gandalph Posted December 17, 2014 Posted December 17, 2014 Roller-followers is another stab-in-the-dark. http://en.wikipedia.org/wiki/TappetEarly tappets had rollers to reduce wear from the rotating camshaft, but it was found that the roller pivots wore even faster and also that the small radius of the rollers also tended to accelerate wear on the expensive camshaft. Facilis descensus Averno (the descent to hell is easy). The qualifying adjective in the quote from Wikipedia is "early". I believe in general terms, i.e. not referring specifically to Jabiru engines, that problem has been solved for quite some time now. Does anyone have factual information on whether the Jab roller rocker set up suffers as suggested by the Wiki quote?
Guest Ornis Posted December 17, 2014 Posted December 17, 2014 No ambiguity in the Wikipedia comment. The tappet is the part that runs on the camshaft. The early tappets were rollers. They were abandoned due to excessive wear. I binned a J3300 at ~1300 hours. There was no detectable wear on the mushroom cam-followers (tappets). Rollers: Another wrong answer to a real problem. Who cares if the Jabiru setup wears or not? If it does it's just another problem introduced in an attempt to confuse everybody and avoid the question: Why did the valve clearance need to be adjusted every 25 hours?
Guest Ornis Posted December 17, 2014 Posted December 17, 2014 Two things, "deborah". (1) You keep talking as if you run a Jabiru engine and you don't. (2) I never had 25 hours pass without the clearance needing adjustment on several heads - and not always the same ones. Whether you record it in the logbook or not make no difference to the phenomenon. Just more obfuscation from the sophists. And yes, the Jabiru engine ran too hot - installed in a J200 as per instructions, with a CHT thermocouple under a plug on #6 - factory installed. First it cooked ground-running because the design of the cowl shed the air from the prop. That's if it started at all, and it wouldn't in cold weather, even with a truck battery.
facthunter Posted December 17, 2014 Posted December 17, 2014 It is good practice to record all tappet adjustments on any engine. (Aero or otherwise). The maker gives a period between checks , but if they are stable you can push the check periods out on that basis. I would NOT do that on an aero engine that has any problems with excess heat or tending to... Check compressions by feel on preflight. Know what they should feel like IF they don't feel right. check why.. If your motor runs rough investigate it. Don't just continue to use it and hope it comes good.. If it's a radial the maker recommends turning it through more than two rotations to ensure no hydraulic lock likely.. Having a spark plug not tensioned correctly is a no no.. Unused motors corrode unless treated. I bet not 1% of you have ever done anything about that.. Nev 1 1
gandalph Posted December 17, 2014 Posted December 17, 2014 No ambiguity in the Wikipedia comment. The tappet is the part that runs on the camshaft. The early tappets were rollers. They were abandoned due to excessive wear.I binned a J3300 at ~1300 hours. There was no detectable wear on the mushroom cam-followers (tappets). Rollers: Another wrong answer to a real problem. Who cares if the Jabiru setup wears or not? If it does it's just another problem introduced in an attempt to confuse everybody and avoid the question: Why did the valve clearance need to be adjusted every 25 hours? Ornis, 1. With respect, I did not suggest or imply that the wiki article you quoted was ambiguous. I merely drew attention to the modifier "early". That suggested to me that this problem was identified early in the development of the internal combustion engine. I'm happy to be proved wrong. 2. I asked if anyone had factual information with regard to wear and roller rockers in Jabiru engines. Your first hand information on solid lifters is valuable but doesn't relate to roller rockers. 3. I know what a tappet is, but thank you for explaining it. 4. Were roller rockers the wrong answer to a real problem? Quite probably. I wasn't suggesting that they weren't. I understand that CAMit does not use roller rockers on the CAE engines presumably with good sound and well researched reasons. 5. You ask "Who cares if the Jabiru set up wears or not?" Surely that's a rhetorical question? A final point about roller rockers - I think you'll find that they are still very popular with builders of high performance engines. The claim that they were abandoned due to excessive wear is misleading. I can understand your dissatisfaction with Jabiru engines given your experience with them. (edited..mod. Play nice)
