Rolled Thread Engine Through Bolts Available as alternative

[ianboag]

Well that's all pretty blunt, but it's about where we got to ...... undersized bolts -> pull/distort threads -> relax clamp -> case fret/bolt break .....

 

We went to ARP bolts/nuts but anything with tight threads will work

 

 

[facthunter]

It's that simple is it Clive? Nev

 

 

[Guest Maj Millard]

Facthunter, a late reply to your post #64 if I may. I know the Gypsy Major engine was, and is, a great engine for it's day, and I know many still give great service on a daily basis. 1000 reliable hours back then was great stuff, but in todays' world there are engines available to flyers that easily give 2000hrs plus, without requiring a major rebuild or constant upgrades at 500 hrs. And of course there are a couple more on the horizon, also more than capable of giving a reliable 2000hrs or so, for todays aviators. Some of these are already appearing on the latest aircraft models, and they do indeed appear to be another step in the right direction, as far as engine reliability goes.

 

It is 2012, piston engine technology was pretty much perfected well before WW2, we do not have to put up with rubbish in this day and age. There simply is no reason to.

 

A crankcase through-bolt is a very important, and critical component of an engine crankcase. Apart from holding the case together, it is used to primarily provide, and maintain, the all -important 'crush' on the bottom end, and main crankshaft bearings.

 

Anyone who has rebuilt any German engine (VW etc), will know that it is this 'crush', attained and held by the crankcase through-bolts, that is the the key to any engines' longevity.

 

When there is a demonstrated and known problem with something, inteligent people discuss the problem, and seek to come up with a better solution.

 

This is what we have done on this forum, and the solution that we have come up with is a better throughbolt !.

 

I was instrumental in suggesting the rolled-thread alternative, simply because that's what every other aero engine uses, and have done for years.

 

On Lycoming or contenental engines no retorquing of through-bolts is generally necessary, because they are using the correct bolt/nut set-up.

 

The only time you have to disturb, or retorque a throughbolt on those engines, is when a cylinder is changed, and only then when the throughbolt is used to secure the cylinder base flange.

 

Remember, we are having to do this because the factory wasn't, and we are on the right track with the new non-Jabaru rolled-threaded throughbolts..................................................................................Maj...

 

 

[facthunter]

I absolutely agree with all that you have said Maj. I have supported the use of the new studs /bolts and I am aware of all the points you make because I have built motors since the mid 50's, and aligne bored bearings and know what crush means. Surely we are both on the same train. This is basic engineering principles. Nothing new in it..Nev

 

 

[Guest Maj Millard]

I thank you for your very understanding reply facthunter, it appears we are indeed on the same train !.........................Maj...

 

 

[Clive J]

Smoke and mirrors....

 

 

[facthunter]

Not on my part I can assure you. I have NO association with Jabiru whatsoever. I have some difficulty with you simply dismissing my input as "rubbish", and as part of a plot/ attempt to create confusion, as you would no doubt if a considered and comprehensive input from you was was dismissed, in such an offhanded manner. .

 

You have NO idea where I am coming from. I need more than an assertion of 'conspiracies". from you to be impressed by your contribution.. Nev

 

 

[Clive J]

Hmm, not sure who you're replying to, have looked up the thread and don't see 'rubbish' anywhere, my comment 'Smoke and mirrors' was to the content of several recent SB's blaming all manner of reasons as to why mods are being suggested and to also answer your question, 'Is it as simple as that'

 

Yes, the bolts are manufactured with a poor thread and the rest is smoke and mirrors by Jabiru.

 

I believe the real reasons for many suggested 'improvements' are attempts to fix development faults, if they are admited as development faults then liability would come with it. So they are 'improvements' and 'upgrades'.

 

I'ts early for you so you probably haven't had a coffee yet so that would explain the CAPITALS.....:-)

 

I love some heathly discussion and exchange of ideas and thoughts, also differing opinions, if everyone thought the same it would be a boring world.

 

Regards, Clive

 

 

[facthunter]

Sure , Clive Let's have the discussions ( which we have been doing here for quite a while) When a comment like "Smoke and Mirrors" is a complete post from you and follows mine, how would that be meant or taken other than the obvious.

