dmech

Having shown the close-up photos of the broken through-bolt in-situ to several learned and experienced people associated with steel-making and structural engineering (in plentiful supply in my location), the verdict is a unanimous one - FATIGUE.The question is why did a pair of through-bolts let go at 675 hours when they are supposed to do 1000 hours before being worked on as part of the top-end overhaul? If we had been experimenting with this engine and making adjustments to it then I could perhaps understand. But this engine was maintained by the book and "a good runner" in every respect with never a hint of trouble, no high temps or low pressures at all. In short, this engine ran perfectly until a sudden and inexplicable failure.

 

Trying to torque-check these bolts, especially on the underside of the engine, is not easy. No special tool seems to exist (such as the cylinder base-nut wrenches for Lycomings and Continentals), and it appears we are left to take it on faith they will not loosen in 1000 hours. In the absence of any signs of crankcase fretting, one has to assume they were tight until the moment of failure. Either that or there is an issue with metallurgy, design, assembly or all three.

 

So I am at the head-scratching phase of the investigation. Meanwhile I have an AOG, an engine somewhere between here and Bundaberg (and hopefully not under three feet of mud) and no seeming solution in sight except the expense of another engine.

 

I had expected better.

dieselten can you tell me which bolts failed top bottom and on which side

thank's A.D.

 

 

Offset is actually 0.5 mm. ........... Bob

How do you arrive at that figure bob , holden manual quotes 1.00mm , are they wrong!!

 

 

I'll rephrase the question. Looking at the bottom of the piston, is the gudgeon pin offset towards the lump or away from the lump? It can only be one or the other, surely.

Ornis Offset is neither towards or away from lump lump is on pin axis looking at bottom of piston with lump towards you the offset will be to the right of pin axis, and is obvious by just looking at open end /bottom of piston

 

 

Dmech,are the old type pistons the same (offset) etc? I'm about to put new rings in (@500 hrs) which is an opportunity to consider this (depending on what else needs to happen)

also is there any effect in your model with regards to the flycut pistons - is the weight imbalance (and one bank of pistons has that imbalance on the opposite side) of any significance?

 

Ralph

NOT SURE ,if fly cuts are the same size,then you would have to swap from one side to the other to change piston orientation , will look at this but sure that can be done

 

 

Question. Is the lump under the piston on the side of the offset? YES/NOhttp://www.jabiru.net.au/images/AVDALSR088-1_Piston_Offset.pdf

holding the piston upright and arrow or lump away from you,or forward , , the pin will be offset to your right , that side also happens to be the major thrust side when fitted to the holden. Please note : jabiru 's engineering paper's quote offset of only .05mm [ .020"] . Offset that I have measured is 1.00mm [ .040"] this is also confirmed by the holden vn engine manual. Pistons with valve relief 's is still the same holden piston .

A.D.

 

 

Dmech,are the old type pistons the same (offset) etc? I'm about to put new rings in (@500 hrs) which is an opportunity to consider this (depending on what else needs to happen)

also is there any effect in your model with regards to the flycut pistons - is the weight imbalance (and one bank of pistons has that imbalance on the opposite side) of any significance?

 

Ralph

will talk to night or tomorrow, off to fly behind one of those modified motors today. would like to upload holden engine manual but must be to large for this site if you have an email I can email to you / would prefer every one could see it though ,if you know of a way to get it onto this thread/ forum, please let me know how.

A.D.

 

 

So would fitting them the wrong way round leave us with slightly retarded ignition timing?

