '79 450 SEL 6.9. I would have to say that while my '02 Dodge Ram did have leather and A/C (and 4 doors) it was by no means comparable in it's luxury. It's not comparable to my '88 5-series even. It's a pretender at best.

Here's what I saw happening as a kid who turned 16 in the '80s. Power had been and was still neutered - 180 hp 5 litre engines in the US "muscle cars". Everything going front wheel drive with the exception of the pony cars, the 'Vette and the odd luxo-barge like the Town Car. About the only thing available with a v8 and rwd were trucks, so as consumers, those that couldn't spend into a one of the few remaining rwd cars, went for trucks. This in turn bred the demand for more car-like trucks and fostered the birth of the SUV.

That's likely not the industry line, but that's why my friends and I started buying trucks. Of course, they weren't 40, 50, or $70,000 a piece at that point either...

Edited by Canuck, 02 May 2010 - 15:06.