Jump to content
  • Welcome to Recreational Flying!
    A compelling community experience for all aviators
    Intuitive, Social, Engaging...Registration is FREE.
    Register Log in
Sign in to follow this  
Camel

Major weaknesses addressed

Recommended Posts

I own an original VFR750 - the direct result of Soichiro Honda decreeing that the the problems of the VF750R would be not just addressed but obliterated! It is a magnificent piece of engineering and urban legend says it was sold at a loss to the company. Of that I have no certainty, but what I do know is that the machine I have is the first in a line of the most successful sports/touring bikes produced in the world. Your appreciation of a particular situation at Honda is entirely correct, but I happen to be someone who already knew that. I completely agree with your summary.

 

Absolutely nobody who has accessed the reams of information available could reasonably argue that there are not design flaws in Jabiru engines. There is incontrovertible evidence of that. Whether these are 'major' depends on the definition of 'major'. I suggest that 'major' is a basic, fundamental lack of fitness for purpose. 'Major' is not, in my personal opinion, a problem that can be addressed by upgrading the size of a bolt here or adding a dowel there - but I concede that this is a subjective area. This is highly relevant to the discussion of this thread, because it brings into question the very basis of what CAMit is undertaking by way of addressing the issues attendant with Jabiru engines.

 

However, with regard to your latter point about stepping down from my plinth: both you and Major Millard have made extremely dogmatic assertions regarding various aspects of the discussion on Jabiru / CAMit engines. I have asked both of you to provide any - I repeat ANY - supporting evidence. In the absence of that, I have to conclude that these are simply unsupported statements of personal opinion that lack any measure of verification. There is a crude expression for such statements, that refers to the results of the bovine excremental process.

 

No, I am not going to 'step down from my plinth' in the face of unsupported opinions. You (and Major Millard, in whose corner you have evidently placed yourself) have made statements - now provide the explanatory material that will prove them. Can you do that?

 

And, I'm not a Mate. Don't presume a relationship with me that you have so far failed to earn.

 

 

  • Agree 1

Share this post


Link to post
Share on other sites
Well guess what Oscar, I'll back Major's practical skills against exhaust gas any time.

You do that. It's your neck on the line. I'll rely on my own sources and resources that have a proven track record from F16's downwards, are (genuine) test pilots, have done the type certification of a number of significant Australian aircraft, have built 5,000 plus aero engines, blah yaddah. Each to his own, I say.

 

 

Share this post


Link to post
Share on other sites

Lot of genuine test pilots flying behind Jab engines also, I have number of test hours behind a Jab engine and have no problem flying in one, just wouldn't take it the places I take my Rotax.

 

Correct each to their own.

 

Just like Holden & Ford lovers shame they will both be discontinued in a few more years.

 

Alf

 

 

  • Helpful 1

Share this post


Link to post
Share on other sites
I really hope these engines are a good ( better) thing, I'd have one for my next project if I was confident they're going to last,,,,,and really don't care if they have or have not breached some IP or copyright , so I'd like to know important stuff,,, like how much$$$ , what's the TBO, what's the warranty ,,,,I'd have thought these would be relevant questions , they are for me anyway , Oscar are you part of the company, will they be doing some promo at Natfly ,I'd love to have a talk to someone about themMatty

In 2010 at Natfly I sat in on the Jab engine talk and heard good mentions about a mod in the west on the 2200 4 cylinder engine by installing phosper bronze valve guides and setting the solid lifter engine clearance at plus 2 thou on the specified setting; with the engines getting good hours. The valve guides quote was $300 back then for both. Perhaps the Camit engine is incorporating this sort of change to the Jab engine. I thought if I was to get a Jab engined aircraft I would consider the about information. Cheers Mike

 

 

  • Like 1

Share this post


Link to post
Share on other sites

Jeez I dunno , I had a partial engine in a jabiru back in 1998 I guess I was one of the original "test pilots " of the jabiru new engines . Anyway it seems to me that they have been having problems since then to now. Anyway getting back to David's post ( or how ever he spells his name). Mate I couldn't give a flying fark whether it is CAMit or CAMIT. All they have done is make boat anchors for the last 20 years. You guys can go on about " visit the factory. , you will be impressed" etc . That's well and good but it doesn't explain engines failing with under 100 hours on them TT. Just sayin

 

 

  • Agree 2

Share this post


Link to post
Share on other sites

Having read through most of this forum I wonder what is wrong with the existing Jab engine. The way some people talk it seems that they must be failing daily.

