RA Aus Maintainers Authority

[rankamateur]

Andys@coffs' date=' post: 401769, member: 94[/email']]... and that I didn't miss a dozen vital clues along the way that all wasn't well......Andy

And even destroy that evidence as you go along so it isn't there to show to the trained eyes when you finally concede defeat.

 

 

[fly_tornado]

How awesome is owning a Jabiru some days?

 

That is all

 

 

[DrZoos]

. For example I was told that the crosshatching on the new cylinders wasn't as per J's spec, even though they came from J. I would just have assumed they were Ok. The expert sent them out to an overhaul company to do again with the right hones because J wouldn't accept that they were done wrong.....another set at Narromine for another overhauler were also identified independently as wrong. if they were just fitted as supplied (crosshatching way too fine) then I was told oil consumption after reasonably small time would shoot up (actual out, all over the lower surface of the plane) and another overhaul would be called for....which is Ok, after all it was cheap! NOT!!!!Andy

That would be a reportable defect would it not ?? I found a defective bracket on my elevator bell crank during our 25 hourly and my L2 reported it. He said he didnt have a choice. So wouldnt yours be a reportable defect?? Its not good if they are coming out of the factory like this. There is plenty of punters that would slap that together and then suffer the consequences down the track.

 

 

[facthunter]

Not a reportable defect. Once the engine has been in service a short while the fine crosshatching tends to polish to a shiny finish that doesn't hold an oil film well. It happens with ALL steel cylinders. Quicker when the finish is shall we say "too good" and the cylinder is not nitrided. More permanent when the pattern is a bit coarser and the cylinder is hardened. The oil control rings may be a bit too effective, but we are getting into opinions rather than black or white matters of which there are very few. Nev

 

 

[DrZoos]

Nev i work on Rotax Kart engines and Yamaha Kart engines all the time. We cross hatch for a very important reason and I would be very very unimpressed if my cylinders / sleeves had no proper cross hatching. We run these things at very high rpm (two stroke ) but four stroke its still very important, and although most rebuild after these two bangers after 10 to 15 hours. We get 25+ hours and all thanks to our cylinder prep work. We have no tradeoff in power but we get way longer out of our engines due to good cylinder work. Others ive seen lots of blow by after 10 hours. I pulled apart my sons a few weeks ago its got 30 hours and looks like the day we rebuilt it. I could still see all the cross hatching. And thats doen some serious work quantity at 30 hours doing 12,000+ rpm. We measured everything and it was exact measurements that we built it. Even the ring gap was spot on perfect.... So i would be very un impressed, as I guess as Andy is if it where mine.

 

I thought anything out of the factory faulty was reportable. Thats why mine got reported, and i guess we will see an AD soon. Its indicative of procedures not being adhered to.

 

 

[Oscar]

Not a reportable defect. Once the engine has been in service a short while the fine crosshatching tends to polish to a shiny finish that doesn't hold an oil film well. It happens with ALL steel cylinders. Quicker when the finish is shall we say "too good" and the cylinder is not nitrided. More permanent when the pattern is a bit coarser and the cylinder is hardened. The oil control rings may be a bit too effective, but we are getting into opinions rather than black or white matters of which there are very few. Nev

Actually, a bit more complex than that: the optimum is a combination of depth, angle and separation of cross-hatching to provide both oil retention in the grooves plus sealing on the 'lands' of the cross-hatching. It's not a 'one size fits all' equation: the analysis machine that can measure and calculate the optimum is a very expensive bit of kit indeed. It takes into account the ring size and configuration, the service revs, the cooling efficiency of the barrels. What works for a four-stroke air-cooled engine at 3000 rpm is just not the same as what works for a two-stroke, water cooled engine at 10,000 rpm . It IS fairly black-and-white, if one has access to the gear and the expertise - but there are only a few engine-builders in this country who have that combination. As far as I am aware, only one engine manufacturer in Australia is utilising this expertise in the development of a better engine, but once testing is completed I believe we will see some very, very encouraging results.