H beam vs. I beam rods

[BlownV6]

I had JE pistons design what they thought I needed to make 1800-2000Hp when I bought my packages. They wanted to use .990 x .180wall wrist pins.
And that is exactly what I ordered!! So far not one issue from the pistons or pins , except when the rods folded!! Mike

 

[Alky V6]

Mike. I noticed that your beam configuration is an I. Is there a reason why aluminum rods are typically I beam?

 

[Alky V6]

I had JE pistons design what they thought I needed to make 1800-2000Hp when I bought my packages. They wanted to use .990 x .180wall wrist pins.
And that is exactly what I ordered!! So far not one issue from the pistons or pins , except when the rods folded!! Mike

I've heard of problems even with the .990" with the V8 guys. If they're having problems, then you should pay some attention. I'm sure you're loading even more than them. I here the pin to use is 1.030"?

 

[BlownV6]

What does rod to camshaft look like? Are you moving the camshaft?
When I was working on the v.3.0 combination I did a CAD of the crank and camshaft locations and built a digital rod. The idea at the time was to use an aluminum rod. The room wasn't there for the extra bulk of an aluminum rod. Are you trying to get the strength by simply going as wide as you can, even with the camshaft problem? I'm wondering if going wider is as strong? I would guess it isn't.

With the aluminum rods I dropped from 3.750 stroke to 3.550 stroke to try to creat enough clearance for the rod to miss the cam. On even fire engines the rods and cam all try to make contact with all the rods with large stroke. Oddfire just has the issue with 2, 4 & 6.
Do you mean wider beam or wider big end?? There is no doubt in my mind that the widest beam possible is better in high HP applications!! The big end on mine is .940 wide because that is the stock size for a SBC and can easily get bearings, also was a wider bearing surface to handle the load Im putting on it. Mike

 

[BlownV6]

I've heard of problems even with the .990" with the V8 guys. If they're having problems, then you should pay some attention. I'm sure you're loading even more than them. I here the pin to use is 1.030"?

1.030 would defenetly be better than a .990 pin. I havent had any problems thus far with the .990 pins. If I were to start over and didnt have 4 sets of pistons I would probably go with the 1.030 or bigger!!

In addition for a BBC that has say a 4.500" bore compared to my 4.030 bore with equall amount of cylinder pressure ( say 3000PSI )the larger bore will exert more pressure on the pin than mine will. Mike

 

[Alky V6]

With the aluminum rods I dropped from 3.750 stroke to 3.550 stroke to try to creat enough clearance for the rod to miss the cam. On even fire engines the rods and cam all try to make contact with all the rods with large stroke. Oddfire just has the issue with 2, 4 & 6.
Do you mean wider beam or wider big end?? There is no doubt in my mind that the widest beam possible is better in high HP applications!! The big end on mine is .940 wide because that is the stock size for a SBC and can easily get bearings, also was a wider bearing surface to handle the load Im putting on it. Mike

The contact area, IIRC is on one side of the big end at the base of the beam as the beam blends into the big end. I would suppose both the beam and big end would need to be as wide as possible to make up for the less material at that location to clear the cam.
From an engineering stand point, would the wider, but less thickness at that location be enough to prevent the big end from going out of round during tension?
When I did the CAD work on my engine, that was with a 3.060" stroke, and it still wasn't enough.

 

[Alky V6]

1.030 would defenetly be better than a .990 pin. I havent had any problems thus far with the .990 pins. If I were to start over and didnt have 4 sets of pistons I would probably go with the 1.030 or bigger!!

In addition for a BBC that has say a 4.500" bore compared to my 4.030 bore with equall amount of cylinder pressure ( say 3000PSI )the larger bore will exert more pressure on the pin than mine will. Mike

But the pressures will not be equal. With the V8, the overall pressure is spread across 8 pistons. 6 with you.
If you're trying to match V8 performance, and with your smaller bore and missing 2 pistons, and running a parasitic blower, you will need much more cylinder pressure than the V8 guys. You're findng that out too.
Most V8 nostalgia alcohol guys are boosting in the 20-30s psi. You're at 40s now?