 

I ran a 1600 Jab that I couldn't stop leaking oil and was a bit short of power on a hot day, so I upgraded to a 2200 Jab with solid lifters, Factory zero timed. the only problem I haver had with it was caused by a bad batch of fuel.

 

In my opinion it would be a better engine if they ditched the Bing carbie and used a TBI with mixture control and fitted with 4 CHT and 4 EGT gauges. That way you could see any upcoming problems.

 

Camit seem to be fitting new rocker gear, but one of the problems seems to be failing valves, not rockers. The increased instrumentation would reduce that problem.

 

Oscar. Are you running an engine overhaul business in bundy?

 

 

Share this post


Link to post
Share on other sites
Having read through most of this forum I wonder what is wrong with the existing Jab engine. The way some people talk it seems that they must be failing daily.I ran a 1600 Jab that I couldn't stop leaking oil and was a bit short of power on a hot day, so I upgraded to a 2200 Jab with solid lifters, Factory zero timed. the only problem I haver had with it was caused by a bad batch of fuel.

 

In my opinion it would be a better engine if they ditched the Bing carbie and used a TBI with mixture control and fitted with 4 CHT and 4 EGT gauges. That way you could see any upcoming problems.

 

Camit seem to be fitting new rocker gear, but one of the problems seems to be failing valves, not rockers. The increased instrumentation would reduce that problem.

 

Oscar. Are you running an engine overhaul business in bundy?

The failing valves and guides is associated with rocker gear due to the side angles valves are pushed.

 

 

  • Agree 1

Share this post


Link to post
Share on other sites

Yes, once the guides develop play there is a fair chance the valve head is going to detach. At least the seating of it will be compromised and that is the beginning of a problem. Never run a motor in an aircraft with compression down on any cylinder without investigating why and rectifying it. Nev

 

 

Share this post


Link to post
Share on other sites
The failing valves and guides is associated with rocker gear due to the side angles valves are pushed.

So, use some Aussie ingenuity and fix it....the solution has been out there for years in the form of roller rockers. Plus major components on that engine are CNC machined. you know how easy it is to adjust the operating program on a CNC mill ?.........just do it................Maj.....014_spot_on.gif.1f3bdf64e5eb969e67a583c9d350cd1f.gif

 

 

  • Like 1
  • Agree 1
  • Haha 1
  • Informative 1

Share this post


Link to post
Share on other sites

"If he had known they would have done things differently...."

 

I bet if Mr Stiff could have his time over he would have blown up 5-20 engines on a stand in the process , sorted out all the problems, redesigned and re-engineered and only then get it certified.

 

Unfortunately like all rapidly growing businesses he would have been cash flow poor (ie less R&D / more production) and he would have probably got that engine certified way quicker then he should have in hindsight....

 

CAMit on the other hand have all the benefit of hindsight, having watched the Jab story (a very successful one irrespective of some mistake) played out.

 

On the big plus side Jabiru and the way he ahs done it , he could today never sell another aircraft and still be a very successful parts supplier. And im not Jab bashing i mean that in a positive way.

 

I see the biggest problem with all these small engine producers is they wait years having customers put hours on engines , instead of months doing it properly on stands and seeing what fails with all the data available.

 

CaMiT have all the benefits of seeing the Jab mistakes and testing to use, so hopefully they are off to a flying start compared to those re-engineering from the ground up.

 

 

  • Agree 6

Share this post


Link to post
Share on other sites

What do you want me to do, drive to Bundy, break in, change the settings and run before the cops come, I don't have any connection with Jabiru or Camit, nor have I ever seen a CNC machine except in pictures, maybe you might have contacts at Casa and could force Jabiru to make the changes to their engines to be more reliable that Camit are doing. Old lycoming took a long time to go with roller rockers for some of their engines e.g o-320 H2AD modification. As much as I realize Jabiru have problems there are others with problems too and you take a chance with any engine and the new UL and D motors may or may not be any better. I do believe the 3300 Jab motor with mods could be a good engine, I have one without mods that I fly and believe that if it is not overheated that I may have a trouble free run with it, fingers crossed. It's 24 rego so if I modify it goes experimental, not an option at the moment but could be safer !

