H-beam and I-beam rods

[cruisintalonawd]

whats the difference in them other then the H and I part

[jcurcillo]

For years the battle has raged on as to which is better, an I-beam or an H-beam. In pure tension and compression, they are both equally capable, assuming equal cross-sectional area. But when you add the fact that some components of the combustion event attempt to screw the piston down the cylinder, the greater distance from the centerline of the pin to the edge of the beam gives the H-beam an advantage in resisting such twisting forces. We’ve seen both designs used successfully in a wide variety of extreme applications, so the jury is still out. Perhaps the biggest advantage of the H-beam design is that it gives the manufacturer more flexibility when sculpting the rod into the most effective form from a strength-to-mass standpoint.

I-Beam on left. H-Beam on right.

[TunaTalon]

The strength of a rod in tension is mostly determined by it’s cross sectional area, not the shape. All else being equal, heavier rods are stronger in tension. Resistance to bending force is more strongly influenced by shape. For equal weight, the H beam rod will handle more bending force. The V8 hot rodders have been using H beam rods for years as upgrades.

For much more about rod design see http://www.grapeaperacing.com/GrapeA...ectingrods.pdf

[jcurcillo]

Keep in mind, a heavier rod equals more rotating mas. Low reving, high horse power engines would gain more from a heavier H-Beam rod. A lighter I-Beam rod would be more suitable for high reving engines.

[TunaTalon]

Originally Posted by jcurcillo

Keep in mind, a heavier rod equals more rotating mas. Low reving, high horse power engines would gain more from a heavier H-Beam rod. A lighter I-Beam rod would be more suitable for high reving engines.

All true. I selected H beams for my stroker project because all of my design compromises were made in favor of low end torque. Your mileage may vary.

For more on how rod forces are affected in the 4G63 by stroking for more torque or destroking for higher RPM, please see page 36 of http://www.kidzuku.com/StrokeOrNot.pdf.