Groden Aluminum Rods a must for serious power....Take 2!
Jan 10, 2008, 08:07 AM
#16
With the concern for fatigue failure with these Al rods, why doesn't anyone question the piston's fatigue life?
Also, is there any weight difference between the higher end steel rods vs the Al rods?
Also, is there any weight difference between the higher end steel rods vs the Al rods?
Jan 10, 2008, 09:21 AM
#18
Do you have any links pointing out the different stresses between the different engine components?
Jan 10, 2008, 11:24 AM
#19
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Aluminum rods are nothing like a steel rod when it comes to fatigue life. It's heat cycles is what kills them. There is no way of telling how long a aluminum rod will live, some have made them live for years, others have only had them live for 1-2 seasons. It just depends on how you treat them and what not. Main thing with aluminum rods is you MUST have the oil temp up a bit before you go a beat on it.
Bottom line is here if you need an aluminum rod then chances are you are going to be tearing into the motor long before the rods give out. There isn't really any reason for a 400whp car to have aluminum rods. Don't look at the rods as "hey those look cool and I can say I have aluminum rods" You need to determine if a aluminum rod is the best choice for your application. It's safe to say that an 800+whp car can benefit from aluminum rods considering at that power level the rod bearings get beat to all hell spinning the motor past 10k and with that amount of power with a steel rod.
Yes there are alot of people running aluminum rods on daily drivers. Most company's that build aluminum rods have changed there alloys for stronger, longer lasting ect. Alot of the bad rep that aluminum rods got were back in the day when people started to use them, they used a completely different alloys.
Here is some food for the thought on aluminum rods, I know it's not going to answer alot of questions, but you still get an idea.
http://www.rrconnectingrods.com/aluminumrods.htm
These are the rods that I run, after a full season of beating the snot out of them, they came out looking brand new!
Bad thing about them is they can't be reconditioned like a steel rod, simple fact cause of the bearing lock pin and the serrated rod caps. So if the rods ever go out of round from rod life, then there done, plain and simple. So to answer some questions, yes a steel rod will out live a aluminum rod, just the simple fact that you can recon steel rods while as a aluminum rod you cannot.
Aluminum rods have it's downfalls just as much as a steel rod does. It's a toss up really. Either the steel rod or the aluminum rod, both have there pros and cons.
Bottom line is here if you need an aluminum rod then chances are you are going to be tearing into the motor long before the rods give out. There isn't really any reason for a 400whp car to have aluminum rods. Don't look at the rods as "hey those look cool and I can say I have aluminum rods" You need to determine if a aluminum rod is the best choice for your application. It's safe to say that an 800+whp car can benefit from aluminum rods considering at that power level the rod bearings get beat to all hell spinning the motor past 10k and with that amount of power with a steel rod.
Yes there are alot of people running aluminum rods on daily drivers. Most company's that build aluminum rods have changed there alloys for stronger, longer lasting ect. Alot of the bad rep that aluminum rods got were back in the day when people started to use them, they used a completely different alloys.
Here is some food for the thought on aluminum rods, I know it's not going to answer alot of questions, but you still get an idea.
http://www.rrconnectingrods.com/aluminumrods.htm
These are the rods that I run, after a full season of beating the snot out of them, they came out looking brand new!
Bad thing about them is they can't be reconditioned like a steel rod, simple fact cause of the bearing lock pin and the serrated rod caps. So if the rods ever go out of round from rod life, then there done, plain and simple. So to answer some questions, yes a steel rod will out live a aluminum rod, just the simple fact that you can recon steel rods while as a aluminum rod you cannot.
Aluminum rods have it's downfalls just as much as a steel rod does. It's a toss up really. Either the steel rod or the aluminum rod, both have there pros and cons.
Last edited by evil_eagle; Jan 10, 2008 at 11:27 AM.
Jan 10, 2008, 12:49 PM
#20
As for the prospect of Al rods for long-term street use, the only ones who seem to be promoting this are the makers of the rods themselves, so it's hardly an objective argument (especially given the limits of legal liabilities). I'm all for experimentation (for those who are willing to risk it), but as for myself, I'd find said arguments more convincing with the support of even one published long-term study, or, even just one instance where an OEM uses them (and AFAIK, none will touch them).