 

[951le]

Donnie,Is the TA block a true on-center?Do you have any pics of your rods in the engine?Are they I beam or H beam?

 

[Alky V6]

Donnie,Is the TA block a true on-center?Do you have any pics of your rods in the engine?Are they I beam or H beam?

The TA block is an on-center. Just as on-center as the Buick on-center block. With an even fire crank, there is still some offset in the piston. If I had to guess, I think the offset is around .060".
The rods are I beam with no built in offset.
Picture, http://www.turbobuick.com/forums/2532965-post67.html

 

[BlownV6]

The contact area, IIRC is on one side of the big end at the base of the beam as the beam blends into the big end. I would suppose both the beam and big end would need to be as wide as possible to make up for the less material at that location to clear the cam.
From an engineering stand point, would the wider, but less thickness at that location be enough to prevent the big end from going out of round during tension?
When I did the CAD work on my engine, that was with a 3.060" stroke, and it still wasn't enough.

There were hundreds of competition eliminator motors built with 3.400 stroke and aluminum rods that turned over 9000 rpm so there is no doubt that it can be done. MGP cam up with a rod design that he feels will get the job done and still miss the cam lobe. Im quite sure that your cad program must have been slightly off base on this one. BTW Im at or above 60# of boost!!
Mike

Also must consider that evenfire crank pin is 2.250" but my oddfire is 2.100" , that makes quite a difference also.

 

[Alky V6]

There were hundreds of competition eliminator motors built with 3.400 stroke and aluminum rods that turned over 9000 rpm so there is no doubt that it can be done. MGP cam up with a rod design that he feels will get the job done and still miss the cam lobe. Im quite sure that your cad program must have been slightly off base on this one. BTW Im at or above 60# of boost!!
Mike

Also must consider that evenfire crank pin is 2.250" but my oddfire is 2.100" , that makes quite a difference also.

60 psi. Yikes. Well, you helped make my point.

2.100. Good. That would certainly help.

Comp E motors are n/a?

The CAD was not off base. I double checked it with physical measurements. Do you think I would trust a computer? I had to digitize it for a rod manufacturer so he could have something to look at. He told me, "No way. I pass."

 

[951le]

The TA block is an on-center. Just as on-center as the Buick on-center block. With an even fire crank, there is still some offset in the piston. If I had to guess, I think the offset is around .060".
The rods are I beam with no built in offset.
Picture, http://www.turbobuick.com/forums/2532965-post67.html
So did you decide to run the rods without any offset or did Oliver make that decision?Have you had any trouble with those rods?

 

[The Radius Kid]

IIRC,a 1.030" diameter pin has about an 8% strength advantage over a .990" pin,all else being equal.
I don't know if it's possible Don,but I wouldn't mind seeing your rod design.
If I know you,it could be interesting.:smile:

One big problem with structural design: abrupt changes in direction of material "flow" can cause stress "risers" that lead to failure.
That's why you usually see highly stressed parts with smooth transitions and curves...not a lot of sharp corners.

 

[Alky V6]

The TA block is an on-center. Just as on-center as the Buick on-center block. With an even fire crank, there is still some offset in the piston. If I had to guess, I think the offset is around .060".
The rods are I beam with no built in offset.
Picture, http://www.turbobuick.com/forums/2532965-post67.html
So did you decide to run the rods without any offset or did Oliver make that decision?Have you had any trouble with those rods?

They were off the shelf 6.5", on-center, wide big end, .927" pin, Oliver rods. If I remember right, I wanted the rod on the heavy side. I wasn't looking for anything that was lightened. I gave them a 1200 hp spec and that's it. Nothing more fancy than that.
I didn't think of putting any offset in it, and they didn't ask.

The rods have been in the motor going on five years now. The last time I had it apart, everything looked very good. Except for the wrist pins having a slight bend (.001") to some of them, but they slid in and out of the pistons and rods fine. No binding.

 

[Alky V6]

I don't know if it's possible Don,but I wouldn't mind seeing your rod design.
If I know you,it could be interesting.:smile:

I know the file is on the desktop at home, but it's down at the moment. Monitor isn't working. After I get it back up, I'll try to remember to find the file and post it. It was an interesting exercise.
I contacted various manufacturers and when most heard the 1200 hp spec with alcohol, they were quick to say nope. BME was the only one that took the time to look over my specs carefully, and then they bowed out.

