thehelix112 Posted April 9, 2009 Share Posted April 9, 2009 Greg, Yeah I didn't think the twisting would be causing enough deformation to rub out the bearings, but I don't understand enough about harmonics (amongst other things) to comprehend why the crank would be whipped about as you suggest (and is evidenced by the worst bearing wear occurring in the middle). Or how to fix it. Makes sense that the more time you spend at the natural frequency (harmonic frequency?) of the block the larger the oscillations will be and the more deformation will be involved. I can only think that its the load on the front by the accessories and/or dry sump thats keeping it from being terrible there as well. Does someone understand why/how the twisting deformation transforms into deformation along the axis? Dave Quote Link to comment Share on other sites More sharing options...
blackwidow Posted April 9, 2009 Share Posted April 9, 2009 Maybe you can get a custom one made for your app. Possibly Ati, fluidamper, or bhj dynamics. I think the latter carries rebello dampers. Good luck man:burnout: Hey helix I will send ya something if ya want. Pm me. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted April 9, 2009 Share Posted April 9, 2009 One other thing to consider is that the crank was slightly bent by a hydrolock event. Quote Link to comment Share on other sites More sharing options...
Xnke Posted April 9, 2009 Share Posted April 9, 2009 Or that the block itself could have been deformed as well, just because they are iron and literally bullet proof (having shot an L26 P30 block with a .303 and not even caused a nick), dosen't mean they can't move. In your case, the reduced integrity of the largely bored out 3.1L engine could allow for that, especially if the crank was inducing a harmonic movement of the block that happened to be out of phase with the movement of the crank, i.e, the crank moving at the 5th harmonic, and the block at the first or third. Before the idea gets poo-pooed as not being possible because no one has noticed it, I posit that the number of 3.1L stroker motors that DIDN'T have this problem does not matter, it's only the motors that DO have this problem that really make a difference...because only the ones that have observable problems are the only ones that we can find solutions for. Anyway, all of the above can be attributed to lack of sleep, and me having been playing with the function generator and oscilloscope for hours now.... Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted April 9, 2009 Share Posted April 9, 2009 Xnke: nice. Sounds plausible to me. I wonder if there is any good (read: cheap DIY) way of detecting such a thing? I have DIY detonation detectors (earmuffs with hose attached to copper pipe bolted to the block), I wonder if it'd be possible to hear this. I'm thinking unlikely over the valves slamming closed all the time. Gira, are you willing to share any more details about the oscilliscope + accelerometer setup you're going to use to try and identify this occurring? Dave Quote Link to comment Share on other sites More sharing options...
Daeron Posted April 9, 2009 Share Posted April 9, 2009 Xnke: nice. Sounds plausible to me. I wonder if there is any good (read: cheap DIY) way of detecting such a thing? I have DIY detonation detectors (earmuffs with hose attached to copper pipe bolted to the block), I wonder if it'd be possible to hear this. I'm thinking unlikely over the valves slamming closed all the time. Gira, are you willing to share any more details about the oscilliscope + accelerometer setup you're going to use to try and identify this occurring? Dave I think the closest thing we could get to it would be a long bar with a series of tuning forks attached to it at calibrated frequencies. In all honesty, with a tuning fork of the right frequency range and an electric guitar pickup, you ought to be able to make something.. but any low tech approach towards analysis of this problem is likely going to revolve around tuning forks in some manner. Quote Link to comment Share on other sites More sharing options...
