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CASA Consultation Draft

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CASA Consultation Draft

Postby Anonymous » Tue Feb 10, 2015 10:15 pm

Posted by: RogerLewis on 10:44:46 01/16/15 Fri

I am pleased to say that the CAMit Aero Enginee and products are not affected by CASA`s draft consultation.

CAMit engines are in the process of gaining LAA approval and will be an ideal alternative to the Jabiru range of engines.

Please contact me direct if further information is required.

Roger L£$*s
Anonymous
 

Re: CASA Consultation Draft

Postby Anonymous » Tue Feb 10, 2015 10:15 pm

Posted by: Bob P on 11:14:08 11/14/14 Fri

Looks like there is a particularly bright (Camit) rainbow at the end of years of (Jabiru) dark gloomy clouds.

I read that Camit are now making make new engines that have the Jabiru "reliability issues" designed out, and that they also have a range of retro-fittable design improvements for the Jabiru engine.

But do they supply the complete range of Jabiru compatible engine spares? (I was going to say just in case Jabiru were to cease trading - but given a choice of buying a genuine Jabiru spare part or a Camit made spare part I think I'd buy the Camit part anyway).

Bob
Anonymous
 

Re: CASA Consultation Draft

Postby Anonymous » Tue Feb 10, 2015 10:15 pm

Posted by: RogerLewis on 16:49:29 11/14/14 Fri

In theory,CAMit can supply any engine component for the Jabiru engine but in practice, only the later generation of Jabiru solid lifter engines are supported and of course full support for the CAMit 2200 and 3300 engines.

Kits are available to convert problematic hydraulic engines back to solid lifter configuration. Currently one aircraft has beeen cleared to fly with the CAMit conversion kit.
Anonymous
 

Re: CASA Consultation Draft

Postby Anonymous » Tue Feb 10, 2015 10:15 pm

Posted by: Gary on 19:01:36 11/14/14 Fri

Roger
Do you have a price list for replacement engine parts please
Gary
Anonymous
 

Re: CASA Consultation Draft

Postby Anonymous » Tue Feb 10, 2015 10:15 pm

Posted by: RogerLewis on 08:54:43 11/16/14 Sun

Please email your address and i will post a price list to you
Anonymous
 

I hesitate to ask but here goes....

Postby Anonymous » Tue Feb 10, 2015 10:15 pm

Posted by: Peter Knight on 18:15:04 11/16/14 Sun

There seems to be a view that solid lifters are better/safer than hydraulic lifters in Jabiru engines.

I have had two jab engines. The first, a 2200, had solid lifters. Not a problem but I did spend several hours in a cold hanger adjusting them until I was confident that they were set at the correct gap. I think I knew what I was doing but would still occasionally get the old tappity tap sound that indicated that one was not quite right. I can understand how inexperienced owners might not get this aspect of routine maintenance correct.
My current engine, a 3300, has hydraulic lifters and as far as I am concerned this is a significant improvement. No tappets to adjust. Engine is smooth and reliable. The lifters seem to work exactly as they are intended to work and successfully take up any play in the valve train. The system is certainly easier to maintain for the inexperienced owner that the solid lifters version.

As far as I am aware all modern car engines use hydraulic lifters. There are discussions on performance car web-sites about the respective merits of hydraulic versus solid lifters but the consensus appears to be that hydraulics win every time unless you are operating at high revs when the hydraulics are not able to follow the cam profile as well as they should and concerns about hydraulics starting to 'pump up' materialise. But the issue appears to be at revs above 6000. Twice the operating maxima that Jabiru engines work at. (Incidentally the performance car community seems to like roller cam followers with their hydraulic lifters which seems to be the latest Jabiru modification).
So what's going on? Is there a potential problem with the hydraulic lifter system that I am not aware of or is it simply that people feel more comfortable with the inherently simpler solid lifter as there is less to go wrong?
I am not intending to take sides (I am not an engineer) if this becomes an impassioned debate but I am genuinely curious as to why what seems a slightly out of date system (solid lifters) is preferred by some enthusiasts.
Peter
Anonymous
 

Re: I hesitate to ask but here goes....

Postby Anonymous » Tue Feb 10, 2015 10:15 pm

Posted by: Ralph on 00:21:37 11/17/14 Mon

Jabiru hydraulic lifters are not preferred by private owners because every modification made to the engine since then seems to have caused significant failures - throughbolts, valvegear etc. Its no coincidence the latest change has been to the pistons which now have clearance pockets milled into the tops.
A major advantage to you in checking valve clearances every 50 hrs is they should not require adjustment - often the cause might be overheated heads or loose seats 'moving about' and you wont get any warning from hydraulic lifters.
Rotax lifters design is reasonably reliable, so theres nothing wrong in principle, just in practice. All my Honda cars have been not hydraulic, BTW. And with 16 valve heads, it takes a while
Anonymous
 

Re: I hesitate to ask but here goes....