 

I completely support the "higher strength" studs, as some of the originals appear to be inferior. Loose fit of threads is not for aero engines.

 

The problem in certified engines is that it wouldn't be a "legal" mod.

 

The engines have other problems, and I will not be surprised if the stronger studs break as well. Nev

 

 

[Guest Maj Millard]

I think you have hit the nail on the head there facthunter, especially with your last line.

 

Sort of reminds me of the Beechcraft Bonanza deal where Beechcraft would never admit to there being a fault in the V-tail even after literally hundreds of them had separated from the aircraft, killing many good pilots and passengers. They didn't want to admit liability as it probabily would have sent them broke.

 

It wasn't until an outside group (Beechcraft owners Assoc) came up with the fix that the tail problem was solved, with the simple addition of plates at the foward edge to stop the tail fluttering.

 

I have it on good authority never to fly in a Bonanza that doesn't have the tail mod, and I never have.

 

There will always be jab owners who will never accept that the engine has faults. The CASA safety digest each month shows otherwise with two or three listings each edition now.

 

Even former staunch advocates like Deiselton and Chris Stott have suffered serious failures with the engines, and in Deiseltons case experienced the less than ideal factory support.

 

What unsettles me most is that these engines are going out to the world with a proud Australian flag on them, and they are probabily no more reliable as your latest basic Rotax 2-stroke......................................Maj...

 

 

[skeptic36]

What unsettles me most is that these engines are going out to the world with a proud Australian flag on them, and they are probabily no more reliable as your latestbasic Rotax 2-stroke......................................Maj...

I agree about the Australian product but I think your being a little tough on the little Rotax aren't you?

Regards Bill

 

 

[Guernsey]

I agree about the Australian product but I think your being a little tough on the little Rotax aren't you?Regards Bill

I agree skeptic, I think Rotax should join two or three 503 engines in line then we would have a good engine. (Tongue in cheek).

 

Alan.

 

 

[Guest Maj Millard]

skeptic 36 and guernsey, Didn't mean it that way at all, I have the greatest respect for the latest 503/582 range which are fine and very reliable engines. I flew for several hundred hours with the earlier single plug, single points ones and the current DCDI ones are just so much nicer..I was using them as a comparision to what I consider to be the lack of reliability in the jab engines, sorry !................................................Maj...

 

 

[facthunter]

Well generally, 2-strokes are considered less reliable than 4-strokes, but there may be exceptions.

 

I would consider a 582 with about 100 hours on it and having all the temps where they should be to be a quite reliable thing.

 

People have to know how to operate a two stroke. Years ago (10 or 12) they were everywhere.. They are light and powerful for their weight. Californian Laws probably heralded the demise of them Almost, hang in there those who have them.. Nev

 

 

[Guest Maj Millard]

 

I've got a lot of 2-stroke hours in my logbooks, mostly 503 and 582. But I've also flown with the 532,447 and 125cc Rotaxs. the 125cc Rotax was a small single cylinder direct-drive ex-firepump engine, converted and used on the canadian produced Lazair aircraft. The never let me down if you had the idle set right. The had a single points ignition and one plug, were very basic two strokes and would easily 'deisel' if you let them. That's flying !!..

 

The only 2-stroke that ever put me in a paddock was an air-cooled 447 at 175 hrs from new. It was forced air-cooled and always ran high CHT on take off (up to 400F). It didn't miss a beat for 175 hrs then spat a top (dykes) ring on me about ten minutes after takeoff, when the temps had come back and stabilized. I was always fussy with oil and don't think it was oil related.

 

In all my 503 and 582 time, 15 years worth they never missed a beat on me, or even gave me a scare.

 

I am happy to say that I have flown the 912 for some years now, and they are at an even higher level of reliability.............................................................Maj...

 

 

[Dieselten]

More personal opinion:-

 

First, I am with the good Maj Millard on Rotax 2-strokes; the Rotax 503/582 engines are remarkably reliable if they are operated and maintained correctly. I have over 1100 hours being hauled around by them in the past. My first Rotax 582 outlasted my first Jabiru 2.2L engine!