YES Factory fitted wrong way, offset IS relevant to rotation ,has nothing to do with prop thrust, or flywheel , thrust , because this engine rotates opposite to the holden engine that these pistons were originally designed for and since adapted by jabiru for their engine, the arrow should go towards the flywheel . This will definitely improve smoothness of engine and performance . The conrods are way to short also 1.53:1 c.r.s.r, I have made longer rods and barrels for my engine ,but have not had it running as yet. offset was originally introduced in the auto industry to correct angularity problems due to shorter c/rods as the demand for more compact engines were required by the auto industry. Piston slap is certainly caused by fitting these pistons with offset to minor thrust side , and this would have to be happening in the jab engine ,absolutely! Offset has often been thought to control slap, but its main roll to correct angularity of c/rod at max cylinder pressure ie. 15- 17 deg atc. There is a number of modern engines that don't have any offset on pins and these do not suffer from piston slap , 2 examples are Subaru ea81 /ea 82. I have both of these engines ea 81 176k and a ea 82 282k and these engines don't have any piston slap noise. some engines ,Honda for example have actually offset the cylinder centre line to the c/shaft centre line by as much as 14mm t achieve simular results .

I made up a model 20 months ago which clearly demonstrates the effects on the engine with pistons fitted wrong way around, since then a number of engines have been changed with good results . and no detrimental effects at all!.

 

The piston used in jab engine has 1.00 mm [.040] pin offset . jab claim .05mm [.020"] offset [see pin offset link ] on jab site. see attachments below. Changing pistons creates a more favourable angle of rod between piston and crank centre line for the smoother transmission of load. With piston wrong way ,it imparts a more jerky motion into crank ,which then is absorbed by the engines rotating mass which results in abnormal loads on flywheel/ prop hub/ prop/and their fasteners, it also imparts an opposite and equal force to the engine block and accessories ,which to some extent is restrained by engine mounts[ vibration felt in air frame]. A recent survey indicating top thru bolts on oil filter side and lower bolts on opposite side failing , tend to indicate that this opposite force may contributing to the bolt failure

 

Piston pin orientation does not change max piston velocity but does change the position that max velocity occurs . Changing pistons around will retard ign tming as it will bring tdc earlier . however as the piston dwells longer as it travels thru tdc this would have a correcting factor, and does not appear to have effected the engines that have been changed , as they seem to have a small increase in power, and run cooler , side benefit of changing pistons is better oil control [ less oil in catch can].Changing pistons according to my model indicates a small effective change in valve timing [ retarding ] , however this engine has long manifold runners and probably results in less flow thru of a/fuel mix into the exhaust during valve overlap resulting in lower egt. Another indication from model is that more of the power stroke is used before ex valve opens ,should result in less stress on ex vale and contribute to lower egt These engines have a history of valve problems , mainly when using avgas , im sure I have a simple fix for this , I mentioned this to Ian Bent some weeks ago & he indicated he would try it out , so wont mention that tonight.

 

Another problem I cant under stand ,is why jab have fitted the oil pressure switch between the pump and filter instead of the main oil gallery this would give error readings especially when cold , also fittings for oil cooler at filter are to small.

 

Also using a sealer over the complete crank case halve is an invitation for disaster, as is the use of Loctite on certain other parts

 

could not load holden manual or jab pin offset link . Could be checked at your holden dealer manual for vn commodore v6

 

A.D.

 

 

Only ever snapped one on the j160, it was number 2 cyl upper fwd and upper rear bolts that snapped. Of note this engine had the shims under the base of the barrels with goop on both sides, not a great setup.

Thank's deadstick , would like to hear from other jab owners ,re bolts. Had a few replies so far involving 11 bolts , seems to be a pattern emerging , all bolts on filter side are upper bolts and other side are lower bolts, I think I know whats doing this but more data would be helpful

Thank's

 

A.D.

 

 

True but Jab cannot have it both ways, they are producing ex amount of horse power with a aircooled engine that has a smaller cubic compacity than a equivalent Lycoming or Continental. Hence IMO with tighter engine tolerances, they are suffering from over heating in the training environment when climbing out during circuit training.

Hi dazza, Jab runs higher rev's

 

 

Ladies and gents, I would like to share my experience thus far with this product and the factory that makes them.I own 2 Jabirus, a 230-D and a 160-C both aircraft have been an absolute nightmare when it comes to reliability.