As for engine stress engineering, I don't have any convenient links on combustion engine structural engineering at my fingertips, although there are some good books and studies floating about.
Jan 13, 2008, 12:33 PM
#24
4G63DSM, I don't mean to target you with this or anything, just discussing some things you have said.
Interesting, I was always under the impression that the Young's modulus is pretty constant for alloys of a given base metal. Can you give me some examples of these alloys that have a drastically different Young's modulus then the base metal?
The force transmitted through the rod will compress the rod regardless of material. Distortion energy may be a better term for what you are trying to describe then force though. Provided you are not over stressing the rod, the rod should not experience plastic deformation, only elastic deformation. Any energy absorbed by the rod will be released back to the crank at the end of the power or exhaust stroke as elastic deformation just reacts like a spring and the majority of the energy is eventually returned. The only energy not returned is from frictional losses within the metal, which should be negligible.
As far as I know, most aluminum rods actually stretch over time due to the stress seen as the piston tries to rip apart at top dead center when piston acceleration rates are the highest. I think you actually look for rod length increases.
Aluminum does not have a fatigue limit. Over time, it will fail from fatigue induced cracks. The fatigue life is based on the amplitude of the stress cycle as well as number of stress cycles seen. You are right in saying a fatigue life of 70,000 miles seems a little suspect without taking into context the amount of force seen by the rod. This includes the stress from high RPM and high power levels.
Although aluminum has a lower Young's modulus, you are neglecting that the aluminum rod has a cross sectional area roughly 2X larger then a steel rod. Overall stiffness is probably 1/3 lower then the steel rod, or less, not the 2/3 lower the Young's modulus initially looks to give. I don't have my design books around, but it would be interesting to see how the materials stack up on material selection diagram of density verses stiffness.
I am surprised to see etched inscribing on the side of the rod (stress risers).
But has anyone actually looked at what sort of alloys they use in these rods? there are some ridiculously stiff aluminum alloys out there, as well as some super lightweight steels, that have a lower modulus than your regular steels...
Anybody know of any Titanium rods for evos? how about Magnesium?
Anybody know of any Titanium rods for evos? how about Magnesium?
and finally, one more thought...
if alum rods are able to "cushion" the bearings, what kind of force does it take to actually compress the aluminum? Wouldn't this force be better utilized pushing the crank than deforming the rod? And while bearings seem to be a popular topic, what about the rod itself? Anybody ever measure rod length after heavy usage? if the rod itself, is able to "soften" the blow of each combustion event, some of that deformation will be plastic deformation. (Aluminum likes to crack, not rebound...) how much is allowed before the rod is scrapped?
if alum rods are able to "cushion" the bearings, what kind of force does it take to actually compress the aluminum? Wouldn't this force be better utilized pushing the crank than deforming the rod? And while bearings seem to be a popular topic, what about the rod itself? Anybody ever measure rod length after heavy usage? if the rod itself, is able to "soften" the blow of each combustion event, some of that deformation will be plastic deformation. (Aluminum likes to crack, not rebound...) how much is allowed before the rod is scrapped?
As far as I know, most aluminum rods actually stretch over time due to the stress seen as the piston tries to rip apart at top dead center when piston acceleration rates are the highest. I think you actually look for rod length increases.
I am surprised to see etched inscribing on the side of the rod (stress risers).
Jan 13, 2008, 08:03 PM
#25
What you are asking about is specific strength. The best aluminum alloys are around 90ksi yield strength and ~0.10lb/in3. They fall off badly with temperature though, and the 7xxx series stuff is worse than 2xxx series. For steel, 300M is 280-290ksi yield strength and 0.284lb/in3. Titanium is the same story, 6Al4V heat treated is 160ksi yield and 0.160lb/in3. There is one obscure grade of Ti that is better than this, but you better have VERY deep pockets to make anything from it.
So, we have no clear winner based on yield strength to density ratio.
All these materials also have very definite fatigue or endurance limits. The US DOD has a couple good documents out with fatigue testing information with and without notches. The tests without notches are good for continuous-grain specimens (like forged rods should be) and with notches for cut-grain specimens (from billet plates). For the most part though, if you stay at half the material's tensile (ultimate) strength, fatigue life is generally pretty good. Tensile strength vs density puts steel and Ti about even, but aluminum not quite as good.
