RE: JetJoe OWNERS thread
 

Bewwwwwwdiful Smithy :D

I see you have the A/B going on a JJ-3000 now.

Any ideas on the overall increase in thrust? Or the obvious increase in the copious amounts of juice it must drink when you open the taps?

And just wondering if your design still based on your jj-1800 mod using the 'hot streak' ...

Nice work mate,

BJ:)

RE: JetJoe OWNERS thread
 

oops.... double post... sowwy...

BJ:)

RE: JetJoe OWNERS thread
 

Now can you imagine hitting that in mid flight.. afterburner light rings out your heart out... :D

RE: JetJoe OWNERS thread
 

With two JJ-3000's sitting out in the garage just waiting to meet "Mommy"... you don't think I'm sweatin on Knobby to send me some plans for the ultimate RC AfterBurner....?

LoL

BJ:)

RE: JetJoe OWNERS thread
 

[/quote]
Bewwwwwwdiful Smithy :D

I see you have the A/B going on a JJ-3000 now.

Any ideas on the overall increase in thrust? Or the obvious increase in the copious amounts of juice it must drink when you open the taps?

And just wondering if your design still based on your jj-1800 mod using the 'hot streak' ...

Nice work mate,

BJ:)
[/quote]

Hey BJ,

Thrust increase is in the order of ~30-35% depending on ambient conditions etc...The engine itself, (without burner) is good for ~30-31lbs, add to this ~35% and we get ~40lbs of static thrust at full noise. Yes, I run a "hot streak" system with this engine, I tried using other methods but nothing worked as well.

Cheers,
Smithy.

RE: JetJoe OWNERS thread
 

Having a bad time recently with turbines[:@] first my wren blew up because the shaft tunnel broke, and now after just fitting a new inconel combustion chamber and new tailcone to my JJ1400, and having it run better than it ever did with more thrust and nice egt's, it also blew up on a flight on Sunday due to a rear bearing failure caused not by any fault of the turbine, but by a broken festo fitting [:@]

It is really annoying that a part costing about a fiver done about $500 worth of damage.

It was only when I opened the starter cover I saw the culprit hanging broken at the bend, I realised what had happened.
No was'nt going to be the gas one that broke had to be the one feeding the lube pipe ! even the fuel one would have just caused the turbine to stop.

Easier to state what I don't need to rebuild it, Starter housing, Diffusor and Cumbustion Chamber, need all the rest, even the case has been pulled out of shape on the rear flange.

Dont know what caused the elbow to break but must have had a hairline crack in it I never seen, I did on occasion find the inside of the cover a bit damp and always suspected bad alignment of the pipes out of the fittings which will cause a festo to leak.

RE: JetJoe OWNERS thread
 

OUCH!!!

Two Turbines ker-poofed...

Major Bugger...

BJ:)

RE: JetJoe OWNERS thread
 

Hi Xairflyer

Sorry to read about your two turbines,which had a failure. I`ve been using Festo fittings for a while now and I noticed on my JJ 1800,that the plastic section of the Festo elbow fitting,was very "brittle". It just looked different in appearance,when compared with ones which I bought from our Festo Dealer. I replaced these fittings with new ones and they are working very well. I`m in the process of making the necessary tooling,to make a new combustion chamber,as there was two vapouriser tubes,which had come loose on the rear comb strut. My TIG welding machine had a "brain fart" and as I tried to weld them back into position,a huge hole appeared - combustion chamber scrapped. So I`m now making a few changes to the engine,which will improve the overall performance. New shaft,shaft tunnel and combustion chamber.

That Festo fitting which broke,caused the oil supply to the rear and front bearing,to be "cut-off",while the engine was running. My JJ 1800 has the fuel supply,"prioritised" to the bearings and then to the fuel injector ring. This is different to what it was,when I received it. I changed it,so that the bearings will get oil first and then the fuel flows to the injectors. In the event of the Festo fittting breaking off,the engine will most likely suffer a "flame-out",due to the way that the fuel/lube system is connected. Also,an insulin needle is used as an orifice,to regulate the oil flow to the bearings. This idea was given to me by Jesus de Acros of Artesjet and I`ve never lost a bearing,due to insufficient oil flow.

Regards

Craig

RE: JetJoe OWNERS thread
 

Hey Xair , sory to hear that !

But weldone for posting your problem on this forum because this will save many peoples turbines!

I did always think that the push fittings supplied by JJ are abit crap.

I use the real festos , they wont last for ever but will last longer than jjs .

Fellas, change your festos every couple of years, I spoke to a distributer for festos and they dont even recomend using any fuels with these, so we should change them at least once every 2 years or so because fuel does change the plastic over time..

also a pic of my wrenjj

RE: JetJoe OWNERS thread
 

I never would have thought the festo would give up like that, just maybe leak over time rather than break off.

