Flywheel flywheels flywheels.
08-12-2020, 07:36 PM
#576
The part number i needed was fmz004c-cw3 but is unavailable anywhere, shame on companies selling flywheels without their own counterweight needed. The weight i ordered has no available part number just that it fits multi flywheels as a rear counterweight. It was a matter of getting something over nothing. Id come to the conclusion if they all look like ducks and and weigh the same as a duck it must be a duck.
08-12-2020, 07:52 PM
#578
This all started as i assumed the clutch was on its way out (wont actually know what the problem is till i take it apart) , cursory reading had said flywheel should be resurfaced/replaced on clutch upgrade/replacement. So here i am at the bottom of the world (Australia) fighting ridiculous dealership prices and back orders of what should be sold togeather
08-27-2020, 05:31 AM
#580
Spoke to supplier of the weight i needed today, he confirmed as team said that they're basically all the same and the only difference if any is a couple of grams here and there. They arent designed to work with matching flywheels but are "weighted according to the rx8"
08-27-2020, 12:50 PM
#581
Kimura - Poor balancing should not lunch the bearings in 21k unless you are sitting on/near redline all the time.
Not sure what you mean by "self balanced" but my understanding is they would counteract the balance of one part (rotor for instance) with another part (the second rotor).
The OE flywheel is counterbalanced so there is no way to check except as an assembly. All aftermarket flywheels mount to the automatic counterweight and should be neutral balanced. If using an aftermarket flywheel, it should be balanced separately so parts can be changed later without major influence to the balanced engine. Not sure about other brands, but ACT has a maximum imbalance of .25 ounce inch. The clutch and flywheel can be done additionally to the assembly but position needs to be marked since the hole patterns are symmetrical.
Not sure what you mean by "self balanced" but my understanding is they would counteract the balance of one part (rotor for instance) with another part (the second rotor).
The OE flywheel is counterbalanced so there is no way to check except as an assembly. All aftermarket flywheels mount to the automatic counterweight and should be neutral balanced. If using an aftermarket flywheel, it should be balanced separately so parts can be changed later without major influence to the balanced engine. Not sure about other brands, but ACT has a maximum imbalance of .25 ounce inch. The clutch and flywheel can be done additionally to the assembly but position needs to be marked since the hole patterns are symmetrical.
As for side seals, from what I hear they were always done with the method they used on the Renesis. While I can't find any information on if they were using a similar lettering scheme, I do see kana next to each side seal on older rotors.
08-28-2020, 02:38 AM
#582
nope, Renesis rotor weights are all over the board according to my builder who goes through swapping a bunch of them out of PDC inventory and does super critical balancing
which rotating balance on factory engines is also all over the board is what he told me a long time ago
so the idea of the CW being fine tuned really doesn’t mean much in my book, because unless you balance the entire assembly it’s a crap shoot. You’re more likely to win the Mega Lotto than to be anywhere near balanced putting this on any engine that wasn’t already balanced and blueprinted by a builder.
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which rotating balance on factory engines is also all over the board is what he told me a long time ago
so the idea of the CW being fine tuned really doesn’t mean much in my book, because unless you balance the entire assembly it’s a crap shoot. You’re more likely to win the Mega Lotto than to be anywhere near balanced putting this on any engine that wasn’t already balanced and blueprinted by a builder.
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Last edited by TeamRX8; 08-28-2020 at 02:55 AM.
08-28-2020, 09:13 AM
#583
77 cylinders, 4 rotors...
nope, Renesis rotor weights are all over the board according to my builder who goes through swapping a bunch of them out of PDC inventory and does super critical balancing
which rotating balance on factory engines is also all over the board is what he told me a long time ago
so the idea of the CW being fine tuned really doesn’t mean much in my book, because unless you balance the entire assembly it’s a crap shoot. You’re more likely to win the Mega Lotto than to be anywhere near balanced putting this on any engine that wasn’t already balanced and blueprinted by a builder.
