tag:blogger.com,1999:blog-6582429758941507301.post86484766115149356..comments2024-03-18T08:25:40.019-05:00Comments on Knucklehead Theology: The Grey Goose 2013St. Leehttp://www.blogger.com/profile/01238671101561121436noreply@blogger.comBlogger13125tag:blogger.com,1999:blog-6582429758941507301.post-56725689852609640582013-05-06T19:09:08.024-05:002013-05-06T19:09:08.024-05:00Wow, I cannot believe how long it has taken for me...Wow, I cannot believe how long it has taken for me to get back and answer this last comment - sorry. I finally got around to chucking up the rear plug and cutting off the base. Here is what I found. There are some specs of shiny aluminum, however there are no sign of any black specs. Also there is no damage to the porcelain. I would expect detonation to damage the porcelain before or at least at the same time it holed a piston, but I am no expert. <br /><br />The reports I have are that the engine sound changed at the top of 3rd gear, which I assume is when the piston became ventilated. On the other hand I know the bike was on and off the throttle several times on the previous run due to being blown off course by cross winds. If I remember correctly, the pilot previously told me that he likes to take it easy through the first couple gears (something I did not necessarily agree with, but then I have never been to Bonneville, so I did not feel qualified to comment).<br /><br />Anyway, now you have me worried about having too much timing! I'd feel much better if I was still convinced that it was just the wasted spark. Maybe I should back off the timing a little and see what the plugs look like after some dyno time. Wish I was a better tuner and/or that a really first rate tuner would be at Bonneville with the team. <br /><br />Any volunteers?St. Leehttps://www.blogger.com/profile/01238671101561121436noreply@blogger.comtag:blogger.com,1999:blog-6582429758941507301.post-77994445799403672022013-04-22T19:56:09.646-05:002013-04-22T19:56:09.646-05:00Lee,
Don't mean to beat detonation into the g...Lee,<br /><br />Don't mean to beat detonation into the ground (I think I already have), but…….<br /><br />I'm not necessarily suggesting that it did or didn't occur, just noting that in my mind, "holed" pistons and detonation (high energy waves in the combustion chamber) go together like fire and smoke. We tend to time engine ignitions for optimum power, which has to be somewhere shy of detonation. However, if anything in the performance equation changes (increased temperature or pressure), the system can be perturbed into an operation regime where detonation does occur. That said, since the piston reached a temperature where the yield strength of the alloy was exceeded (it caved in), it had to experience a very significant temperature that was well beyond the "normal" operating condition. It would therefore be reasonable to suspect that as rear cylinder temperature climbed, combustion could very possibly move from a normal combustion event to a regime where detonation occurred or perhaps dominated the combustion process. <br /><br />Since detonation is the product of heat, pressure and time, it would preferentially occur at lower, rather than higher engine speed because detonation takes time to occur, i.e., an engine that rattles (detonates) when lugged, may operate detonation-free if engine speed is increased significantly. In light of the foregoing, if detonation were occurring, the highest probability for occurrence would be just after a shift point when the engine is operating at the lowest speed in the recovery phase. Did the driver by any chance note when the piston "holed", i.e., what gear, just after a gear change, at the top of a gear, how far into the run, etc?<br /><br />I suspect when the piston "holed" the sparkplug was contaminated with oil or carbon, making it difficult if not impossible to read for detonation. I wonder if the plug residue could be gently washed away (gentle rinse with carb cleaner?) to reveal any information the plug might hold. Perhaps if the plug base were cut off in a lathe, to reveal the full porcelain length, some detonation telltale might be visible. Then again, maybe there is no telltale and maybe detonation didn't occur at all. I'll stay tuned.WZ507noreply@blogger.comtag:blogger.com,1999:blog-6582429758941507301.post-62703830773332768052013-04-14T21:24:50.802-05:002013-04-14T21:24:50.802-05:00WZ, thanks for commenting again. I find your insi...WZ, thanks for commenting again. I find your insights valuable. <br /><br />About your comment on the wasted spark not lighting a mixture that is not compressed. That was my initial reaction, but upon further consideration I came to the conclusion that it should burn. After all, if you pour gas on the floor and light it, it will burn absent compression. My take is that the compression adds enough pressure to the burn to make an engine run, but it still will burn as long as there is fuel, air, and spark. Don't know how many BTU's are burned during overlap, but...<br /><br />The next thing is that I am seeing no evidence of detonation, at least not as I understand the term. The intake and exhaust pockets of the rear piston both sagged, but only the intake side actually melted through. There are no other signs (that I can find) anywhere in the chamber or on the plug indicating detonation.<br /><br />Word has come from Joe Taylor, the owner, that the Goose will run the mag with the new single fire plug wires from Joe Hunt. Part of his decision is based on simplicity, but also an attempt to remain true to the original purpose of replicating Joe Petrali's 61" land speed record Knuck.