The J230 suffered its first engine failure at 225 hours requiring a complete Top end, subsequently it suffered multiple component failures up until its final demise at 700 hrs with Jabiru admitting it was the failed thru bolt design that destroyed the bottom end and not once did they offer any support even after requests.

 

The J160 suffered an in flight engine failure under 200 hours since the factory performed a top end overhaul( thru bolt failure)! since I have owned it three heads have failed due cracking and valve seat movement multiple other component failures and the nail in the coffin for this engine was a valve seat falling out at idle on the first pre-flight run up of the day all within 300 hrs of the Top end overhaul.

 

The factory have not once offered to help, never shown the slightest empathy or a desire to support a customer, and display a complete disregard for factual evidence when providing an excuse why a component failed.

 

I have been bullied, ignored and treated like a fool.

 

Not one Jabiru engine in my local area has made the 1000 hr TBO and not one owner would purchase another Jabiru.

 

The business manager has treated me with arrogance of the highest order and display's what I can only describe as an extremely deceptive nature.

 

The business manager flat out refuses to return my property, and will not listen to any reason or evidentiary facts stating that they must return it.

 

One investigation conducted by the company as to why a cylinder dropped a valve seat and had cracking, had three different conclusions over multiple days.

 

I regret the day that I purchased both of these aircraft, they have cost me a small fortune to keep running and I warn others to do their home work thoroughly before spending your money with them.

Hi deadstick would be interested to know your experience's with thru bolt issues , in particular , which side and whether top or bottom on each side ie oil filter side or dipstick side

A.D.

 

 

Hi dmech, being in the engine re-manufacturing business myself, I am really interested in what steps your have taken to eliminate the resonance problems. I absolutely agree that the bigger bolts will still break in the long term or in the short term shift the problem elsewhere. The flywheel bolt failures are the first red flag for me and I really question the logic in changing from all wood to a composite propeller.JimG

HI JIM, I would like to advise our steps to eliminate problems , however there would be jab owners wanting to modify their engines , since this would require dismantling of engine, it might lead incorrect assembly and resultant problems that could be blamed on the modification it self , as we have seen . L2'S might not want to do the job as they are supposed to adhere to the manufacturer build instructions, this may put there privilege's at risk, could end up in a legal system , then expert witness's ,probably from j... and we know what they would say, and all in front of a judge who wouldn't know where a tow ball goes!! . I contacted rs jan 2013 and was told that there was no problems with their engines , before I could explain any thing he bought my call to an end. A letter was sent to casa regarding the fix march 2013 , not by me but by owner of first engine modified . I believe CASA contacted jab end of 2013 but nothing productive resulted . I believe the present action is a shot across the jab bow, next shot might be direct hit [ really hope it doesn't come to that]. I have sent a letter to CASA detailing the fix , and a fix for valve problems. that was last week. I'm about to send another letter to CASA with supporting engineering data , today or tomorrow.So with the above in mind and the fact casa has my info , I think it's probably best to wait and see how casa deal with it . after that if nothing eventuates, I can make our findings available. However, any mods you do are at your own risk, however I know you wont be disappointed.

The engines mod. here so far, are going fine.

 

A.D. [email protected]

 

 

This has my interest; I fitted a big, heavy spinner to the front of my Jab2.2 partly because I felt the increased flywheel effect would reduced stress on the crank. More knowledgeable people have since told me this might make thing worse. I'm just a bit out of my depth here and would appreciate some expert opinion.

yes it will make problem more pronounced , increased flywheel effect ,ie your spinner will put prop hub bolts under increased stress as it is trying to smooth out irregular motion that is created within the motor, will also impact more on thru bolts, a harmonic damper of any kind mounted on crank won't help either , prop should be as light as possible, at least until problem is sorted

A.D.

 

 

Accellerometer used for prop balancing should pick a tv spike upI have one and it can be set up to read results alll the time.

