UR Pulleys & Harmonic Balancers - in general
05-28-2003, 06:31 AM
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UR Pulleys & Harmonic Balancers - in general
Lately there has been much debate on the subject of harmonic balancers, internally balanced engine, etc.
Many guys have been saying not to worry oabout the lack of the UR crank pulley also serving as a harmonic balancer because the VQ engine is internally balanced. While the VQ is internally balanced, this has nothing to do with harmonic damping due to torsional distortion of the crankshaft.
Balancing an engine is done to keep it from vibrating and shaking itself apart, reduce bearing wear, increase moving part lifetime, etc. Mass damping (via harmonic balancer) serves an entirely different purpose.The UR pulleys have no rubber damper ring and are not tuned to cancel out any harmonic frequencies inherent in our VQ engine.
You may remember from school that almost any solid object has a point of resonance when struck. An example is twanging a ruler over the edge of a desk. All resonant systems are characterized in physics as having a mass and an elastic component. Increasing the mass decreases the frequency of resonance.....increasing the elastic modulus (spring constant)increases the frequency of resonance. So, if you tape a pebble to the end of the ruler, the resonant frequency decreases.
Most resonant systems have a primary resonantfrequency and also have some other frequencies (harmonics) at which they can be persuaded to resonate, though not as efficiently as at the primary frequency. These harmonic frequencies occur at even multiples of the primary resonant frequncy. All musical instruments have distinct sounds characterized by their combinations of primary and overtone (harmonic) resonant components. If you've ever heard a pure sine wave, you know just how rare it is to hear such a sound in nature.
Another property of resonant systems is that they tend to keep going for some time after the input energy source stops. A good example is a guitar string-......you pluck it, and it keeps resonating for a few seconds afterward, until the friction of the string and of the surrounding air damps it out.
So why do we care about resonance in crankshafts? Because steel is dense, and makes pretty good springs, it also makes good resonant systems. It also structurally fails when repeatedly stressed to near the yield point (fatigue). Since resonance is a repetitive deflection, it's easy to see how continued resonance can cause structural problems over time.
To see a good example in practice, look at the footage of the collapse of the Tacoma narrows bridge. Wind blowing over the deck of the suspension bridge essentially made it into a giant aeolian harp string. The bridge resonated until the deck collapsed from fatigue. The failure mode, incidentally, was torsional vibration.
With our crankshafts, we don't worry much about resonance in the bending axis--there are main bearings and they do a pretty good job of encouraging the crank to stay straight. Of more concern, though, is the fact that our steel cranks resonate quite well in a twisting(torsional)mode. like the bridge.... if they resonate too much, they'll exceed the safe limits of deflection and begin to weaken/fatigue. The harmonic frequencies of resonance are damped by the stock crank pulley attatched to the crank.
Since the strength of the exciting impulse is proportional to the peak torque of the engine, we need to be concerned about running our engines in high torque conditions... like above 3500 rpm. Also as MaxHax stated in another thread, the use of N2O would not be very smart if running without a harmonic damper due to serious amounts of torque generated.
The solution Nissan chose for the engines was to add a second resonant system with a damping
factor to the end of the crankshaft. Basically, when the exciting frequency approaches the vulnerable frequency of the crank, the rubber and steel system begins to resonate as well, and dissipates the energy of vibration as heat generated by internal friction in the rubber layer of the damper.
Bottom line is if you are wanting to run UR pulleys, do so at your own risk.....
I hope this has given some of you a better understanding as to why we need our crank pulleys to have a damping effect. You can't just throw a smaller, lighter pulley on there and be fat dumb and happy thinking you now have extra power.... You are slowly killing your engine.
Many guys have been saying not to worry oabout the lack of the UR crank pulley also serving as a harmonic balancer because the VQ engine is internally balanced. While the VQ is internally balanced, this has nothing to do with harmonic damping due to torsional distortion of the crankshaft.
Balancing an engine is done to keep it from vibrating and shaking itself apart, reduce bearing wear, increase moving part lifetime, etc. Mass damping (via harmonic balancer) serves an entirely different purpose.The UR pulleys have no rubber damper ring and are not tuned to cancel out any harmonic frequencies inherent in our VQ engine.
