I beam vs H beam

[Barry_R]

Originally Posted by Dominik

The notch effect from the oil is highly reduced using aftermarket H-Beam vs stock I-Beam.

What is a notch effect?

[RICK LAKE]

Guys the differents between rods is that and I beam is stronger and far less flex. The H rod has more flex but is lighter. depending on rpm range is which rod you go with. Less weight, easier and faster for rpm spin up. I run "H" rods and have had no problems with them. I do limit my motors to 6,500 rpms. If I was looking for more rpms, I would go to an "I" rod. It's all about the application. rod big end size too. Honda 1.88 rods are a trick to run but know of guys doing this with a light piston. Rick L.

[Dimis]

I work at a Uni & today I bumped into a mate of mine at lunch who is a mechanical engineer academic (Masters degree) who happens to also work on the drive-lines for Caterpillar (he is just as hands on as theoretical & one of few academic engineers who actually knows how to twirl a spanner), so I asked him the question (Duh... I really should have thought about this earlier).

Below is a summary of his theories:

The I beam is stronger in compression and can therefore transfer a greater load to the crankshaft during the power stroke & the H beam has slightly less strength on the power stroke but has more strength in tension, provided that all else is equal.

He also concluded that it's all about piston speeds.
If you're building a low piston speeds ie: low RPM or short stroke motor that makes lots of power or torque use I beam.
If the motor is going to experience high piston velocities - ie: high rpm or long stroke, then use H beam.

Practical summary -
A NASCAR for example would most likely experience faster piston velocities than an F1 engine with high revs but very short stoke.
Thus NASCAR most likely got for H-Beam & F1 most likely for I-beam theoretically (if they didn't custom design).

The H beam will fail first if the rod is overpowered on the power stroke. The I beam will fail first if the weight of the piston & pin assembly is too great for the rpm. This assumes that all else is equal.

He was also adamant that the quality of the material & composition is more important than weather the design is an I or H beam & that either would work equally well in most cases. Thus in 100% agreement with Barry R.


I asked this question as I'm trying to research the parts I'll use for my engine build.
My conclusion - I or H beam is not relevant as brand quality in this instance and for my application.

Many thanks to all for your responses thus far.

[fordracing65]

Go with the H beam, it costs more than an I beam on Keith crafts web site so it has to be better.

[elmariachi]

Originally Posted by RICK LAKE

If I was looking for more rpms, I would go to an "I" rod.

Originally Posted by Dimis

Below is a summary of his theories:

If you're building a low piston speeds ie: low RPM or short stroke motor that makes lots of power or torque use I beam.
If the motor is going to experience high piston velocities - ie: high rpm or long stroke, then use H beam.

Your opinions (or that of the Cat guy) are direct opposite of one another.

[blykins]

Originally Posted by RICK LAKE

The H rod has more flex but is lighter.

Not always the case.....

A lot of H-beam rods are much heavier than their I-beam sibling...up to 50-60g difference.

[Jerry Clayton]

Depending on the use or maybe budjet--either type can get the job done---



One thing i do like about the I beam is how you can oil the pin--seems all the aftermarket cranks and rods no longer have the oil spray holes to oil the upper inner parts of the engine--

Any way, I'm glad that there was some dialoque on the subject as I had posted that same artical on another site and altho several views, only one reply and that was just basicly to tell me Hi---

[Dominik]

Okay, maybe my german-english translator failed me:

You polish metal parts to make them resistant agains notching (ie. from oil). A wider beam has a bigger surface to attract such failure ("Kerbwirkung").

Imagine the oil wasn't liquid but little knifes trying to dig into the metal.

[RICK LAKE]

Elmarachi Jim goto Grapeaperacing.com and read their theories on connecting rods. I do agree with them. A also said that alot of this has to do with application. The other issue is that the exhaust stroke is the hardest cycle on the connecting rod. No loads. Weight of "H" or "I" rods can be the same. I like the fact of spreading out the load on an "h" rod over a "I" rod. Most rods with "I" design have a narrowed out center to save weight. So to some degree they are an "H" rod. They are just not grooved out of the centers. Like I have been looking at GPR rods of aluminum for next motor. with proper setup and warmups, see no problem with these rods working for years and weight about 110grams less than BBC rods. This also means dropping weight in the crank shaft. Need more clearance for rod to grow in motor of about .005-.008" depending on rpm. Other side note, there is a big different between a diesel motor bottom end and a gas motor. Just compression alone and the extra amount of hours or miles a diesel runs more than a gas motor. Oiling system is different also. Can't compare apples to bananas. Rick L.

[ERA Chas]

Rick-Linkie no workie....

[Don]

*** Question to Callies Performance Products:

I Beam vs H Beam connecting rods:

What are the pros, cons, of each type ?
Is the metal etc the same in both or ?

*** Reply from Callies: Quote

" For Callies (mentioning that because the answer may and will probably differ from company to company via engineering and product design) Our H and I-beam's are made out of the same metal and everything, the main difference for our product is the H-Beams tend to be a little less expensive (due to ease of machining) and will give a little less clearance and not be as strong and are a tad bit lighter. So the inverse, the I-beams are more expensive, give a tad more clearance and are heavier and stronger. Main reason behind the strength and weight qualities is in the way they were designed. Other companies H-beams are heavier and stronger, where as we are the inverse, all comes down to design of the rod. "

[RICK LAKE]

ERA Chas Got the name right now. Chas. Grapeaperacing.com Rick

[ERA Chas]

Originally Posted by RICK LAKE

ERA Chas Got the name right now. Chas. Grapeaperacing.com Rick

Thanks, 1000 WHP has my attention. Will study their findings and who they are.