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New JetJoe J-Junior 4lbs turbine

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New JetJoe J-Junior 4lbs turbine

Old 04-06-2009, 06:46 PM
  #151  
idleup1
 
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Default RE: New JetJoe J-Junior 4lbs turbine

found camera.
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Old 04-06-2009, 06:52 PM
  #152  
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Default RE: New JetJoe J-Junior 4lbs turbine

landing gear
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Old 04-07-2009, 03:12 AM
  #153  
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Default RE: New JetJoe J-Junior 4lbs turbine

idleup1, did you run the JJJ yet ?
Old 04-12-2009, 12:52 PM
  #154  
j_rc_heliman
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Default RE: New JetJoe J-Junior 4lbs turbine

I too am anxiously waiting to hear from you!! How does it run or fly? do you get the full 4 lbs of thrust? and how does the turbine perform at 240K?
Old 04-12-2009, 04:51 PM
  #155  
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Default RE: New JetJoe J-Junior 4lbs turbine

I just returned from racing nashville this morning and I finished a test stand. I ran a flightworks 100c pump as I had 3 here.I used isopro gas (mix) with the supplied valve. I used a bypass (Tee fitting with lube resticter returned to uat) It started and came to an idle quick. exuast temp at idle was 640c. at 240,000 temp was 825c. supplied limit at 1000c. I tought it accellerated smooth and quick. no vibation at all . I had motor on a stand and did was not able check thrust. When I mount it in the airframe I can hook it to a digital strain gauge. I felt as if was close to advertised . I took some pictures I can post later . I'll try to make a video also.
Old 04-12-2009, 06:23 PM
  #156  
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Default RE: New JetJoe J-Junior 4lbs turbine

It was starting to get dark so tail cone glow was visable. I might want to open tailcone some to bring temp down a little.
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Old 04-12-2009, 06:40 PM
  #157  
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Default RE: New JetJoe J-Junior 4lbs turbine

Firstly I would like to say that I am amazed that JJ has actually managed to copy the Lambert and get it to anywhere near a running state. I have one of these juniors and I am really surprised that it actually works. The UK importer had two and I had the pick of either. One had little or no pre load and the turbine wheel looked like it had got to a million degrees during testing, the other looked like the compressor was balanced using an angle grinder and also had a ticking bearing, this is one I took... It's hardly a work of art in the way it looks but it does start and run.

It comes with an auto start ECU which is too big and one of those old heavy brass Jetcat style fuel valves which is ridiculous bearing in mind the size of the engine. There was no gas valve or Li-Po supplied. The ECU would not power the glow plug until the setting was 80 and then smoke came out the ECU. Surprisingly enough the ECU still worked so I took the plug setting right down and connected another plug to it and left it on the bench to fool the ECU into thinking it was connected to the engine and lit it with lighter. Once lit, the fuel ramped and it went to idle with no fuss at all. Ran it to full power tonight and all seems well but something is telling me that it might not be an engine that lives for very long.
Jason
Old 04-12-2009, 06:47 PM
  #158  
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Default RE: New JetJoe J-Junior 4lbs turbine

Your probably right-1500 deg F is not associated with long life. Scott
Old 04-12-2009, 06:53 PM
  #159  
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Default RE: New JetJoe J-Junior 4lbs turbine

Yep, 1500 deg F + 245,000 rpm = Bang[X(]
Jason
Old 04-12-2009, 07:38 PM
  #160  
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Default RE: New JetJoe J-Junior 4lbs turbine

new ecu I got is about 1/2 the size of the older style. valve is smaller than the older one but not micro. I never run a gas valve to save weight and prevent a fire in a crash. I just run a check valve. It appear that the final balance was done as an assembly. My preload feels perfect after 4 starts. Test run with ultra low sulfer diesel and 3.5%turbine oil(mobil). I'll try later this week with kerosene base but i've not seen much difference.
first pictuire is bypass.
second is new next to old ecu.
third is jj pump next to lighter flight works.
supplied with a light 2 cell lipo 850 15c 2s1p
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Old 04-13-2009, 02:40 AM
  #161  
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Default RE: New JetJoe J-Junior 4lbs turbine

idleup1, why did you have to do a fuel bypass ?
Old 04-13-2009, 06:06 AM
  #162  
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Default RE: New JetJoe J-Junior 4lbs turbine

smoother idle when using a large pump on a small motor. I plobably don't need it with the small pump.
Old 04-13-2009, 06:18 AM
  #163  
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Default RE: New JetJoe J-Junior 4lbs turbine

and is a restrictor really needed in this case ? can you explain the reasoning behind this please ?
Old 04-13-2009, 07:09 AM
  #164  
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Default RE: New JetJoe J-Junior 4lbs turbine

He's using a fixed resistance on the return line. Probably so he can go with a higher pump voltage at idle. These cheap pump can motors don't like a low rpm. So with a restricted bypass line you can raise your minimum pump motor voltage for engine idle rpm. The engine sees the same fuel pressure it always has at idle, but it is a more controllable pressure at idle rpm using a bypass with restriction. At the same time top engine rpm will yield a higher pump motor voltage. Correct me if I'm wrong...

MACE
Old 04-13-2009, 10:28 AM
  #165  
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Default RE: New JetJoe J-Junior 4lbs turbine

Well I managed to get another run out the JJJ today. I have to say that this engine starts and runs as smooth as any engine I own. It ramps up perfectly without a pop or fart, it could not run better, until........ yes you guessed it, it all went wrong. At first I thought the bearings were shot but they seem fine. It's actually the pre load that has decided to fail. There's a poor quality wavy washer which gives the pre load and that has decided not to be wavy any more. The front bearing sits in a very soft O ring which I think could drag on the bearing and stop the pre load working.

