Alum rods in diesel?? January 04, 2012 09:21PM
Is anyone using alum rods in there diesel puller? Building limpro and wondering if going to a alum rod to save weight with less rotating mass would be a benefit? Not sure if they would hold up to abuse of a diesel. Thanks in advancne for any info.
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Re: Alum rods in diesel?? January 04, 2012 10:25PM
There are definately some guys using them and some of the top builders selling them. But, Aluminum doesn't have as high a tensile strength as cast or billet. So they will stretch over time and you can plan on replacing them every couple years for sure.
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Re: Alum rods in diesel?? January 05, 2012 12:49AM
Are the alum rods cheaper than billet rods? Other than weight what would be the benefit of the alum over billet?
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Re: Alum rods in diesel?? January 05, 2012 03:15AM
billet is not a material. are you talking about billet aluminum rods vs cast aluminum rods or billet steel rods vs cast steel rods or billet steel vs cast aluminum or billet aluminum vs cast steel. what about forged rods? Yes that's right we need to know if we are talking about forged steel rods or forged aluminum rods. material matters. and thats not even including all the different alloys for the given material.

billet, casting, forging are manufacturing techniques and not materials so please be more specific.
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Re: Alum rods in diesel?? January 05, 2012 03:39AM
yep he's right. "Billet" mean machined from 1 solid piece. I love how people throw the word billet around and most people will throw big money around to get it!
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Re: Alum rods in diesel?? January 05, 2012 05:14AM
Billet steel rods would be my choice and they are more durable for a Diesel powered engine. If you are planning on running Alcohol, i would go with billet aluminum for sure. Billet aluminum rods won't last very long in a high horsepower Diesel engine. The high compression of a diesel puts to much stress on the rods.
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Re: Alum rods in diesel?? January 05, 2012 10:51AM
Of course properly forged steel rods would be stronger then billet steel rods!!
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Re: Alum rods in diesel?? January 05, 2012 12:33PM
Sorry about the confusion. I was just wanting to kno benefit of using an alum rod ovr a steel one and if pullers are using them in there diesels.
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Re: Alum rods in diesel?? January 05, 2012 12:52PM
deutz,,,,,,factory aluminun !!!!
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Re: Alum rods in diesel?? January 05, 2012 03:28PM
Must be new Deutz, older ones had steel rods. MACK
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Re: Alum rods in diesel?? January 05, 2012 04:06PM
Brian,

I think you better do some homework here.

Bear with me and please research my comments.... My metallurgy class was on saturday mornings in college. Some details are still a little foggy!!!

Assuming you could use a rod as forged, I concurr. Typically a billet rod is produced of 4340 at 40 Rockwell. A forged rod would be in the mid to high 20's by process. The higher heat treat would yield a greater set of material properties. So you say, heat treat the forgings... By doing this, you would be resetting the grain structure to bar type form. Therefore neglecting most benefits of the forging process. The only benefit from forging that I can see is a compression of material to yield a higher density. I would say at this point the cost would not justify the minimal gain...

Brad
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Re: Alum rods in diesel?? January 05, 2012 04:24PM
bl913f
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Re: Alum rods in diesel?? January 06, 2012 04:28PM
Heat treating is performed at a lower temp than the forging temp. Heat treating a forging will alter the grian structure, but not the grain flow produced by the forging process. The reason bar, plate, or round stock has grain running its length is because that is how it was formed. The hot rolled process is very similar mechanicly to forging as the near melting steel is drawn into desired size and shape by rolls and dies. This results in the longitudinal grain flow patterns found in these shapes. You do not however get the bigger advantage of forging that relies in the compressing of the material produced by the forging process. This greatly improves fatique and fracture failure resistance. It is similar to shot peening only at a much higher level! The big drawback is of course expense and the inability to change part dimensions much without creating new forging dies. Since most rods are forged with at least 3 dies that would get pretty pricey!
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Re: Alum rods in diesel?? January 06, 2012 11:25PM
Thats all neat info but still doesnt really answer question of benefits of using an alum rod ovr a steel one in a diesel...
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Re: Alum rods in diesel?? January 07, 2012 12:40AM
The only benifit would be weight reduction so you could run higher rpm's. Since diesel burns pretty slow and won't make power at lots of rpms like 7000+ I would say aluminum rods offer no benifits in a diesel pulling application. Aluminum is roughly 1/3 as strong as steel for the same size and shape. If you were running a long stroke small bore engine aluminum rods would be of more benefit than in a big bore short stroke application from a weight standpoint, but since a long stroke motor with the same deck height runs a more severe rod angle usualy it applies more bending stress to the rod and as such aluminum would be a tradeoff in performance at best. FWIW I would not build an aluminum rod diesel pulling engine as I think more power can be found other places without sacrificing as much durability and maintenence costs.
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Re: Alum rods in diesel?? January 07, 2012 10:00AM
No benefit whatsoever in a diesel application.The only reason to use it there would be POSSIBLY less damage to parts in the event of one letting go.
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