H beam vs. I beam rods

[Alky V6]

You are right and I agree but you should hear the phone calls I get from people that won't use a rod that is 20 grams or a crank that is 2 pounds heavier than a different brand because they think they will never win with the extra weight. When trying to move 2,500-3,000 pounds of car, a few grams here or there simply does not make much difference on the track especially when they are running a bracket program where they are competing against their own time.

Very good point, Tom.
When I ordered my crank and rods, I was very clear that I preferred the crank designed heavy. In fact, I was very clear to state that I wanted no lightening tricks at all done to the crank. If you study the picture I posted of the bottom end, you'll notice that the counterweights on the crank are full weight. Although, I did have to machine the sides of two of the counterweights to clear the webbing of the stock stage II on-center block I was using in the v.2.0 build.
The same with the rods. I was looking for rods that were on the heavy side. If it penalized me, it penalized me. Although, the engine does seem to be performing much better than expected, so I don't think the extra weight hurt me too much.

 

[BlownV6]

You are right and I agree but you should hear the phone calls I get from people that won't use a rod that is 20 grams or a crank that is 2 pounds heavier than a different brand because they think they will never win with the extra weight. When trying to move 2,500-3,000 pounds of car, a few grams here or there simply does not make much difference on the track especially when they are running a bracket program where they are competing against their own time.

I have been on that side of the fence before when I ran NA motors. And lets face it , that is where the light weigh rods came from in nascar motors , they kept making them lighter because they didnt need all the beam weight to surrort 550HP so in turn that allowed lighter cranks , etc.
Well now with increased turbos/blowers/boost/better heads/cam etc we are collectively pushing the limits of what was considered to be adequate beam structure. Blown hemis have been down this path 30 years ago and most of you know the size rods you would find in a Promod car now!! We are at the point where thinking within the norm is not going to work!! Whatever a Promod Hemi uses should be considered as the basis for what I need!! I think the majority of parts suppliers have the mindset of "its just a V6" it cant make that much power or dosent need this much beam strength in the rod.
I feel at 60# of boost I have found that next level of rod structure required.
I can put more boost to it but Im not even confident in the titanium rods the I have been running. The 2 motors with the MGP aluminum rods however I am extremely confident in , and they will get pushed even farther than 65# +.
We need larger , stronger , beams in these motors pushing past 1200HP!!
Thats my opinion!! Mike

 

[Alky V6]

The simple answer is, an H-beam is more prone to bend in one axis and the I-beam is more prone to bend in the other. Like I said earlier, MOST rods do not break in compression they break in tension. In a case of detionation or an actual overload / buckling failure, the rod will bend in the direction of least resistance regardless of the beam type.

The rod design used is then simply a compromise situation. Especially in an offset crankpin situation.

Thank you so much, Tom. Your input into this thread is so much appreciated. Thanks, again.

 

[Alky V6]

I have been on that side of the fence before when I ran NA motors. And lets face it , that is where the light weigh rods came from in nascar motors , they kept making them lighter because they didnt need all the beam weight to surrort 550HP so in turn that allowed lighter cranks , etc.
Well now with increased turbos/blowers/boost/better heads/cam etc we are collectively pushing the limits of what was considered to be adequate beam structure. Blown hemis have been down this path 30 years ago and most of you know the size rods you would find in a Promod car now!! We are at the point where thinking within the norm is not going to work!! Whatever a Promod Hemi uses should be considered as the basis for what I need!! I think the majority of parts suppliers have the mindset of "its just a V6" it cant make that much power or dosent need this much beam strength in the rod.
I feel at 60# of boost I have found that next level of rod structure required.
I can put more boost to it but Im not even confident in the titanium rods the I have been running. The 2 motors with the MGP aluminum rods however I am extremely confident in , and they will get pushed even farther than 65# +.
We need larger , stronger , beams in these motors pushing past 1200HP!!
Thats my opinion!! Mike

Very well put, Mike. I agree completely!!

 

[K1tom]

Very good point, Tom.
When I ordered my crank and rods, I was very clear that I preferred the crank designed heavy. In fact, I was very clear to state that I wanted no lightening tricks at all done to the crank. If you study the picture I posted of the bottom end, you'll notice that the counterweights on the crank are full weight. Although, I did have to machine the sides of two of the counterweights to clear the webbing of the stock stage II on-center block I was using in the v.2.0 build.
The same with the rods. I was looking for rods that were on the heavy side. If it penalized me, it penalized me. Although, the engine does seem to be performing much better than expected, so I don't think the extra weight hurt me too much.