.
which rotating balance on factory engines is also all over the board is what he told me a long time ago
so the idea of the CW being fine tuned really doesn’t mean much in my book, because unless you balance the entire assembly it’s a crap shoot. You’re more likely to win the Mega Lotto than to be anywhere near balanced putting this on any engine that wasn’t already balanced and blueprinted by a builder.
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So while Mazda's weight tolerances seem very sloppy, I believe there is more afoot here as far as dynamic balance is concerned, and Mazda was aware of this in designing this engine.
08-28-2020, 09:20 AM
#584
77 cylinders, 4 rotors...
I believe there is another factor going on here that Mazda knows, and others have not really spoken about. While balancing the entire assembly is beneficial and should be done, and the builders that do it are surely spending their time wisely, the oil sloshing around in the rotors provides a balancing effect, like the LeBlanc balancing ring on a clothes washer, (or filling your motorcycle tires with Slime! ) for the rotors themselves, constantly changing with rpm, which means there is a constant balance/imbalance situation going on depending on how much oil is remaining in rotor cavity, and how much rpm, and thereby centrifugal force, and oil flow and volume is present to force the oil into and out of the rotor cavity.
So while Mazda's weight tolerances seem very sloppy, I believe there is more afoot here as far as dynamic balance is concerned, and Mazda was aware of this in designing this engine.
So while Mazda's weight tolerances seem very sloppy, I believe there is more afoot here as far as dynamic balance is concerned, and Mazda was aware of this in designing this engine.
08-28-2020, 01:00 PM
#585
I like that line of thought Kevin, when you chase minimum or beyond tolerances you may gain something but you lose something else in the trade. That said I don't see the harm in a good balance itself and I know at least several machinists account for the weight of the oil in the rotor during balancing. Of course, they wouldn't disclose to me how they do that...
08-29-2020, 04:33 AM
#586
Well I only know what a well established rotary race engine builder starting from the mid 70s told me. IMO the only other person I would even consider possibly equating to his experience with the Renesis might be David Haskell who was at Speedsource. There are multiple dyno graphs posted on here demonstrating his work. The factory results are well known too, ugh.
You want to fill you buckets of hope with that other stuff, be my guest.
I have the original release document from Japan on the RX8 breaking all the components of the car down with profiles of the engineers in each section explaining things. Frankly, I’ll put my faith more in my engine builder than a corporate engineer.
You want to fill you buckets of hope with that other stuff, be my guest.
I have the original release document from Japan on the RX8 breaking all the components of the car down with profiles of the engineers in each section explaining things. Frankly, I’ll put my faith more in my engine builder than a corporate engineer.
Last edited by TeamRX8; 08-29-2020 at 04:45 AM.
09-01-2020, 05:42 PM
#587
I’ll also just add that prior to the Renesis it was understood that a rotary engine should not exceed 8000 rpm without having the rotating assembly balanced. The Renesis had a 9000 rpm redline from the factory and it’s not unusual for people to reprogram that higher still. Further, the rotor balance isn’t just rotational about it’s own centerline. It’s the weight variance between each rotor relative to them both rotating about the e-shaft centerline at the same time. Same builder told me they varied as much as 50 grams from each other Within the same Letter designator. So even though they might be balanced about their own centerline, if one weighs 50g different than another on the same e-shaft that’s going to throw the forces being applied to the e-shaft to not be balanced. Which that rotor weight variance also seen among the earlier 13B rotors too. He also said the front and rear counterbalance weights were not really all that well balanced. So that idea about oil inside the rotor is not going to address those issues at all.
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09-01-2020, 10:30 PM
#588
77 cylinders, 4 rotors...
I’ll also just add that prior to the Renesis it was understood that a rotary engine should not exceed 8000 rpm without having the rotating assembly balanced. The Renesis had a 9000 rpm redline from the factory and it’s not unusual for people to reprogram that higher still. Further, the rotor balance isn’t just rotational about it’s own centerline. It’s the weight variance between each rotor relative to them both rotating about the e-shaft centerline at the same time. Same builder told me they varied as much as 50 grams from each other Within the same Letter designator. So even though they might be balanced about their own centerline, if one weighs 50g different than another on the same e-shaft that’s going to throw the forces being applied to the e-shaft to not be balanced. Which that rotor weight variance also seen among the earlier 13B rotors too. He also said the front and rear counterbalance weights were not really all that well balanced. So that idea about oil inside the rotor is not going to address those issues at all.