Postby Anonymous » Tue Feb 10, 2015 10:15 pm

Posted by: BobP on 18:21:40 11/19/14 Wed

If you read the UL engine website you will note that although a relatively new design and although they offer modern ignition and fuel injection systems they decided to use solid lifter technology. Equally I'm sure camit could have implemented a reliable hydraulic mechanism, but why go to a heavier and more expensive mechanism then is necessary.From memory the UL website describes their design philosophy with regard to tappets; something along the lines of "if the engine is designed properly and uses quality components the valves do not need regular adjusting" (I think they are just taking the p**s out of Jabiru's incompetence).

Sadly with Jabiru the hydraulic lifters were designed as a sticking plaster to mask a problem rather than tackle it at source. The real problem was distorting heads due to marginal cooling (OK works well on many aircraft but lots of engines do have problems). As the heads overheat they progressively warp and the tappet clearance moves. The problem may have been compounded by some valve train parts wearing prematurely on some engines due to incorrect hardening and problems with defective rocker bushes.

Nothing wrong with well designed hydraulic lifters - they are perhaps better in an otherwise totally reliable engine design, and the production costs for a high volume automotive engine manufacturer may be less because it eliminates the need to set up the valve clearances manually (a nightmare for an overhead cam 4 valve per head engine). But on the Jabiru you won't get early warning of distorting heads, worn rocker bushes, stretched valve stems, sinking valve seats, etc etc.

So better (in my view) to have tappets to give early warning of any problem.

Unfortunately rather than just masking an existing problem the hydraulic valve mod was badly "designed" (I even hesitate to use that word). There have been a series of subsequent revisions including: redesigned cam (hydraulic engines were well down on power); different spec lifters (didn't work as intended); design changes because early lifter engines were prone to filling their rocker covers with oil and the oil down the valve guides caussing other reliability issues; and premature cam wear because the edge of the lifter comes into contact with the cam.

Its pretty sad to think that all of the above could have been eliminated if only Jabiru had applied a bit of common sense how to duct air to keep the heads cool and where to mount the CHT sensors so it actually measured the head temperature.

Then there are all the other Jabiru "good ideas" that go on and on and on (through studs, flywheel mounting, carb jetting etc etc.
Anonymous
 

Understood

Postby Anonymous » Tue Feb 10, 2015 10:15 pm

Posted by: Peter Knight on 09:41:49 11/21/14 Fri

Thank you Bob and Ralph. That explains a lot.
I think my conclusion would be that given that the skill of owner/maintainers will always be variable a well designed hydraulic lifter is probably a better solution as it removes the risk of poor maintenance leading to incorrect clearances in the valve train and subsequent damage.
I completely accept that with the cooling problems that some Jabiru engines experience the automatic adjustment that is inherent in a hydraulic lifter can disguise a cooling problem/ head leak. Therefore solid lifters are valuable as an aid to early detection of problems for the more knowledgeable maintainer.

I suppose it remains to be seen whether or not the latest variation of the hydraulic lifters (Cam roller followers, extra run-off for oil etc ) qualifies as the final design.

I'll chance my luck with another question. One problem that I did experience with the early hydraulic lifters was significant wear in the rocker bearings at 300 hours. Some were badly scratched, looked as though they had been running dry. All had to be replaced. At the time the bearings were only lubricated by stray splash from oil in the rocker cavity. The newer engines have hollow pushrods which means that the rocker bearings get forced lubrication. I assume this should be a 'good thing'. The only possible downside is that the previous system squirted oil direct onto the valve springs and valve stem and that lubrication is now less direct as those components now rely on oil spraying from the rocker bearings.

As far as I can see the oil supply via hollow pushrods seems fairly comprehensive and hollow pushrods seem the norm in modern auto engines. Anyone got any concerns about this aspect of the hydraulic lifters v solid lifter debate?
Peter
Anonymous
 

Rocker bush wear, Hydraulic engine

Postby Anonymous » Tue Feb 10, 2015 10:15 pm

Posted by: Clive on 13:04:28 01/11/15 Sun

The reason for the wear is there rocker is always under tension. There is therefore no 'slop' or slack for any oil to get under the bush as there is with a solid lifter with some clearance. The oil in that case is 'whirled' round the bush.
The oil leaking from the lifter directed up the push rod is a good solution to this and is something Jabiru completely missed when they designed the first lifter engine. Also a few other things were missed of course.
New rockers are needed to utilise the oil from the push rods.
Which serial number do you have?
regards, Clive
Anonymous
 

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