BJ64

Hmmm...interesting.

To a n00b like me, it's starting to sound like a compressor failure...

You've had the Turbine since new, yah? Nothing untoward during any previous start-up?

Did you inspect the compressor from the front and the turbine blades from the rear when you got it? (I will be having a darn hard look at both of mine now - just to see if there's any tell-tale marks of bad-casting, blade knicks etc.)

Hope you/we find out the cause - I would have thought a band spanking new JJ-3000 would be a lot more reliable that the older ones.

But then again, as I've said so many times before, I will be sending my Tubes off to someone like Smithy before I ever put them into something other than a test-bench...

BJ

snir2001

My Feedback: (1)

Oh yes BJ,

Did all around inspection before the first start.
The engine looked flawless and clean.
As we know, the compressor not made by Jetjoe, so I'm not sure it's Joe's fault...
I'm almost sure the problem was a micro crack inside one of the blades, because the engine was well balanced and nothing sucked in during the operation.
But, again, I will post here the final conclusion after professional inspection.

As I said before in one of my posts, the next engine WILL be JJ3000. (Well, now I hope to get one in replace )

leopaul

Sad day for me as well, From the first start of my engine(JJ1400), it was not able to reach more than 142000 rpm with really high temp. Tried moving back starter as requested, try to apply oil on the o-ring as suggested, move back the temp probe to be sure that it not extend more than 1mm as per request without succes etc....

Today, after the 13th run of 7 min of the engine, it flamed out in the air, causing a hard landing of my airplane. We found that the engine was jammed....

We decided to inspect it and some damage was caused to the rear bearing, ngv and combustion chamber. probably from running too hot from the start.....

Contacted JJ, still waiting for a reply of what they will do next...

Lesson learned, buy cheap, buy twice.....

BJ64

Oh...so it wasn't a JJ compressor you had in the Turbine, Snir?

And I'd be interested in why your JJ1400 was running hot Leo, before putting it down to just a 'cheap' Turbine. Flying with it when you knew it was running hot is a risk I wouldn't have taken - not without finding out why I had over-temp readings.

It would be pretty reasonable to expect the rear bearing to fail on an overly hot Turbine, since this bearing is the one that has to perform in the most adverse conditions. I'd be looking at my physical set-up and my ECU parameters, my fuel-oil ratio (you did use the proper ratio of good quality Turbine oil, right??) and anything else that would lead to hot running conditions before I flew anything using that Turbine. And if I couldn't find anything wrong with it that way, I'd have sent it off to a JJ Rep to have a look at.

On a new, out-of-the-box combo set-up from Jet Joe, the Turbine should run ok from the get-go. If it's running way hot it indicates a problem - one you need to correct before you go flying with it...

BJ

BJ64

PS - as an afterthought Leo, are you running an on-board Propane can, or do you start with remote can which you disconnect once the Turbine switches across to Kero during spool-up?

BJ

snir2001

My Feedback: (1)

Slowly BJ...
I did not say the compressor is not JJ's.
The compressor is the one that come with the engine, but we all know that JJ buying the compressors from a third party company (turbo manufacturer) or isn't it???
So, I hope it's not JJ's fault, because if so, thats indicate a poor QC.

erazz

Snir,

Can you take out the compressor and picture it?

A failure like this is extremely rare. The impellers are made by TC companies with a lot of experience with casting. They're usually able to spot flawed impellers before they go out the door.

I doesn't look like FOD either. FOD usually leaves traces on all blades and especially on the LE (look at the picture). It does look like the failure originated at the back of the wheel which is why you should look at the back of it.

BJ64

Not that this has anything with the other two failures Erazz, but those are interesting melt-marks on the Festo fitting at 3 o'clock there.

What caused that? Blow-back on the Propane??

BJ

erazz

Flooding [:@]
This is a *well used* and *very experimental* engine.

BJ64

Ooooooo.....the dreaded 'wet start', hey?

Still... nice fireball - pretty to watch

BJ

Xairflyer

My Feedback: (1)

BJ
Yes the Compressors are a JetJoe part but they are not made by JetJoe, many other turbine manuf also use commercial turbocharger compressors. The wren 54 uses a Garratt compressor, I am not sure what the JetJoe ones are, but they all come from Turbo Chargers. All I know is in the case of the JJ1400 it is not inter-changable with the wren 54 one as the profile is different.

erazz

They're not made by JJ but they are modified by JJ.
All impellers have to be modified in one way or another before we can use them for our engines.