Of course, none of us have true control over how our rods are made or what they are really made from, so this is purely academic. For drag-only motors, aluminum comes out as king in real world scenarios.
Kevin
Jan 14, 2008, 06:02 AM
#27
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Awesome!
03whiteGSR and Kiggly, I applaud you! great posts, much betterreading than argueing about pictures of rod bearings...
but I question your statement about Aluminum not having a fatigue life... it most ceratinly dies, and yes, crack propagation will be the mode of failure, and how do the cracks form? repeated loading and unloading of the part... this is the material's fatigue life.. quite frequently in the areospace world, aluminum can be designed with as low as 120,000 cycles in use.. ANy decent engineering book ought to have S-N diagrams for fatigue..
As for the young's modulus, Perhaps, I over exagerated, the biggest difference I can find is for steels is a range of about 30GPa, admittedly not all that much.... but tensile and yeild strength can still vary a lot!
03whiteGSR and Kiggly, I applaud you! great posts, much betterreading than argueing about pictures of rod bearings...
but I question your statement about Aluminum not having a fatigue life... it most ceratinly dies, and yes, crack propagation will be the mode of failure, and how do the cracks form? repeated loading and unloading of the part... this is the material's fatigue life.. quite frequently in the areospace world, aluminum can be designed with as low as 120,000 cycles in use.. ANy decent engineering book ought to have S-N diagrams for fatigue..
As for the young's modulus, Perhaps, I over exagerated, the biggest difference I can find is for steels is a range of about 30GPa, admittedly not all that much.... but tensile and yeild strength can still vary a lot!
Jan 14, 2008, 07:22 AM
#28
[quote=4G63DSM;5151762]Awesome!
03whiteGSR and Kiggly, I applaud you! great posts, much betterreading than argueing about pictures of rod bearings...
but I question your statement about Aluminum not having a fatigue life... it most ceratinly dies, and yes, crack propagation will be the mode of failure, and how do the cracks form? repeated loading and unloading of the part... this is the material's fatigue life.. quite frequently in the areospace world, aluminum can be designed with as low as 120,000 cycles in use.. ANy decent engineering book ought to have S-N diagrams for fatigue..
As for the young's modulus, Perhaps, I over exagerated, the biggest difference I can find is for steels is a range of about 30GPa, admittedly not all that much.... but tensile and yeild strength can still vary a lot
Ive been having these same disccusions with TedB over the phone. He has done a great job explaining Fatigue life with aluminum and why aluminum can take the beating of what i do but not daily driving them.
Lucas is going to test them on his Daily driven 400-500whp. Take them out about 30k miles check them for stretch and wear.
03whiteGSR and Kiggly, I applaud you! great posts, much betterreading than argueing about pictures of rod bearings...
but I question your statement about Aluminum not having a fatigue life... it most ceratinly dies, and yes, crack propagation will be the mode of failure, and how do the cracks form? repeated loading and unloading of the part... this is the material's fatigue life.. quite frequently in the areospace world, aluminum can be designed with as low as 120,000 cycles in use.. ANy decent engineering book ought to have S-N diagrams for fatigue..
As for the young's modulus, Perhaps, I over exagerated, the biggest difference I can find is for steels is a range of about 30GPa, admittedly not all that much.... but tensile and yeild strength can still vary a lot
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Groden Rods
I have a set of Groden aluminum 5.99 rods for Chevy 400 journals n.I.b . Paid $1500 asking $800. 724-397-8168. Sean
Alright guys ive chatted with the Mods and lets keep this thread clean Lots of good info in here. We have allot of big builds coming out this year
Here are the pics of Pauls bearings from the 1014whp, 20 passes and 30+ dyno pulls.
This was the 1009 whp, 20 dyno pulls and 7 passes on the steel Oliver rods.
We just pulled our motor out today and held our breath as we pulled the caps off the rods and WOW the bearings are gorgeous. This is the 3rd time we have done this and each time our bearings have been awesome. We have had miss fires at 57psi to 22 deg of timing on the dyno for ***** out pulls. My radiator is even a liittle bowed from so much timing
(I pushed the timing button on the aem Lucas did not do that) I'm also shifting at 10k rpms. The rods are going to the machine shop in the morning and getting check out so i will get pics up real soon.