We use he same thing to measure wear rates in large electric motor bearings

yes 2 accelerometers and interface to dual trace cro , mine is a TECKTRONIX 488 DIDGITAL STORAGE, , however one from jaycar or alltronics / labscope or sim d trace, however I already know where these torsional movements and spacing's. are happening within the engine cycle and I think they are responsible for almost all of the problems associated with this engine incl.[ exept valves], fly wheel prop hub fasteners , comp. props ,c/case fretting , although we have seen some of this after mods were done but engine did have 80 hrs on it before mod , so time will tell on that one [ except valve 's] but they are also easily fixed , as are the vibration probs which we have already sorted, just need more data re thru bolts so that I can positively associate these failures to the above vibration issues, with info so far, it looks very much like it is . WITH all the bolt problems reported, there must be a lot more data out there . I need to know side and if upper or lower bolt incl studs, to get a definite pattern indication .

[email protected]

 

 

Vibration at insidious levels. Plenty of cylinders with double the pumping and combustion pressures and making ridiculous high BMEP levels relative to a Jab that are held on with less.It's a 550cc cylinder with 8:1 compression making a measly 20 hp for goodness sakes, it ain't cylinder pressures knocking them off.

but then second thought's it is actually abnormal cyl pressure that's causing ,as we have found and mostly eliminated in more than a dozen jabs, no broken bolts in 2 yrs so far 800hrs on one engine fts 160

 

 

Vibration at insidious levels. Plenty of cylinders with double the pumping and combustion pressures and making ridiculous high BMEP levels relative to a Jab that are held on with less.It's a 550cc cylinder with 8:1 compression making a measly 20 hp for goodness sakes, it ain't cylinder pressures knocking them off.

hear hear dead right there bex

 

 

I don't think what side is of any consequence they are through bolts after all. It was oil filter side, broke off at base of nut. Tom

Thanks Planesmaker we just need to see if there is any pattern to these bolt failures . we have found the resonance problem and eliminated about 90% of it in several jab engines , since then [18] months ago we have had no trouble 1 eng 800 hrs at least 2 others around 700 hrs all still operating, engines run smoother /50 deg cooler climb small increase in power, 200 hrs was about all you could expect out of these engines before a major repair, used in F.T.S . 2200 hydr lifter . the way the bolt has broken certainly indicates[ cyclic loading ] , even if they increased size to 5/8 would probably still fail. the base cause needs to be addressed, rather than just beefing up bolts , seems to be an Australian manufacturers trend, if it breaks , just make it bigger.

Your bolt failure position and the other one I have ,ARE ALLREADY indicating a pattern that I suspect would be associated with this resonance . bit like the violin and glass trick. I'v been engine remanufacturing since 1976 full time , I have seen large diesels have ends break off cranks 4"diameter all because of resonance.

 

So again , thank's for your reply. ALL other bolt failure position indications would help ANYONE !. Could be a goose chase , but who knows , has to start some where.

 

A.D.

 

 

Bex,No, I have just replaced thru bolts on 2200 that had broken a top bolt. Flying school using avgas and maintained to the letter. Done about 400 hrs from factory bulk strip / repair where ,if I recall correctly , new thru bolts were fitted. Tom

Hi Planesmaker the top bolt u mention which side was that on oil filter side /dipstick side would appreciate your reply on this

A.D.

 

 

Can anybody inform me which thru bolts are the most common to break ie. upper or lower and on which side of the engine , any bolt size. Just doing some research on this.

 

thanks

 

A.D.

 

 

Fuel, interesting and always comes up as a possible cause.Our first through bolt popped on an engine that had spent 100% of its life on AVGAS.

I accept that someone may be very unlucky and get a carby full of dodgy fuel. Maybe, once in a blue moon. I know it doesnt have the same regulation of AVGAS, but the higher quality fuels should be ok, after all, people put it in cars worth much much more than our little jabirus's. Imagine the uproar if a bad batch caused the destruction of a few mercedes and a couple of porshe's.

 

The engines we have run on high octane mogas look so much better when stripped, no lead deposits, nice charcoal colour instead of grey. What is the mod required to Lyc engines to allow them to run on Mogas? I know it aint bigger through bolts and liquid cooling:)

yep its the fuel ! if the engine didn't have fuel it would nt snap bolts

 

 

whats happened with this thread, look's like an engine failure . thrue bolts snapted, prop come off, what!.I'V had a lot of response via email several l2's and owners , even a law firm from usa.

