Aluminium Flywheel for X-flow

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YW Sin
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The objectives is to have lightned fly wheel. Well, just grind off some materials from the exsisting steel fly wheel and There you go, what what more do you want?? Shiney fly wheels to look at? A ll standard, Classic 1.7 X-flow Edited by - yw sin on 1 Feb 2003 16:16:52
Ken Numsaki
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Hi all, Thank you for your kindly reply. I think that heavy flywheel does not have necessity in light weight Seven. Heavy inertia makes easy start for gran mama who drive the normal passenger car. If light FW put on to the normal car, it is very difficult to start the car for lady maybe. But but, seven man has skill and wish more performance to the motor. A heavy flywheel also has a risk of making a crack in the end web ( FW side No8) of a crankshaft. In high rev,Crankshaft is little bit bend then heavy FW makes more stress to the corner(fillet) of No8 web and main journal. As you know,Xflow has Cast crank, so I think light weight FW is good for crank health and me . Moreover, since there is little inertia, I think that a gear shift becomes easy. However, as you taught (thanks everyone ), the problem of a ring gear and a friction should be solved. I should be ask the Dave bean such about risk. Regards
AMMO
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Ken There are lots of companies selling aluminium flywheels. Do a search on Google. One company is Fidanza in the States, www.aluminiumflywheels.com. I have used various types of aluminium flywheels. The one thing you should be very scared of is the starter ring gear. If this breaks up it will separate the gearbox from the engine and do a lot of damage. Make sure you get the flywheel from a reputable company and you will not have any problems in this area. It is no more dangerous than a stock ring gear. Problems arise when stupid people try to make the ring gear lighter too, not thinking about the potential consequences. The friction surface is usually a steel plate which is screwed to the aluminium. No problem of the clutch plate wearing out the flywheel. You are correct about the improved shift. As the engine will decelerate faster, gearchanges become easier. AMMO
R2D2
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I really think that the question of light flywheels is just as serious as Tony has already stated and the risk involved in failure is very serious and could have fatal consequences. The only way to sure that a critical component such as a flywheel is safe to use is to carry out the correct degree of stress analysis and to try to model the duty cycle. Suggesting that F3000 cars use this type of design and therefore it must be OK really misses the point being made. A flywheel or any other part used in F3000 and other cars of this typeis a very short life component. These engine are routinely dismantled and inspected and any component that may suffer from fatigue is changed. A classic example is a gear in an F1 gearbox which has a life that is rated in terms of seconds for lower gears and hours for higher gears. A flywheel is certainly being subjected to fatigue loading from both changes in engine speed and the torsional vibrations that are being produced by the engine. Lightening the flywheel can increase the magnitude of these torsional vibrations and it will also cause the reverse torque loadings seen during a gearchage to increase quite substantially. A typical high performance engine may produce 150Nm of steady state torque but the peak torques can be very much higher and need considering. The other concern about aluminium is more concerned with basic characteristics of the material. It is well known that all engineering steels exhibit an "endurance limit", this is a stress below which there will never be a fatigue failure and there are various tools used to assess the fatigue life of individual components relative to this endurance limit. Aluminium does not exhibit this characteristic and it can always fail in fatigue providing that it accrues a sufficient number of cycles. It is very important to try to assess the stresses in this type of component and to try to assess risk. The ability of an engine to slow down quickly and its affect on gearchanging must to some extent depend on the type of gearbox. The rate the engine slows is a function of the engine inerta and the vehicle inertia until the gear is disengaged, at this time only engine inertia and friction have any effect providing the engine is not being fuelled. In a syncromesh gearbox the gearchange cannot take place until speed are reasonably matched or the system will baulk and I guess that low inertia may help speed up gearchanges but I would need someone to confirm this point more accurately. If a dog box is used the situation may be different. If the dog to dog speed difference is zero, I don't think that you can change gear at all. If the dog to dog speed is too high then the torque loading generated at the dogs will cause a failure. If an engine