Matching rod weights - Page 5

Henry Schmidt · Henry Schmidt's Garage

All things come around if you wait long enough.

In the beginning of this thread, we were faced with a set rods that were 20 grams out of balance. Knowing that Porsche balances their rods on the side by the bolts, I argued that 20 was too much to remove.
snowman argued 20 grams was easy to remove. Now it appears that he is saying we shouldn't remove weight from the side.

My point is that the rods were designed to have the weight removed from the sides. That is why Porsche actually balances them that way.

I agree that very little weight should be removed from the sides. This seems to support the contention that 20 grams is too much.
Time to put this one to rest. Nice try snowman. Once again your own words get you.

BTW: We took the poorly balanced set of rods, replaced it with a set that would easily balance and the owner won.

snowman · 11-06-2006, 06:28 PM

I do not agree that Porsche balances their rods on the sides. Give a referance ot prove it.

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally posted by snowman
I do not agree that Porsche balances their rods on the sides. Give a referance ot prove it.

If a picture is worth a thousand words, what's three pictures worth. Oh BTW I can post many more..... If you're honest, you'll admit these rods were balanced on the side.

All three of these rods were from engines that had never been apart. You've called me a number of things, you best not call me a liar.
Pankl titanium

87 3.2

91 3.6

snowman · 07:43 PM

THat shape is there by design, it is not a balancing pad.

I did NOT call you a lier. I said prove it.

You gave your opinion, I gave mine, now get some proof or cool it.

I suspect that Porsche dosen't grind anything, they just group weights from their mass of rods.

Real high quality rods do not even need balancing. All have the same exact density, the exact same dimensions, they should all weigh exactly the same, within one or two grams.

The Pankl titanium rod has a larger cross section at the interface, why? Because the stress it higher here and they need more room for the alignment pin.

They necked it down to save weight, But that gives some insight to how much they are lacking in the design area. Rotating weight, the weight of the big end is not much of a problem, a little more makes little difference. But the reciprocating weight at the small end of the rod is extreemly important and companys that know what they are doing will go to every extreem to lighten the rod there. Give a good lock at any modern rod, Carrillo has been that way for a very long time. They keep the dimension on the side of the big end constant as it makes little difference and it makes the rod stronger. Those big round things on the bottom of a Carrillo, look just like the big round things on the bottom of some Porsche rods. Carrillo uses them for balance. But like I stated, a good rod only needs a gram or two to balance it.

As to the origninal post, 20 grams. As long as the rod has no defects in it, 20 grams from the massive big end will make no difference. remember its only the weight of 20 one dollar bills.

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally posted by snowman
THat shape is there by design, it is not a balancing pad.

I did NOT call you a lier. I said prove it.

You gave your opinion, I gave mine, now get some proof or cool it.

I suspect that Porsche dosen't grind anything, they just group weights from their mass of rods.

Real high quality rods do not even need balancing. All have the same exact density, the exact same dimensions, they should all weigh exactly the same, within one or two grams.

The Pankl titanium rod has a larger cross section at the interface, why? Because the stress it higher here and they need more room for the alignment pin.

Why do you insist on saying things that just aren't true?
The rods were machined. How do I know? I measured them. If they were forged that way, the rods would all be the same. In none of these sets are all the rods the same width (measured bolt to bolt). It's an easy measurement.
Want to guess again?

BTW: There is no alignment pin. The Pankls are aligned by the bolt itself, just like the earlier production steel rods.

20 grams is more than any quality engine builder will remove from a Porsche rod. Remember the list I posted.

"Ollies won't grind 20 grams" Ike
Costa Mesa R&D " 20 grams if you have a weight pad to grind, otherwise 6-10 grams depending on which end" John
EMS "Won't try 20 grams" Bill
Riddle Machine ( Rimco)"7-10 max" Greg
Aasco " 20 grams, NO NO" Dennis Aase
I'll add one more Walt at Competition Engineering.
All top quality builders. Now you get to name one that will.

Jim_Brown · 09:25 PM

Snowman-

I suspect we may not be using the same terminology to describe areas of the rod. All of the graphics in your previous post showed broken rods where the mode of failure was a fatigue failure in the beam section. If I am wrong please provide a slide number for the Fatemi presentation where the mode of failure is at the bottom of the big end: the midlle of the rod cap.

edit: (Location of material removal by Porsche is noted in blue)

The graphic below is from the Fatemi presentation for a rod in tension. Note that the area where Porsche removes material (in very small amounts) is located in the areas noted by the yellow ellipses. The area noted in red is the bottom of the big end - a location where you appear to be advocating the removal of up to 20 grams of material.