A lot of people do not realize that rotating weight is mass that is mass that is already in motion and only is only accerated. Reciprocating weight must be stopped and restarted twice every stroke. Imagine tying a 8,000 pound weight to a steel cable and dropping it off from a bridge. It takes a huge amount of energy to stop the weight and even more to get it moving again. Now do this 100 times per second. When you consider the 8,000 pound weight is not an unusual number to see in most engines, the rotating weight acceration number is quite pale in comparison.

 

[Alky V6]

A lot of people do not realize that rotating weight is mass that is mass that is already in motion and only is only accerated. Reciprocating weight must be stopped and restarted twice every stroke. Imagine tying a 8,000 pound weight to a steel cable and dropping it off from a bridge. It takes a huge amount of energy to stop the weight and even more to get it moving again. Now do this 100 times per second. When you consider the 8,000 pound weight is not an unusual number to see in most engines, the rotating weight acceration number is quite pale in comparison.

Yes. That's pretty much how I felt about it. The only place a heavy crank was going to hurt me was while trying to get the turbo spooled up. A slight difference in the rpm rise rate. Similar to the difference between a heavy flywheel compared to a light flywheel, but maybe not that much of a difference, since the extra weight in the counterweights is closer to the rotating centerline.
I figured that since I was using nitrous to help spool the turbo, the nitrous might also make up the difference for the heavier crank. Which it seems to have done just that.

 

[K1tom]

Very well put, Mike. I agree completely!!

NASCAR engines are now in the 800-850 HP range and have a minimum rod weight rule of 525 grams and the rod must be made of steel. A 525 gram rod looks scary enough but when you see one that has as much weight trimmed off from the pin end and rod beam as these do, it becomes even scarier. These teams know reciprocating weight costs power so they move as much of the 525 grams of rod weight as they can to the rotating side of the rod. These engines live in a completely different environment than a V6 Buick and Mike is in an area that has different / special needs that most other Buick owners do not.

 

[K1tom]

Yes. That's pretty much how I felt about it. The only place a heavy crank was going to hurt me was while trying to get the turbo spooled up. A slight difference in the rpm rise rate. Similar to the difference between a heavy flywheel compared to a light flywheel, but maybe not that much of a difference, since the extra weight in the counterweights is closer to the rotating centerline.
I figured that since I was using nitrous to help spool the turbo, the nitrous might also make up the difference for the heavier crank. Which it seems to have done just that.

Since most of the spooling done before the race even starts, within reason, it doesn't really make much difference does it? Also keep in mind that heavier parts that are spooled and in motion are stored energy and actually help launch the car.

 

[Alky V6]

More questions people want to know the answers to. :biggrin:

How does crankshaft stroke play into the durability of the rod?

Does a longer stroke put more loads on the rods?

A shorter stroke will usually demand a longer rod. How does that play? Long beam length vs. short beam length?

Long beam length with a short stroke? Short beam length with a long stroke? Durability differences between the two configurations?

Does a longer or shorter stroke change the natural frequency of the components?

 

[Alky V6]

I'm going to make an assumption here on the point of natural frequency.

I would guess that a tighter package (short stroke) as it relates to the rotating centerline would have better (more durable) natural frequency characteristics than a long stroke situation.

 

[K1tom]

How does crankshaft stroke play into the durability of the rod?

Does a longer stroke put more loads on the rods?

A shorter stroke will usually demand a longer rod. How does that play? Long beam length vs. short beam length?

Long beam length with a short stroke? Short beam length with a long stroke? Durability differences between the two configurations?

Does a longer or shorter stroke change the natural frequency of the components?

Very good questions. Regarding longer strokes, lets say you have two engines. One with a long stroke and one with a short stroke and both engines have the same cylinder pressure due to fuel burn. The engine with the longer stroke will have compressive load on the rod because the crank will turn easier due to leverage. Think of tightening head bolts with a 12" long wrench then doing the same with a 24" long wrench. The bolts turn easier with less effort with the long wrench. Now on the tension side, due to higher piston speed (assuming the same RPM), the piston becomes more difficult to stop so there is much higher tension (pulling) load on the rod. This is where it starts to get interesting. Now keep in mind the longer stroke engine should make more power due to more cubic inches and there is actually less compressive load on the rod. That is one of the reasons why we do not rate rods by power. There is simply too many variables to provide an accurate number. While a lot of companies put power ratings on their rods, the number they give out is what I call a "brown number". For those who do not know what a brown number is, it is one that is pulled out of someone's rear end and has just about that much meaning.