JJ also balances the impeller. Given JJ's history I'd like to see the back of that impeller. Could be illuminating could be naught.

leopaul

Engine was purchased from Mark at JetJoeUS...

Like i said, i have done step by step moving back starter, they send me a new bendix, then put oil on the o-ring, as everyhting was fine, i moved back the temp sensor from 3mm to 2 mm...Then to 1mm...

Even asking on this forom here, see previous page, and everybody toward me to a false temp reading....In fact , i was not, now i'm thinking that something was causing drag internally, probably draggy bearing from the start or maybe what??

Total of 7 run of +/- 6minutes....

I'm using 5% oil mixed with the kerosen with is the double of what i'm using on my SuperBee.....

BJ64, yes , i'm using an external propane tank that i disconnect before flight.

BJ64

What oil are you using Leo?

BJ

AdriFlyBoy

I see that many of you has problems with JJ's overheating.To begginer in turbines like me,I am interested can that be solved(cooled doiwn)?

leopaul

I'm using BP2380 Turbo Oil....

Xairflyer

My Feedback: (1)

I think you mentioned this before regarding the balancing marks on my wheels, I just got a new compressor for my wren from a turbo charger supplier and balancing has been done by milling as used by Jetjoe in the past, maybe not preferred but is an acceptable method if the compressor manuf do it.

BJ64

Is that Tubo-charger oil, or Turbine oil?

I'm running Mobil II synthetic Turbine oil. Others have run 2-stroke oil etc successfully, but I'm not willing to put a couple of grand of Turbine on the line just to save a few bucks on oil...

BJ

BJ64

IHMO, compressor...or indeed Turbine blades can be a bit of an enigma.

At the speed those things spin, you only need a tiny flaw in casting, or a nasty knock that happened somewhere along the way that you don't know about, and a blade can be compromised. Perhaps without even so much as a tell-tail hairline crack or mark??

I guess the only real way to tell is to use magna-fluxing or x-rays etc - but that would add a fair bit of cost I would suspect.

BJ

erazz

That's exactly why they x-ray every turbine.

Xairflyer:
I'll be honest with you. If I saw that on a JJ I would be less at ease. Being, as it is, from a Wren I at least have some confidence it won't break apart. I once did a computed analysis of a turbine which has been milled deeply and it showed it to be too weak to stand up to full throttle runs.

The impeller is also highly stressed. My guess is that if you don't go too deep and too near the root it's still ok. That's exactly why I'd like to see Snir's impeller. Like I said: could be illuminating (could be not)

leopaul

I'm using this one, wich is sold for turbine engine purpose....

http://www.greathobbies.com/producti...d_id=GHPBP2380

myring

I don't think the deeper thermocouple will get a false reading. It's right that tip of probe is the sense part. The reading is converted from a electromotive force which varies directly with the temperatrue not heat of hot part of T/C. The industry standard for fluid temperature detection point should be at the center of path. The reason that the deepth of T/C protrusion not more than 2mm is due to engine start character. The start EGT can not remain below 800 so withdraw a little of T/C to get lower temperature to make a successful start. Usually running EGT can remain within 800.
So according my opinion the reading is not the highest temperature. nevertheless the turbine can endure higher temperature more than 1000 in a short time.
Comments?

BJ64

That doesn't make sense to me. Milling is milling - the part probably comes from the same factory, so why would it concern you if you saw that kind of thing on a JJ Turbine, but not a Wren?

Isn't it the compressor manufacturer who's doing the balancing (via milling in this instance), and not JJ or Wren or whoever..??

BJ

erazz

Milling is milling but where you mill and how deep depends on your experience and knowledge.

And though the impeller does come preliminarily balanced the turbine manufacturer has to do some balancing in-situ.

BJ64

Oh, ok.

I just assumed that once they're balanced by the compressor/turbine wheel manufacturer, they were good to go (??).

So - they still do some fine-tuning at the engine manufacturer as well? If that's the case, then yes, I could see it being a problem for the unintiatied to go drilling holes and filing bits off.

Re balancing in general - I remember chatting about the subject with Brett ('Smithy'), and that he remarked that he once balanced each piece individually (shaft, compressor, turbine wheel etc), only to find that it still didn't balance all that well when assembled, and that balancing the entire unit as a whole seemed to give better results. Which kinda makes sense - the complete assembly (including woodruff keys etc) needs to spin nice and balanced, for it is the whole unit that is spinning when the Turbine is actually running...

BJ