3300A : A tale of two (hydraulic) lifters, one with no spring.

[facthunter]

How easy have you found it to bleed an oil filled follower down completely?  The little ball should be able to be unseated with a piece of straight piano wire that goes through the hole visible with the pushrod removed. Utter cleanliness should be observed when servicing followers and the hollow pushrods Sludge  will affect their operation .  As far as I'm concerned they are something else to fail and I nearly got at least seriously Injured when one on an O-300 Continental failed, when I had little height and a field of thick tree stumps for a landing site.  Even ONE follower failed meant the plane would not climb well under max wt for the conditions .Nev

Edited June 1, 2021 by facthunter

[RFguy]

Hi Nev

Yeah and when I was going through them, I had my magnifiers on , so I could see any lint from the shop rag I was using to handle them.

I  found it pretty easy to bleed them down, well in this case I took them apart and gave them a wipe in the bottom of the piston, but leaving enough oil  there to still get good lube on the first start . There was a *little* more sludge or thickness to the oil  in the rear ones than the front ones.

 

One thing should be said- you have to be REALLY gentle with the check ball spring/ball.

 

Yes, a poker to 'pop' the lifter down, but one must be careful at that point because if you push on it again after the bleed down, you can dislodge the ball and spring assembly depending on how much clearance is under the ball and the ball cap.

 

I've found that under pressure, they'll bleed completely by 1 hour elapsed. Of course when you remove them, they extend and suck in some air. 

 

The jabiru lifters run with very little operating travel, a few mm. Failure of a lifter - which might be seizing of the lifter piston, or the main spring breaking , and then the check ball cover coming adrift would probably mean in the closed portion of the cycle, that the  valve would be (stuck) open a couple of 2mm worse case.. (because it never runs with much clearance to start with..... On the OPEN end of the cycle,  a bent push rod is possible . perhaps a valve collision  but I haven't worked through if the maximum lift is restricted by cam travel (and a bent rod maybe ) or the rocker  geometry ...

 

If the check ball cover is unseated and the spring/ball assembly is out of service (ball adrift, ball spring  broken , BUT the spring ball cover does not get itself sideways, I would say just a loss of some opening would be the result. but it would make  quite a bit of noise....

 

There are a few possibilities, but most failure modes would change the sound the engine is making.

 

I suspect oil quality and oil viscosity  might affect ball-spring operation 'quite a bit'

 

In the case of my single 'failed' lifter- there was little effect because the lifter was pushed all the way in on static  (nearly no clearance)

Edited June 1, 2021 by RFguy

[RFguy]

Given that the O-360 Lycoming manual has about half a dozen different pushrod length options, I think this length is a bit more critical that Jabiru think it is. 

 

certainly, running minimum bled clearance, a hydra  lifter failure is not such a big deal, since with minimum bled clearance, the lifter is operating more like a solid lifter with a tiny bit of compliance.

 

But then the failure elsewhere becomes more critical.

 

Now, in my above analysis- I did not consider a failure such as a stuck valve , or unhappy valve spring.

 

In those cases, running minimal bled clearance would be B-A-D because the lifter would extend on the cam inactive return and then next cycle you might end up with a bent rod or stuck valve.

 

That's worse.

 

People think that the  self adjusting hydra lifter gives them carte blanch but really it can produce awkward outcomes with various failure modes.

 

 

 

 

 

[facthunter]

It's not designed to operate bottomed out. The compression check will maybe indicate it's failed but not definitely. It could be warped valve or damaged seat  of insert or valve.. I'd expect a hot engine to have more valve clearance but you can't be sure. I'm not advocating working near a running engine. With the cowl off, it overheats. LIVE props are deadly.

 I'd be much happier with the latest engine. There's a lot of things done better with it. . The airframe is not the kind that should worry you much. 230's are fine that way. Nev

[RFguy]

The calcs I did (Jabiru engine) suggested the crankcase, rods, bores, head etc roughly neutral on thermal expansion. Leaving the VALVE STEM to get hot and expand and reduce clearance under the tappet.

It is the one thing Nev that I like- that is the 230D airframe. If Jabiru would accept 912ULS/914 in those airframes they would sell like hot cakes. with icing.  912ULS in the 230D, 914 in the 430.

 

I think the Gen4 had the cooling sorted well enough, and the solid pistons, and hopefully push rod lengths sorted out.

So, despite all this frustration , I will probably STILL BUY a GEN4, if I dont get a C172....

I'm also investigating a 912ULS in a J230D airframe. with a modern prop like an Eprop, weight is good, W&B will be right on the money, and that the rotax will pull happily at 85% all day , that will be similar performance. 

Jabiru really needs to extend olive branches to many engine clients.  Might improve their reputation.

 

 

[facthunter]

That's all been gone into. COST and complexity.. I thought the engine was heavier and weight in the tail was needed. THAT if true is a  minus. If you wish to go much faster you won't have enough nose down trim.  A SIX is a much sweeter engine than any flat four. Fit your starter drive behind the prop where the flywheel doesn't have to put up with it.  125 knots is fast enough for that chariot. Nev

[RFguy]

W&B is OK for 912. 914 is getting a bit heavy, maybe OK with battery moved..