 

 

  • Like 1

Share this post


Link to post
Share on other sites
Having read through most of this forum I wonder what is wrong with the existing Jab engine. The way some people talk it seems that they must be failing daily.I ran a 1600 Jab that I couldn't stop leaking oil and was a bit short of power on a hot day, so I upgraded to a 2200 Jab with solid lifters, Factory zero timed. the only problem I haver had with it was caused by a bad batch of fuel.

 

In my opinion it would be a better engine if they ditched the Bing carbie and used a TBI with mixture control and fitted with 4 CHT and 4 EGT gauges. That way you could see any upcoming problems.

 

Camit seem to be fitting new rocker gear, but one of the problems seems to be failing valves, not rockers. The increased instrumentation would reduce that problem.

 

Oscar. Are you running an engine overhaul business in bundy?

 

Would be a bit difficult - I live south of Sydney.... and nope, I'm not running ANY sort of engine repair shop! Used to build (amateur, for my own car) a few racing engines way back in the day, but working on a Jab. has tricks and quirks that you'd get the flavour of from the Jab. engine manual but to be honest, having seen the real guys doing it (and realising just how much special tooling you really DO need to get things schmick-duck), I'd not attempt it for anybody else to fly behind. For a little while, 'between projects' as they say, I used to repair-weld alloy cylinder heads for an engine rebuilder shop in Canberra years ago and they'd allow me to use their gear to build my own engines (the owner was a fellow racing mate), but when you see the sort of tooling and equipment CAMit has, you quickly realise that your old 'hand-build' skills aren't any match for laser-measuring etc. in a controlled environment.

 

However: the upside of having 'built' our own engine is that we know what's in there. If anything changes - e.g. a nut or bolt goes soft on torque - we think we'll have have a pretty damn good idea of what might be going on and what to address - and how seriously to take notice of that change. Since ours is a thick-finned head engine, it's going to be a fairly rigorous test for some of the mods. / 'fixes' that CAMit have introduced. We'll absolutely be running 4 CHTs and 4 EGTs - and our heads are so old ( in years, not hours - think of them as NOS that's been sitting around for many years) CAMit had to build us a new jig to add the CHT probe pick-up points between the plugs! There is a reason we didn't move to new heads, but that's a future story.

 

 

Share this post


Link to post
Share on other sites

Re engineering it from the ground up would be like changing cylinder centres and all kinds of things. Most mods are incremental with detail rather than LARGE redesign.. At any time a builder could asses the engine and find if it is capable of further development, or already over the limit. Sometimes a "new" model has It's own peculiar faults in a component that never gave problems in it's previous situation.

 

Testing doesn't cover all situations a motor may be subjected to. There are a lot of variables. Stale fuel, poor cooling. Mixture /timing wrong, incorrect prop. Head tensioning is often not done properly. It's quite possible CASA's testing regime is better suited to much earlier engines operating every day on avgas. Using mogas in an aircooled aero engine is a risk as it's not quality assured for the purpose . Nev

 

 

Share this post


Link to post
Share on other sites

Well it's not the whistle that pulls the train, so it's going to be interesting to watch actual production engines in operation.

 

 

  • Agree 1

Share this post


Link to post
Share on other sites

IF you can identify some particular part then It is relatively simple to just fix a few things and make a big difference. I'm not sure that is the situation with these motors. I have MY views on a few mods but I keep them to myself. I believe the engines can be operated to a level of reliability equal to the current level of things like Gypsy Majors etc. I have never been too terrified of a Jabiru going silent, when I'm flying in it, but there might be some that I might want to check up on how they are treated ( flown/serviced). I will be in Bundy in about 8 months and will have a look at Camit, as I am very interested in what is happening. Nev

 

 

  • Agree 2

Share this post


Link to post
Share on other sites
Having read through most of this forum I wonder what is wrong with the existing Jab engine. The way some people talk it seems that they must be failing daily.I ran a 1600 Jab that I couldn't stop leaking oil and was a bit short of power on a hot day, so I upgraded to a 2200 Jab with solid lifters, Factory zero timed. the only problem I haver had with it was caused by a bad batch of fuel.

 

In my opinion it would be a better engine if they ditched the Bing carbie and used a TBI with mixture control and fitted with 4 CHT and 4 EGT gauges. That way you could see any upcoming problems.

 

Camit seem to be fitting new rocker gear, but one of the problems seems to be failing valves, not rockers. The increased instrumentation would reduce that problem.

 

Oscar. Are you running an engine overhaul business in bundy?

