Friction Reduction and Reliability....
- Thread starter Shannow
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A good read and such shows how far we've come in better understanding cause and effect of the many variable stresses. A little story-I recall 'a talk' given some years ago by an old retired Buick powertrain engineer who was also involved in 'real world' testing. He spoke of 'torture testing' the 'new' '67 lightweight 400/430 V8's replacing the heavy 'nailhead' engines they drove instrumented pre-production cars from Flint to the desert proving grounds. The first attempts broke 3" crankshaft mains and so that was moved to 3 1/4" and those survived. He said the lightweight block flexed too much under severe loads. When I asked how the heck Buick could justify a 'fix' based on the rotating assembly 'stabilizing' a weak block he kinda smiled and shrugged.
Even worse, I'm old enough to know what you are talking about. I'm still way back on 2.3 seizure and figure 4&5, wondering how to answer my own questions I posted on Dustyroad's Diesel UOA thread. Nothing like painting myself into a corner.
Edit; With the flexing/harmonics issue, the hot rod fix is more bearing clearance and thicker engine oil.
Edit; With the flexing/harmonics issue, the hot rod fix is more bearing clearance and thicker engine oil.
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Yep, the days of a flat bottomed engine block with a couple of main bearing caps standing out like a city skyline are long, long gone.
Lapham3, that's one thing people lack in understanding...the hydrodynamic film can impose incredible forces, and in whatever direction the apparent load is at the time...if the crank is trying to keep the block straight, it will.
userfriendly, I agree, that's a prime reason for opening up the clearances, especially on an engine that's going to go through a massive thermal transient over 10-15 seconds.
:sigh:... my turbine days are behind me, but aligning a 210 tonne train, half the length of a swimming pool, with 5(+) rotors, 14 bearings, and managing the catenery were great mental gymnastics.
Lapham3, that's one thing people lack in understanding...the hydrodynamic film can impose incredible forces, and in whatever direction the apparent load is at the time...if the crank is trying to keep the block straight, it will.
userfriendly, I agree, that's a prime reason for opening up the clearances, especially on an engine that's going to go through a massive thermal transient over 10-15 seconds.
:sigh:... my turbine days are behind me, but aligning a 210 tonne train, half the length of a swimming pool, with 5(+) rotors, 14 bearings, and managing the catenery were great mental gymnastics.
A great read Shannow. With a MS in Physics and worked as a Porsche tuner in the early 70s, I still need to review and try to understand certain topics in the article. This is the first, I heard of flexural harmonics. Thanks again for the article. Ed
Originally Posted By: Shannow
Yep, the days of a flat bottomed engine block with a couple of main bearing caps standing out like a city skyline are long, long gone.
Lapham3, that's one thing people lack in understanding...the hydrodynamic film can impose incredible forces, and in whatever direction the apparent load is at the time...if the crank is trying to keep the block straight, it will.
userfriendly, I agree, that's a prime reason for opening up the clearances, especially on an engine that's going to go through a massive thermal transient over 10-15 seconds.
:sigh:... my turbine days are behind me, but aligning a 210 tonne train, half the length of a swimming pool, with 5(+) rotors, 14 bearings, and managing the catenery were great mental gymnastics.
Was very taut piano wire involved ? That is what the machinists used to align propeller shafts and elevator rails. Or was a transit used? Now a days, they use lasers, don't they?
Yep, the days of a flat bottomed engine block with a couple of main bearing caps standing out like a city skyline are long, long gone.
Lapham3, that's one thing people lack in understanding...the hydrodynamic film can impose incredible forces, and in whatever direction the apparent load is at the time...if the crank is trying to keep the block straight, it will.
userfriendly, I agree, that's a prime reason for opening up the clearances, especially on an engine that's going to go through a massive thermal transient over 10-15 seconds.
:sigh:... my turbine days are behind me, but aligning a 210 tonne train, half the length of a swimming pool, with 5(+) rotors, 14 bearings, and managing the catenery were great mental gymnastics.
Was very taut piano wire involved ? That is what the machinists used to align propeller shafts and elevator rails. Or was a transit used? Now a days, they use lasers, don't they?