<br /><br />Your reccomendations about dyno tuning, etc. are noted and well thought out. I hope those precautions will will be taken, but time and money have a way of slipping away from all of us...St. Leehttps://www.blogger.com/profile/01238671101561121436noreply@blogger.comtag:blogger.com,1999:blog-6582429758941507301.post-7987089261269109782013-04-13T08:58:44.118-05:002013-04-13T08:58:44.118-05:00From your recent post it sounds like The Team is u...From your recent post it sounds like The Team is up in the air right now with respect to which particular ignition system to fit. My $0.02 would be to go for the "as high tech as possible" version that allows independent timing of each cylinder (for whatever reason the rear may not tolerate the timing of the front cylinder), has a knock sensor interfaced in real-time with the ignition module, and can automatically retard the timing if/when detonation is detected. Given the time and energy that goes into building an engine (and bike) it seems to me that if such an ignition system kept the engine together, it would end up being reasonably priced insurance. <br /><br />Perhaps with the new ignition system the rear cylinder heat issue will be gone entirely and it will be business as usual. Nevertheless, I still wouldn't venture onto the salt without conducting steady state dyno testing. This would be the test where fuel mixture and ignition timing are fine tuned and the system configured to assure that if detonation occurs, timing is retarded an appropriate amount to eliminate it. If the exhaust temp can be stabilized at WOT for each cylinder, under a heavy load and over an extended period of time, you should be good to go, as this suggests that all critical parameters are under control. If exhaust temp can't be stabilized, troubled waters lie ahead, and you've got to understand why they can't be stabilized, and assure that they are ultimately stable. <br /><br />To conclude on an optimistic note, successful steady-state testing should give The Team all the encouragement they need to head to the salt assured, optimistic and enthusiastic. Hard to believe it's only 4 months away!WZ507noreply@blogger.comtag:blogger.com,1999:blog-6582429758941507301.post-47471622695550072182013-04-13T08:57:32.612-05:002013-04-13T08:57:32.612-05:00The Blog would not allow the posting of my comment...The Blog would not allow the posting of my comments due to the length (a few hundred characters over the limit), so I split it into 2 consecutive comments. Hope it makes sense in split form.<br /><br />I'm still puzzling over the Goose's rear cylinder instability and can't get a grip on cause and effect of the failure other than the obvious - it over heated and detonated. But why? I certainly don't have an answer but since feedback is encouraged here, I offer the following speculation in the matter. <br /><br />Assuming there are no mechanical issues with the engine I think overheating can be distilled down to 2 critical parameters - air/fuel ratio and ignition timing. If there were no issues with either parameter I don't see things going south and we wouldn't be having this conversation. <br /><br />It has been suggested that the bike was run in an excessively rich condition, so fuel doesn't seem likely to be the smoking gun here, and if it was a factor at all, one would think the dyno testing would have identified it straight away. Therefore, IMHO the prime suspect here is ignition related.<br /><br />I do appreciate the point about wasted spark and agree that it is a bad situation that needs to be eliminated. I personally can't see wasted spark lighting any mixture in the absence of compression (near TDC at overlap), but to play devil's advocate, lets assume it does momentarily light some minor fraction of the charge, which serves to "spoil" the real ignition/combustion event later in the cycle by contaminating the charge with some minor fraction of partially combusted hydrocarbons (like minor EGR in a flathead causing black combustion). If so, the spoiled combustion event might be of poor quality (slow), and hence convey more heat (where heat eventually leads to detonation) to the system via the prolonged combustion time. Who knows? At any rate I'm glad "wasted spark" is now in the past tense so this subject can be checked off the list of possible ignition related issues.<br /><br />Another aspect of ignition timing relates to the relative temperature of the engine and the ability to run in a detonation-free state. As noted by you and other contributors here, there is night and day difference between drag racing and LSR racing, i.e., both events are WOT, but one event occurs in 10 seconds with a lukewarm engine, the latter goes on for well over a minute (which is nearly an eternity relative to anything we'd normally do to an engine) with an engine that is typically at full operating temp at the start. Thus, ignition timing that is tolerable for the drag strip may be inappropriate for the long haul on salt, due to the difference in engine operating temp. I'm suspecting that as heat builds during the run, the rear cylinder, for whatever reason (aerodynamics of the fairing, wasted spark/EGR, or whatever?), is not cooling like the front cylinder. This leads to detonation in the rear cylinder which in short order destroys the engine. If this is so, what could one do about it?WZ507noreply@blogger.comtag:blogger.com,1999:blog-6582429758941507301.post-29357097317214578142013-03-06T22:55:45.332-06:002013-03-06T22:55:45.332-06:00Good reading Lee!Good reading Lee!pathttps://www.blogger.com/profile/07500014252781274237noreply@blogger.comtag:blogger.com,1999:blog-6582429758941507301.post-89313249810703973782013-02-08T11:26:05.281-06:002013-02-08T11:26:05.281-06:00Hi Tim, yes I do follow that blog. What he is doi...Hi Tim, yes I do follow that blog. What he is doing and has done with that Knuck is very impressive.