H-beam..I-beam

[Fired Up]

Which is considered the stronger rod? Assuming both are steel is there one that is considered "better"? I don't know enough about rod design or dynamics.

[BGMAN203]

I think H beams are stronger.

[shaun]

This may not be true and i could be misinformed, i'm no expert but if i recall correctly H beam rods are suppose to be better for FI builds where I beams are better for NA applications.

[BGMAN203]

When you say FI build, what do you mean?? Fuel Injection??
I assume when you say NA build you mean carbs and not blowers, turbos or NOS?

[Infomaniac]

I cannot speak for the design, but the stronger rods are "I" beam.
Would have to ask the mfg's why they choose "I" beams for the stronger ones.

[cstraub]

I-beams are stronger. I have had this discussion with French Grimes and Kirk Jager on different occasions. It has to due to the transfer of stress to the pin area as the rpm increases. Both say H-beams are fine for lower rpm, under 6000, and are a fine choice. For blown and turbo applications they both have said an I-beam would be the rod of choice.
Chris

[superdave013]

Are my Carrillos are H or I beams?
What ever they are they are some tuff mofo's. I think I'll keep 'em.

[INEEDAV]

I thought that the h-beam rods were generally rated for more horsepower than the I-beam. Now I am confused:confused: .

[cstraub]

Most of what the general racing population sees is the forged I-beam stuff, and yes it is rated lower. When you get into the billet stuff is where the I-beams get the 1000 HP ratings or more.
Most of you realise who I work for and that we do the majority of the Cup stuff. We get fully assembled Cup short blocks all the time for checking clearances for pan fabrication. These engines contain I beam rods. At 830HP at 9500 rpm for 500 miles, I would call that an endorsement for I-beams.
Chris

[INEEDAV]

Originally posted by cstraub69
Most of what the general racing population sees is the forged I-beam stuff, and yes it is rated lower. When you get into the billet stuff is where the I-beams get the 1000 HP ratings or more.
Most of you realise who I work for and that we do the majority of the Cup stuff. We get fully assembled Cup short blocks all the time for checking clearances for pan fabrication. These engines contain I beam rods. At 830HP at 9500 rpm for 500 miles, I would call that an endorsement for I-beams.
Chris
Chris
When rods experience catastrophic failure, where is the primary location of the falure?
Billy

[Fiat48]

Originally posted by superdave013
Are my Carrillos are H or I beams?
What ever they are they are some tuff mofo's. I think I'll keep 'em.
Carrillo's makes both but sure they are H beams. Those rods are in a class by themselves. More to rods than H beam or I beam. I have seen Carrillo's and Crowers so abused and the rod totally beat out in the bearing housing area(spun bearings) yet the rods hung on for dear life and never came apart.
Beware the Carrillo copycats.
If I were building a steel rod motor my choices would be:
Carrillo
Oliver
Lunati I beam (my rod of choice currently)
Crower I beam
Because I have never seen a failure.
But then I have used the 7/16 Chevy dimple rod in 1200 Hp applications and never had a failure either.
Most rod failure I have seen have been a bolt failure. I did see a set of Manley H beams come apart right in the middle of the beam in a 800 Hp type application. May have been a fluke but no Manley rods for me.
Lots of Eagle rods out there and I am not hearing bad things so I guess they are o.k.

[superdave013]

yeah, I had a set that was really old and RPM'd those things in the high 8K range all the time.
When I went stroker I just could not see buying anything else. This new set is gun drilled to oil the wrist pins. Not an everyday set of cheepo knock offs for sure.
I'm sure there is better like the one's Chris sees in those cup engines. I just didn't know about them when I put my coin down. I'm still glad I went the way I did. I always broke postions at the wrist pin area.

[cstraub]

Ineed,
alot of variables here depending on a whole lot of things.
Most H-beams I see are at the big end. Bolts, bearings out it, things like that. Most have been mild rpm engines.
High rpm, pin area. Depending on piston speed their is a point at which the stress on the pin area becomes a jerking motion, this point varies, but once the engine reaches that the load force on the pin area is multiplied greatly.
Let me add this, alum. rods are intended for high rpm engines. Ever see an H-beam designed aluminum rod? I haven't in a high performance application.
Chris

[shaun]

FI = Forced Induction
NA = Naturally Aspirated
I could have it backwards, or wrong, just what i heard.

[INEEDAV]

Originally posted by cstraub69
Ineed,
alot of variables here depending on a whole lot of things.
Most H-beams I see are at the big end. Bolts, bearings out it, things like that. Most have been mild rpm engines.
High rpm, pin area. Depending on piston speed their is a point at which the stress on the pin area becomes a jerking motion, this point varies, but once the engine reaches that the load force on the pin area is multiplied greatly.
Let me add this, alum. rods are intended for high rpm engines. Ever see an H-beam designed aluminum rod? I haven't in a high performance application.
Chris
The pin area being high failure kinda surprises me.
It would seem, to my feeble mind, that the stresses on the pin end would be primarily tensive and compressive and therefore easier to engineer for. Which granted there is a lot to be said about cycling metal between tension and compression and how much it takes before it yields.
However the lstresses on the big end, even though it is much stouter in build, seems like it would see more abuse with the tension, compression, and lateral loads that it sees from being "thrown" around in a circle.
Your right I have not seen a h-beam aluminum rod. Actually I have seen only a couple aluminum rods at all. I live a pretty sheltered life:D.
I am half tempted to draw both in ProEngineer and see what it looks like when ran through a simulation and stress analysis. Maybe that would help me to see better the failure mode when those failures do occur.
Thanks for the explanation Chris.

