NickJ Posted June 26, 2022 Share Posted June 26, 2022 For sure its beaten up pretty bad, but is there any sign of fatigue in there evident that a fracture started at the oil holes? Hard to tell from the photos but appears to be a transition in cross section so holes just happen to be in the likely failure region? 1 Quote Link to comment Share on other sites More sharing options...
Roman Posted June 26, 2022 Author Share Posted June 26, 2022 16 minutes ago, NickJ said: For sure its beaten up pretty bad, but is there any sign of fatigue in there evident that a fracture started at the oil holes? Hard to tell from the photos but appears to be a transition in cross section so holes just happen to be in the likely failure region? Sorry will take a better picture. But on the other side, it's a break through all of the holes. Yeah it's pretty hard to know cause or effect though. If I can't find the wrist pin in the sump I might go for a walk near where it blew up and see if I can find it haha. But I just wonder, if it was the rod that broke first, how do you end up with damage like that? Like the pin has been pulled out downwards rather than smashed up by a broken rod. Quote Link to comment Share on other sites More sharing options...
xsspeed Posted June 26, 2022 Share Posted June 26, 2022 Flailing rod gave piston a good smack? Quote Link to comment Share on other sites More sharing options...
xsspeed Posted June 26, 2022 Share Posted June 26, 2022 Some of its clear fracture, some looks a bit more bashed I dunno Quote Link to comment Share on other sites More sharing options...
deankdx Posted June 26, 2022 Share Posted June 26, 2022 1 hour ago, Roman said: If I can't find the wrist pin in the sump I might go for a walk near where it blew up and see if I can find it haha. if it's in a paddock near by, be sure to flatten the grass in a circular fashion while working the metal detector, this will ensure maximum chance of finding the lost bits.. 1 3 Quote Link to comment Share on other sites More sharing options...
Popular Post Roman Posted June 26, 2022 Author Popular Post Share Posted June 26, 2022 When I was a kid, my Mum taught me that it was rude to take basically anything offered to us kids when we went somewhere. So we go to someone's house, and they're expecting us, so they've made some chocolate biscuits especially for us to eat. Which are the best thing ever because I'm like 8 years old. Fucking delicious! However. I'd been conditioned to say "No thank you" because doing otherwise was rude. For the person who baked something especially for us arriving, it's was disappointing that no one wanted their food. "How could kids not want delicious my biscuits?" "Are they especially bad?" "What did I do wrong?" How could my Mum not understand how mutually disappointing this situation was? It didnt make any sense to me then, and I've still no idea who profited from this situation. The people were happy to give me a biscuit, and I was happy to eat it. Surely this is the worlds simplest situation to keep everyone happy. I fucking love biscuits, and it tears me up thinking how many I missed out on, at the stage of my life when they were the most delicious. God damn. For some reason, tonight I have had a revelation that refusing willing help from people here draws parallels to this situation. I have been conditioned to feel shameful about accepting assistance that's willingly offered. Why? So for anyone who's willing to chip in a few bucks, I can promise you this: I'll spend any contributions towards a Prius motor, and maybe exhaust parts. I will not spend any contributed money on psychological counselling for my unresolved childhood trauma about missing out on biscuits. I also promise I will come to your house and eat your biscuits if you invite me over. https://givealittle.co.nz/cause/finding-a-cure-for-the-atkinson-cycle Thanks to anyone that wants to help, and by all means dont anyone feel obligated. 18 12 3 Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted June 26, 2022 Share Posted June 26, 2022 2 Quote Link to comment Share on other sites More sharing options...
ThePog Posted June 26, 2022 Share Posted June 26, 2022 I am pleased you are taking the biscuit. 1 2 Quote Link to comment Share on other sites More sharing options...
cletus Posted June 26, 2022 Share Posted June 26, 2022 I'm going to throw out a wild conspiracy theory that your stock pistons could do 9275 rpm before the top comes off, because of the exhaust backpressure pushing down on the top of the piston Once you have a free flowing exhaust your piston lids will come off at 9021 rpms Might be time for some stronger piston return springs 4 1 1 Quote Link to comment Share on other sites More sharing options...