I think the rocker mod reduces side loads on the valve stem thereby doing something about valve failure. Laurie

 

BTW, is it a full moon?:rotary:

 

 

  • Agree 1
  • Haha 1

Share this post


Link to post
Share on other sites

By way of some background, there's an old article by Phil Ainsworth that's really worth reading: http://www.aeromech.usyd.edu.au/AERO1400/Jabiru_Construction/jabiru.html

 

You need also to remember that FEA packages - at least on a scale of cost available to operations such as Jabiru - were not (as far as I know, anyway) readily available when Rod and Phil headed down the somewhat brave path of deciding to build their own engine. Yes, large organisations had been using it for years, but it required access to large computing resources (mainframes) and basically personnel dedicated to undertaking the data entry required to actually develop a useful model of the element itself. I do not know whether Rod Stiff had used FEA in developing the original Jab. engine so I am merely conjecturing when I suggest that, by and large, I think he was using his conventional engineering skills in making the decisions about components. Others may be able to fill in the blanks here.

 

Jabiru certainly tested their engines as best they could at the time; I remember visiting the factory in the early 90's and seeing the wee Diahatsu (I think)-mounted engine test rig that Alan Kerr would take down the end of Bundy airstrip, with his sandwiches and coffee, and run the things for hours on end. (there's a piccy of it in the 'Jabiru history' article in a recent Sport Pilot). It took me 10 minutes to stop laughing when I first saw it.. I also saw CAMit's engine production line, with an assembly-line of engines that would have looked entirely possible as Honda's motorcycle engine line - and those are jewels assembled by comparison with your average Lycoming/Continental/ and car engine. The only engine I have personally ever worked on (other than motorcycle engines) that even comes close in terms of plain beautiful engineering excellence is a Gardner diesel.

 

It's all-too-easy to toss-off derogatory statements about Jabiru engines, we see it on every thread here about Jab. engines. I don't recognise any of those who do as having achieved a comparable contribution to the development of ultralight activity in this country as Jabiru.

 

Let's look at a few companies who have ultimately failed/ceased operation in the production of small piston engines for aircraft. Rolls-Royce, with Continentals built under licence. Franklin. Porsche. Diamond. KFM. Where are the Gypsies of yesteryear? Seriously major companies who have never entertained the idea of using their engine-building expertise for the production of small, piston-engined aero engines: BMW, Mercedes, Volkswagen, GMH. Ford, Chrysler, Honda, Yamaha, Kawasaki. FIAT used to build aero-engines - but never for the ultralight market. There are only two manufacturers who have a serious presence in the market for ultralight engines: Rotax and Jabiru. Rotax is of course owned by Bombadier. Bombadier had an annual income for 2012 of 19 BILLION (Canadian) dollars. That's AUD$20 BILLION. One could, I think reasonably, suggest that Jabiru is punching somewhat above its weight in that company.

 

With that sort of corporate backing, you'd expect that Rotax would have unbreakable QA systems. Remind me of how many engines affected by recalls for a faulty crankshaft Rotax had on the 912 recently?

 

CAMit are, as they say, addressing issues with the Jabiru engines. If they succeed (and I personally believe they will), then that opens a way forward for what are now Jabiru-engined aircraft to expect a better factor of reliability in what twists the prop. The proof of that pudding is progressing at a decent rate. If you are a current Jabiru engine owner, you have but to wait for the results of operational experience to come in. Of course, if you are a rabid and fundamentally ignorant Jabiru knocker, nothing will stop you ranting on and this site has an adequate supply of those.

 

One side of the argument is going to be proven right. I know where my money has been put.

 

 

  • Like 2
  • Agree 1
  • Winner 4

Share this post


Link to post
Share on other sites
I think the rocker mod reduces side loads on the valve stem thereby doing something about valve failure. LaurieBTW, is it a full moon?:rotary:

Yes it does - and yes it is. Surely you could tell by the dogs howling in the night?

 

 

  • Haha 1

Share this post


Link to post
Share on other sites

The rocker ends move through an arc of a circle and the valves operate straight up and down. There is an ideal geometry but that does nor avoid all the load, it just minimises it, but it should be correct. Roller equipped rocker ends are sometimes used, but not universal. All engine fits have wear limits as well as minimum running clearances, You can check the wear in situ but it's not simple for the average person who hasn't been shown.