ianboag Posted December 17, 2014 Posted December 17, 2014 The only reasons to install only 1 x thermocouple, are budget or ignorance I'm afraid. Tell that to the Jabiru factory ...... 3
facthunter Posted December 17, 2014 Posted December 17, 2014 Incorrectly designed roller followers would not be as good as the flat faced type, but are less critical of cam profile. Camshaft wear and edge crumbling are very common and the wear faces are one of the most critical parts to lubricate on a motor, requiring special additives of the preventing scuffing kind. AS stated, many high performance motors have run them for ages. They might end up adding a small amount of weight being a bit more bulky and costing more. I'm happy to not run them provided all is done right in the set up and the metals are good enough. Nev 1
ianboag Posted December 17, 2014 Posted December 17, 2014 YOU (the purchaser) are the ones not choosing to fit 4 or 6 CHT's, not the factory. On the Jab site it's called the "Option A" panel. I didn't find the bit where it says that if you buy this one you are either a cheapskate or an idiot and that you should not be surprised if you have overheating problems ..... 5 1
BPN Posted December 17, 2014 Posted December 17, 2014 Deborah, your defence and devotion is admirable . But IMO you are blinkered to reality .
Captain Posted December 17, 2014 Posted December 17, 2014 On the Jab site it's called the "Option A" panel.I didn't find the bit where it says that if you buy this one you are either a cheapskate or an idiot and that you should not be surprised if you have overheating problems ..... I had no trouble arriving at what was really an engineering decision to fit 6 X CHT's and 6 X EGT's to allow me to best understand and manage my 3300. If others are incapable of making such a decision that is their issue. Mind you, I may have been wrong in arranging to do that, but I still feel that this is essential and would do the same thing with a 912/914 or any other engine in order to monitor any short & long term changes and trends in order to pick up issues early. 1 1
ianboag Posted December 17, 2014 Posted December 17, 2014 engineering decision to fit 6 X CHT's and 6 X EGT's ... if others are incapable of making such a decision that is their issue. Good on yer mate. The factory has an "option A" on factory-built aircraft with just one CHT and no EGT. How is a buyer supposed to know that this factory option is (in your opinion) dumb? Could there be other dumb ideas from this factory? Perish the thought. 4
planesmaker Posted December 17, 2014 Posted December 17, 2014 I wrote to Jabiru to suggest that CHT's should be fitted to every cylinder on every aircraft that leaves the factory, I received a reply saying that they are considering it but so far they have traditionally resisted to keep the price down. So there you have it, to provide us with a well priced aircraft. Tom 1
Oscar Posted December 17, 2014 Posted December 17, 2014 Good on yer mate.The factory has an "option A" on factory-built aircraft with just one CHT and no EGT. How is a buyer supposed to know that this factory option is (in your opinion) dumb? Could there be other dumb ideas from this factory? Perish the thought. Well, for sure. Or, you could decide to spend more than $40k installing a Rotax, rather than $2k installing a full EMS using an MGL Extreme and just perhaps been able to monitor your engine management and get a decent life out of the engine you decided to throw away? Yet - if I remember correctly - you were the guy who replaced your aileron hinge pins with bronze wire to save the cost of changing the hinge pins to the recommended material.
Guest Ornis Posted December 17, 2014 Posted December 17, 2014 I can understand your dissatisfaction with Jabiru engines given your experience with them. (edited..mod)No need to sweet-talk me, gandalph, (edited..mod) I binned the J3300, (edited by mod ..play nice people) When my aircraft was finished, Don Richter came over. No mention of additional equipment. (edit again..mod) EDIT. The J200 Ian Boag once owned doesn't have a Jabiru engine either now. Binned.
motzartmerv Posted December 17, 2014 Posted December 17, 2014 Yea. Engines fitted with 6 channel monitoring don't fAil aNd spit head bolts ... Oh ... Wait.... Yes they do.. But at least you get to watch your engine grenade is awesome 6 channel resolution... 1 1 1 1
Guest Ornis Posted December 17, 2014 Posted December 17, 2014 Yet - if I remember correctly - you were the guy who replaced your aileron hinge pins with bronze wire to save the cost of changing the hinge pins to the recommended material. I don't think there's anything special about steel for the pins but I could ask Ian Boag PhD (Chemical Engineering).
