What is a Fractured Connecting Rod? Cracked Rod? Advantages and Disadvantages.

in this video we're going to be discussing what is a fractured connecting rod [Music] when you first hear the term fractured split connecting rod you may be thinking this is what they're talking about but that's not what they're talking about and if you think about it for a little bit you'll come to this you see this is actually a fractured split connecting rod you can see that the two ends the connecting rod and the rod cap are actually broken apart they're not a machined surface something has cracked the rod cap off of the rod hence giving it its specific profile and the seam is pretty much invisible when put together you see it's not a smooth surface there are little pits and valleys and no connecting rod and rod cap are the same on a fractured rod now this is a traditional machined rod cap end you can see that it's flat there are machine marks right there and generally there's going to be an alignment dowel to help identify and match a specific end to a specific rod now both can use the same style bearings and both can be about the same weight and both can be found on the same style engines so that answers the question as to what a fractured connecting rod is but it doesn't answer the question as to why they exist well from the research i could do they first were developed around 2003 so they're fairly new invention or not really an invention but manufacturing process to a traditional connecting rod now why would a manufacturer go to this opposed to a traditional connecting rod well the reason is it's because it's about 30 percent cheaper to produce a fractured rod than it is to produce a traditional machined rod and if you think about it a traditional machined rod typically not always is manufactured by having your rod end and your rod cap in you then have to mate the two install dowels for alignment purposes and make sure that the two match a specific bearing journal size because the rod bearing is going to fit in that eyelet and if it doesn't fit correctly you're not going to get crushed on the rod bearing and then you're going to have a spun rod bearing which is a very bad thing now if you could machine a single connecting rod and then break it with basically no damage other than where the brakes at obviously you would have a much lower manufacturing cost that's why they exist now they're also supposedly stronger but that doesn't mean the entire rod is stronger just means they're stronger in the area where the two mating surfaces are in my experience though you don't see rods fail in that area if you do see them fail in that area it's probably because a bolt failed not necessarily the rod and generally if a rod is going to be damaged it's going to be from a spun rod bearing or from something hitting the piston like a hydraulic cylinder or a drop valve something like that and then typically the rod will bend or break not at the bearing end but on the shaft and closer to the piston from my experience okay so it sounds like all good things why do they still make traditional machined rods though well there's a couple disadvantages with a fractured rod as well one of them is for the mechanic i hate fractured rods and the reason for that is when handling them you have to be a lot more careful than with traditional rods and the reason for that is they're fractured but where the fracture is obviously it's not flat or smooth so there's all these little ridges and pits and valleys and they have to mate perfectly back together or they're going to become damaged so when installing pistons and rods into cylinders or putting bearings on cleaning these parts if you were to drop them if you are to hit them or ding them on something you can chip those pieces away and then they're not going to mate properly ever again and you basically just ruin the rod whereas a traditional machined rod a small mishap probably not going to damage your rod now the other thing is you need to be extra careful when installing the rod cap to the rod because you don't want any sort of oil any sort of lithium grease tire soap from the liner to get between the two mating surfaces since they're not flat you may get a spot in the cap and the rod there where that fluid or liquid gets trapped and it could damage the rod again so i don't like them mostly because assembling engines with them makes them much more fragile and much harder to basically just putting these parts back together are there any other disadvantages with them well even though they're cheaper to manufacture the manufacturing process is more specific and what i mean by that is you need more specialized equipment than just a way to measure your rod cap end you now have to use a special high carbon steel when you're making a connecting rod a fracture connecting rod whereas a machined rod you add more leeway on what materials you could use not only that you need specialized machinery to actually crack and score this rod opposed to something that basically just at the end product measures out okay so it does save you in the long run by producing each rod cheaper but it's more specialized manufacturing when it comes to producing each individual rod now can you mix and match traditional and fractured rods on the same engine or the same crankshaft and the answer to that is well it depends now i'm talking about cats specifically here you'd have to check each and every single manufacturer for a specific answer on this but on cat it depends because let's say a c7 those came with traditional machined rods and fractured rods especially if you're doing a rebuild traditionally they would have been made with a machined rod but if you've ever replaced a cylinder pack or a piston and got new rods they could have been machined or fractured and on the c7s cat says it's okay to mix and match them now the ones from the video was actually off of c13 and those are a little different traditionally they were machined but they make fractured rods now for them and you do not want to mix and match depending on what the rod cap end style is and the reason is not due to the manufacturing process but due to the weight differences in the rods you see there were two different styles on the rod end or the bearing end of the rod connecting rod and one weighs more than the other one does so if you mix and match those you'll have an unbalanced crankshaft not really the fractured rod fault there but it's something to keep an eye out for alrighty can't really think of anything else to talk to you about on these fractured rods hope you enjoyed the video thanks for watching [Music] you

Channel: Adept Ape

Views: 60,662

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Id: 5Nm5hNbtfoY

Length: 7min 36sec (456 seconds)

Published: Sun Jan 17 2021