h beam or i beam

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06-02-2008, 05:56 PM

#31

onlyflash944

1.5 BAR

Join Date: Oct 2006

Posts: 964

Re: h beam or i beam

Quote:

Originally Posted by stenseltizm

Depends on which direction the rod will fail. I have no fact content to support my opinion so read on only for my 2 cents, I dropped out of ME like a drunk idiot.

I can't see how rods would have near the side loading to make an H rod better suited the application. The big end of the rod is basically reciprocating front to back at a high rate while the little end sits still. So the rod's going to want to flex in that direction. Then factor in the assembly going up and down in the cylinder and the forces trying to compress the rod it's going to want to bend in the same direction. Most broken rods I've seen were bent in that direction before they broke, not bent towards the other cylinders.

Isn't the point of an h or i beam to separate the material in the same direction as the bending force? basically separating it into two bars, one in compression and one in tension?

With those thoughts I've always wondered which is better and why aftermarket forged rods are H-beams, but I have opinions about cost of manufacturing.

Yes it does matter the direction they would fail. A I beam loaded from the oposite direction is a H beam. I would imagine that the majority of rod failures are in the form of bending. Since we can't be sure of the mode of failure (the plane in which the bending occours), it would be difficult to make any comparison without some serious destructive testing. Again, this depends greatly on many factors, and most engineers who have worked with this stuff could probably make a great guess as to what would happen.

06-04-2008, 12:52 AM

#32

cloud

1.5 BAR

Join Date: Jun 2005

Posts: 875

Re: h beam or i beam

Quote:

Originally Posted by onlyflash944

so you quoted an article that has no factual evidence on why they chose what they chose other than, "well those guys are using it, so they must be right"? There still is no valid comparison anywhere in any of your posts. I'm not saying you are wrong, I am trying to point out that what you are saying is based on nothing more than a belief that evidently can't be confirmed by you.

yes, your right. I haven't found any actually data on why it's stronger, but do I really need to. I'm sure they have already and this is creditable to me. I'm sure I could drudge up some structual engineering books that confirm this.

06-15-2008, 01:23 PM

#33

nascarfan

0.0 BAR

Join Date: Oct 2007

Posts: 0

Re: h beam or i beam

STOCK BEAM ftw unless its a d

06-21-2008, 07:11 PM

#34

E-b0la

3.0 BAR

Join Date: May 2006

Posts: 1,967

Re: h beam or i beam

Here's what I think.

An "H" and an "I" are the same ------- shape, just turned 90 degrees

You can make a rod wider perpendicular to the crank, as long as it clears the base of the bore, more easily than you can make the rod wider parallel with the crank. You'd be limited by the size of the journal.

Therefore the H beam provides more room to leave more material, thus making the rod beefier and stronger than the I beam.

Maybe the I beam is a stronger shape if the two rods use the same amount of material, I don't know. What I do know is H-beams for an LS are a lot cheaper and are stronger and beefier. Therefore buy H-beams

But I don't know ----. I'm done babbling.