strok question
10-30-2011, 06:46 PM
#76
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Jerry Feather
10-30-2011, 07:35 PM
#78
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Just post the data which will allow people to decide for themselves how much offset/stress they are willing to live with or without.
No one will disagree with the fact that center is theorically best, so just post the data.
No one will disagree with the fact that center is theorically best, so just post the data.
10-30-2011, 08:32 PM
#80
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10-31-2011, 01:44 AM
#81
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10-31-2011, 02:02 AM
#82
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The problem forming here is that when you have a somewhat complex (its not complex , really, though) and abstract mechanic conversation, and it takes place in a public forum like this, everyone can "contribute" - and I suppose rightfully so. The PROBLEM here, however, is that when you allow everyone to contribute, as we must, you can't avoid the inevitable "monkey in the courthouse" sort of situation. Someone who is so purposefully ignorant and who fundamentally misunderstands even the most simple concepts, yet takes others comments as some form of false-positive on the righteousness of his "opinion" - and therefore is almost a "self-propelled" problem.
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10-31-2011, 02:05 AM
#83
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I have no idea how many cranks Phil Theshie bought, but as far as I know, his results were 0%.
Since I get an amazing amount of calls from people that have stroker engines that don 't run (I had four of these calls, last week alone!), burn so much oil they can't drive them, or have other catastrophic problems, I have always assumed the the "early stroker" attempts (Marc Thomas/Devek) had a success ratio of less than 10%. Marc might know the exact number....but he's never seemed to want to talk about this.
I'm not convinced that Carl is far enough along to be able to count anything he is doing. I believe he is setting back and still talking all this information in.
10-31-2011, 02:55 AM
#84
Former Sponsor
If the wrist pin can be .050 inches offset in one direction there is absolutely no reason the the rod cannot be offset by at least that much in the other plane. Simple as that. So long as the clearances needed are met, and the pistons provided by Porashe have sufficient clearance between the pin bosses, there is not any problem with the offset.
If the lack of centering were such a big deal or any big or little deal at all then why is it not a problem for the center of thrust to be offset now in and on the rod bearing journal as with the Carillo offset rod?
The fact is that there are probably very many ways to deal with the fact that the stroker cranks made to use Chevy rods have rod journals that do not line up centrally with the cylinder bore. The offset has to go somewhere.
Jerry Feather
If the lack of centering were such a big deal or any big or little deal at all then why is it not a problem for the center of thrust to be offset now in and on the rod bearing journal as with the Carillo offset rod?
The fact is that there are probably very many ways to deal with the fact that the stroker cranks made to use Chevy rods have rod journals that do not line up centrally with the cylinder bore. The offset has to go somewhere.
Jerry Feather
This is the logic that doomed most of the "early" 928 stroker engines.....and continues to "haunt" builders that are trying to build a 928 stroker engine, today. I've said that several times....but I want to make sure you completely understand my point!
There is a rod offset in almost every internal combustion engine...the crank journal width is seldom exactly proper for the bore offset. Apparently, the "zero" offset in the newer Chevy engines is the "rare" exception.....and I'm sure that this was a major "design" requirement, for these engines.
All internal engine manufacturers always have centered the "pin end" and positioned any "offset problem" at the crank end. They didn't do this, by accident. It's all about the lever....and the lever, in this case, is the connecting rod.
If the offset is postioned at the pin end, this will twist the beam of the rod....exactly as Ali "drew" the problem, in this thread. The piston pushes down uniformly on the pin. Any offset at the pin end results in an unequal force, which "twists" the connecting rod. Remember that the beam of the rod is thin, relative to the size of the junction at the crankshaft end. Once the lever (the beam) "twists", the piston rocks severely (pistons are always rocking some, but this is a huge force), the rod bearing gets pinched...all very bad things.
This is the problem with all 928 engines that have "Chevy" offset rods!
If the pin is centered on the rod, there is no twisting moment on the beam (the lever) of the connecting rod, since the force on the piston pin is "balanced" (equal on both sides, relative to the connecting rod beam). Since the beam of the connecting rod isn't being forced to flex, the pressure on the piston is transfered directly down the beam of the rod. The piston only rocks, in the bore, a "normal amount". If there is any "offset" at the pin end, there is certainly a slight "offset" transfer of this force to the crank but it is very slight, since the bearing is very wide and the lever is very, very short, at this end.
How can you not understand this?
It's so simple and basic.
The real question is: Why would you ever think that putting the offset at the pin end was/is the correct way to do this?
Last edited by GregBBRD; 10-31-2011 at 03:37 AM.
10-31-2011, 10:11 AM
#85
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Greg, I'm sorry that you had to end that diatribe with a question, or even two for that matter. That almost always compells me to actuallty give you the answer. However, I think I will simply take them as rhetorical and let them go.
At this point you have offered nothing to substantiate your thory; and the viewers have heard what I have to say about this, so I am sure they can now make up their own minds about what might really be required in regard to the offset. Your theory will help you sell the high dollar rods and mine will get me nothing because I am not selling Chevy rods.
So, I will take you at your word that this is in fact only "one more time" and hopefully "one last time" and I will respectfully bow out of this astute discussion myself.
Jerry Feather
At this point you have offered nothing to substantiate your thory; and the viewers have heard what I have to say about this, so I am sure they can now make up their own minds about what might really be required in regard to the offset. Your theory will help you sell the high dollar rods and mine will get me nothing because I am not selling Chevy rods.
So, I will take you at your word that this is in fact only "one more time" and hopefully "one last time" and I will respectfully bow out of this astute discussion myself.
Jerry Feather
10-31-2011, 10:48 AM
#86
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I swear even a blind man could see the problem with the rod offset issue Jerry.
You say Greg Brown has nothing to substantiate his theory, well when you have built as many WORKING strokers as Greg has I, see it as a fact, not as a theory.
You are the one with a theory and not a thing to back it up.
So you go ahead and build your grenade, get back to us when you have a couple of thousand miles on it.
You say Greg Brown has nothing to substantiate his theory, well when you have built as many WORKING strokers as Greg has I, see it as a fact, not as a theory.
You are the one with a theory and not a thing to back it up.
So you go ahead and build your grenade, get back to us when you have a couple of thousand miles on it.
10-31-2011, 10:51 AM
#87
Jerry is a lawyer, his job is to take bull**** and make it look real. This is going to be a very interesting conversation at 3rd Coast Jerry, I'm curious to see if you can hold my attention for at least 3 minutes before I have to walk away w/o shaking my head.
10-31-2011, 11:58 AM
#89
10-31-2011, 12:42 PM
#90
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