has a high motoring torque and a very low inertia decel rates of 100 000rpm are not uncommon, so if you have a dog box you will need to be quite sharp in changing gear or low inertia may not be too great. I have to say that aluminium flywheels do worry me. It is obvious that they can be designed to work but they do need thinking about and considereing from a fatigue point of view. The mean torque, peak torque, reverse torque loading and the distribution of these profiles can have a very significant effect on life and affect how long you should leave this component in the engine before it is replaced. Even the most basic examination of the stresses involved will show that a 10 to 15% increase in transient torque could reduce life by factors of 3 to 4. The motoring torque of the engine also will have an impact on the transient behaviour and how quickly the engine slows so friction within the engine is also very important. If you are going to build high rpm engines with light flywheels I would also consider using steel starter rings to replace the cast iron that are commonly used on old Ford engines. Edited by - chris flavell on 3 Feb 2003 17:09:10
AMMO
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Chris and Tony. Exactly how many broken aluminium flywheels have you seen? The Tilton, Quartermaster and AP open design clutch baskets are aluminium. They don't fail if correctly installed. Why should a properly designed aluminum flywheel fail? Are you aware that there are a lot of US based companies offering aluminium flywheels? Do you think they would do this if they were dangerous? I have been selling aluminium flywheels since 1986 for a specialist motorcycle application. The engine in question is dimensionally large and more akin to a car than a bike. It is a closed clutch twin plate design. I have never had one fail. Could we please have some real life experiences that you have witnessed? I don't know you guys personally, but you are both obviously come from engineering/motorsport backgrounds. Not meant to be a pop at either of you, I like exchanging views with people with a common passion, but real life experiences are much more important than saying "it may have fatal consequenses". It is right that this should be pointed out. Crossing the road to buy a loaf of bread may kill you if you don't look where you are going (I tell my kids all the time to be careful when crossing the road). So back to the original question. How many broken alunminium flywheels have you seen? If you came up with real life examples of failures I would be more inclined to agree with you. AMMO
Tony C
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Ah, that would be none for me. Don't have any data to suggest an aluminium flywheel is not a good idea either. Never even heard of one failing. Don't know you either AMMO, but from your postings, it seems you're an experienced, practical engineer with a lot of common sense and good ideas. However, my engineering cringe factor goes off the scale when I think of the rotating mass of a flywheel made from aluminium alloy; starter ring of steel and clutch contact insert made of steel - all whizzing round and helping to damp out the crank harmonics and shock loading. Three individual items fastened together instead of one solid mass. Sorry, I wouldn't be able to sleep at night. My personal opinion only - no hard facts. Cheers, Tony Waiting for my BRG SV kit. (Superior Version) - 9 weeks to go!
R2D2
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AMMO, I think you are missing the real point that I am trying to make, which is just to say that messing with flywheels needs to be considered quite carefully. All I am trying to say is that lighter isn't automatically better if the engineering isn't well founded. Flywheels are potentially dangerous if they do break and either incorrect lightening or a poor design can cause this to happen. The design of any relatively high speed rotating component needs to be looked at in detail and the faster it goes the more critical it becomes. The clutch basket that you describe is a good example as the inertia is not too high due to the relatively small diameter. This will significantly reduce stresses and give a much better fatigue performance. To tell people that "Aluminium flywheels are OK" is not a great idea as this could result in some really poor components being made and used. To qualify the statement with "XYZ's flywheel" for a particular engine is reliable is a perfectly reasonable statement and much more helpful. I remember a guy posting some really scarey photos of an exploded cast iron flywheel that had been lightened. I am sure he was advised that lightening is a great idea, he just took it a little too far. I haven't seen the caveats that the manufacturers of ally flywheels use to protect themselves from litigation but if they are US based they probably make interesting reading. I would be interested to see the design of an alloy crossflow flywheel and see how the inertia compared to a lightweight steel flywheel and the percentage difference that it makes to the total engine inertia.