 

Yeah I am pretty sure the Gen4 will be fine, if certain things have eagle eyes on them . The starter yeah. A soft start starter (as we have discussed) would be desirable. needs a different starter from what is used because  it has to be spun up to engage...EVen a semi soft start would be an improvement.  Yes, the 6 sounds nice. 

 

The difference now, well I now know a thing or two about these engines, everything except the crankcraft, and that doesnt give trouble.  And so I can mitigate by preventative maintenance with specific focus.

Alternative is a 172M etc . slower, but a different utility.   And the lack of being able to change something for something I like in the instrument panel because its a certified aircraft might just  be something I am not willing to give up compared to LSA. 

We'll see how I feel when I get the 230D up flying again. talk is cheap. 

 

 

 

Edited June 1, 2021 by RFguy

[John Robert]

LSA is not easy to make any mods. Any changes no matter how minor must be approved by the manufacturer. If you follow regulations, it is not much easier with Experimental LSA. Changes still require approval but that can be authorised by a "CASSA Authorised Person" There are not many & some are quite expensive as they are putting their heads on the line with the approval. CASSA control LSA, RAA only administer LSA under the strict CASSA rules. I understand that is because CASSA also both control & administer LSA that are registered under GA.

As an example to fit a prop different than the one approved by the aircraft manufacturer, approval must be obtained by the manufacturer. The alternative is to change to Experimental LSA & get a certificate from a CASSA Authorised person. That may cost as much as the prop as it would also require  weighing the prop & if there was a weight difference a new W&B would need to be done,  by a CASSA approved person on certified scales.

If you do not believe this contact "Tech" at RAA.

[RFguy]

yeah, the prop change you describe -  that's a "MAJOR" in the tech manual.

 

[John Robert]

A prop change may have been a bad example as minor changes are also included. A better example may have been the use of a none original Rotax oil filter. In the case of Flight Design they state that the engine be maintained to comply with Rotax maintenance. Rotax state that a genuine oil filter must be fitted. This would make the aircraft none compliant if an alternative was fitted.

The Flight Design specs give the air pressure to all tyres as 32PSI. It was said by some pilots that this could allow the tyre to turn damaging the valve in a heavy landing. A general approval was obtained &  I have a copy  approval from Flight Design that allows inflation to 45PSI.  This is an indication of how little can be changed with LSA to keep the aircraft compliant.

I guess if the manufacturer changed the recommended pressure to 45PSI it may give someone who had experienced damage due to under inflation to have a claim against the manufacturer. There is  so much time spent trying to protect ars** from litigation.

[Thruster88]

2 hours ago, RFguy said:

W&B is OK for 912. 914 is getting a bit heavy, maybe OK with battery moved..

 

Yeah I am pretty sure the Gen4 will be fine, if certain things have eagle eyes on them . The starter yeah. A soft start starter (as we have discussed) would be desirable. needs a different starter from what is used because  it has to be spun up to engage...EVen a semi soft start would be an improvement.  Yes, the 6 sounds nice. 

 

The difference now, well I now know a thing or two about these engines, everything except the crankcraft, and that doesnt give trouble.  And so I can mitigate by preventative maintenance with specific focus.

Alternative is a 172M etc . slower, but a different utility.   And the lack of being able to change something for something I like in the instrument panel because its a certified aircraft might just  be something I am not willing to give up compared to LSA. 

We'll see how I feel when I get the 230D up flying again. talk is cheap. 

 

 

 

This could be the aircraft for you RF. It has the 172's dependable engine with a little more hp, more speed than a jab and the experimental freedom you want. A nice all rounder.  

[walrus]

Pushrod lengths? Hmmmmm, I seem to recall that Lycoming or Continental has a range of pushrod sizes so you can pick the one that gives closest to the recommended clearance.

[RFguy]

And the CASA action on Jabiru was like a blunt hammer. CASA's big stick did not drive any long term cultural change at the organisation.

 

What CASA should have done is require them to install an appropriate  quality assurance/quality management system. Yes I know it doesn't mean quality,  but what it would have done is provide a reporting system and a driven outcome  for examples like my reporting a missing valve spring in a hydraulic lifter to Jabiru.  At the moment , NOTHING will come of my reporting to Jab of this. It will just be like. "oh that's interesting'.

 

[facthunter]

CASA's action  sent the engine manufacturer  broke . Nev

[RFguy]

Yep it was poorly executed IMO, an example of (some of the )public servants not understanding business. I dont know the full story . Like for example, if the company refused assistance/change. 

[facthunter]

It was confused then and will be moreso if we continue  here now I suggest. due to time passing mainly and humpty dumpty can't be put together again.  Nev

[RFguy]

right. 
moving on.  will have another go with sorting out  these push rods next week. Get this plane flying. 