 

Speaking of Jabiru, they gave me all the factory warranty backup they were required to do. They met their obligations fully. They couldn't solve one problem because they were unable to reproduce the symptoms on their test-stand. To reproduce the symptoms they would have needed to mount the engine on an airframe and actually fly it, but they were unable to do so - or they chose not to because it was impractical for them. In either event it does not matter. The problem (rough-running at high RPM and heavy load) has since been resolved. Sorting out problems with their existing engines is one thing, but the company needs to be looking well into the future, and the future does not lie with gasoline-powered aircraft-engines.

 

If Jabiru are going to spend R&D money trying to iron out the issues with their current engines, and a partial re-design is their answer, then why not go the whole hog and design a 4-cylinder 4-stroke compression-ignition aircraft engine? Avgas is a finite and limited resource due to a number of pressures. Mogas is likewise. Aviation kerosene is a less hazardous material to transport and store. Like it or not, it is the aviation fuel of the future. It can be synthesised, and will be a lot cheaper per unit of energy than batteries, and lighter too.

 

Any company that can design and manufacture a reliable, economical compression-ignition aircraft engine in large numbers and get it out there hauling thousands of aeroplanes around is definitely a company with a bright future. I question the wisdom in spending time and money on re-designing an existing powerplant when the entire sport, light and GA markets are still waiting for the Holy Grail; a diesel-cycle aircraft engine that actually works.

 

Thielert showed how to make a good engine hamstrung with all sorts of unrealistically short overhaul times - and went broke in the process. Zoche has shown us a vapourware aero-diesel - there isn't a single Zoche-powered aeroplane anywhere in the known universe, and there never will be. Wilksch in the UK have a few engines of surpassing ugliness (and drag, with the intercooler) out there. Diesel Air in the UK? SMA in Europe? Both conspicuous by their absence on any flying aircraft in anything but prototype form. We are still waiting for the Lycoming aero-diesel...don't hold your breath! Manufacturers announce their aero-diesels with loud fanfare - and all we hear is a thundering clap of silence.

 

I wouldn't put it past Rotax to be quietly developing such an an engine in the Rotax version of the "Skunk Works" right now. That company is deadly serious about making good engines, and it has a track record which other makers must envy. When Rotax sell an aero-diesel, it will work.The R&D will have been done, the test-flying likewise. I believe it's just a matter of time.

 

If Jabiru are serious about being in the engine making business, then by all means try to sort out the issues with current powerplants, but long-term the engine-of-choice will be the compression-ignition unit. Start working on that, and make sure it is a viable, reliable, maintainable unit before hanging it on the front of an aeroplane, let alone selling it.

 

The short-term alternative is to offer a choice of current gasoline-powered engines; theirs or the Rotax. I still maintain that if they did this they wouldn't be able to build airframes fast enough to keep up with the demand. They build tough, durable airframes. Great airframes for training aircraft. Their Achilles Heel is the powerplants. Maybe it's time for their next generation of engines to be revolutionary instead of merely evolutionary.

 

 

[fly_tornado]

Jabiru will never match Rotax, Rotax make millions out of snow mobile and bike engines every year and pour that a lot of that money into development of their manufacturing process.

 

 

[jetboy]

Jabiru can't arrange good enough throughbolts to hold a diesel together.

 

Dieselten, Facthunter, Maj, all right on and I'd love to find a suitable kero burning engine - have been following every type mentioned plus all the rotaries that have claimed multifuel development and all turned to cinders before a single unit got sold. A 3 cyl. 2-stroke would suit me best. Just yesterday I was studying here

 

http://www.enginehistory.org/engines.shtml

 

the Juno history particuarly interesting

 

Ideally Jabiru might fix all the issues but we have to wait a couple more years because the current mods have not worked yet. I can understand why there would be no reason (for them) to make an option to use the 912 or UL260 if it's any good. Their decision to build their own engine when forced to and reasons for not using the 912 is well documented in their history.

 

The option to fit a better engine and do your own approvals is still open. Presumably those fitting the Rotec liquid heads or the SA fuel injection will already be obliged to get the same approvals for these, as I don't see any sign of Jabiru doing it for anybody.

 

Like everybody, I keep looking for a better alternative - the truth is nothing exists so in the meantime I hope my aged 2200 without the "improvements" can hold out till a replacement is available.