Like the idea of feeding the lube pipe first.
Also thought about doing away with the elbows and fitting streight connectors exiting the starter housing like other makes, more for installation reasons but at least would be an all metal fitting. Or all metal elbows.

By the way the new inconel combustion chamber is really nice very well made with a good snug fit to the NGV and neatly welded.

RE: JetJoe OWNERS thread
 

Who is making these these inconel combustors then ?

RE: JetJoe OWNERS thread
 

Jetjoe

RE: JetJoe OWNERS thread
 

That reminds me - I really must take a peek inside my Twins one day (or get Brett to have a squiz for me :D).

They are about 12 months apart in age, and I've hear the iconel chambers are pretty much 'standard' these days (???)

BJ:)

RE: JetJoe OWNERS thread
 

yep.. they come in any new JJ as far as I know..
I have brett check everyone that comes in for a customer when he assembles them.

RE: JetJoe OWNERS thread
 

What can cause the EGT to be high, my 2 flight of today, the engine was not able to reach more than 150 000rpm with 820-840 deg ..

Do you think that the FOD can cause too much restriction?


Last flight was in march where the outside temp was aroung 7deg, the engine was running up to 160 000 and if i remember, temp around 750deg.

Today outside temp was 28 deg.

Any clue appreciated!!

Thanks,
Alex

RE: JetJoe OWNERS thread
 

Alex
Check that the thermocouple isn't too far inside the tail cone. Should be no more than 2 mm.

RE: JetJoe OWNERS thread
 

My engine runs at 580deg, if I pull the thermocouple out by approx 0.6mm the temp drops 500deg or so , this shows how sensitve it is.

My thermocouple is in about 3mm or just slightlyunder .

RE: JetJoe OWNERS thread
 

Yes first check your egt probe for calibration and fitting, 2-3mm max is enough, it will read higher if in about 5mm, a bad fit around the case and the diffuser will raise the egt as will too high a preload (normally not enough preload on a JJ, but may be stuck - more common) also too small opening of your tailcone.

I recently removed the rear O ring on mine which also dropped the egt's

RE: JetJoe OWNERS thread
 

I've been reading with interest the discussions regarding the amount the EGT probe tip protrudes into the tailcone.

It sounds that a depth difference of only a mm or two can make a huge difference in temp readings.

Surely, there has to be a better way - particularly since the EGT readings are so critical to how the FADEC controls the Turbine.

BJ:)

RE: JetJoe OWNERS thread
 

The probe should not read the highest temp level? To be safe.....let suppose we read 750 at 2mm in, but 850 at 4mm, at 850 we are close to damage the engine??

RE: JetJoe OWNERS thread
 

I think its more along the lines of getting a false reading, Leo.

The bit that does the sensing of the temperature is just the join of two dissimilar wires that are located right at the tip inside the probe. If too much of the thermocouple is exposed inside the tailcone, the body of the probe behind the actual sensor part will also start to glow red-hot and probably upsets the readings by supplying background heat where it's not wanted.

I just find it interesting that a part that is so critical to the way the Turbine functions has such a small margin for error. You'd think that by now, there'd be some kind of temp sensor that was a lot more tolerant to its fitting position...

BJ:)

RE: JetJoe OWNERS thread
 

Well guys, sad day...

Yesterday, me and my friend went to fly the the F15 with the JJ300.
After fitting new fuel lines and a new filter and some other ECU settings, the JJ starts nice, few seconds ramp time, and went to a nice idle.
Rev it up to 115K, nice and fast with EGT 650c.
After few seconds, the engine blown and flames all over the place [sm=48_48.gif]
The extinguisher was in a reach of hand, so nothing happened to the F15, but the engine... went to pieces.
After it cool down (with the assistance of the fire extinguisher) I open the front case and you can see in the picture that the front compressor failed.
The engine is a wreck now...
What you think? maybe poor compressor casting? a small crack? [sm=72_72.gif]

RE: JetJoe OWNERS thread
 

At first glance, it would be easy to say "compressor blade failure"

But what's the history on this thing?

Has it always run an FOD screen? Was anything ever sucked into the front end?

What's the black markings on the blade at 5:30?

BJ:)

RE: JetJoe OWNERS thread
 

Actually, no history, the engine is new with less than 1 hour.
Always with FOD screen, never take it off.
The black marking is from the factory, nothing to do with me...

Other than compressor blade failure, nothing in sight.
I will send the engine back for inspection and post here the answer.

RE: JetJoe OWNERS thread
 

The compressor is a commercial part from some turbo charger, would think it rare it would fail, maybe smithy would have more info on that, but possibly could have had a crack or flaw in one blade.

I see you have a FOD guard so would'nt think anything got in and nothing appears to be missing (screws) around your diffusor cover.