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They talk about the counterweights here also. No bueno:
https://themotorhood.com/themotorhoo...-rotary-engine
09-02-2020, 02:48 AM
#589
Claims can be made that Renesis rotors are balanced on their own axis but I have never seen one that had any signs of balancing. Not sure if you were just saying that to say it but I think it's well enough known at this point. Just looked at your link Kevin and it does say the same. Rebuild time is coming sooner every day.
09-03-2020, 12:43 PM
#590
50g is less than 2 oz. in US terms, but as rpm increases it becomes greatly magnified. That and a light flywheel can also cause idle stability issues (hint-hint).
Otherwise, you aren't going to “see” anything (except possibly the end results upon disassembly in the most serious cases) unless you actually carry out the balancing method yourself. That’s the central issue here; you don't fully understand why dynamic balancing is essential for the rotors spinning freely on-center rather than the e-shaft bending/flexing and allowing them to tip over into the side plates (there isn’t a center plate e-shaft bearing, just on the end plates), excessive wear on both the e-shaft and rotor bearings, extracting the last HP out of it (see my dyno posts), and so on. Oil pressure plays a role in that too; another thing people here didn’t and still don’t fully understand why that is in their past discussions of the S2 changes.
Maybe the light will starting brightening some after you read this.
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Otherwise, you aren't going to “see” anything (except possibly the end results upon disassembly in the most serious cases) unless you actually carry out the balancing method yourself. That’s the central issue here; you don't fully understand why dynamic balancing is essential for the rotors spinning freely on-center rather than the e-shaft bending/flexing and allowing them to tip over into the side plates (there isn’t a center plate e-shaft bearing, just on the end plates), excessive wear on both the e-shaft and rotor bearings, extracting the last HP out of it (see my dyno posts), and so on. Oil pressure plays a role in that too; another thing people here didn’t and still don’t fully understand why that is in their past discussions of the S2 changes.
Maybe the light will starting brightening some after you read this.
.
Last edited by TeamRX8; 09-03-2020 at 12:53 PM.
09-03-2020, 04:35 PM
#591
77 cylinders, 4 rotors...
50g is less than 2 oz. in US terms, but as rpm increases it becomes greatly magnified. That and a light flywheel can also cause idle stability issues (hint-hint).
Otherwise, you aren't going to “see” anything (except possibly the end results upon disassembly in the most serious cases) unless you actually carry out the balancing method yourself. That’s the central issue here; you don't fully understand why dynamic balancing is essential for the rotors spinning freely on-center rather than the e-shaft bending/flexing and allowing them to tip over into the side plates (there isn’t a center plate e-shaft bearing, just on the end plates), excessive wear on both the e-shaft and rotor bearings, extracting the last HP out of it (see my dyno posts), and so on. Oil pressure plays a role in that too; another thing people here didn’t and still don’t fully understand why that is in their past discussions of the S2 changes.
Maybe the light will starting brightening some after you read this.
.
Otherwise, you aren't going to “see” anything (except possibly the end results upon disassembly in the most serious cases) unless you actually carry out the balancing method yourself. That’s the central issue here; you don't fully understand why dynamic balancing is essential for the rotors spinning freely on-center rather than the e-shaft bending/flexing and allowing them to tip over into the side plates (there isn’t a center plate e-shaft bearing, just on the end plates), excessive wear on both the e-shaft and rotor bearings, extracting the last HP out of it (see my dyno posts), and so on. Oil pressure plays a role in that too; another thing people here didn’t and still don’t fully understand why that is in their past discussions of the S2 changes.
Maybe the light will starting brightening some after you read this.
.