Oscar Posted December 17, 2014 Posted December 17, 2014 I don't think there's anything special about steel for the pins but I could ask Ian Boag PhD (Chemical Engineering). Perhaps for your safety, you should do that, with reference to the electrical potential of different alloys. That is, if you don't want your control surfaces to drop off.
ianboag Posted December 17, 2014 Posted December 17, 2014 Well, for sure. Or, you could decide to spend more than $40k installing a Rotax, rather than $2k installing a full EMS using an MGL Extreme and just perhaps been able to monitor your engine management and get a decent life out of the engine you decided to throw away? Yet - if I remember correctly - you were the guy who replaced your aileron hinge pins with bronze wire to save the cost of changing the hinge pins to the recommended material. Sigh. The old mud-wrestling-with-pigs problem. Moderator please note - this is getting personal ..... New fatter pins as a long term solution didn't cut it as the (ally) hinges were flogged out. Jab had sent me some new stainless ones that didn't fit the old holes. The (fatter) brass pins were a stopgap so I could keep flying for a couple of months until I could organise fitting the new hinges ... but I said all that before anyway .... Back to the point of all this. If a Jabiru aircraft needs an all-singing EMS to get a reasonable life out of the engine, then one might wonder why the factory doesn't see it that way. Funny you should mention the Xtreme - I put one in my Rotaru. Amazing how you can fit it all on a 5" screen .... I'm a fan. (watching thread Ian...mod)
Guest Ornis Posted December 17, 2014 Posted December 17, 2014 Perhaps for your safety, you should do that, with reference to the electrical potential of different alloys. That is, if you don't want your control surfaces to drop off. Gee. Never thought of that. I'll have a look amongst my degrees. Good heavens, there's an old MSc. Incidentally, aluminium pins don't wear significantly in 500 hours.
Guest Ornis Posted December 17, 2014 Posted December 17, 2014 BPN, thanks for your concerns however my track record of over 1k hours in Jabs with my signature on the MR has taught me a thing or two about them. Certainly learned enough not to buy another one,. You defected to CAE.
Guest Maj Millard Posted December 17, 2014 Posted December 17, 2014 this was posted on Jab's facebook page last weekPartnerships... Further to my last correspondence and finishing words of Lies, Damned Lies and Statistics:- There is no doubt that statistics can be a useful tool. It has been proven by many that collating numbers from a small data set will not result in meaningful results.....except if you want to use a number to make a point. In reality anything can look good or bad at the press of a button. The question then arises on what intent the people producing the statistics might have. Statistical evidence can easily be used as a tool to make a pre-conceived point or push through an agenda. Statistics produced from independent sources with no political or otherwise agenda are the most useful and are what allow us to be pro-active in our approach. We take all statistics we receive seriously. The statistics we have collected ourselves and compared to CASA which were supplied by the RAA do lead me to another question. The question is, if I buy a Jabiru or in fact any other aircraft, will it be reliable? A simple question, I wish there was a simple answer. There are three major parties that come together in this equation - the manufacturer, the operator and the maintainer. The manufacturer is responsible for many things and it is perceived and or expected that he should be able to design and build a “bullet-proof” product which is somehow tolerant of every foreseeable handling, maintenance or operational variable that could and does occur. I do not know of any “bullet-proof” engine. The manufacturer can do his best but without the partnership of proper operation and proper maintenance the equation starts to come unstuck. As a manufacturer it is our responsibility to provide manuals on how to operate and maintain the product in the correct way for the product to achieve its optimum performance. Our team put a lot of time and hard work in to manuals which are freely available and user friendly. To complete the equation the operation and maintenance must then be carried out in accordance to the manuals provided. When I learnt to fly I was taught first to read all the manuals and manage the engine. First of all I had to do a pull through and with