Long rods allow the piston to decelerate more at TDC and reduce the tension (pulling) load on the rod. They also keep the piston in the top portion the piston travel for a longer amount of time so you build higher cylinder pressure from the same amount of fuel burned.

All parts have their own natural frequency and changing the mass changes the frequency.

Shortening the stroke does not necessarily mean you need a longer rod because when ordering pistons, you can specify a different wrist pin location to make up the difference. Just keep in mind that lowering the wrist pin generally means a heavier piston and higher tension loads on the rod.

 

[Alky V6]

LOL... Brown number. I like that. I just learned an important new engineering term. :biggrin:

 

[BlownV6]

LOL... Brown number. I like that. I just learned an important new engineering term. :biggrin:

My Oliver rods defenetly had some of that BROWN number engineering

LOL sorry I just couldnt pass that up!!! Mike

 

[Alky V6]

my oliver rods defenetly had some of that brown number engineering

Lol sorry i just couldnt pass that up!!! Mike

lol!

 

[K1tom]

My Oliver rods defenetly had some of that BROWN number engineering

LOL sorry I just couldnt pass that up!!! Mike

Mike,

I may have found something that was machined out of tolerance and could have caused or at least contributed to your problem. I am trying to confirm before I say anything else.

Tom

 

[cruzn57]

your opinion of these?

I have a set of Childs and Alberts steel rods, 6.5 long, I beam construction,
are these as strong as current K1 style rods? any guess's on HP limits?
here are few pics
thanks

 

[K1tom]

I have a set of Childs and Alberts steel rods, 6.5 long, I beam construction,
are these as strong as current K1 style rods? any guess's on HP limits?
here are few pics
thanks

C and A made some ok parts but always seemed to have problems with getting the bearing notches correct. Look at the photos and you can see the notches do not look deep enough and maybe not long enough for the tabs on the bearings to fit into without reworking. If the notches are not deep enough the bearing will make contact with the crank and burn. C and A also quit making steel rods about 8 years ago and closed their doors a couple of years ago.

Everyone wants a Power rating for rods. Go back to my example about increasing power by increasing stroke. Once again power ratings are brown numbers.,

 

[turbobitt]

I don't mean to hijack the good tech in this thread but I thought I would just say that I wish that there were more people like Tom in performance world. Tom may not remember but I delt with him directly on a 4.5 stroke Mopar crank a few years ago that I bought from a mopar vendor in Florida. Tom called me personally to work through issues and got them resolved quickly. This was after the crank was bought and paid for and in my possesion for 1 year. Tom takes his quality very seriously and listens to the end user. It is very clear to me that he strives to not be in the same catagory as Scat, Eagle, or any of the cheaper stuff.

I'm Glad to se Tom active in the Buick comunity and maybe he can find a market for a run of cranks or something.

Allan G.

 

[K1tom]

I don't mean to hijack the good tech in this thread but I thought I would just say that I wish that there were more people like Tom in performance world. Tom may not remember but I delt with him directly on a 4.5 stroke Mopar crank a few years ago that I bought from a mopar vendor in Florida. Tom called me personally to work through issues and got them resolved quickly. This was after the crank was bought and paid for and in my possesion for 1 year. Tom takes his quality very seriously and listens to the end user. It is very clear to me that he strives to not be in the same catagory as Scat, Eagle, or any of the cheaper stuff.

I'm Glad to se Tom active in the Buick comunity and maybe he can find a market for a run of cranks or something.

Allan G.

Hi Allan,

Actually I do remember you. You bought your parts from Dan at Performance Only. I am glad we were able to work things out to your satisfaction. Thank you for the kind words.

Tom

 

[turbobitt]

Hi Allan,

Actually I do remember you. You bought your parts from Dan at Performance Only. I am glad we were able to work things out to your satisfaction. Thank you for the kind words.

Tom

Tom,

Yes, thats me. Glad that you remembered. Another example to your seriousness in customer satisfaction. I'm proud to say that my 572 Hemi has a K1 bottom end. My machinest was very satisfied with your product and he's difficult to please.

P.S. , I'm currently having some fun watching a friend of mine(whom didn't follow my recomendations to buy K1) having issues with his "other brand stuff". Rods went .004" out of round after 3 retorques.

Allan G.