Lightweight Crank Pulley Check-In

[300dollarGSX]

Engine torque has nothing to do with when the crank will reach it's natural frequency. This will be solely a function of RPM. The power applied to the crank will affect the intensity (or amplitude) of the effect. Lower output engines have less to worry about, because while still passing through RPM ranges which contribute to this, they produce less power thus keeping magnification to a minimum. Any RPM/2 point outside of these ranges will work against the cranks natural frequency.

Right, engine torque output isn't important. The torque spikes caused by each power cycle are greater than the mean torque output of the engine. They are the force the crank sees.

We don't exactly disagree, we just have two different points.

Another, better, way to say it: it cannot be made not to jumprope. There's more force being applied to the center than each end; about twice as much. Thus one reason you see why the amplitude of the 4cylinder vibration is so high. The other being the frequency of power strokes for the total length of the crank.

I'm not quite sure what you mean here. The center of the crank will have a seperate mode of vibration that will cause a higher frequency. Is that what you mean?

Also concerning what I put in bold. We're talking twisting. "twisting" is not bending of the crank arms. It is twisting the crank due to the forces exerted on the crank arms. Looking at it like this helps one appreciate how "easily" a crank twists. Yes, the leverage is greater with longer strokes. But there is still plenty of leverage there. Enough for a 4g61 to have been given a damper from the factory by the mitsu engineers.

By twisting, do you mean rotating? I'm not really sure how this ties to the sentence you put in bold for me unless you are talking about rigid body motion as mentioned in the article posted by donniekak. I'm not sure that's what you mean, though, since you talk about deflection later in your post.

All in all, we're simply arguing some of the finer points and seem to be in agreement for the most part. Use a damper/absorber/harmonic balancer. In the words of dsm-onster, "If it doesn't hurt and could very possibly help. . ."

Something else I noticed in the article above that I thought was interesting is that the author wrote that the tolerances specified for an OEM damper have a range of around 16%. That's quite a bit of leeway. No wonder the EVO guys who have stroked engines in the thread posted above see good results from even their stock damper. It appears that even the stock device has more range than I gave them credit for having. It should technically wear faster attached to an engine that creates vibrations at the limits of its range, though... not that we know what those limits are.

 

[rx7ttlm]

Ok, so the thing on the end of the crank is called a harmonic balancer. People always mistake this for having to do with actually balancing the crank. In this case it has nothing to do with it. The function of a harmonic balancer is to dampen the vibrations of the crank. So for every firing event the crank twists a bit, and that creates resonance. The thing on the end of the crank dampens this. Using an aluminum pulley is dumb. Notice in the highest levels of motorsports this is not done. So why the Blank would a street car guy do it? I run the fluidamper type with an arp fastener to hold it on. With a 400hp the stock dampener is fine. BUT DO RUN ONE. the inline 4 has the worst harmonics of any engine that I know of. I have seen hondas and mitsubishi's alike that my friends snapped cranks for seemingly no reason. 80% of them had those crap pullies. If you hate your crank, run the aluminum pulley If your really worried about rotating mass. I have a great condition aluminum awd 7 bolt flywheel thats going up for sale (only because I have a 6 bolt now).

Cheers,

 

[1997_GSX]

I am running a Fluidampr on my Eagle crank, I wouldn't ever touch the lightweight crank pulleys. I have the light weight wp and ps pulley, I would have one on my alt but I run a Saturn alt.

 

[ramsack]

The more inward you go on something that has torque being applied to it, the more torque there is. If you have a lever 1 foot long and apply 2 lbs to it, it will have a torque of 2 lb-ft. If you have a lever 2 feet long and apply 2 lbs to it, it will have a torque of 4 lb-ft.

Ok, so the thing on the end of the crank is called a harmonic balancer.

It is really called a harmonic damper. It dampers the harmonics. You don't balance harmonics, you damper them.

 

[2gdsm_nc]

READ ME all the reading I needed to explain how and why.