a Lycoming this can be a bit tricky. There was a well regimented pre-flight check. We were taught to look for nicks or cracks in propellers, followed by fuel water checks. Fuel contents checks using a dipstick and physically sighting the fuel in the tank. External check of control rod ends with freedom of movement, tyres for bald patches and on it goes. Start up and then a warm up period, advance the throttle slowly and climb away. In flight we were taught to maintain cylinder head temperature and oil temperature by adjusting our climb rate and our speed. There were no sudden throttle movements and no rapid cooling and always within engine limits. For maintenance the aircraft went to the local LAME. He did it by the book. His first check was for applicable AD’s (Airworthiness Directives) and Service Bulletins. Standard 100 hourly on a C172 was 13 man hours, brakes and wheel bearings were additional. Now the question is was my brand new Cessna 172 reliable? Well generally it was, except at 400 hours from new it seized a valve (does that sound familiar) and put me in a paddock with four people on board. No harm done. The local LAME came and changed the cylinder and a few days later I flew it home. The engine ran well to its TBO of 2200 hours. Now back to statistics. Valve issues and through bolt failures are shown to be the major contributors to the statistics. To strengthen our partnership we are going to ask you to look at valves and through bolts on existing engines. At top overhaul or full overhaul engines will be upgraded to 7/16” bolts. Valve relief pistons will be fitted as standard. This will bring existing engines close to new production engines which are performing very well. Given that each of these incidents could now be reduced significantly with Service Bulletin implementation, statistically we would be more reliable than our major competitor. Isn’t it marvellous what statistics can do!! So are all engines reliable you say. Well, they are probably as reliable as the partnership of the manufacturer, the operator and the maintainer. One if the key duties or responsibilities of a manufacturer would be to listen to the complaints of customers wouldn't it ?......and to react correctly to eliminate the cause of those complaints. jabiru hasn't done that at all in the past 20 years and it has caught up with them.
gandalph Posted December 17, 2014 Posted December 17, 2014 Note to the Moderator. A bit heavy handed there Mod. I answered him politely and wished him well with his project. No insults, no derogatory comments. What's the issue? See Even Ornis is laughing
Guest Maj Millard Posted December 17, 2014 Posted December 17, 2014 "Checked" not necessarily "adjusted" every 25 hours with the information recorded in the engine log book. A cool running engine could be pushed out to at least 50 hours.How many people do what I do and record the tappet clearance with feeler gauge before adjusting them? By doing this, I know exactly which valves are receding into the heads or otherwise and then I can pre-emptively determine which valve or head needs work. Low and behold, usually the ones that close up are the hot heads! If you are relying on your mechanic to do this work and it's not being recorded in your log boom then find another mechanic as you are flying blind ! Valve clearances close up on new engines for a couple of reasons, which is why close checking of valve clearances is required initially, and then periodically through the life of the engine. One reason is the valve-face seating into the valve seats. this is normal 'bed in'..Secondly the valve stem will stretch and even more so if the clearance is not maintained or is non existent. The correct methods for checking valves for stretch is to either measure the length of the stem itself, or to use radius gauges to check the radius of the 'tulip' , or back of the valve head.
Guest Maj Millard Posted December 17, 2014 Posted December 17, 2014 Quite the contrary Ross, if they weren't listening, why did they introduce hydraulic lifters and the other dozens of improvements over the years? Well they wern't listening close enough to somebody were they, because it hasn't worked has it ?..You'll note Camit are using solids on their engines.
Guest Ornis Posted December 17, 2014 Posted December 17, 2014 Quite the contrary Ross, if they weren't listening, why did they introduce hydraulic lifters and the other dozens of improvements over the years? You like Jabiru's hydraulic lifters so much you bought a CAE.
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