More news about the 2015 truck frame
 

2015 Ford F-150: Engineers Create a New Frame - PickupTrucks.com News

Discuss.

Sounds good. Now, if it drives, rides smooth with no driveline shuddering, etc., no Ecoboost whatchamacallit mess failures, no 5.0 oil consumption issues, we'll be good!:-drink

well I`m already sold just a question of them actually being on the market for sale....I hope race red is still a factory color choice though :-X04

So 10 million miles of intense driving. Was that actual or simulated? Seems like real world testing is too expensive to even do but if they did it most of the problems would be found and be fixed.

It says lab miles... but you can be assured that many thousands, probably millions of miles have been spent conducting real-world testing as well.

Believe the 70 ksi yield strength steel is a marketing ploy.

Believe the main design criterion in the frame design is rotational stiffness.

Boxed side rails compared to open side rails increases rotational stiffness.

Additional cross members also increases rotational stiffness.

Have a 1973 F250 with 8100 lbs GVW with all open side rails and five cross members which are all riveted, not welded. Can find no welds in the frame. Curb weight equals 3700 lbs.

Believe the GVW rating for the 1973 F250 is based on "in plane" bending and not rotational stiffness.
The open rail frame would have much less rotational stiffness
than the newer boxed rail frame with welded cross members.
Eight welded cross members would result in greater rotational stiffness than five riveted cross members.

Resistance to frame twisting is felt when hitting big pot holes at 65 MPH.

70 ksi yield strength steel has basically equal elastic modulus properties as 40 ksi or 50 ksi steel. Given equal cross section, each alloy will deform equally up to the yield strength.

So, given two identical geometry frames, one fabricated of 40 ksi yield strength steel and the other fabricated of 70 ksi yield strength steel , both will deform equally with same applied load. The state of stress in the material is a function of the deformation. So, if each frame deforms equally then both frames will have equal state of stress developed in the material. The higher strength steel will take more load and more stress before yielding.

In structual engineering deformation limit governs over stress limit as a design criterion in some circumstances. Believe a truck frame is an example.

Also the higher strength steel is more sensitive to fatigue cracking than the lower strength steel. The lower strength steel is actually more durable and less prone to fatigue cracking.

In order to have multiple thicknesses of the boxed frame rails, sections must be welded.
Welds are a source of stress concentration and fatigue cracking.

However, it appears the new frame is more weight optimized than previous designs from a geometry standpoint.

You make a strong point about rotational stiffness. When GM first marketed their boxed frame for the HD trucks, they would drive a front corner of the truck over a steep ramp to illustrate that nothing happens and all wheels stay on the ground.
When they drove a superduty over the same ramp, the tailgate would pop open and bend like a pretzel among other damages. Of course, this was a GM commercial but it made their point.

Considering that today's F-150's can be had with 7200lb, 7700lb and 8200lb GVWR's and can tow up to 11,300 lbs, it shows great advances in technology in frame materials, how it's formed and how it's designed.

In truth, the average joe like me doesn't really care about all this frame stuff as long as it protects me in the event of a side impact.

Like the Ford F150 commerical where a pallet of concrete blocks is dropped in the middle section of the bed, resulting in an impact load on the frame.
This test proves the structural integrity of the frame for "in plane" bending.

The light truck frame is the backbone of the vehicle and sets it apart from a unibody automobile. Some folks use a light truck as an automobile for style, while others use it to haul payload or trailers.

Believe Ford designs the frame to meet the demands of the latter.

To my knowledge there is no industry standard on light truck frame design and no industry standard on testing.

With all the robotic welds in the multiple sections of the new 2015 frame it is imparative that extensive dynamic testing is performed on the frame structure.
Believe that FMCO is meeting that demand for the new generation F150, light truck.

After doing some reading of what people have said about frame flex...its good too have so the frame does not snap at any point. But there is a possibility of too much.

Test data on the 2014 F150 frame shows greater rigidity in torsional mode than the other three full size light truck makers.

Since the new 2015 F150 frame is ~75% high strength, 70 ksi yield strength steel, compared to ~25% higher strength steel for the out going frame means the incoming frame would be less rigid to justify the additonal use of high strength steel.

A less rigid frame would result in greater deflection and resulting greater state of stress in the material requiring a higher strength steel , which is consistent with the media release information indicating the new frame weight is reduced by 60 lbs compared to the out going frame.

Design weight optimization may compensate for the reduction in overall frame weight resulting in equal torsional rigidity to the outgoing frame.

The suspension will perform better with less torsional compliance.