josh817 Posted April 9, 2009 Share Posted April 9, 2009 Or that the block itself could have been deformed as well, just because they are iron and literally bullet proof (having shot an L26 P30 block with a .303 and not even caused a nick), dosen't mean they can't move. In your case, the reduced integrity of the largely bored out 3.1L engine could allow for that, especially if the crank was inducing a harmonic movement of the block that happened to be out of phase with the movement of the crank, i.e, the crank moving at the 5th harmonic, and the block at the first or third. Before the idea gets poo-pooed as not being possible because no one has noticed it, I posit that the number of 3.1L stroker motors that DIDN'T have this problem does not matter, it's only the motors that DO have this problem that really make a difference...because only the ones that have observable problems are the only ones that we can find solutions for. Anyway, all of the above can be attributed to lack of sleep, and me having been playing with the function generator and oscilloscope for hours now.... I agree, when I was researching before my build I decided to stay back with a 3.1L rather than a 3.2L because at that point block integrity may be questionable, and thats for a hot street motor. He's out there hounding down on a 3.1L for a couple of hours and I can see stuff happening. Well... in all racing, **** happens, but thats besides the point. I think its the N42 block that has the... non webbed cylinders and the F54 has the webbed or something like that. I forget but one of them is claimed to be more suitable than the other when it comes do overboring, heavy racing, and regidity. I'm more so curious about Greg's findings rather than his setup with the o-scope which may be private. The block is iron so I would say just go look up the natural frequency of iron but I think manufacturers mix nickel and other **** into them too. And for what Daeron is saying,I would agree but thats a lot of forks.... Quote Link to comment Share on other sites More sharing options...
woldson Posted April 9, 2009 Share Posted April 9, 2009 Is the block actually an iron/nickel alloy? Also, has the crank been modded in any way, knife edged? Was the pressure plate and flywheel balanced? I know you are an extrem professional, just curious. Also, what could happen if the input shaft bearing on the tranny started to have some play?(even a very small amount?) Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted April 9, 2009 Share Posted April 9, 2009 A simple piezo sensor does just fine for listening to anything it is attached to. Radio shack sells them as piezo buzzers but they are good pickups as well. I use them on electronic drums..........check the electronic drum forums and you should find many threads discussing frequency response and even part numbers. The hard part is deciding which material to use to mount them and finding the right sensor that has sensitivity in the desired frequency range. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 9, 2009 Share Posted April 9, 2009 Our L28 Bonneville Motor had peak power at 8250rpms, and we 'inched up on it' for four years before pulling it to go with the 2L engine which has a power peak 'around 9K' but our bearings looked like new after four years of that kind of beating. What kind of weight are we talking about for the whole Flywheel/Pressure Plate assembly---and how closely is it balanced with the rest of the rotating assembly. Ou low-inertia Tilton flywheel/clutch assembly weighs in slightly under 15#, and even that is 'heavy' for what we need. The more weight you hang off an end, the more potential damage you can do. It's curious that bearing and the scoring...you didn't have a filter diagnosis done and look at what you had in the oil filter by chance did you? I'm wondering if you were sucking air/pumping air and it damaged the bearing, or perhaps you have a filter relief valve lift at some time dumping a load of swarf donw the central feed galley into your crank area? On the L28, we ran to at least 8500 before shifting. El Mirage wasn't that long in each gear compared to Bonneville. i wish I had a video to show of a Bonneville Run. It is definately 'inching' above 8K for more than 2 miles, we are at close to terminal speed with our 3.36 near the end of mile one, and then 'inch' floorboarded for the next two miles. And I know our oil feed is good, as is drainback...throw in some corners and I could see how oiling could be more of a problem than in our ideal 'straightline' torture test. Do you have the external oiling modification for the stock pump? Puzzling... Quote Link to comment Share on other sites More sharing options...
gira Posted April 9, 2009 Author Share Posted April 9, 2009 Again, all good plausible ideas. Tony D.- that's the first comment related to inching up to a harmonic and there couldn't be much more inching up than with a 3.36 in top gear, my lord! We're not running a dry sump on this engine, just a typical alternator and juiced up turbo pump up front. The clutch is very very small, a 5.5 inch Tilton with only two discs. I don't know the total weight or if the assembly was balanced on the crank but it's pretty small and it's rotational mass is pretty centralized. We did look at the oil filter while at the track but only to decide if we were going to hang it up or keep going. We knew right away there was an issue with a bearing, heck the oil pressure went away big time before we shut it down. We will concentrate on double checking the balancing, change the cam spec to lower the peak HP range, use a rev limiter, and try a different harmonic balancer. When these engines are working properly, it's amazing how good the parts look. If you get it right, don't mess with it!!! Greg Ira Quote Link to comment Share on other sites More sharing options...
josh817 Posted April 10, 2009 Share Posted April 10, 2009 After seeing a couple of clips of you on youtube, I do think a request of videos would be suitable eventually. >_> Yah know? Quote Link to comment Share on other sites More sharing options...