Originally Posted By: Lapham3
A good read and such shows how far we've come in better understanding cause and effect of the many variable stresses. A little story-I recall 'a talk' given some years ago by an old retired Buick powertrain engineer who was also involved in 'real world' testing. He spoke of 'torture testing' the 'new' '67 lightweight 400/430 V8's replacing the heavy 'nailhead' engines they drove instrumented pre-production cars from Flint to the desert proving grounds. The first attempts broke 3" crankshaft mains and so that was moved to 3 1/4" and those survived. He said the lightweight block flexed too much under severe loads. When I asked how the heck Buick could justify a 'fix' based on the rotating assembly 'stabilizing' a weak block he kinda smiled and shrugged.
I drove a couple of "225 VOLTs" with the big nail heads and they had plenty of low end. Didn't rev much though.
A good read and such shows how far we've come in better understanding cause and effect of the many variable stresses. A little story-I recall 'a talk' given some years ago by an old retired Buick powertrain engineer who was also involved in 'real world' testing. He spoke of 'torture testing' the 'new' '67 lightweight 400/430 V8's replacing the heavy 'nailhead' engines they drove instrumented pre-production cars from Flint to the desert proving grounds. The first attempts broke 3" crankshaft mains and so that was moved to 3 1/4" and those survived. He said the lightweight block flexed too much under severe loads. When I asked how the heck Buick could justify a 'fix' based on the rotating assembly 'stabilizing' a weak block he kinda smiled and shrugged.
I drove a couple of "225 VOLTs" with the big nail heads and they had plenty of low end. Didn't rev much though.
Grooves, Figure 15. Patterns of dimples, cool stuff.
Originally Posted By: andyd
Was very taut piano wire involved ? That is what the machinists used to align propeller shafts and elevator rails. Or was a transit used? Now a days, they use lasers, don't they?
Rarely was the machine opened up far enough to do a piano wire front to back, that's typically on initial assembly...mostly dial guages and wedge guages, in a coupling to coupling basis.
Need to find where the rotor is in relation to the stator, and then try to get the bearings aligned within that envelope (moving casings is a big deal).
When you get it right, there's a "bridge guage" that you have dowelled to the bearing keep, and record the 12:00 and 3:00 gaps.
If you have a crash, a bridge gauge lets you get close quickly. Once had a temperature issue, ad found a massively wiped bearing ... it had dropped some thousandths of an inch...we scraped it to a reasonable blue, then shimmed it back to the bridge gauge reading, and got it running again in 4 days from gaining access (takes a week to cool down).
Was very taut piano wire involved ? That is what the machinists used to align propeller shafts and elevator rails. Or was a transit used? Now a days, they use lasers, don't they?
Rarely was the machine opened up far enough to do a piano wire front to back, that's typically on initial assembly...mostly dial guages and wedge guages, in a coupling to coupling basis.
Need to find where the rotor is in relation to the stator, and then try to get the bearings aligned within that envelope (moving casings is a big deal).
When you get it right, there's a "bridge guage" that you have dowelled to the bearing keep, and record the 12:00 and 3:00 gaps.
If you have a crash, a bridge gauge lets you get close quickly. Once had a temperature issue, ad found a massively wiped bearing ... it had dropped some thousandths of an inch...we scraped it to a reasonable blue, then shimmed it back to the bridge gauge reading, and got it running again in 4 days from gaining access (takes a week to cool down).
Not saying that they did it for the reasons in the article, but my Nissan turbodiesel (shared with Renault) has 4 valves per cylinder, but the inlets and exhausts are across the head, not along one side.
Here's a place that you can look at what they are
http://www.alibaba.com/product-detail/Patrol-ZD30-Engine-Cylinder-Head-11039_60148777971.html
It's probably really so that Nissan could do their inlet port gymnastics as opposed to having a lower bending moment on the engine.
For the port gymnastics, they've got the two inlet ports per cylinder, and a singe exhaust (obviously the exhaust from one valve travels across the back of the other valve)
Inlet side, there is a low port that introduces the air tangentially to the cylinder, creating swirl.