You may remember from school that almost any solid object has a point of resonance when struck. An example is twanging a ruler over the edge of a desk. All resonant systems are characterized in physics as having a mass and an elastic component. Increasing the mass decreases the frequency of resonance.....increasing the elastic modulus (spring constant)increases the frequency of resonance. So, if you tape a pebble to the end of the ruler, the resonant frequency decreases.
Most resonant systems have a primary resonantfrequency and also have some other frequencies (harmonics) at which they can be persuaded to resonate, though not as efficiently as at the primary frequency. These harmonic frequencies occur at even multiples of the primary resonant frequncy. All musical instruments have distinct sounds characterized by their combinations of primary and overtone (harmonic) resonant components. If you've ever heard a pure sine wave, you know just how rare it is to hear such a sound in nature.
Another property of resonant systems is that they tend to keep going for some time after the input energy source stops. A good example is a guitar string-......you pluck it, and it keeps resonating for a few seconds afterward, until the friction of the string and of the surrounding air damps it out.
So why do we care about resonance in crankshafts? Because steel is dense, and makes pretty good springs, it also makes good resonant systems. It also structurally fails when repeatedly stressed to near the yield point (fatigue). Since resonance is a repetitive deflection, it's easy to see how continued resonance can cause structural problems over time.
To see a good example in practice, look at the footage of the collapse of the Tacoma narrows bridge. Wind blowing over the deck of the suspension bridge essentially made it into a giant aeolian harp string. The bridge resonated until the deck collapsed from fatigue. The failure mode, incidentally, was torsional vibration.
With our crankshafts, we don't worry much about resonance in the bending axis--there are main bearings and they do a pretty good job of encouraging the crank to stay straight. Of more concern, though, is the fact that our steel cranks resonate quite well in a twisting(torsional)mode. like the bridge.... if they resonate too much, they'll exceed the safe limits of deflection and begin to weaken/fatigue. The harmonic frequencies of resonance are damped by the stock crank pulley attatched to the crank.
Since the strength of the exciting impulse is proportional to the peak torque of the engine, we need to be concerned about running our engines in high torque conditions... like above 3500 rpm. Also as MaxHax stated in another thread, the use of N2O would not be very smart if running without a harmonic damper due to serious amounts of torque generated.
The solution Nissan chose for the engines was to add a second resonant system with a damping
factor to the end of the crankshaft. Basically, when the exciting frequency approaches the vulnerable frequency of the crank, the rubber and steel system begins to resonate as well, and dissipates the energy of vibration as heat generated by internal friction in the rubber layer of the damper.
Bottom line is if you are wanting to run UR pulleys, do so at your own risk.....
I hope this has given some of you a better understanding as to why we need our crank pulleys to have a damping effect. You can't just throw a smaller, lighter pulley on there and be fat dumb and happy thinking you now have extra power.... You are slowly killing your engine.
Last edited by N74DV; 05-28-2003 at 06:44 AM.
05-28-2003, 07:52 AM
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Is the pic of the snapped crank from a Z33 or another make/model? Real interesting and informative write-up. I understand the concept, but the specifics are a wee bit over my head... still, you definitely sum everything up with your last statements about the fact that you're taking a risk and slowly killing the engine by not having a dampened crank pulley.
I'm curious to hear what others have to say. I'm wondering if UR, or even one of our genius board members, will come up with a dampening solution for the UR crank pulley...
I'm curious to hear what others have to say. I'm wondering if UR, or even one of our genius board members, will come up with a dampening solution for the UR crank pulley...
05-28-2003, 08:00 AM
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Originally posted by Alev
Is the pic of the snapped crank from a Z33
Is the pic of the snapped crank from a Z33
05-28-2003, 08:28 AM
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This is a very old debate, and I for one am not qualified to choose one side or the other, however I always had one nagging question.
It seems to me that the ideal situation would be to reduce the load on the crank (which is what frees up HP) while retaining the balancer. Couldn't this be done by simply making larger pulleys for the accessories that are being driven by the crank pulley? While you won't get quite as much HP from this solution since you are not getting the benefit of reduced weight of the crank pulley, you should be pretty close.