This picture shows where Henry has seen many (lots of) rods with material removed for balancing.

Also, contrary to your claim regarding the spacing of arrows indicating the loading in a free body diagram: it is the arrow length, not the spacing, that indicates intensity of loading. Long arrow=high loads, short arrow=low loads.

Cheers,
Jim

snowman · 10:27 PM

The arrow lengths in these picts has nothing to do with the ammount of stress per unit area. All the arrows are the same length. The spacing bewteen the arrows in some of the other diagrams, not shown here, does indicate the stress per unit area. If the arrows indicated strength of stress the red ones would be 2 or 3 times as long as the blue ones, they are not. In any case you have a 300 unit stress applied to a huge area on the bottom of the rod, and only under one condition and without twist, vs a 600 unit stress applied to 1/4 the area with the additon of twist under several conditions. Whats gonna break, deform? Its not the large area with only 300 units of stress. Its like 300/4 vs 600x4 or 75 vs 2400, like none vs a whole lot.

The bottom of a Porsche rod is not like what is shown, it has much more material on the bottom, about three times as much and that is for removing weight. Remove material from the sides, maybe the casting flash, but much more gets risky. The casting flash must be removed from the entire rod, to say this grind mark is for balancing is just speculative.

If the rods depend on the rod bolt for alignment, I would never ever use them in a race engine, cause thats just plain stupid to do do. A case for Carrillo and against the P rod. No rod, no matter who makes it, can match the performance of a rod that is pinned, vs one that uses the rod bolts. any claim that such a rod is better than a Carrillo rod is just total BS. any rod that uses a rod bolt plus a rod nut is clearly inferior to one that uses a rod bolt threaded into the rod itself. Any rod that uses std threads on a rod bolt is inferior to the bolts Carrillo uses ie an asymetric thread. And the rod bolt is the weakest link. Congrats, so far you have shown the P rod is far inferior to a std Carrillo rod.

I can take 20 grams from a std Porsche rod, polish and peen the bottom and no one would ever know I have done so. Its a lot in terms of balance, but NOT a lot of metal from a rod. Of course if you have a vast pile of rods on hand and you can match weight that way, why not? IT doesn't make it any better.

Come up with one, just one referance from a certified factory engineer that they balanced the rods from the sides and I will beleive it. Just waiting....I will put my head where you would like it placed and consume willingly.

At this point you have convinced me that you do not have a clue, none whatsoever. But prove me wrong.

Turbo_pro · 11-07-2006, 08:58 AM

Quote:

Originally posted by snowman
I can take 20 grams from a std Porsche rod, polish and peen the bottom and no one would ever know I have done so. Its a lot in terms of balance, but NOT a lot of metal from a rod. Of course if you have a vast pile of rods on hand and you can match weight that way, why not? IT doesn't make it any better.

At this point you have convinced me that you do not have a clue, none whatsoever. But prove me wrong.

No one is trying to prove you wrong, they're just tying to get you to see from a less pompous point of view.
Everyone else is wrong and you're the only one that knows ?

Henry has supplied a list of who's who in the Porsche machine world and you have offered your own opinion.
Can you supply one other qualified Porsche machinist that believes as you do (20 grams is not too much to remove)?

Quote:

Originally posted by snowman
"Come up with one, just one reference from a certified factory engineer that they balanced the rods from the sides and I will believe it."

If the rods came that way and it's obvious that the machining was done for balancing, what more do you need?

Perhaps the clueless one is the person who refuses to see what all of us see.

snowman · 11-07-2006, 08:14 PM

They have to machine the flash off the sides after forging. DO they design this area for balancing, not likely.

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally posted by snowman
Carrillo rods do not need additional balancing by the customer, cause they are near perfact to begin with. But at the factory, Carrillo removes material from the bottom to balance them.

After getting off the phone with Carrillo it turns out that they recommend balancing their rods on the flat sides adjacent to the bolts. When asked about the bottom they specifically said "stay away".
They said that if large amounts were necessary the diagonal next to the flat is good.

I also asked about the redesign of the Carrillo 930 rods from the 80's. I pointed out to them that the area under the head (pin bushing) looks more stout. I said I had seen some small end failures back in the 80's and he said they were redesigned for strength.

Well engineer Jack, now you're going to say Carrillo is wrong?

Note the flat area along side the rod bolt. Also note how wide the neck is directly under the pin. This area has been greatly improved since the earlier rods.