Cobra_Tim Posted April 10, 2009 Share Posted April 10, 2009 After seeing a couple of clips of you on youtube, I do think a request of videos would be suitable eventually. >_> Yah know? He could show you... but he'd have to kill you... Quote Link to comment Share on other sites More sharing options...
johnc Posted April 10, 2009 Share Posted April 10, 2009 If this is any help: The lightened LD28 crank in my old Sunbelt 3L race engine was straightened, machined, shot peened, nitrided, straightened, balanced, and then checked again for straightness. Sunbelt actually went through two cranks before they were happy with the one that ended up in my engine. So far its still going strong with the current owner. The block used was an early N42 (supposedly because of the higher nickel content) and the bore remained at 87mm. Quote Link to comment Share on other sites More sharing options...
gira Posted April 10, 2009 Author Share Posted April 10, 2009 After seeing a couple of clips of you on youtube, I do think a request of videos would be suitable eventually. >_> Yah know? What do you mean? Greg Quote Link to comment Share on other sites More sharing options...
josh817 Posted April 10, 2009 Share Posted April 10, 2009 If this is any help: The lightened LD28 crank in my old Sunbelt 3L race engine was straightened, machined, shot peened, nitrided, straightened, balanced, and then checked again for straightness. Sunbelt actually went through two cranks before they were happy with the one that ended up in my engine. So far its still going strong with the current owner. The block used was an early N42 (supposedly because of the higher nickel content) and the bore remained at 87mm. Impressive, hopefully they don't charge you for going through 2 cranks or something silly like that. Greg, I am asking for you to upload some race videos so we can enjoy. You should PM me with them so I can hoard them from everyone else. Quote Link to comment Share on other sites More sharing options...
Daeron Posted April 10, 2009 Share Posted April 10, 2009 It's curious that bearing and the scoring... That was a photo of a bearing from Josh; Greg hasn't posted us any images of his bearings yet. The bearing didn't look like the above. His piston looks like detonation or too lean. His bearings look like they wore from junk in the oil, possibly particles coming off during the event. My bearings were through to the copper and got better as you go out. I am wondering what kind of motor oil was being used in the engine.. Chris (ITS owner brother #2. the eldest of the five of us) said he is pretty sure that your motor was extremely low-hours, so any sort of chemical/metallurgical distress (the whole ZDDP thing that usually comes up when someones camshaft gets chewed up) from motor oil probably would not have had time to cause an issue.. but its another datum that needs to be considered. Quote Link to comment Share on other sites More sharing options...
jt1 Posted April 10, 2009 Share Posted April 10, 2009 Greg, is there any sign of metal transfer between the main cap and block? jt Quote Link to comment Share on other sites More sharing options...
510six Posted April 11, 2009 Share Posted April 11, 2009 An ATI Super Damper solves a lot of harmonic problems. + 1 for the ATI , no more loose bolts from harmonics. Quote Link to comment Share on other sites More sharing options...
gira Posted April 12, 2009 Author Share Posted April 12, 2009 Greg, is there any sign of metal transfer between the main cap and block? jt Jt, No not that I know of. We are going to attack this via what I term the shotgun approach. Firstly, the engine will be re-cammed so as to bring the peak hp down a few hundred revs. The block will be align honed and I am going to have a lot of attention paid to the crank. I didn't assemble this engine, but my engine builder is a trustworthy person. He said that during the build the crank turned by hand after he had all the clearances done and the caps torqued. If the crank isn't straight, it won't really do this without a high spot. I am attibuting this problem to some anomoly we have with our set up combination. I am 99% certain it was balanced properly, BUT this is not ruled out. We are also going to try an ATI balancer. Yes, they do build them for Rebello, but they protect him by not selling to the public. LAME. Rebello does his diligence as a respected engine builder. I'd like to get a model number for some of the ATI balancers that have been used by people on this list and what engine. I believe the LD28 crank can't really be compared with the regular L28 crank for harmonics. We used Mobil 1 on this engine. We usually use Redline but this is a play car and we thought this would be fine. It wasn't an oil type problem, I am fairly certain. My GTR uses Mobil 1, I hope it'll work in my 35 year old car. Quote Link to comment Share on other sites More sharing options...
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