Guess what smashed this plug gap shut
#51
Nein. I-beam configuration will always be stiffer in bending for the same weight than H-beam. That's just how it is. Axially if they are the same weight then they are equal in stiffness. If an H-beam is stiffer than I-beam then it weighs more, and you could have made a stiffer I-beam.
Google rod manufacturers that manufacturer both.
Google distributors that sell both.
#52
The reason why there are different designs is because there are different applications. Let's throw Tri-Beam into the mix.
The strongest rods available for the Ecotec that I have found are all I-Beam type made by Manley.
The strongest rods available for the Ecotec that I have found are all I-Beam type made by Manley.
Last edited by Henry3959; 08-02-2017 at 05:24 PM.
#54
Senior Member
iTrader: (1)
I have seen that video before. "All things being equal, the H-beam is stiffer but the I-beam is lighter" makes zero sense. Weight is HUGE (see my comment above) and should absolutely be factored. If weight isn't equal when comparing, then what geometric design constraint is? If you include weight (which you really should) there is absolutely no advantage to H-beam.
Bending stiffness: adv. I beam
Axial stiffness: equal
Buckling: adv. I beam
Crippling (unlikely): equal
I also asked a seller of rods at SEMA. The best he could do was "it doesn't matter because they usually fail in tension." Since I have seen plenty of pictures of bent rods, I just left.
Last edit: Looks like the first comment on Summit's youtube video nailed it.
Last edited by exninja; 08-02-2017 at 06:06 PM.
#55
Senior Member
iTrader: (1)
Taking a quick look at those tri-beam: the reason that they did that is in bending, the further away from the neutral axis the stiffer in bending it is. That is why I-beam is better than H-beam. They moved some material further out so it becomes stiffer in bending. If the cross-sectional area is the same then it is the same stiffness axially, regardless of configuration.
#56
Reciprocating weight is always a concern for high revving gas burners. Not so much for 3000 HP Diesels running H-beam 4032 billet steel rods.
#57
Senior Member
iTrader: (1)
I wasn't being Cobalt specific, I was being general and what is available to the public to purchase. Still with all things for an application being equal, there is more weight and strength in the H design due to the higher mass.
Reciprocating weight is always a concern for high revving gas burners. Not so much for 3000 HP Diesels running H-beam 4032 billet steel rods.
Reciprocating weight is always a concern for high revving gas burners. Not so much for 3000 HP Diesels running H-beam 4032 billet steel rods.
#59
Senior Member
iTrader: (1)
I haven't researched this much but the main difference that nobody seems to be mentioning is the orientation of the beams. Both stiffness structures are really similar profiles just the ratios are different and oriented 90 degrees to each other. I-beam has a narrower thicker flange and H-beam has a wider thinner flange as you can see by the letters and H is just a squished down I. From a column standpoint like has been said either orientation could have the same resistance to buckling. However, looking at pictures it looks like rods tend to bend in the same plane as radially around the crank shaft. This would give the I-beam rod more stiffness or resistance to bending to correctly combat the way your rod will typically bend.
If you have ever seen and I-beam in a structure (with gravity) you will see the flanges run horizontally because they need to resist bending vertically. An analogy to using an H-beam in a typical structure would be like taking a wide-flange I-beam and putting it on its side so the flanges are now on a vertical plane. With my practically non-existent understanding of con-rod design the H-beam design does not seem to be optimized to combat bending in the typical direction a rod will bend.
Found this picture that is a good visual comparison of H-beam vs. I-beam rod orientation
If you have ever seen and I-beam in a structure (with gravity) you will see the flanges run horizontally because they need to resist bending vertically. An analogy to using an H-beam in a typical structure would be like taking a wide-flange I-beam and putting it on its side so the flanges are now on a vertical plane. With my practically non-existent understanding of con-rod design the H-beam design does not seem to be optimized to combat bending in the typical direction a rod will bend.
Found this picture that is a good visual comparison of H-beam vs. I-beam rod orientation
The following 3 users liked this post by jdbaugh1:
#60
Senior Member
iTrader: (1)
Excellent find jdbaugh1. Obviously I haven't researched enough to know just what dimensions the rods are using, but based on the "H-beams are stiffer but heavier" statement my guess is that they are making H-beam rods like the 3rd from left configuration. They're not as efficient in bending but they have more material so they resist axial (tensile or compressive) loading better than a lighter I-beam rod. My point was that you can design an I-beam rod that would have a better moment of inertia (I) than the same-weight H-beam rod but resist axial loading equally. On top of it, an I-beam would be much easier to forge so I'm still left wondering why people started doing H-beams in the first place. They couldn't have been an engineer.
#61
Found 3 like this... Cyl 1,2 & 4. All toward the intake side. Still contemplating what's going on here. Top Rings are all free and as clean as can be. Surprised how nice the cylinders and skirts look for 126k.
#68
Senior Member
#69
the problem isnt the pistons being weak, its the ring gaps are too tight for boost. what happens is with the extra heat the rings will expand more and when the end gaps butt together the ring has to go somewhere so it pushes up breaking the piston. the ecotecs have the top ring so close to the top of the piston it breaks so easily. other engines with the top ring lower down the piston will take a little more before it breaks the piston, however in the meantime it will scuff the hell out of the cylinder wall.
i think the stock pistons would last a lot longer in the 2.2 and 2.4 under boost if you opened the ring gap up. factory top ring gap is between .008-.014", if they were opened up around .018-.022" for the top ring they would be a lot happier.
i think the stock pistons would last a lot longer in the 2.2 and 2.4 under boost if you opened the ring gap up. factory top ring gap is between .008-.014", if they were opened up around .018-.022" for the top ring they would be a lot happier.
So first are the OEM specs for the 2.4 LE5. I will just compare the top compression ring for the sake of simplicity.
6-12 thousandths
Then the SAE recommended ring end gap.
10-20 thousandths
Now, file to fit your application. In this case, my application.
19.25 thousandths