09-04-2020, 02:40 PM
#593
It’s more critical on a rotary than a piston engine imo. First, the rotors don’t really spin; they orbit. That in itself will exacerbate imbalance issues. Also, unlike a connecting rod on a crank shaft, which is a tightly coupled bearing connection, the bearing connection between the e-shaft and the rotor isn’t coupled at all really. The rotor bearing diameter is much larger than the e-shaft journal. The e-shaft journal surface slides along the rotor bearing surface. The coupling is at the gear teeth connection between the rotor and the end plate gears. The two in combination create the orbiting rotor motion as the apex seals transition along the rotor housing surface.
It won’t seem obvious how this is different and why it matters. The easiest way to visualize it is with a new/fresh engine. If you turn the flywheel in the forward direction pushing the rotor along, then stop and lightly reverse the direction you’ll feel a quite noticeable dead spot as the eccentric is turning until it moved the rotor back in the opposite direction. The same thing occurs again if you stop and go back in the other direction, and with every rotation direction change. The first time I ever saw this it concerned me greatly, thinking something is wrong in this newly rebuilt engine. The reason why this is has to due with the non-coupled sliding motion connection between the rotor bearing and the e-shaft journal. There is a clearance between the two surfaces. When the e-shaft direction is reversed it has to transition through this clearance before making contact with the rotor bearing again to move it in the opposite direction. The same thing happens with the crankshaft/connecting rod, but being close coupled the clearance transition from one direction to the other is much smaller and less perceptible.
What does all that really mean? Well consider the cyclic combustion process forces. In rudimentary form for simplicity; as the e-shaft pushes the rotor to compress the intake charge it resists against the e-shaft journal. When the ignition fires, the combustion gases now reverse that force to instead push the e-shaft. Then when the exhaust port opens that force is relieved. Except there are three faces on the rotor and this is all taking place cyclicly on them all at the same time. So on top of that, you have two rotors that are orbiting on a shaft that’s only supported on the ends. When imbalance forces are then added to the equation; what most people perceive on the surface to be this perfect model of things spinning along in perfect, ideal motion ends up in reality to be chaotic cycling shimmying motions and forces that can’t be perceived by eye.
It’s not perfect motion and never will be, but dynamic balancing helps to tame and minimize the situation.
It won’t seem obvious how this is different and why it matters. The easiest way to visualize it is with a new/fresh engine. If you turn the flywheel in the forward direction pushing the rotor along, then stop and lightly reverse the direction you’ll feel a quite noticeable dead spot as the eccentric is turning until it moved the rotor back in the opposite direction. The same thing occurs again if you stop and go back in the other direction, and with every rotation direction change. The first time I ever saw this it concerned me greatly, thinking something is wrong in this newly rebuilt engine. The reason why this is has to due with the non-coupled sliding motion connection between the rotor bearing and the e-shaft journal. There is a clearance between the two surfaces. When the e-shaft direction is reversed it has to transition through this clearance before making contact with the rotor bearing again to move it in the opposite direction. The same thing happens with the crankshaft/connecting rod, but being close coupled the clearance transition from one direction to the other is much smaller and less perceptible.
What does all that really mean? Well consider the cyclic combustion process forces. In rudimentary form for simplicity; as the e-shaft pushes the rotor to compress the intake charge it resists against the e-shaft journal. When the ignition fires, the combustion gases now reverse that force to instead push the e-shaft. Then when the exhaust port opens that force is relieved. Except there are three faces on the rotor and this is all taking place cyclicly on them all at the same time. So on top of that, you have two rotors that are orbiting on a shaft that’s only supported on the ends. When imbalance forces are then added to the equation; what most people perceive on the surface to be this perfect model of things spinning along in perfect, ideal motion ends up in reality to be chaotic cycling shimmying motions and forces that can’t be perceived by eye.
It’s not perfect motion and never will be, but dynamic balancing helps to tame and minimize the situation.
Last edited by TeamRX8; 09-04-2020 at 02:46 PM.
09-04-2020, 04:11 PM
#595
Clearly there is a lot more to it, it was just a basic statement to show agreement. I follow what you said but either you think I missed something that I didn't, or something went so far over my head I haven't a clue.
09-04-2020, 05:14 PM
#597
77 cylinders, 4 rotors...