 

Things can't really wear out suddenly unless there is foreign matter ie abrasive (Dust etc) , a failure of the oil film or incorrect fit, finish and/or incompatible materials used together. This can cause "galling" where a very rough finish forms and wear is rapid. Local heating due to distortion or overloading can destroy the surfaces, but these are not "normal" wear. Nev

 

 

  • Agree 1
  • Informative 1

Share this post


Link to post
Share on other sites
The rocker ends move through an arc of a circle and the valves operate straight up and down. There is an ideal geometry but that does nor avoid all the load, it just minimises it, but it should be correct. Roller equipped rocker ends are sometimes used, but not universal. All engine fits have wear limits as well as minimum running clearances, You can check the wear in situ but it's not simple for the average person who hasn't been shown.Things can't really wear out suddenly unless there is foreign matter ie abrasive (Dust etc) , a failure of the oil film or incorrect fit, finish and/or incompatible materials used together. This can cause "galling" where a very rough finish forms and wear is rapid. Local heating due to distortion or overloading can destroy the surfaces, but these are not "normal" wear. Nev

Are you referring to the contact face where the rocker bears on the valve stem, being finished to the same radius as the radius of the contact point from the rocker-arm pivot? If this geometry is correct, the rocker arm "rolls" on the valve stem, without sliding and thus dragging the valve sideways, even if the arm does not have a physical roller. I suspect some of the the proponents of roller-rockers may not appreciate this point; in fact a physical roller there adds an additional variability to the valve clearance, in that the roller can wear out-of-round. Also, to have a comparable bearing surface radius to a correctly-faced rocker arm, the roller would need to have the same radius as the arm itself - which is of course completely impractical.

 

Secondly, a small amount of sliding friction is not necessarily a bad thing, because it is the main means of inducing the valve to rotate in the guide, which is a major means of maintaining the seating surfaces in good condition. There are a number of subtleties in the design of rockers which are simply not addressed by switching to rollor-rockers.

 

Exhaust-valve guide wear appears to be one ot the first indicators that the engine has been operating beyond its cooling limitations; one sees it in turbocharged Lycomings & Continentals; the point at which this occurs seems to be quite sharply defined. If the guide temperature gets too hot, guide wear is rapid & catastrophic. I doubt it really has all that much to do with the side loads from the rockers.

 

 

  • Agree 1
  • Informative 2

Share this post


Link to post
Share on other sites

Well they usually wear oval Dafydd. Rotating valves are a good idea but are often done by inserting a special washer between the spring and the head . (Not the heat insulating ones) Over the years the major companies have tried to get valve and seat life somewhere near the rest of the engines capability and Continental had some compatibility issues with valve and guide metal getting mixed up with some installers. I accept that a "TOP" is needed before the rest of the engine in most cases and that getting valves to do the distance is not likely. You even get stem erosion in some of them. Not wear but under the head. They have a hard life. Nev

 

 

Share this post


Link to post
Share on other sites

Just by way of a little perspective on what is realistic in real life for a small aero-engine manufacturing company with reference to the Jab. engine development story, here's a shot from the official UL Power site of their engine test rig (or you can see if in action in the video on their site!)

 

http://www.ulpower.com/news/blog/wp-content/uploads/2013/01/Picture-1.jpg

 

I am in no way having a shot at UL Power here - I chose them by way of illustration because they are producing engines of highly-comparable specification to Jabiru, are in a relatively ab-initio phase as manufacturers, are using very comparable manufacturing techniques - and they have provided easily-accessible informative material. Indeed, it's worth reading this whole page on their testing regime: http://www.ulpower.com/news/blog/a-look-behind-the-scenes-of-ulpower-testing-the-ul520i

 

All in all, what Jabiru did by way of testing in their initial development phase is pretty comparable. Nowadays, every engine that leaves CAMit is test-run for 20 minutes on their in-house sophisticated dyno - they aren't just built and crated off the assembly-room floor. That's nothing to get too excited about, I'd imagine it's pretty much industry-standard practice; one would get 'excited' if it weren't the case, I suspect. I imagine that as their manufactured base gets larger, UL Power will move from using that trailer to a dyno as well!.

 

The point I am trying to make here, is that it's a pretty damn hard financial road for a small company to get a product as demanding as an aero-engine off the drawing board (or the CAD-machines, now) and out the door of the factory ready to be bolted up and flown.

 

 

  • Informative 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later for your post to be seen If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...