 

Keep the discussion up- we may get there (perhaps needs shifting to another thread, but talking diesel and having a sturdy crankcase and cylinder attachment is still relevant here)

 

Ralph

 

 

[rogerpl88]

With the problems Jabiru are having with their hydraulic lifter engine, one solution is to go back on step and offer a solid lifter version. While this engine may not appeal to the demands of busy flying schools, I know that many private owners will accept the compromise of reliability and power over the chore of having to adjust the tappets twice a year.

 

Adequate oil flow was the biggest problem with the solid lifter and this would have to be resolved if it were to be my 'forever' engine. In fact the oil flow problem was carried over to the hydraulic engine and in my opinion, one of the major reasons why the new engine was released with so many problems. Proving an engine on a test bed in a controlled environment (including a steady oil pressure) is not representative of an engine that looses its oil pressure when it gets hot. The hydraulic lifter and valve timing depends on a steady pressure.

 

 

[Dieselten]

Still more personal opinion, with a fact or two thrown in:-

 

The reason Jabiru designed and built their own engine was simply because no other suitable engines of the required size and horsepower were available when the Italian KFM engine ceased production. As Jabiru have pointed out, the aircraft was designed around the engine, so a new engine had to be made to fit the existing aeroplane. That aircraft evolved into the little, narrow-nosed LSA55.

 

However, this reason no longer exists - the whole raison d'etre for the Jabiru engine no longer exists. At least one extremely reliable, well-engineered and proven alternative engine exists. Would it not be in the company's the company's best interests to at least offer the choice as factory-approved powerplants on both factory-built and kit aircraft? This would broaden the appeal of the aircraft, not narrow it down. Does Jabiru wish to sell more aircraft, or does it think its market is too big already and should be downsized? You buy a Boeing or an Airbus and you get a choice of powerplants. Where's the big problem for Jabiru to do the same?

 

Realistically, the only alternative powerplant (available right now) is the Rotax 912-family of engines. They have the track-record, with no R&D required for the engine itself - it's all been done. Their through-bolts don't break, their cylinder-heads don't overheat, their valves don't burn out. They don't leak oil, or coolant-fluid either. Their resistance to carby-icing is far superior and their fuel-economy is as good with the advantage they are designed to run on mogas without any lead at all, leading to less cylinder wear and longer oil-life. You have to go with what is proven, not what merely fits under the cowlings. But - and this is a big but - even if Jabiru were to offer the Rotax as an alternative, it is ultimately just a temporary "fix".

 

I'll state it once again, unequivocally. The future for piston aircraft-engines lies with compression-ignition. By necessity this type of engine will have much more robust, well-engineered design. I'd cheerfully carry another 5Kg or even 10Kg of engine weight if it gave me 1000 hours of reliability. Any engine-manufacturer who wishes to remain in the aircraft piston-engine business needs to be looking in this direction - that includes Jabiru.

 

 

[jetjr]

D10 -Im with you regarding kero/diesel engines. Im keen to learn more about them - where do they stand in terms of fuel burn? Also overhaul costs can be very high on auto versions

 

Jabiru sell lots of 6 cyl engines too and without the 4 cyl sales would make the engine business less viable.

 

A 912 would make Jabs more expensive (I guess) and Jabiru would make less money on each aircraft sold so I can see their method here. Not saying I agree with it though. Bit like asking Toyota to supply a vehicle with Nissan engine.

 

Im yet to be convinced of 914 suitability and if it shares the 912 reputation and cost effectiveness

 

 

[turboplanner]

Still more personal opinion, with a fact or two thrown in:-The reason Jabiru designed and built their own engine was simply because no other suitable engines of the required size and horsepower were available when the Italian KFM engine ceased production. As Jabiru have pointed out, the aircraft was designed around the engine, so a new engine had to be made to fit the existing aeroplane. That aircraft evolved into the little, narrow-nosed LSA55.

 

However, this reason no longer exists - the whole raison d'etre for the Jabiru engine no longer exists. At least one extremely reliable, well-engineered and proven alternative engine exists. Would it not be in the company's the company's best interests to at least offer the choice as factory-approved powerplants on both factory-built and kit aircraft? This would broaden the appeal of the aircraft, not narrow it down. Does Jabiru wish to sell more aircraft, or does it think its market is too big already and should be downsized? You buy a Boeing or an Airbus and you get a choice of powerplants. Where's the big problem for Jabiru to do the same?