 

[ramsack]

I especially like this picture:

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[2gdsm_nc]

yep, Now imagine that flywheel moving at full speed, if any out of balance occurs at say 5000rpm, while your applying clutch pressure and releasing it. How do you think that affects the far side of the crank, where a damper would add the necessary balance on the other end to counter the effects.
Imagine riding around in your car w/out any shocks springs. pretty rough ride huh, why would you do that to your engine? Yea sure you can do it. but your A** is going to hate you.

 

[dsm-onster]

I especially like this picture:

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That drawing describs exactly what I was saying. I wish I saw that before. It would have saved alot of my time.

 

[spoonman]

What is the engine's designed application.


DD, Drag Strip, Road Racing?

Are the RPM's going to be kept constant, like during highway DD?
Or are the RPM's going to be swept through their range and not be held constant at an area of critical vibration, like in say track only racing?




I use the stock OEM pulley on stock internal, DD 4g63 engines. I recommend using a Fluidampr pulley on DD 4g63 engines that use after market internals, this is because the OEM damper was designed for that particular set of internals and is less effective with a lighter/stiffer bottom end. If you have an all out, balls to the wall, track only engine use a solid pulley, real racers tear down the engine to check tolerances and bearing wear many times a season.

 

[ramsack]

yep, Now imagine that flywheel moving at full speed, if any out of balance occurs at say 5000rpm, while your applying clutch pressure and releasing it. How do you think that affects the far side of the crank, where a damper would add the necessary balance on the other end to counter the effects.
Imagine riding around in your car w/out any shocks springs. pretty rough ride huh, why would you do that to your engine? Yea sure you can do it. but your A** is going to hate you.

The damper is not a balancer. If something is out of balance it doesn't impart a torsional force on the crank, but radial.

 

[2gdsm_nc]

The damper is not a balancer. If something is out of balance it doesn't impart a torsional force on the crank, but radial.

oh oh let me correct myself as well....No force is applied by it.
We use a Tuned absorber I should be saying rather than "damper" or "balancer"/<<what they are commonly refered to!
It does not dampen or balance the crank. Using a rubber spring element and a inertia ring that is set to the first "Tortional" national freq of the crank. And only. I say again Only reduces the "vibration" at a certain engine speed.



This is where a fluid or gel style "damper" comes into effect. Where the inertia ring is sealed in this fluid. The torsional vibration of the crankshaft forces the fluid through narrow passages that dissipates the vibration as heat. More like a shock absorber like on a car. Non RPM specific.

 

[Boosted98gsx]

The damper is not a balancer. If something is out of balance it doesn't impart a torsional force on the crank, but radial.

There is no such thing as a "radial" force. There are shear, bearing, tearout, torsional, and bending forces (stresses) only.

 

[ramsack]

There is no such thing as a "radial" force. There are shear, bearing, tearout, torsional, and bending forces (stresses) only.

You know what I meant by that. By that note there is not such thing as weak, strong, electromagnetic, or gravitational forces. Or centrifugal, centripetal, torque, tension, compression. I can go on and on...

I meant that balancing has to do with a force that is going away from the axis the crank is spinning on, which is not the same as torsional, so that is a force, and it would kind of be centrifugal.

 

[pboglio]

There is no such thing as a "radial" force. There are shear, bearing, tearout, torsional, and bending forces (stresses) only.

There is no only. You forgot compressive and tensile stresses, which bending stresses are a subset of. In general, you most definitely can have a load applied radially, as well as axially, or anywhere in between. The specific part geometry and displacement constraints would then dictate whether that "radial" force would generate any of the above mentioned stresses, or a combination of such.

The stresses in the crank are a complex combination of bending stresses, torsional stresses, compressive loads on the bearing journal surfaces, on so on and so on. Just saying we know what the guy is trying to say.

 

[Boosted98gsx]

There is no only. You forgot compressive and tensile stresses, which bending stresses are a subset of. In general, you most definitely can have a load applied radially, as well as axially, or anywhere in between. The specific part geometry and displacement constraints would then dictate whether that "radial" force would generate any of the above mentioned stresses, or a combination of such.