As for the parts inside, really very good. Visually, the NGV and wheel castings are some of the best I have seen. And the chamber is not that bad although someone does need some lessons in silver soldering.. The diffuser and shaft tunnel are well made.

I'll get a stock of wavy washers and try again.

By the way, it's running with a restrictor in the pump line and the PW is 450. No need for any bypass valve at all.

Jason
Old 04-13-2009, 05:34 PM
  #166  
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Default RE: New JetJoe J-Junior 4lbs turbine

does anybody have any experience with the Lambert Kolibri? what temperature does it run at at 240k? Is the jj-junior comparable? I assume that 825C is a bit too much temp to get a long life out of the engine.

Maybe with some modification to the tailcone, or creating a 2 piece tailcone could drop the temperature.

Hey Jason, did any damage occur to the turbine or bearings because of the damaged wave washer and bad preload? Do you have a better long term solution for maintaining proper preload?
Old 04-13-2009, 06:23 PM
  #167  
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Default RE: New JetJoe J-Junior 4lbs turbine


ORIGINAL: j_rc_heliman



Hey Jason, did any damage occur to the turbine or bearings because of the damaged wave washer and bad preload? Do you have a better long term solution for maintaining proper preload?

yes there is some damage to the inlet where the compressor rubbed due to latteral movement when the preload failed. If all the JJJ out there have the same quality wavy washers then I recon they will all fail very quickly.

As I said above, I had the pick of two and the other had a dodgy preload and that had only been factory run! They are also a non standard size which means JJ have had them made.

I wonder if heating them up and cooling them down quickly will harden them up?

Jason
Old 04-13-2009, 06:47 PM
  #168  
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Default RE: New JetJoe J-Junior 4lbs turbine


ORIGINAL: j_rc_heliman

does anybody have any experience with the Lambert Kolibri? what temperature does it run at at 240k? Is the jj-junior comparable? I assume that 825C is a bit too much temp to get a long life out of the engine.

Maybe with some modification to the tailcone, or creating a 2 piece tailcone could drop the temperature.

Hey Jason, did any damage occur to the turbine or bearings because of the damaged wave washer and bad preload? Do you have a better long term solution for maintaining proper preload?
JRCH,

I am the US Importer for the Kolibri. At 240K, it will be upper 6's to low 7's. In terms of how comparable they are, since I don't have a JJJ, all I can say is that they look similar. Everything else, I am reading on this thread along with you.

Chad
Old 04-13-2009, 06:54 PM
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Default RE: New JetJoe J-Junior 4lbs turbine

Why?
Old 04-13-2009, 06:56 PM
  #170  
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Default RE: New JetJoe J-Junior 4lbs turbine


ORIGINAL: AndyAndrews

Why?
Because there's no grass.
Old 04-13-2009, 07:28 PM
  #171  
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Default RE: New JetJoe J-Junior 4lbs turbine

hmmm.. can you upload a picture of the wave washer and relative dimensions. I can see if i can find a spring supplier here in the states that may be able to provide a hardened spring washer, perhaps made from inconel alloy sheet. I know that Joe will take care of you though. Im sure he will replace any damaged parts free of charge, he is a great guy to deal with. I had one of the original jj-1200 turbines that had temp problems, compressor surge issues, etc. Joe sent me all new components when he worked out the problems for free and now the turbine runs great!

Its going to take some work though to get temps down to a safe level and near that of the Kolibri. Perhaps some slight modifications can be made to the combustion chamber geometry to get better flow and those temps down a bit further too.
Old 04-13-2009, 07:53 PM
  #172  
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Default RE: New JetJoe J-Junior 4lbs turbine

Here- I will contribute something positive to this thread- You stated that you were running Diesel. Diesel runs about 30 to 40 degrees C hotter than Kerosene.
Old 04-16-2009, 08:46 AM
  #173  
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Default RE: New JetJoe J-Junior 4lbs turbine

Hey Jason, did Joe get new parts out to you yet?

Idleup, have you tried running the turbine anymore times since you last posted? Have you taken any videos of the startup or runnung of the jjj?
Old 04-16-2009, 08:56 AM
  #174  
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Default RE: New JetJoe J-Junior 4lbs turbine

One of the biggest JJ dealers told me that JJ in China knows about the preload problem, here is a quote from his email:

Firdt:
-
Just a quick update on the J Junior. Got a chance to test some yesterday they run very well and easy to start once you get a little practice. However we are having a minor trouble with bearing preload on some of the J Junior's after running for awhile the preload goes away and the turbine starts to vibrate. I know the pre load washer is too thin and the heat causes it to lose tension. JetJoe is aware of this problem and it is a simple fix waiting on a stronger thicker pre load washer made from a more heat resistant material. This doesn't seem to affect all of them but I won't sell any of them until the updated parts are installed. Once this minor trouble is corrected it will be a nice little turbine.
-

Second:
-
JetJoe has informed me that the problem has been corrected. I think they should be fine now but can't say for sure I haven't ran one of the updated ones yet. No news on the autostart yet.
-

So it seems that know of this problem already, and have a replacement.
im really wondering if we are going to face a truly reliable little turbine at about 1.5K$.
Old 04-16-2009, 09:10 AM
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