I've been flying (the club plane - the Brumby) every 10 to 17 days. 17 days was too far apart. 7 days is best. 10 days  is a good compromise.

Similar to playing golf, I am told. -glen

[facthunter]

No you have to play Golf at least THREE times a week or you annoy yourself so I don't bother.. with GOLF any more.

   IF you fly every day in small stuff it becomes very familiar and you might develop  bad habits. How well you fly depends on your mental state and attitude to the task. You have to "Think Aeroplane" when you're in charge of one no matter how long you have been flying. Nev

[RFguy]

WELL an interesting event for engine builders and interested . Pls do not pollute this forum with flippant comments, understood?

-finally got the right time in a hangar available to to the First oil change after the rebuild.  27 hours

 

Leakdowns  80 80 80 80 80 50.

The 80/80. well I couldnt beleive it, so I cranked up the pressure and 90/90 ! Very very difficult to get it up at TDC and hold it, the plane moves.
Well, I guess I did that job right. BUT Now, what about this CYL # 6 ??? hissing out of the inlet and exhaust valves

I feel can ONLY be more head recession causing the valves to not full close. It had recession before (#6), lots of it. 

Pull off rocket cover. YEP  ZERO clearance. cant push lifters back, valves never fully close.
Recall I shortened all the pushrods before because the stock Jabiru ones were TOO LONG (and Jabiru admitted this - they went to shorter rods)  (insufficient tappet clearance ).
Short check leave for 10 minutes with each valve open to bleed down a possibly pumped up lifter . Nope. used to have 0.5mm here. 

Some clues !!!

1)  About 6  hours ago I noticed the static was very slightly down 

2) That cylinder has been running cool. Cool in CHT and EGT. Makes sense now eh ????
When the others were 160CHT/680 EGT  in climbout , that one was 20 deg less.
When the others  were 140 CHT/710 EGT  in cruise, that one was 115CHT, 610EGT ! Reduced  fuel/air charge ....

 
My mantra as you all know is 165 C MAX on top because I measured 20C higher underneath at stationary 2000 RPM. . 

But, I know that the underneath of CYL#6 is absolutely starved of airflow and thus is COOKS the Ally under the head around the lower (hidden) head screw....
So, grounded while I think about what to do next.

Either the head under there is getting still hotter than I estimate OR the previous long term overheating degraded the aluminium. 

-glen
 

[facthunter]

It's normal to do hardness testing if overheating is suspected. I don't know what the metal spec. is They don't fix themselves.

 More than .5mm of travel is needed in my view.  Bit strange it's happened to both valves. I'd expect the problem only with the exhaust. Any colouring or scratching with the bore? Nev

[RFguy]

Hi Nev. 

 

Actually not strange really it has happened to both valves because when the bottom of the head recesses around that lower screw, roughlyin symmetry,  the head pulls closer and BOTH pushrods are affected (effectively become longer) and thus both valves equally affected.  Or did I miss something ?
That or I have TWO bad lifters that are stuck  on the #6 and previously overheated head) cylinder. (they're all like this I am sure and why the valves burn up and give problems because people do not keep enough eye on the tappet clearance (push with thumb on the lifter end of the rocker) . 
Will likely to machine face full cylinder interface flat and select some suitable shim material . Or find another head. 




 

Edited November 2, 2021 by RFguy

[facthunter]

They "fret" more near the  exhaust valve area. The three bolts that are the only ones to move and need the threads wire brushed..  .5mmm gone in 30 something hours? That's pretty unlikely.. Now you know why I prefer MANUAL valve adjustment. (Different camshaft required). Nev

[RFguy]

looked it up... 0.4 mm gone on lash, (it was already the shortest on clearance because it was already recessed)

and roughly 2:1 rocker mmechanical disadvantage so probably 0.20mm gone from the head.

OK on exhuast so you say the head is just hotter near the exhaust port and thus goes very slightly more in that region ?

[facthunter]

You can't deduct the  amount X 2 if it's just the head/cyl face. Your rocker ratio does affect it

   The ones I've examined are mainly affected near the exhaust port area. I'd consider it unlikely to affect the whole area the same way since it's due to thermal expansion and /or metal softening..  Nev

[Old Koreelah]

5 hours ago, RFguy said:

My mantra as you all know is 165 C MAX on top because I measured 20C higher underneath at stationary 2000 RPM…

Glen based on your posts, I’ve become a bit more conservative and adopted 160 as my TNE- Temperature to Never Exceed. The hottest bits are a fair distance from the sensor, so may not register on the gauge.

 

My CHTs were quite acceptable until I installed shrink wrap on the first 200mm of the sensor cables. Since then, some will sneak over 150C on climb, but stabilise at around 135 on cruise. After lots of testing I discovered these readings are pretty close to the temp underneath the exhaust ports.

 

5 hours ago, RFguy said:

But, I know that the underneath of CYL#6 is absolutely starved of airflow and thus is COOKS the Ally under the head around the lower (hidden) head screw....

A good argument for updraught cooling.