The stresses in the crank are a complex combination of bending stresses, torsional stresses, compressive loads on the bearing journal surfaces, on so on and so on. Just saying we know what the guy is trying to say.

Damn, forgot those.

Yes, you can have a load applied in any direction. I was just trying to help him describe what he's trying to say a bit more accurately.

 

[ramsack]

It's like doctors...you can't say slang words like "my dick burns" to them. They get really offended, like they are above everyone else...because they do know what you mean.

 

[Boosted98gsx]

It's like doctors...you can't say slang words like "my dick burns" to them. They get really offended, like they are above everyone else...because they do know what you mean.

It's because there are proper terms to use.

 

[ramsack]

Which are retarded. It would be okay if doctors were the most common job in the world, but it's not. They can say pee in the cup instead of make urine. You don't make urine, your kidneys do. It's so retarded and I will not go to a doctor because of crap like this...thinking they are above everyone and that they are the only people who save lives, and they don't, unless they are the doctor who invented that particular cure.

 

[300dollarGSX]

The more inward you go on something that has torque being applied to it, the more torque there is. If you have a lever 1 foot long and apply 2 lbs to it, it will have a torque of 2 lb-ft. If you have a lever 2 feet long and apply 2 lbs to it, it will have a torque of 4 lb-ft.

I'm guessing you meant outward or away from the object (or I'm just reading it backward). Yes, a longer torque arm will make more torque. We're not changing the length of the torque arm, though. We have 4 equal length torque arms that are at different distances from the "load" of the flywheel. This would be like using a ratchet and socket on a bolt directly, applying 10 ft/lbs of torque, then using a 3" extension and applying 10 ft/lbs of torque.

He was saying that there was about twice as much force in the center of the crank as there was at each end. I don't think the "force" he's talking about is torque, necessarily, but frequency. The nodes created near each end of the crank will cause the center of the crank to vibrate at a separate, higher frequency because it is effectively a shorter length, but the same stiffness. The nodes won't necessarily "separate" cylinders 1 and 4 from 2 and 3, though. Again, I'm only assuming that's what he was trying to say.

 

[dsm-onster]

I'm guessing you meant outward or away from the object (or I'm just reading it backward). Yes, a longer torque arm will make more torque. We're not changing the length of the torque arm, though. We have 4 equal length torque arms that are at different distances from the "load" of the flywheel. This would be like using a ratchet and socket on a bolt directly, applying 10 ft/lbs of torque, then using a 3" extension and applying 10 ft/lbs of torque.

The torque is added as the power stroke changes from one torque arm to the next . . . This is frequency ANd an increse in torque . Resonance is when the recoils add together just right.

If you did ratchet a bolt and then there was a special adapter that allowed your friend to wratchet that same bolt at the same time with the same ratchet arm: the torque is doubled, assuming he's not stronger than you. The material used to form the ratchets may be of weak material, but working together you can double the torque without fatiguing of the weaker metal and break the bolt loose. Or break the crank at the flywheel end since the fly wheel is "ground"; and the crank arms are at resonance with their recoil. That's why it breaks there. Lets not confuse the most total movement with where the most torque is seen. The deflection of each crank arm relative to the journal before it is about the same.

 

[300dollarGSX]

The torque is added as the power stroke changes from one torque arm to the next . . . This is frequency ANd an increse in torque .

This is correct when the power strokes overlap (though not peak torque unless you have 2 or more cylinders that fire at the same time), but these are 180 degrees apart. There is one power stroke at a time in our inline 4. In engines with more cylinders, the torque spikes are closer together. This will provide a smoother, more consistent torque delivery with a higher average torque.

I was just trying to figure out what you meant when you said there would be more force at the center of the crank.

 

[dsmfa9nutter]

I like how there is little to no proof that using a solid pulley causes crank breakage yet everyone, including the site founder, is sitting here being an armchair engineer. WHERE are the pictures of the dozens of broken cranks? One picture from 5 years ago means NOTHING to me. The multiple people (and muliple pictures posted) say a lot more than 4g63 myths spawned from the mouths of people who have no idea reiterating what one or two people that might know what they're talking about have said. Just like how others pass over actual PROOF that it doesn't destroy bearings just because the guy didn't post a clickable link? That's ####ing pathetic! The ignorance in this thread is mind blowing.