It’s more critical on a rotary than a piston engine imo. First, the rotors don’t really spin; they orbit. That in itself will exacerbate imbalance issues. Also, unlike a connecting rod on a crank shaft, which is a tightly coupled bearing connection, the bearing connection between the e-shaft and the rotor isn’t coupled at all really. The rotor bearing diameter is much larger than the e-shaft journal. The e-shaft journal surface slides along the rotor bearing surface. The coupling is at the gear teeth connection between the rotor and the end plate gears. The two in combination create the orbiting rotor motion as the apex seals transition along the rotor housing surface.
It won’t seem obvious how this is different and why it matters. The easiest way to visualize it is with a new/fresh engine. If you turn the flywheel in the forward direction pushing the rotor along, then stop and lightly reverse the direction you’ll feel a quite noticeable dead spot as the eccentric is turning until it moved the rotor back in the opposite direction. The same thing occurs again if you stop and go back in the other direction, and with every rotation direction change. The first time I ever saw this it concerned me greatly, thinking something is wrong in this newly rebuilt engine. The reason why this is has to due with the non-coupled sliding motion connection between the rotor bearing and the e-shaft journal. There is a clearance between the two surfaces. When the e-shaft direction is reversed it has to transition through this clearance before making contact with the rotor bearing again to move it in the opposite direction. The same thing happens with the crankshaft/connecting rod, but being close coupled the clearance transition from one direction to the other is much smaller and less perceptible.
What does all that really mean? Well consider the cyclic combustion process forces. In rudimentary form for simplicity; as the e-shaft pushes the rotor to compress the intake charge it resists against the e-shaft journal. When the ignition fires, the combustion gases now reverse that force to instead push the e-shaft. Then when the exhaust port opens that force is relieved. Except there are three faces on the rotor and this is all taking place cyclicly on them all at the same time. So on top of that, you have two rotors that are orbiting on a shaft that’s only supported on the ends. When imbalance forces are then added to the equation; what most people perceive on the surface to be this perfect model of things spinning along in perfect, ideal motion ends up in reality to be chaotic cycling shimmying motions and forces that can’t be perceived by eye.
It’s not perfect motion and never will be, but dynamic balancing helps to tame and minimize the situation.
It won’t seem obvious how this is different and why it matters. The easiest way to visualize it is with a new/fresh engine. If you turn the flywheel in the forward direction pushing the rotor along, then stop and lightly reverse the direction you’ll feel a quite noticeable dead spot as the eccentric is turning until it moved the rotor back in the opposite direction. The same thing occurs again if you stop and go back in the other direction, and with every rotation direction change. The first time I ever saw this it concerned me greatly, thinking something is wrong in this newly rebuilt engine. The reason why this is has to due with the non-coupled sliding motion connection between the rotor bearing and the e-shaft journal. There is a clearance between the two surfaces. When the e-shaft direction is reversed it has to transition through this clearance before making contact with the rotor bearing again to move it in the opposite direction. The same thing happens with the crankshaft/connecting rod, but being close coupled the clearance transition from one direction to the other is much smaller and less perceptible.
What does all that really mean? Well consider the cyclic combustion process forces. In rudimentary form for simplicity; as the e-shaft pushes the rotor to compress the intake charge it resists against the e-shaft journal. When the ignition fires, the combustion gases now reverse that force to instead push the e-shaft. Then when the exhaust port opens that force is relieved. Except there are three faces on the rotor and this is all taking place cyclicly on them all at the same time. So on top of that, you have two rotors that are orbiting on a shaft that’s only supported on the ends. When imbalance forces are then added to the equation; what most people perceive on the surface to be this perfect model of things spinning along in perfect, ideal motion ends up in reality to be chaotic cycling shimmying motions and forces that can’t be perceived by eye.
It’s not perfect motion and never will be, but dynamic balancing helps to tame and minimize the situation.
And, I could have this wrong, but somewhere in there there are forces sufficient to produce at least 155 (ish) lb/ft of shaft torque through an (effective) 3:1 overdrive that need to be controlled and routed for output through one shaft, with only 2 main bearings, as you indicated.
Like you said, these engines go hmmmmmmm, but really there is a lot more going on.
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