It seems to me that the ideal situation would be to reduce the load on the crank (which is what frees up HP) while retaining the balancer. Couldn't this be done by simply making larger pulleys for the accessories that are being driven by the crank pulley? While you won't get quite as much HP from this solution since you are not getting the benefit of reduced weight of the crank pulley, you should be pretty close.
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05-28-2003, 08:32 AM
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larger pulleys will turn the acces. slower, but larger pulleys also means more rotational mass.
Since more realized gains are acheived by the reduction of rotational mass than by under driving acces, I'd suspect that the added rotational mass of larger access pulleys would negate the gains by under driving them.
A smaller/lighter crank pulley is desired, but only if it retains a damper.
Since more realized gains are acheived by the reduction of rotational mass than by under driving acces, I'd suspect that the added rotational mass of larger access pulleys would negate the gains by under driving them.
A smaller/lighter crank pulley is desired, but only if it retains a damper.
05-28-2003, 09:53 AM
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ok I'm no engineer of physicist but isn't the design of the UR crank pulley somewhat compensating for the dampner. First of all it's aluminum and light weight 5 lbs lighter and there are a series of holes through out the crank pulley that would help dissapate resonation, wouldn't it.
Kind of like what happens when you cork a baseball bat. Or look at drilled brake rotors.
Most stock crank pulleys I've seen are solid pieces of metal, which you can usually find some time of dampening device on them. Some stock crank pulleys I've seen without and dampening I find have holes drilled into them at certain points.
Isn't this what UR has done by making it lighter and putting a series of holes through them?
Kind of like what happens when you cork a baseball bat. Or look at drilled brake rotors.
Most stock crank pulleys I've seen are solid pieces of metal, which you can usually find some time of dampening device on them. Some stock crank pulleys I've seen without and dampening I find have holes drilled into them at certain points.
Isn't this what UR has done by making it lighter and putting a series of holes through them?
05-28-2003, 10:09 AM
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damping can only be done when the mass damper is tuned to the resonant frequenies.
The UR pulleys are MUCH lighter than the stock pulley. Less mass means higher resonant frequency.
THE UR pulleys are NOT tuned to damp the VQ's crankshaft torsional distortion....
The holes have nothing to do with damping effect. The holes exist to reduce rotational mass.
The UR pulleys are MUCH lighter than the stock pulley. Less mass means higher resonant frequency.
THE UR pulleys are NOT tuned to damp the VQ's crankshaft torsional distortion....
The holes have nothing to do with damping effect. The holes exist to reduce rotational mass.
05-28-2003, 10:24 AM
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I don't think the holes are just there to reduce the weight, though that is one side product. The holes should help reduce resonation.
Look at corked bats or police batons. They have a hole drilled the center of them so if you hit something the vibrations won't sting your hands.
Another example are drilled rotors. Take a regular rotor and tap it with a hammer... listen to the sound. Then do the same to a drilled rotor... the resonation is less.
Even in martail arts the bo is a solid piece of wood but much more stronger and affective with a small hole is drilled throughout the bo. The same with Kendo sticks, hollow bamboo...
Look at corked bats or police batons. They have a hole drilled the center of them so if you hit something the vibrations won't sting your hands.
Another example are drilled rotors. Take a regular rotor and tap it with a hammer... listen to the sound. Then do the same to a drilled rotor... the resonation is less.
Even in martail arts the bo is a solid piece of wood but much more stronger and affective with a small hole is drilled throughout the bo. The same with Kendo sticks, hollow bamboo...
05-28-2003, 10:47 AM
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In a sense you are correct... drilling holes does in fact alter the resonant frequency... The only reason the resonant frequency is raised is due to less mass.
Holes alone have nothing to do with frequency tuning... it's the reduced mass that alters tuning.
I guarantee that the UR pulley is NOT tuned to the same harmonic frequency range as the stock crank pulley.
This is not my opinion but it is science.... Science is not wrong.