Popular Post Roman Posted June 26, 2022 Author Popular Post Share Posted June 26, 2022 I think you could be right about that. If the piston is trying to fly apart, where the top of the piston is trying to carry on upwards, and the pin is pulling it back down. So the material strength around the pin is the weakness. Then on the exhaust stroke this force is lessened, and when the cylinder is full, on the compression stroke this force is lessened too. The engine didnt fail when it was approaching max rpm, it failed just after a gear shift where throttle got cut to zero. So the worst case scenario would be zero throttle, high vacuum, high rpm on the compression stroke. I'm not sure if these forces are on the same magnitude as each other though. However, I can indeed increase my piston return spring value. I can use e-throttle to set a minimum high rpm throttle value to something like 10% or 20%, and then use a fuel cut and/or pull zillions of ignition timing out to cut power instead. This might bring a host of its own issues, but might be a bodgey solution I guess haha. Flat shifting, interestingly enough, would also help haha. The incredibly clever @Lith made a calculator ages ago that works out forces on pistons/rods. Entering 1NZ stuff. Peak accelleration on the piston at 9000rpm is 4991G! I'm not sure what sort of numbers I was expecting, but thats bloody lots. Then the PEAK piston speed is 41.7 meters per second. Which is 8200 feet per minute. Which is zillions high when 3500fpm is the reccomended mean value. 12 2 Quote Link to comment Share on other sites More sharing options...
Guypie Posted June 27, 2022 Share Posted June 27, 2022 How's the ring gap? I have heard of ring gap closing up when pistons get hotter than intended from the factory setup then wedging in the cylinder. Maybe it happened at tdc and the rod yanked the bottom of the piston off. Probably unlikely but another thing you could check on the other pistons. Maybe do some maths with thermal expansion coefficients and see if it would be likely to close the gap in the temperature ranges it could be experiencing. 1 Quote Link to comment Share on other sites More sharing options...
Popular Post GARDRB Posted June 27, 2022 Popular Post Share Posted June 27, 2022 Proud of you kid. Eat the fricken biscuits 10 Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted June 27, 2022 Share Posted June 27, 2022 1 hour ago, Roman said: I think you could be right about that. If the piston is trying to fly apart, where the top of the piston is trying to carry on upwards, and the pin is pulling it back down. So the material strength around the pin is the weakness. Then on the exhaust stroke this force is lessened, and when the cylinder is full, on the compression stroke this force is lessened too. The engine didnt fail when it was approaching max rpm, it failed just after a gear shift where throttle got cut to zero. So the worst case scenario would be zero throttle, high vacuum, high rpm on the compression stroke. I'm not sure if these forces are on the same magnitude as each other though. However, I can indeed increase my piston return spring value. I can use e-throttle to set a minimum high rpm throttle value to something like 10% or 20%, and then use a fuel cut and/or pull zillions of ignition timing out to cut power instead. This might bring a host of its own issues, but might be a bodgey solution I guess haha. Flat shifting, interestingly enough, would also help haha. The incredibly clever @Lith made a calculator ages ago that works out forces on pistons/rods. Entering 1NZ stuff. Peak accelleration on the piston at 9000rpm is 4991G! I'm not sure what sort of numbers I was expecting, but thats bloody lots. Then the PEAK piston speed is 41.7 meters per second. Which is 8200 feet per minute. Which is zillions high when 3500fpm is the reccomended mean value. interesting. That could be around 1500kg yanking on the rod, which would have a yield of like 15x that, but I have absolutely no idea what im taking about. Quote Link to comment Share on other sites More sharing options...
keltik Posted June 27, 2022 Share Posted June 27, 2022 2 hours ago, Roman said: However, I can indeed increase my piston return spring value. Some kind of air spring could work. Perhaps using a compressor driven by otherwise wasted exhaust energy? No don't do that....yet. 2 Quote Link to comment Share on other sites More sharing options...
Muncie Posted June 27, 2022 Share Posted June 27, 2022 Just need some variable compression ratio rods. 4 Quote Link to comment Share on other sites More sharing options...
yoeddynz Posted June 27, 2022 Share Posted June 27, 2022 Or just put your head on a big hinge... 1 1 1 Quote Link to comment Share on other sites More sharing options...
Muncie Posted June 27, 2022 Share Posted June 27, 2022 Hmm more rods to throw out of different areas of block 1 minute ago, yoeddynz said: Or just put your head on a big hinge... Quote Link to comment Share on other sites More sharing options...
RUNAMUCK Posted June 27, 2022 Share Posted June 27, 2022 It will have been metal fatigue that will have killed the rod. They're a pretty light rod, so the rod bolts wont have been tugged to death. I expect the endless dorting to infinity will have been enough to induce the failure. 2 Quote Link to comment Share on other sites More sharing options...
Yowzer Posted June 27, 2022 Share Posted June 27, 2022 I'm thinking, that since you have blown out both sides of the block, the rod was still attached to the crank when it went for a flail. So I'm guessing that the piston was the first to fail. 2 1 Quote Link to comment Share on other sites More sharing options...
shrike Posted June 27, 2022 Share Posted June 27, 2022 @Romanmaybe you could look into forging your own pistons like Burt Munro? "They were hand-cast using sand from local beaches in a variety of receptacles, including tin cans. They were then painstakingly finished with file and lathe,” Pretty sure you could improve on that with some 3dprints etc for molds Break up some broken pistons to melt down etc 6 2 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.