<br /><br />WZ - Thanks for the comments, I appreciate your input. If I understand correctly, you are suggesting that the "sag" may have started from cylinder pressure on the annealed aluminum at a temperature which it may have withstood if it had been unmodified. That is certainly possible, I suppose, but testing it would involve running next year with new pistons and wasted spark.<br /><br /> The anecdotal evidence seems to show that rear piston was doomed to fail either way - perhaps the Goose would have lived longer (to a higher speed and temperature)with an unmodified piston, but we may never know for sure.<br />St. Leehttps://www.blogger.com/profile/01238671101561121436noreply@blogger.comtag:blogger.com,1999:blog-6582429758941507301.post-51307451336991113312013-02-07T22:36:48.454-06:002013-02-07T22:36:48.454-06:00I don't think we're concerned so much abou...I don't think we're concerned so much about the piston alloy melting point, but rather the difference in yield stress of the alloy in the annealed and hardened state (perhaps 5X ?). This ultimately becomes a circular discussion, because if there is excessive heat in the system and the piston is exposed to it, the piston can become softened in use, and then it makes little difference whether it started soft, or was compromised during use, as it fails either way in the softened state. <br /><br />In doing blown engine post mortems where the piston is suspect, one of the 1st things a piston vendor does is check the hardness of the piston, which provides a clear picture of the thermal history the piston has experienced, where they are always soft if they've been overheated. <br /><br />This is an intriguing discussion and I'll be sure to stay tuned for the next chapter.<br />WZ507noreply@blogger.comtag:blogger.com,1999:blog-6582429758941507301.post-29895167351039089122013-02-07T21:43:32.409-06:002013-02-07T21:43:32.409-06:00I like girlie looking flower blossoms.....I like girlie looking flower blossoms.....Weshttps://www.blogger.com/profile/03503024324258040862noreply@blogger.comtag:blogger.com,1999:blog-6582429758941507301.post-65666760364627291002013-02-07T20:24:14.591-06:002013-02-07T20:24:14.591-06:00Very interesting stuff Lee,I'm glad your takin...Very interesting stuff Lee,I'm glad your taking us along for the ride. Also wanted to know if you follow the "Quartermile Knucklehead" blog.<br /><br /> Tim47str8leghttps://www.blogger.com/profile/04699315777900809370noreply@blogger.comtag:blogger.com,1999:blog-6582429758941507301.post-61530854886801349412013-02-07T17:51:49.295-06:002013-02-07T17:51:49.295-06:00Well, you are right that I had the piston speed wr...Well, you are right that I had the piston speed wrong. It should have read feet per minute not feet per second. I misread the data from Pipemax. I will correct it ASAP. <br /><br />Pipemax also shows the max piston speed of 86.2 ft per second at 77.5 degrees, so we are on the same page.<br /><br />I agree about the lower strength of the welded piston, and that was my initial thought as well. However that does not explain others with non-welded pistons experiencing the same problem on the rear cylinder only. The front piston looks as good as when I installed it. If the rear piston had not sagged I would attribute the hole to the welding, but as far as I know the annealing and lower strength should not affect melting temperature.St. Leehttps://www.blogger.com/profile/01238671101561121436noreply@blogger.comtag:blogger.com,1999:blog-6582429758941507301.post-12942620591013273412013-02-07T16:44:30.681-06:002013-02-07T16:44:30.681-06:00I'm enjoying your description and just thinkin...I'm enjoying your description and just thinking out loud as I reflect on your thoughts. <br /><br />I don't know the dimensions of the motor, but if a stock EL, I think it would be 3.5" stroke and 7.468" rod length. With those dimensions at 5500 and 7500 rpm wouldn't this give instantaneous piston speed at 3 deg ATDC of 6.3 ft/sec and 8.6 ft/sec, with a maximum instantaneous piston speed at 7500 rpm of 86.3 ft/sec occurring at 77 deg ATDC ? Your numbers seem way too big.<br /><br />The rear cylinder obviously faired differently in this build than the front, and I'm not disputing the fact that they are different, or that heat caused the failure. But I wonder if the welded piston is a significant contributor to the "holing". Once welded I believe the filled area would be soft, fully annealed material and of significantly lower strength than the virgin piston. I note from the pictures that the area adjacent to the "hole" appears collapsed where it was softening. I wonder if it could have survived with fresh 2618 alloy pistons? Did the front piston show any piston deformation in this region?WZ507noreply@blogger.comtag:blogger.com,1999:blog-6582429758941507301.post-81837997532478037212013-02-07T13:16:21.169-06:002013-02-07T13:16:21.169-06:00I know you're not supposed to look a gift hors...I know you're not supposed to look a gift horse in the mouth, but I feel that I need to point a couple glitches with "Blogger" once again.<br /><br />I cannot write "S&S Cycle" in a post without it being published as some gibberish. My guess is that Blogger reads the "&" sign as an html command.<br /><br />The other pet peeve is that both a numbered list or bullet points always become girly looking flower blossoms (at least in my viewer). Neither of these are big issues, but I wanted everyone to know they are not by my choice.St. Leehttps://www.blogger.com/profile/01238671101561121436noreply@blogger.com