AMMO
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Tony C If you would lose sleep at night then it is only right that you should not fit one. Chris Let me say that I agree with everything you say regarding safety. This is not a "I'm right and you're wrong" type discussion. We are here to exchange views. If I had a flywheel knocked up by a mate on a lathe during his lunch break from a lump of ali pulled out of a skip, I too wouldn't sleep at night. A properly engineered product is a completly different proposition. I would never over-lighten a cast flywheel. I have run lightened cast flywheels on my Minis to 8,000 rpm with no problems. How to lighten these is well documented. There is a limit which you should not go beyond, after which you should fit a stronger steel one which can afford to have smaller sections. I have seen steel flywheels which I would put in a skip. I even built an engine for a Danish customer where I refused to fit a steel flywheel he supplied unless he signed a disclaimer. The crank balancer also requested he sign a disclaimer. I never heard from the guy again. Hopefully the disclaimers he had to sign may have made him think and fit something else. The failure I have seen are: Flywheel coming loose from crank due to a customer error. The incorrect grade bolts were used (8.8 instead of 12.9, they looked the same to him). Result was that traction was lost and the flywheel spun on the crank spigot. Had it come off the end of the crank the result been very different. Ring gear exploding on a very expensive Swiss flywheel / clutch. This was due to the fact that the designer was an idiot and I was too green to know what I was looking at. He had a skimpy ring gear which was attached by six M5 countersunk screws (stress raisers galore!). When the engine reached 10,000 rpm the ring gear exploded and separated the gearbox from the engine. Luckily no one was hurt. That such a skimpy lightweight steel part could do so much damage was really shocking. We did continue to use the ali flywheels with no ring gear and just bumped the engines. The ali bit was OK, just the ring gear was completely wrong. However bad clutch operation and high friction material wear eventually made us put the three clutches we purchsed at £800.00 each at 1988 prices in the skip. An expensive and potentially fatal mistake. The product was reassuringly expensive and came from Switzerland. How wrong can you be. A friend who now works at Lotus Engineering had a flywheel explode when he worked at an engine test facility maybe 15 years ago. The place was called Scott Gibbin or something like that. The flywheel parts went through the test cell wall, then through the ceiling, through the roof and embedded themselves in next door industrial unit's chimney. Sometime I will go into a test cell to make an adjustment or have alook at something. I never stand anywhere near the flywheel. At rolling road sessions I never stand along side the car in line with the flywheel. If it lets go it will kill you to death. I have never personally seen (or ever wish to see) a flywheel explode. I know of people using ali clutches on MGB's years ago and are still alive to tell the tale. Yankeedoodoo, who posts here from California, runs a Fidanza ali flwheel (and while we are at it an Esslinger ali crank pulley). As for the USA and disclaimers, I bet you cannot buy a packet of peanut M&M's in the States without some fairly hefty disclaimer attached. My experience is that components fail either because they are incorrectly designed, because they are incorrectly assembled, or a combination of the two. I can't do the maths because I am not a fomally trained engineer. Maybe someone can tell me this: Is an ali flywheel less likley to explode at high speed because it has less mass? AMMO
R2D2
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AMMO, I agree with your comments, specifically about good design, this is the point I have been trying to make. In regard to your question about Alloy flywheels being less likely to explode because they are lighter, the short answer to the question is that reduced mass will produce lower bursting forces but that isn't the complete picture. If you just copied a standard flywheel in Aluminium the stresses would reduce but the fatigue damage could still be a problem and this is my greatest fear. To calculatesteady state bursting forces and to select a material with sufficient strength is not too difficult. The grade of aluminium used is important along with its heat treatment condition as this will have a very significant impact on fatigue life. To carry out a fatigue analysis is more difficult. I will try to find some time and see what I can work out. I guess I should summarise my concerns and then not make any more comments: I don't think alluminium flywheels will break beacause they have insuffieicnt strength to withstand steady state bursting forces. I am not convinced that much, if any attention has been made to the fatigue life in the presence of fluctating stresses. If the flywheel fails in fatigue the stater ring will be the most dangerous component as it flys around. I agree with AMMO, if you use an alloy flywheel buy it from a reputable manufacturer who has a good track record. I will stick to chrome-moly alloy steel for the time being. .