 

Realistically, the only alternative powerplant (available right now) is the Rotax 912-family of engines. They have the track-record, with no R&D required for the engine itself - it's all been done. Their through-bolts don't break, their cylinder-heads don't overheat, their valves don't burn out. They don't leak oil, or coolant-fluid either. Their resistance to carby-icing is far superior and their fuel-economy is as good with the advantage they are designed to run on mogas without any lead at all, leading to less cylinder wear and longer oil-life. You have to go with what is proven, not what merely fits under the cowlings. But - and this is a big but - even if Jabiru were to offer the Rotax as an alternative, it is ultimately just a temporary "fix".

 

I'll state it once again, unequivocally. The future for piston aircraft-engines lies with compression-ignition. By necessity this type of engine will have much more robust, well-engineered design. I'd cheerfully carry another 5Kg or even 10Kg of engine weight if it gave me 1000 hours of reliability. Any engine-manufacturer who wishes to remain in the aircraft piston-engine business needs to be looking in this direction - that includes Jabiru.

While not defending the long running series of cylinder clamping issues, we need a dose of reality.

 

1. Quite a few people have departed the recommended fuel

 

2. Quite a few people have departed the recommended oil

 

3. Quite a few people have departed the recommended service standards, with some service methods being unsuitable for chaff cutters

 

4. Quite a few people are apparently unaware of the temperature limitations

 

5. Some people are having repeated failures after doing their own work, in some cases having no idea of torquing accuracy or bolt stretch

 

So having read the various twists and turns of this thread I suspect a lot of the failures could have been avoided.

 

Very few people are aware of the cost of development. A few million here or there is practical on big jets, but the design and test costs, not to mention a two or three year development programme are very significant. The development has to include spare parts analysis, numbering, stocking level etc.

 

If you add the cost of that development to the significantly higher cost of the Rotax (if you go by parts prices), you probably finish up with a $120,000 or $130,000 J170.

 

Would there be a market for that product?

 

Yes there would be, but the million dollar question is how many per year?

 

I've faced the same question as this many times with dealers wanting new truck models for more power etc. It all goes swimmingly until they find out they'll have to pay an extra $5000.00, then they go cold and say they can't sell them.

 

If it was my business I'd fix the bolt problem.

 

With a name like Dieselten, I supposed we could expect another selling job, but I wouldn't be so quick to put extra vibration into an airframe, and the extra 5 or 10 kg could easily turn into 20 or 40 kg with accessories (it's 45 kg on a typical small 4WD), and I hate to disappoint you but I've seen diesels with far more problems than the Jab engine, although in generic terms engine life is longer.

 

Doesn't hurt to dream though.

 

 

[skeptic36]

While not defending the long running series of cylinder clamping issues, we need a dose of reality.1. Quite a few people have departed the recommended fuel

 

2. Quite a few people have departed the recommended oil

 

3. Quite a few people have departed the recommended service standards, with some service methods being unsuitable for chaff cutters

 

4. Quite a few people are apparently unaware of the temperature limitations

 

5. Some people are having repeated failures after doing their own work, in some cases having no idea of torquing accuracy or bolt stretch

 

.

I don't think the Rotax comes with a university degree in aero engine maintenance either so why do we see such a vast difference in TBB (time before breakdown)?

If the law of averages is applied they would be maintained by similarly meticulous (or not) group of owner operators you would think.

 

Regards Bill

 

 

[turboplanner]

1. Dieselten tells us Rotax are designed to run on Mogas

 

2. Rotax may be less susceptible to creative oil changes

 

and so on.

 

I agree with your owner cross section, in other areas the Rotax may be less prone to fiddling errors/provide less opportunities for someone to fiddle

 

 

[Guernsey]

I understand Jabiru's reluctance to make small or regular improvements to certified engines because of the cost of re-certification, however, could they not also produce a non certified engine for buyers who do not require a certified engine. This would enable them to make improvements and when they finally thought they had got it right, could then certify it. Does this sound a bit too simplistic?

 

Just my 2 cents worth.

 

Alan.