Holes alone have nothing to do with frequency tuning... it's the reduced mass that alters tuning.
I guarantee that the UR pulley is NOT tuned to the same harmonic frequency range as the stock crank pulley.
This is not my opinion but it is science.... Science is not wrong.
05-28-2003, 11:07 AM
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This is not my opinion but it is science.... Science is not wrong. [/B][/QUOTE]
Bro, you know that this statement is not correct. If science is not wrong than how do you explain helicopters. By physics they should not be able to fly.... but they do.
Anyhow, I wrote a email to UR asking them to explain how they designed the crank pulley to compensate for the dampening issue. UR is a good company. I doubt they would make such a mistake as this. Just have to see what they say.
Bro, you know that this statement is not correct. If science is not wrong than how do you explain helicopters. By physics they should not be able to fly.... but they do.
Anyhow, I wrote a email to UR asking them to explain how they designed the crank pulley to compensate for the dampening issue. UR is a good company. I doubt they would make such a mistake as this. Just have to see what they say.
05-28-2003, 11:12 AM
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Originally posted by SizongZ
Bro, you know that this statement is not correct. If science is not wrong than how do you explain helicopters. By physics they should not be able to fly.... but they do.
Bro, you know that this statement is not correct. If science is not wrong than how do you explain helicopters. By physics they should not be able to fly.... but they do.
It's a farce that helicopters and bumble bees are "not supposed to fly" and many people buy into it....
I'd go into exaclty why they are able to fly, but it's not prudent to do so on this forum... if you really wanna know PM me.
On the matter of the UR pulley... it's math dude... THe UR pulley has less mass.... therefore using math you can deduce that it has a higher resonant frequency than a stock pulley with damper. The UR pulley provides no damping effect within the frequency range that matters to us.
If you want to argue that 2+2 is not 4 I'd love to hear your arguments.
Last edited by N74DV; 05-28-2003 at 11:18 AM.
05-28-2003, 11:21 AM
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hahaha.... helo's are a different story though I am greatly fascinated by them.
But Science is not always right... it's always changing. I'm in the telecommunications world and science is always saying one thing and than later on they say something else....
Ok helicopters is probably a bad example to use but still...... point being science is not always right.
Anyhow back to the pulleys. I just recieved email back from UR on the pulleys... here it is
People are getting the pulleys confused with the harmonic dampers found on 90 degree V8 and V6 engines. The pulleys on most of the new import and smaller domestic engines have an elastomer (rubber ring) incorporated into the pulley that looks similar to a harmonic damper. The durometer in the OEM pulley serves as an isolator, which is there for noise suppression from the A/C compressor, P/S pump and the alternator, What the manufacturers call NVH (Noise Vibration & Harshness) when referring to passenger compartment noticeable noise and
vibration. If you look at some of the pulleys on older imports there is no rubber to be found. We have samples of mostly Honda, An Altima, 1.8L Eclipse, 2.3L Ford, Chrysler 2.2L, 1.8L VW and a few others all with no rubber. The purpose of a traditional harmonic damper is to keep the crankshaft from cracking
which is not necessary on your engine. You have probably heard stories about bearing and oil pump failures. Any abnormal bearing wear is due to a lubricating issue, The most common examples are using the wrong weight of oil, a faulty head
gasket or poor engine assembly practices. The idea of increased bearing wear from not having a damper on the engine is false. Using too heavy of an oil can shatter the oil pump gears. Most of the time oil pump failure is caused by something being sucked up into the pump. The fact of the matter is the pulleys have been out there running for over 5 years and there have been no failures
attributed to the pulleys. There is a lot of internet hearsay about the pulleys, too often people are too quick to blame the pulley first rather than looking into why there was a problem and then go and post it on a message board. You really have nothing to worry about. If you would like to read more info on the subject, visit the FAQ section on our web site
But Science is not always right... it's always changing. I'm in the telecommunications world and science is always saying one thing and than later on they say something else....
Ok helicopters is probably a bad example to use but still...... point being science is not always right.
