You can spin it either way if structure is what matters. If you were to take the same amount of material from a C channel frame and make a closed box frame out of it, even with the thinner structure wall (keep the overall cross section the same), the boxed frame would in theory have the same ability to handle the same load as the C channel. torsional resistance will be MUCH higher though, and this can play a big role in trucks like the F150, because the A arm suspension puts a lot of torque on the front of the frame rails. This is a big reason why ford opted for the famous (or infamous) twin I beam suspension for 1980, because it offerers the same handling performance, without the added stress on the frame.
Also, when using A arm suspension, the frame width usually changes near the front at the moving parts, this again means the potential for torsional stress, and a boxed frame is better suited to controlling any metal flex or even fatigue that may occur. So if we use the same AMOUNT of material, the frame is stronger than an equal weight C channel frame, although much more complex.
The ability to use A arms, and the higher stiffness means a truck with a boxed frame would also handle much better on hard, dry pavement.
Now for the disadvantages. The big one for me is corrosion resistance, since we know that the steel thickness is smaller (if we assume the same weight), we know it will rust away more quickly, and since the frame is boxed, salty road sand is more prone to collecting in the frame, so corrosion can spread that much more quickly. What is even worse about this situation, is that if the rust starts inside the box of the frame, the damage may not be immediately known until its too late.
Boxed frames also allow a unique opportunity for builders. Where in the past, a C channel had to be made out of one piece of thick steel, boxed frames can be made of thinner, shorter sections of thinner steel, this makes the stiffer frames easier to make and modify as the vehicle evolves into newer versions, retooling is also cheaper. The problem is, the wields in the frame are not subject to the normal scrutiny of say, a home built vehicle. As a home mechanic, and a wielder by trade, I have seen some wields on fords, chevs and imports that are all well below the standard that I could ever get away with as a wielder.
The overlapping sections of the frame sections make it strong enough for a crash test or normal use, but there is no real telling how these frames will hold up after 10 or 20 years of abuse. The front end of the 1988 chevy is heavily boxed and prone to cracking in many places around the suspension components and engine mounts (steel is very thin in places), this is one of many reasons why nothing but ford superduties are used in the logging industry where I live, and even they break often.
The flexible frames, believe it or not, actually help ground contact for uneven terrain, where even a slight difference in weight from one wheel to the next cam mean the difference between getting stuck or making it through. I have twisted my F150 about 12" easily without any problems, but this does make for more pops and groans.
It comes down to a matter of preference, both types can be designed to hold up just fine, and both types can fall apart if not. sorry for the long post.
FYI.....(if you didn't already know) Super Duties after '05, and the Tundra all have a fully boxed front section.
After the front section, the Super Duties go to C-channel.
The Tundra uses a double wall C-channel after the front section that turns into a regular C-channel under the bed.
Priot to '05, the Super Duty was 100% C-channel. (actually made it easier to knock out the rivets and bolt my shock hoops on for my lift.... )
FYI.....(if you didn't already know) Super Duties after '05, and the Tundra all have a fully boxed front section.
After the front section, the Super Duties go to C-channel.
The Tundra uses a double wall C-channel after the front section that turns into a regular C-channel under the bed.
Priot to '05, the Super Duty was 100% C-channel. (actually made it easier to knock out the rivets and bolt my shock hoops on for my lift.... )
sure....the superduties are c-channel......they also don't ride as well....handle as well....they aren't nearly as quiet.....and they're not 5 star safety rated....but i'm sure boxed frames don't have anything to do with that.....
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sure....the superduties are c-channel......they also don't ride as well....handle as well....they aren't nearly as quiet.....and they're not 5 star safety rated....but i'm sure boxed frames don't have anything to do with that.....
I've been trying to find some clips of the superduty but haven't had any luck so far, I'm curious to see how it compares. I'll post it if I find anything. Heres another crash with an old ford (1967-1973), soposedly this is 70 MPH:
they didn't get clearance to test them against iraqi bunkers?
I guess not, all the info I get refers to ratings for side, frontal, rollover etc, but instead of showing the actual info, it just reads "not tested", is the superduty exempt from NTSB testing??????????
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sure....the superduties are c-channel......they also don't ride as well
Yup, has nothing to do with a +-2000 pound higher GVW.
Quote:
Originally Posted by Ryan50hrl
....handle as well
I think sombody watches too many commericials.....You forgot that they don't handle as well going backwards either.
Quote:
Originally Posted by Ryan50hrl
....they aren't nearly as quiet.
Really? You have actual proof of this??? Recent Motor Trend test has the Tundra as the quietest truck they've ever been in. (I know you're comparing the Super Duty but I threw the MT test in there for effect)
Quote:
Originally Posted by Ryan50hrl
.....and they're not 5 star safety rated....but i'm sure boxed frames don't have anything to do with that.....
They're not??? So Ford's Super Duties are unsafe??? (I honestly didn't know that, thanks)......the truck I purchased (without the boxed frame) actually got the insurance institutes safest ranking for pick ups...whew, dodged a bullet there by not getting another Super Duty.
Last edited by DOHCmarauder : 02-05-2008 at 02:21 AM.
I'm guessing the GVW makes 'em exempt from testing.....do you think someone was making up that they don't get 5 stars???
[I guess that's true if they don't get rated ]
Just found the answer, and it looks like you're right. All vehicles above 8500lb GVWR are exempt from crash testing and fuel economy testing. Looks like it won't be so hard to built a truck after all.......
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If we want US auto manufacturers to survive, we all have to get over this macho, mine is bigger, faster than yours attitude.
The US has fianally realized what a fossil fuel based economy does. It make us dependant on foreign suppliers. "Over The Barrell"
The futureof US manufacturers, if there's going to be one, is going to have to be in lighter, more effcient vehicles. I cannot beleive that 80% of F150 owners need a 10K lb towing rating. And a 400 HP engine.
I'm a Contractor and need trucks to do my job. I own a couple of older F250 Diesels, because they are the most efficient trucks I can find, that'll do the job. If you look at most of the trucks on the hiways, you cannot say the same thing.
We need to get the F150 back to what it's supposed to be, a 1/2 ton truck. Not a glorified, over grown commuter vehicle. It needs to loose 1500 lbs, and get more efficient. For the sake of the whole country. Let alone, our beloved Ford Motor Company
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