 

 

yen . that grey stuff on the pistons is lead!. av gas here is loaded with it. this will also play havoc with your valve guides then valves. most jab owners i know don't use it, use 98ron and a little flash lube to protect valve seats in cars we use about 500 ml for 5000 kms . to much will cause soot build up under rings and may cause them to jam in grooves dmech

 

 

We could do what GA does even for homebuilt Experimental aircraft. That is maintenence in accordance with CASA Schedule 5.Schedule 5 is well known to LAME's and easy enough to comply with. Look at the Maintenance Guide for Engineers, by cASA and it will be explained.

As far as checking the oil in Jab engines, their method only works in Jab airframes. If I fill my taildragger to the full mark, a large proportion of the oil will end up under the belly.

Hi ANDY

 

CAN YOU FILL ME IN A BIT ABOUT THE CLASS ACTION TOU MENTIONED PLUS ANY LINKS PLEASE. I am interested because i have located a significant fault that jab have unwhittingly applied to there engines due to lack of knowlege.this problem has been inherent for more than 10 yrs and should have been sorted by now. i'm supprised there hav'nt been more legal action against jab.

 

REGARD'S dmech [email protected]

 

 

BarryThe statement you reproduced from Jabiru is a risk reduction statement crafted by a lawyer, fundamentally it seeks to limit liability to Jabiru as you would expect.

 

That all said, it changes nothing that I wrote in my previous email. If you buy the engine and then use it to power a concrete mixer, then more power to you (quite literaly) You may well have issues on collecting a warranty claim, but lawyers from J arent going to parachute in and wrap you in legal tape whether you followed the installation guide or not.

 

Im not arguing that people should simply do their own thing, in general it would be foolish to do that, but not universally so. The J through bolt issue that is playing out at present is a perfect example where in consideration of the benifits that the non approved J alternate offers, to me far exceed the J approved alternate. My perhaps incorrect understanding is that the approved alternate is more about moving the spotlight away from a QA issue (which then raises Q's of negligence) and trying to focus it on a design issue that couldnt be forseen.... In any event the class action in the USA is likely to probe that area I would have though so I'll sit back and watch what occurs.

 

Andy.

 

P.S the Oil issue........Another example where slavishly following the instructions will probably do no harm...except to your wallet. In my J if I fill to the 1/2 way mark then I get, higher oil temps for the 10 min's or so that it takes the engine to chuck it overboard till it gets down to the slightly above min mark that I know the engine is happy to operate at. I guess some will say Im foolish for not filling to the 1/2 mark.....if thats the case then I guess I'll have to live with that knowing it will worry me for literally seconds.....

Rick, i have looked thru most comment,s re jab engine . Have there been any comment's posted by Jabiru?, i would be interested in what they have to say with the numerous failures that have plaqued this engine over so many years , and still not resolved.I have done a lot of research my self since i would like to see an ausie engine make the grade. I believe i have found the smoking gun, which i am 100% sure is responsible for 9o% of problems like thru bolts breaking, excessive brg. wear, flywheel bolts coming loose , heating problems, high fuel use. detonation problems , high ring loading causing prem. ring wear,problems relating to head seal leak's, head bolt problems, prop. hub problem's etc. ALL caused by one simple easy to fix low cost solution and this simple oversight would be embarrasing to jabiru factory. I can't elaborate any further at this stage because it would be to hard to ex plain why this is happening , in this post. allso i need to contact jab.first to see if they will listen to me , and i need to verify some other details.

 

I have been a engine reconditioner since 1976 and involved in speedway with many successful engine build's with 4 state titles and many other major win's

 

All the post's [ not including valve related problem's, that's another issue which i'm still looking at]don't go any where neer to the actual cause.

 

if you would like to contact me you could by email [email protected]