[cstraub]

Ineed,
Your welcome. I am far from any engineer, just alot of "hands" on experience and a wealth of info from industry gurus.
Chris

[superdave013]

INEED,
They fail when trying to turn the piston around. You send it up real fast and it wants to keep on goin. A light piston gets heavy real quick when you try and change it's direction of travel at a high RPM. I've always had the wrist pins try to pull ot of the pistion.

[Fiat48]

Pay attention to these guys that see these motors through many applications and get the feedback on what works and what doesn't. Hard to put a price on that and all you have to do is listen.
Why my signature is what it is. And Chris knows it's true.

[INEEDAV]

Originally posted by Fiat48
Pay attention to these guys that see these motors through many applications and get the feedback on what works and what doesn't. Hard to put a price on that and all you have to do is listen.
Why my signature is what it is. And Chris knows it's true.
I am listening. I just like to understand a subject as well as I can before I move on to the next;) .

[cstraub]

I can appreciate that. Years ago I was given the definition of a salesman: one who solves problems. With that I figured out the first sale to a customer is not as important as the 100th. With that said, I give the advice l think is best for application and for him in the long run.
Chris

[INEEDAV]

Originally posted by cstraub69
I can appreciate that. Years ago I was given the definition of a salesman: one who solves problems. With that I figured out the first sale to a customer is not as important as the 100th. With that said, I give the advice l think is best for application and for him in the long run.
Chris
To give you an idea of how I like to ask questions, I have two full notebooks of PM's and emails that Fiat48 has answered for me, totaling over 700 pages. There is another folder half full of questions I have asked others here on the boards. Never throw information away, ever.

[Jrocket]

Oliver!!!!!
Now what about rod bolts,who has the best?

[Fiat48]

I think ARP has about taken over the bolt market. I'm seeing everything with arp.
Ineedav:
700 pages!!! :eek:

[cstraub]

A-1 has the best stuff. SPS is next or as good. MSA after that. then the rest.
chris

[Fired Up]

I'm glad I threw the question out there. As usual, those of you with the know and the know-how came through with good info......Thanks.............my notebook is getting thick too!

[DogHouse]

I have two thoughts on why I beam is better than H beam:
First possibility is that the cross sectional moment of inertia (a measure of cross sectional area and how that area is distributed away from its center) for the I beam is greater than that for the same cross sectional area of the H beam. This comparison is illustrated by looking at two pieces of tubing, one small diameter thick wall, and one large diameter thin wall. When both are the same weight, the larger diamter tube will be stiffer. I'd have to dig out some old texts and try to remember how to calculate that shiznit to know for sure.
Another possibilitiy is that the H pattern or I pattern, given identical cross sectional moment of inertia, will provide the same strength as long as it is stressed in pure tension and pure compression. However, when you mix in any sort of bending stress in one plane or another, things start to vary and one will buckle or yield before the other. Since a rod is connected on both ends by a pin and bearing, those connections can only provide bending moment in a single plane aligned with the axis of the bearing. The I beam rod has it's largest cross sectional area aligned so as to provide the greatest resistance to the bending moment that the piston may impart if the combustion pressure isn't perfectly distributed across the face of the piston or if the weight distribution of the piston isn't perfectly even. That means that the I beam rod should be more resistant to deflection when stressed.
A third possibility is that I'm full of sh!t! :D
-brian :confused:

[INEEDAV]

Originally posted by Fiat48
I think ARP has about taken over the bolt market. I'm seeing everything with arp.
Ineedav:
700 pages!!! :eek:
That doesn't even include the threads that I have printed off of here on subjects that caught my interest. Lot of good information on here. I actually still have to print out a few hundred more pms from the last 6 weeks or so. Im writing a book:D.

[INEEDAV]

http://www.hotrod.com/techarticles/82378/
Not a bad read on the subject.

[DogHouse]

Originally posted by INEEDAV
http://www.hotrod.com/techarticles/82378/
Not a bad read on the subject.
That was interesting, especially the sidebar comparing H and I beams. They concluded that the cross section layout of the H was better. I'd like to see some measurements of two equal weight rods and the math to compute the moment of inertia to see what the real answer is. My gut feel is still I beam but the math would prove one way or another.
-brian

[INEEDAV]

Originally posted by DogHouse
That was interesting, especially the sidebar comparing H and I beams. They concluded that the cross section layout of the H was better. I'd like to see some measurements of two equal weight rods and the math to compute the moment of inertia to see what the real answer is. My gut feel is still I beam but the math would prove one way or another.
-brian
I saw another website dealing with that more while I was researching that yesterday. If I come across it again I will sent it to ya.

[Dave C]

Good stuff guys. thanks.
I have a picture somewhere of a Carillo rod with the piston still attached that got tossed out the side of the pan, from a spun bearing. Its mangled beyond belief and blue as hell but still connected to the piston!!! Bolt finally gave way.
I agree with Fiat. If someone is paid to break this stuff and find a way to make it better I am gonna put more weight into his opinion.
CSTRAUB... correction. first job of a salesman..... earn commission then help customer ;) ;)
Originally posted by cstraub69
I can appreciate that. Years ago I was given the definition of a salesman: one who solves problems. With that I figured out the first sale to a customer is not as important as the 100th. With that said, I give the advice l think is best for application and for him in the long run.
Chris