Anyhow back to the pulleys. I just recieved email back from UR on the pulleys... here it is
People are getting the pulleys confused with the harmonic dampers found on 90 degree V8 and V6 engines. The pulleys on most of the new import and smaller domestic engines have an elastomer (rubber ring) incorporated into the pulley that looks similar to a harmonic damper. The durometer in the OEM pulley serves as an isolator, which is there for noise suppression from the A/C compressor, P/S pump and the alternator, What the manufacturers call NVH (Noise Vibration & Harshness) when referring to passenger compartment noticeable noise and
vibration. If you look at some of the pulleys on older imports there is no rubber to be found. We have samples of mostly Honda, An Altima, 1.8L Eclipse, 2.3L Ford, Chrysler 2.2L, 1.8L VW and a few others all with no rubber. The purpose of a traditional harmonic damper is to keep the crankshaft from cracking
which is not necessary on your engine. You have probably heard stories about bearing and oil pump failures. Any abnormal bearing wear is due to a lubricating issue, The most common examples are using the wrong weight of oil, a faulty head
gasket or poor engine assembly practices. The idea of increased bearing wear from not having a damper on the engine is false. Using too heavy of an oil can shatter the oil pump gears. Most of the time oil pump failure is caused by something being sucked up into the pump. The fact of the matter is the pulleys have been out there running for over 5 years and there have been no failures
attributed to the pulleys. There is a lot of internet hearsay about the pulleys, too often people are too quick to blame the pulley first rather than looking into why there was a problem and then go and post it on a message board. You really have nothing to worry about. If you would like to read more info on the subject, visit the FAQ section on our web site
05-28-2003, 11:25 AM
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All I can tell you is the UR response is a load of crap.....
do the research yourself if you want.... in the end you will learn that you are risking excessive crank torsional distortion if you remove the damped stock pulley.
I have experienced first hand what happens when an engine has had the HB removed... snapped crank... in a plane at 2000 feet above the ground...
I have the NTSB and Metallurgic reports to prove it.
do the research yourself if you want.... in the end you will learn that you are risking excessive crank torsional distortion if you remove the damped stock pulley.
I have experienced first hand what happens when an engine has had the HB removed... snapped crank... in a plane at 2000 feet above the ground...
I have the NTSB and Metallurgic reports to prove it.
05-28-2003, 11:31 AM
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Ok.. that is a plane with a big as propellor right?
This is a car.... not a plane.
But he is right though.. there are cars out there with no rubber or harmonic balancers. Can you explain those?
My uncle owns a mechanic shop I went over to look at crank pulleys when this debate started. Noticed several different kinds of crank pulleys. Some with balancers, others with dampeners, some with just a rubber ring and some without anything just plain metal?
I'm not going to run N20 so the problem Max had is null and void to me.
But I will most likely run turbos.... I deal with that when I get to it.
But thanks for the good debate
and for UR's response being crap? I don't think they'd risk something like that.... that can be a huge lawsuit. False Information
This is a car.... not a plane.
But he is right though.. there are cars out there with no rubber or harmonic balancers. Can you explain those?
My uncle owns a mechanic shop I went over to look at crank pulleys when this debate started. Noticed several different kinds of crank pulleys. Some with balancers, others with dampeners, some with just a rubber ring and some without anything just plain metal?
I'm not going to run N20 so the problem Max had is null and void to me.
But I will most likely run turbos.... I deal with that when I get to it.
But thanks for the good debate
and for UR's response being crap? I don't think they'd risk something like that.... that can be a huge lawsuit. False Information
Last edited by SizongZ; 05-28-2003 at 11:33 AM.
05-28-2003, 11:38 AM
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hey... like your avatar says.... "To each his own"
it's your Z and your crank.... if your Z develops problems due to the UR pulleys within the warranty range you can bet your a$$ Nissan will tell you to forget it..
besides..... do you wanna risk your warranty and a jacked crank for a measly 10 hp??
it's your Z and your crank.... if your Z develops problems due to the UR pulleys within the warranty range you can bet your a$$ Nissan will tell you to forget it..
besides..... do you wanna risk your warranty and a jacked crank for a measly 10 hp??
Last edited by N74DV; 05-28-2003 at 11:45 AM.