I'll issue a challenge to the naysayers, put up or shut up. Show me the wiped bearings and the broken cranks that seem to happen the instant someone puts on a solid crank pulley. If you haven't actully used a solid pulley, get out of the thread.

After actually reviewing the pictures and actual testimonials (80k and bearings are fine, 50k with pictures and all good), I'll be using a solid pulley.

 

[Locke]

I don't think anybody in here said that using a solid pulley will cause your crank to break, instantly or otherwise, rather that using a solid pulley will increase the risk of such things occurring.

You don't have to see something happen to know that it can or does happened. Very few people have seen speciation occur, but that doesn't mean it doesn't happen. The evolutionary theory has been through the gauntlet of peer review several times and has not been disproved, and applications using the theory work in the real world. Likewise, we know that ringing parts at their natural frequency can be disastrous.
Partnair Flight 394 - Wikipedia, the free encyclopedia - Bolt failure due to resonant vibration.
Angers Bridge - Wikipedia, the free encyclopedia - Soldier marching across it rang the bridge at it's natural frequency.
http://en.wikipedia.org/wiki/Millennium_Bridge_(London) - Bridge swayed at open during a mass public crossing. Fixed before catastrophic failure.

Also, many of us do have proper and credible educations.

 

[pneumo]

I don't think anybody in here said that using a solid pulley will cause your crank to break, instantly or otherwise, rather that using a solid pulley will increase the risk of such things occurring.

Sure there is, here's a recent quote saying just that, "
Likewise, we know that ringing parts at their natural frequency can be disastrous.
Partnair Flight 394 - Wikipedia, the free encyclopedia - Bolt failure due to resonant vibration.
Angers Bridge - Wikipedia, the free encyclopedia - Soldier marching across it rang the bridge at it's natural frequency.
http://en.wikipedia.org/wiki/Millennium_Bridge_(London) - Bridge swayed at open during a mass public crossing. Fixed before catastrophic failure."

Those are some great examples of poorly engineered structures. I hope you're not trying to say that the 4G63 crank was poorly engineered, are you? It's not made of glass.

You don't have to see something happen to know that it can or does happened. Very few people have seen speciation occur, but that doesn't mean it doesn't happen. The evolutionary theory has been through the gauntlet of peer review several times and has not been disproved, and works using the theory work in real world applications.

I don't think this analogy applies. Yes the theory of resonance is sound, but that doesn't mean it's the dominant stressor in a crank. There was a good link posted to EvolutionM forums that showed it takes over 600hp on a 7 bolt EVO crank before early wear of the bearings showed up when using a solid pulley. The HP level matters because it affects the magnitude of the vibrations. BTW the EVO 7 bolt crank uses narrower main and rod bearings than a 6 bolt crank, so the bearings don't give as much support, and the EVO crank is 2 pounds lighter.

 

[ramsack]

The big difference between those structures are that they are assembled and are made of a bunch of pieces, whereas a crank is a solid piece of metal. There is also the fact that they are thinner compared to their relative size. They are long structures and what made them up was thin. A crank is thicker compared to its length than something like a bridge. That makes the bridge more flexible. The airplane wasn't engineered wrong, it was just using non-OEM bolts for the piece that failed. The Angers Bridge was long before our technology today and there was not good metallurgy and ways to protect the metal from corrosion. The Millenium Bridge was a fluke and something that was fixed. It is impossible to account for EVERYTHING that can happen to something while engineering. If we were able to, we would be Gods and we would have machines that operate at 100% efficiency and we could live forever. If we could forge an entire bridge in one piece in a steel mill and just install it somewhere it would be a lot more resilient. The EVO crank being lighter makes things a lot different. That means parts are thinner, and resonant will not be as strong. I really don't get where everyone who is anti-damper is getting this sense that they were just put on engines for no reason. Obviously they were, and not because of bad engineering.