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Hi Tomo, Your mum is an inspiration! I will be staying at the Dellamora Cattery! Hope to catch up. I have your number programmed in my mobile. Best Regards, Bob
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While on the subject of head bolts, and the obvious need to tension them at service intervals, do they undo themselves, or do they stretch? I believe they stretch, rather than undo themselves, maybe there is a limit to the number of times they can be retorqued before they break. Regards, Bob
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Hi Neil, I think it very likely is detonation and to suggest (as per damage report) that it was caused by a leaking cylinder head is a bit fanciful. The engine has no auto spark advance. Instead, it is set at a fixed 25deg btdc, which is a substantial amount of advance. I believe a car engine would ping its head off with that amount of advance, and wide open throttle applied. The J160 is also used for training and some students and others who hire it, will instantly "firewall" the throttle on takeoff and during endless t&g sessions. This puts an enormous strain on the motor and this is when I believe most of the damage occurs. I have observed this on numerous occassions and whilst I bring it to the attention of the instructors, the message does not seem to filter through. I advocate the progressive advance of throttle over 3 or four seconds to at least let the revs build up. I would like to thank you and the other posters for your interest is this saga. Best Regards, Bob
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Hi Neil, Before startup, I always turn the prop thru at least four compressions and its not just cylinder pressure that I check for. I have had the crank bind on a j170 last year, and this was also considered (by the good folk at Bundy) to be caused by detonation. I'm still at a loss as to why they are so prone to detonation. What maintenance procedures can we adopt to eliminate this problem? Regards, Bob
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Thanks Peter, I will make sure the head bolts are torqued correctly. Regards, Bob
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Hi to all on the forum, I got the engine back from Jabiru today and read the damage report. The report indicates that number 3 cylinder had a leak between the head and the cylinder. They do not have a head gasket so they rely on good machining and evenly torqued head bolts. The report suggests that the number three cylinder was detonating as a result of the leak and /or the use of poor quality mogas. ( It has always been run on 100 LL) The leak was caused by uneven tension on head bolts. Apparently the checking of head bolt torque should be done at service intervals. Now the engine is back together complete with new cylinder (No 3 was cracked around base) new exhaust valve in no 3 head and new rings all round. And new through-bolts. Should be good for another 300 hours! I wish I could express confidence that the cause of the problem had been resolved. Confidence is a valuable asset when you're at cruising altitude. Best Regards, Bob
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Hi Catsy and welcome. I too have a fondness for cats and flying. My Black and white mate often sits on my lap when I browse the forums. Have you taken your cat for a fly Jab yet. Regards, Bob
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Hi Nev, The through-bolt is 10mm in the centre and is tapered down each end, to a smaller diameter where it is threaded. Both bolts broke where the thread ends. They are not high tensile bolts with a rolled thread. From what I can gather, they are machined from crome molly rod and not heat treated. Regards, Bob
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Hello Jack, It was on a training flight at the time and climing with the intention to practice turns when the motor started to vibrate and lose power. It had travelled about 12nm at the time. I think the temperature on the ground was in the low 30's. I shall keep you informed as the saga unfolds. Regards, Bob
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Hi Tomo, It was the lower bolts between cylinders 2 & 3 and between 3 & 4 which broke. When the motor is in situ it is hard to see the ends of the bolts. (Especially when they are not there!)Both had broken where the thread ends. This means that number 3 pot was attached by only the two upper bolts. It uses 100LL avgas exclusively, so you would't expect detonation to be the culprit but I'm starting to think it may be. Regards, Bob
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Hello Old Man Emu, When the bolts let go, there is a fair amount of hammering of the main bearings as the two halves of the crankcase are trying to separate. Its possible that the bearings and the crankcase have copped a hiding. Hopefully the good people at Bundy will let us know what causes this. Regards, Bob
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Hi Jetjr, Thankfully, I was't flying it at the time, but the person who was, experienced vibrations and loss of power. Insufficient power to maintain altitude. Fortunately, high enough and close enough to return to the airfield safely. As for the reasons for the bolts breaking, they did not give me any as yet. I was told that there are ten things that can cause this to happen. I'm hoping that they will enlighten me when the motor is stripped. Regarding the possibility of transferring the problem and causing a breakage somewhere else, I take your point, but it's serious enough when three of the four cylinders are coming adrift and oil is pouring out. Thank you for your interest. Regards, Bob
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The engine on my J160 popped its cork last thursday. Two of the through-bolts which hold the cylinders and the crankcase halves together broke with almost total loss of power. Took said motor to the factory in Bundy and it is now being repaired. I have good reason to believe this is a fairly common problem. From a laymans perspective, the bolts appear to be a fair bit too small in diameter and I suggested this to the people at Jab. I was assured that the tensile strength of the bolts were more than adequate and will NEVER be upgraded. There are many reasons why they break so they tell me, none of which has anything to do with the diameter. The bolts are machined out of 10mm chrome molly stock and they taper to 3/8th on the ends. I cannot see how it is possible to guarantee the tensile strength of a bolt with a machined or cut thread. Most high tensile bolts have a rolled thread. The motor was at the latest spec including the new hydraulic lifter cam and had a little over 300 hours on it when it let go. I am not confident that the problem is being properly addressed. Best regards, Bob
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Exadios, I'm sure if you were to make a reasonable donation, they would be more than happy for you to borrow it, provided you pay for the fuel. Seriously though, I remember seeing the prototype vulcan, I think it was 1957. We heard this thunderous roar and raced out the back yard to see this huge bomber fly right over our home. Perhaps it was heading to Amberley. I remember also how terrible I felt when dad told me that it crashed upon returning to England. Does anybody else remember this awsome aircraft. (perhaps I'm showing my age, I would have been five at the time!) Regards to All, Bob
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The hangar bash sounds like a great idea. I will try to make it DD! Regards, Bob
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Welcome, Greg. It's never too late to have a mid-life crisis.:laugh:It's safer than flying a Harley! Cheers, Bob
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I want one. I could throw a rod in and chase the mackerel in the bay!
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It will be interesting to see if Piper too, gets 1000 plus orders like Cessna have claimed now that deliveries of the Flycatcher have been delayed. [/url]
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Hello Toni, Now is a good time to start flying lessons. Welcome to the forums.
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Hi Pete, Has this proposed adventure been cleared with the Director of Domestic Services, The War Dept and She who must be obeyed???
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The end of 2010 is the end of the 199th decade. The same way that the end of 2001 was the end of the millenium (on our calendar). I suppose I need to explain it....... Hi Qwerty, I think you are on the right track, but wouldn't the end of 2000 be the end of the second millenium. First millenium I thought would be year 1 to 1000, second millenium year 1001 to 2000 etc... please correct me if I'm barking up the wrong tree. Best Regards, Bob
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Happy New Year to you Flying Dog and to everyone on the forums. Safe flying in 2010! Best Regards, Bob:clap:
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For those poor souls who have to work..... The more you enjoy flying, the more your job sucks!
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Hi SB, Congratulation on your new 230D. There is nothing like owning your own a/c. You will be able to drag her out of the hanger and go where and when you want. Have a Merry Christmas and Very Happy New Year..... I know you will. Best Regards, Bob
