Hydroforming

[rbattelle]

I've begun reading the latest TDR issue, and there's a short section in there (whose author I can't recall right now) which mentions the hydroforming technique used to make the 3rd gen. frame. He claims that hydroforming works just like stamping except that "water is involved". He also claims that the 4th side of the boxed frame is welded in place.



Correct me if I'm wrong, but I believe this information is wrong. Hydroforming of tubes is normally accomplished using a die and high pressure water, which is forced under high pressure (1000-6000 bar or more) into the center of the section you're trying to form. This causes the steel to expand to fit the shape of the die. The resulting part is all one-piece, so there is no welding required (which is the whole point - that you've eliminated residual stresses associated with welding).



From what I've read, the process is carried out at room temperature, but it seems to me that more efficiency (uniformity) could be achieved by doing it at elevated temperature. This might, of course, dictate the use of something other than water.



If Dodge is actually stamping the frame sections then welding them into a box, this is not hydroforming. However, I have heard of machines which use a single die and a large rubber bladder filled with pressurized water which is driven down into a piece of sheet metal backed by a die. Such a machine is similar to stamping, so it does not have the same strength benefits of a true tubular hydroformed part.



So is Dodge using tubular hydroforming on the 3rd gen. or not?

 

[fbaurley]

I may be wrong, but from what I remember from looking on th e dealers lot it looked like the box tube frame was 2 parts welded together. So maybe each peice was hydroformed and then welded together.

 

[rbattelle]

In hindsight, this should probably be in the 3rd Gen. forum...

 

[C Schomer]

I can relate to that Hydroforming stuff. It happens to my belly every time I go to a bar! Craig

 

[fj40charles]

Not exactly new news. The latest Corvette (LS1 motors) have been using this technique to build their frames.

 

[slavallee]

I believe my build sheet lists my frame as being hydroformed as well. May not be a strictly 3rd gen thing. Us 02 drivers seem to have the best of both worlds.

 

[ETOBICOKE]

It would seem that there are missconceptions about the hydroforming process. Most of the hydroformed frame members that I have seen have been made in short tubular sections under 6ft in length. The vehicle frames produced by this method consists of several swaged sections fitted together and then welded. One of the advantages of producing the frames in this way is that different truck models and wheelbases can be easily produced by just adding or exchanging sub assemblies. With stamped frame rails, several pieces of hard tooling are required for each different model. Think about the number of different cabs and wheel bases offered as well as 2 and 4 wheel drive versions of each, makes a strong pitch for modular frames. I have not seen any sizable heavy gauge stamped parts made by the die-draulic process, although it is very common to form large body pannels this way. Prototype and pre-production stampings are often produced with this process, utilizing soft tooling and then laser trimmed after forming. Hydroformed tubular frame sections offer some interesting possibilities, including producing tapered sections and transitioning cross section shape several times over the length of the part. It is also possible to produce parts with tight curves and deep offsets with this process as well. Currently I have only seen protype fully hydroformed frames, these are not as yet in production vehicles. However hydroformed frame cross members are very common on most late model trucks and SUV's and many cars have hydroformed engine cradles.



Neil

 

[Gary - K7GLD]

Personally, *I* suspect the "hydroforming" as it applies to DC produced stuff is to accomplish 2 primary goals:



1. Savings in production cost

2. Advertising hype



GM has been using THEIR version of "hydroforming" on Corvettes and some other products - including the frames on the GM truck for the last few years - and as a point of interest, the truck versions came under lots of fire in THIS group due to apparent weakness and visual flexing when those trucks are loaded anywhere near their rated load carrying capacity - Second, one significant hazard of the hydroformed frames as employed in the latest Dodge trucks has forced owners and manufacturers to totally re-design the method by which 5th wheel hitches are attached to their trucks, since conventional drilling and bolt-in methods are forbidden in those frames. .



Better? You decide...