With 250 passes on steel rods we were checking and changing bearing every 30 passes from pushing the tune so hard. Not anymore.
Jake Montgomery who has a 1st gen dsm has raced every BOTI with passes in 155-159mph at 9.2 et has won 3 BOTI just now checked his bearings after a full season of racing. They were freaken perfect!. Rods were fine.
Lucas has another set of Groden Aluminums and is going to test them on his daily driver. Groden said you can go 70k miles without checking them so we will see
This is a quote from Jake Montgomery
I'm going to have to say that an aluminum rod is by far the best choice for any car making anything over 800whp. I ran Crower rods for years with no problems with the bearings, that was until started making some serious power (above 800whp)
Above 800whp I was pulling the pan off every 3 events and checking the bearings on the crowers, and as suspected I was not impressed, the bearings would come out looking like ***, but at 650whp the bearings were great with the steal rods.
I made the switch to aluminum rods, I use the R&R aluminum rods and have never looked back. I tossed the rods in with a new set of pistons, rings ect. Never even pulled the motor out of the car, just took the head off and did a quick freshin up job on the bottom end with new rings, the R&R rods, and new pistons (time wasn't on our side since we had a race coming up in a hurry).
Ran a full season on the motor without pulling it apart one time. Running low 9's at 159mph all season long on a 3000lb car (estimated 1000whp) and here is how the bearings looked after the whole season using the R&R aluminum rods ruffly 65-70 low 9sec full blown passes at over 40lbs of boost and 100shot to boot and 10,500rpm shifts.
Needless to say I was very happy to see these results. I plan on running the same rods that came out of the motor for this upcoming 2008 season.
__________________
Lots of good info in here. We have allot of big builds coming out this yearHere are the pics of Pauls bearings from the 1014whp, 20 passes and 30+ dyno pulls.
This was the 1009 whp, 20 dyno pulls and 7 passes on the steel Oliver rods.
We just pulled our motor out today and held our breath as we pulled the caps off the rods and WOW the bearings are gorgeous. This is the 3rd time we have done this and each time our bearings have been awesome. We have had miss fires at 57psi to 22 deg of timing on the dyno for ***** out pulls. My radiator is even a liittle bowed from so much timing
(I pushed the timing button on the aem Lucas did not do that) I'm also shifting at 10k rpms. The rods are going to the machine shop in the morning and getting check out so i will get pics up real soon.With 250 passes on steel rods we were checking and changing bearing every 30 passes from pushing the tune so hard. Not anymore.
Jake Montgomery who has a 1st gen dsm has raced every BOTI with passes in 155-159mph at 9.2 et has won 3 BOTI just now checked his bearings after a full season of racing. They were freaken perfect!. Rods were fine.
Lucas has another set of Groden Aluminums and is going to test them on his daily driver. Groden said you can go 70k miles without checking them so we will see
This is a quote from Jake Montgomery
I'm going to have to say that an aluminum rod is by far the best choice for any car making anything over 800whp. I ran Crower rods for years with no problems with the bearings, that was until started making some serious power (above 800whp)
Above 800whp I was pulling the pan off every 3 events and checking the bearings on the crowers, and as suspected I was not impressed, the bearings would come out looking like ***, but at 650whp the bearings were great with the steal rods.
I made the switch to aluminum rods, I use the R&R aluminum rods and have never looked back. I tossed the rods in with a new set of pistons, rings ect. Never even pulled the motor out of the car, just took the head off and did a quick freshin up job on the bottom end with new rings, the R&R rods, and new pistons (time wasn't on our side since we had a race coming up in a hurry).
Ran a full season on the motor without pulling it apart one time. Running low 9's at 159mph all season long on a 3000lb car (estimated 1000whp) and here is how the bearings looked after the whole season using the R&R aluminum rods ruffly 65-70 low 9sec full blown passes at over 40lbs of boost and 100shot to boot and 10,500rpm shifts.
Needless to say I was very happy to see these results. I plan on running the same rods that came out of the motor for this upcoming 2008 season.
__________________