 

[K1tom]

Correct Mike.
The motive force applied by the piston must be transfered with minimal losses - because it floats between two points.
Too much monkey motion and the HP can by lost as well as a higher likelyhood of failure...as you found out with your Titanium rods.
As with everything mechanical,there's always an optimal balance point.
It's the crazy racers who always try to stretch the limits. :smile:

I think you are all misunderstanding the reason for an "offset" or "on center rod". An offset rod has the beam moved over on the big end and the reason is to put the beam of the rod in the center of the cylinder bore. I have attached a picture of this. The problem with a Buick block comes in because it has a split journal crank and has a web between the two journals and this web moves the rod pin over on the crank and no matter what you do, you cannot move the beam over far enough to put into the center of the bore without hitting the beam with the counterweight of the crank. In the case of BlownV6, he as an odd fire crank which has a common pin (two rods on the same journal) and this changes everything. When the rod beam is not in the center of the bore, the piston will tilt on the power stroke (this is compounded on a turbo charged engine due to the high cylinder pressure). This tilting does two things. #1 it will side load the rod which puts a bending load on the rod beam and can ultimatly cause rod failure. #2, when the piston tilts in the bore, it upsets the ring seal causing a reduction in power.

Tom

 

[K1tom]

Tom,in the picture you provided it shows a true I beam.What about a parabolic beam does it have the same issues?Everyting has some kind of weakness what is the H beam's?Are all of your rods from China? Even the ones in Bigfoot.

A Parabolic beam has a thin section in the middle but it does not have the same thin section with 2 parallel beams that really do very little to support below the wrist pin. The bottom line is a Parabolic beam handles the stress differently and better than a traditional beam. I included a sketch of a traditional I-beam because this is what the thread is all about.

Tom

 

[K1tom]

Tom,in the picture you provided it shows a true I beam.What about a parabolic beam does it have the same issues?Everyting has some kind of weakness what is the H beam's?Are all of your rods from China? Even the ones in Bigfoot.

Yes, the rods in Bigfoot are from one of the same factories that makes all of our rods. They are however a custom design that is made for their application.

Tom

 

[BlownV6]

Rolling around in the mud doesn't solve problems. Mike and I had what I consider a nice chat on the phone today and we will see if we can figure out what happened.

I have an example of why an I-beam is not the hot ticket in high power applications and will try to up load it. Tom

Tom is right. We had a very nice phone conversation and I sent him my old set of rods and pistons and also a brand new set for him to evaluate. I look forward to hearing his input about my Oliver rods.

In the intrest of brain storming about rod design , I have to respectfully disagree with Tom on which rod design is best for high HP blown applications.
Im certainly not an engineer and have no basis for my opinion other than common sense!! While under severe pressure from high Hp I would think that the the rod tries to buckle under the pressure. The beam is weakest through the side of the beam and that is what will buckle under the load!! Check all the pics attached to this thread and that is the direction they all bend first!!
I have bent 5 sets of steel rods along my path, 2-carrillo , 2-oliver and 1-crower. All bent along the short side of the beam , Carrillos were the worst , Olivers were second and the Crowers were only slightly bent. When I look at the side of each of the beams and imagine which one is strongest there is no doubt in my little mind that the H beam Carrillos are the weakest ( no material preventing buckling down the side of the beam) , Olivers are second simply because the width of the I beam is narrower than the width of the crowers.
My common sense "hillbilly brain" looks at this like this. If you were to set a 5000# load on top of a 8' long wooden 2 x 4 standing straight up , there is no question that it will buckle along the short side!!! Now make it a 4 x 4 and it most likely will hold the weight. So from that I get that the side of the beam (width and mass) is possibly the most important part of the beam in a high HP application!!

Thats my story and I dont see anyone convincing me otherwise!! Mike

 

[Alky V6]

Mike, when you say short side of the beam, what does that mean? I need pictures.
Are you talking about what would be one of the flange sides on an I beam rod?