The other, high, port is designed for volume, but during light loads is closed off with a butterfly (so called swirl valve) to provide better mixing for the high EGR volumes that the thing uses.
Here's a place that you can look at what they are
http://www.alibaba.com/product-detail/Patrol-ZD30-Engine-Cylinder-Head-11039_60148777971.html
It's probably really so that Nissan could do their inlet port gymnastics as opposed to having a lower bending moment on the engine.
For the port gymnastics, they've got the two inlet ports per cylinder, and a singe exhaust (obviously the exhaust from one valve travels across the back of the other valve)
Inlet side, there is a low port that introduces the air tangentially to the cylinder, creating swirl.
The other, high, port is designed for volume, but during light loads is closed off with a butterfly (so called swirl valve) to provide better mixing for the high EGR volumes that the thing uses.
MolaKule
Staff member
Originally Posted By: Lapham3
A good read and such shows how far we've come in better understanding cause and effect of the many variable stresses. A little story-I recall 'a talk' given some years ago by an old retired Buick powertrain engineer who was also involved in 'real world' testing. He spoke of 'torture testing' the 'new' '67 lightweight 400/430 V8's replacing the heavy 'nailhead' engines they drove instrumented pre-production cars from Flint to the desert proving grounds. The first attempts broke 3" crankshaft mains and so that was moved to 3 1/4" and those survived. He said the lightweight block flexed too much under severe loads. When I asked how the heck Buick could justify a 'fix' based on the rotating assembly 'stabilizing' a weak block he kinda smiled and shrugged.
You need both, enough crankshaft flexural capability and mass to dampen harmonics a rigid block to minimize distortions.
BTW, that was a good paper Shannow.
A good read and such shows how far we've come in better understanding cause and effect of the many variable stresses. A little story-I recall 'a talk' given some years ago by an old retired Buick powertrain engineer who was also involved in 'real world' testing. He spoke of 'torture testing' the 'new' '67 lightweight 400/430 V8's replacing the heavy 'nailhead' engines they drove instrumented pre-production cars from Flint to the desert proving grounds. The first attempts broke 3" crankshaft mains and so that was moved to 3 1/4" and those survived. He said the lightweight block flexed too much under severe loads. When I asked how the heck Buick could justify a 'fix' based on the rotating assembly 'stabilizing' a weak block he kinda smiled and shrugged.
You need both, enough crankshaft flexural capability and mass to dampen harmonics a rigid block to minimize distortions.
BTW, that was a good paper Shannow.
MolaKule
Staff member
I'll post this here as well:
Another consideration is rolling bearing lubrication, which in jet turbines the lubrication system is different with the bearing "cells" isolated:
Quote:
:
The rotor bearings used in turbofan engines are ball bearings and roller bearings. They are located within sealed bearing compartments. Oil supplied by the pressure pump is directed through individual supply lines and sprayed on the bearings through one or more nozzles per bearing...The oil-wetted areas are only inside the bearing compartments. The oil has no contact to the rotor components outside the bearing compartments and to the gas path. To ensure this the walls of the bearing compartments are sealed against the rotating shafts. For this sealing two types of seals are used: The carbon seal and the labyrinth seal...
The Type 3 jet turbine oils are typically 5.3 cSt@100C oils and have a BV higher than 12,000 centistokes at a temperature of -40° C.
Another consideration is rolling bearing lubrication, which in jet turbines the lubrication system is different with the bearing "cells" isolated:
Quote:
:
The rotor bearings used in turbofan engines are ball bearings and roller bearings. They are located within sealed bearing compartments. Oil supplied by the pressure pump is directed through individual supply lines and sprayed on the bearings through one or more nozzles per bearing...The oil-wetted areas are only inside the bearing compartments. The oil has no contact to the rotor components outside the bearing compartments and to the gas path. To ensure this the walls of the bearing compartments are sealed against the rotating shafts. For this sealing two types of seals are used: The carbon seal and the labyrinth seal...
The Type 3 jet turbine oils are typically 5.3 cSt@100C oils and have a BV higher than 12,000 centistokes at a temperature of -40° C.
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