Try mg-inch, the result is a much smoother engine and bearings last a lot longer.....although mg-mm is still very good.

Thanks for your reply.

many thx for your info..!!

[sm=tongue_smile.gif] I really want one of those !

Where do you remove weight from compressor when balancing an assembled engine ? spinner nut? hub?

like jetcat and other

when i balance first only rotor assembly i grind rear compressor plane

after i balance all assembled engine grinding between compressor blade

like this P70 JETCAT example
http://www.rcuniverse.com/forum/m_90...tm.htm#9270055

[img]{akamaiimageforum}/upfiles/286920/Qj19795.jpg[/img]

OooOOoo....

Doesn't that coarse grinding on the front of the main and secondary compressor blades upset the airflow and/or weaken each ground blade??

BJ

i found this in jetcat 160 and other engine that i repaired
but NEVER on the blade or at the blade base

i balance the rotor assembly first due to obtain low imbalance then i finish the engine assembled
the material to grind after is very is little

jetcat 160 first maintenance

i tested 1 compressor with grinding between blade and other without grinding and no found difference..

The compressor is quite thick in between the blades. You would have to remove a lot of material there before weaking the compressor wheel.

I would have thought that it would upset the efficiency of the compressor, could it not be done on the hub, there always seems to be a bit machined out in that area by the manufacturer

Hi Guys,

Essentially this is the only real way to do it, material removed from between the compressor blades like this is very common and an accepted practice, balancing engines as an assembly or "core" is a good way to get a very good result, although Wren have been able to get good results with their engines using the rotor only method. An experienced balancer will know where to remove material so as to not weaken the assembly, it's better to spread the mass removal over a larger area rather than a large mass from a small area. All the better engine manufacturers use this technique, Jet-Cat, Jet Central, Kingtech, AMT, Behotec etc...the larger the diameter of mass removal the less material has to be removed compared to closer to the hub.

There's no need to disassemble the rotor after balancing which allows the recorded result to not be disturbed. A "rotor only" balance requires the assembly to be disassembled thus disturbing the result. A very good balance job can be obtained using this technique. The method Chrigui is using is spot on..!

Cheers,
Smithy.

example

First step pic : balancing only rotor to eliminate big imbalance
Second step pic : balancing all assembled engine to eliminate little imbalance

That looks great, give an update after a test run .
From where and how much u paid for that machine.

Adrian

i tested and zero vibration

buyed in italy
price depend the status but about $4000

[]

BJ

Hi guys,

Got back my JJ3000 and ran a series of test runs. (You can see the history of that engine in post# 2761)
The engine start and run hassle free, but can't go over 110K. (it should rev up to 115K)
Fuel line is free, with a new clean filter.
Temps around 650 ~ 700c
Battery O.K.
Settings and parameters are O.K
I know it can be due to poor balancing or bad bearings, but both seems to be O.K
Do you have any idea why it happened ?

Hi,

Just la little "heads up" for JJ costumers. We have received several ecus for repair sold by JJ as "genuine", but in fact they are copies of our model 2005. They had took seriously the copy thing, copied my name, scanned our company sticker, etc, but nobody is perfect nor is Mr. Jeff Wong, (AKA Joe) and his gang. In order to help you in to recognize the fake ecus, below you have a couple of pictures that you can check before sending your ecu to us, that of course, will not be serviced.

Externally the differences are:
Thick transparent shrink wrap.
Sticker printed by a inkjet printer.
Copyright readings misplaced. See pictures below, this is the easiest detail to check.

There are more internal differences that is not possible to check without removing the shrink wrap, but some easy to check are:
In JJ copy the components are hand soldered, ours are machine soldered
Capacitors in JJ are of black color, ours blue.
No serial number printed on the PCB on JJ copy.
Datecode on components in genuine ecus are of 2005 (0503) , on copies are dates from 2006. We manufactured this model only in 2005, so it is impossible to have any of our ecus with datecodes older than 2005.





Easy to see the difference, on the copied one there is no space between the "y" and the "G" in "by G.Espiell"




On top side, in the original is possible to see the second zero of the "2005", in the copy only the "5" is visible.

BRG,

Gaspar

So you wouldn't have a problem if someone wanted to use a genuine Gaspar/XiCoy ECU with a JetJoe Turbine??

BJ

Hi all, I have acquired a JJ 1400 in australia. Brett had the engine working on his test bench then packaged it up and sent it to me. I done a silly thing and hooked up the gas line to the fuel line and vice versa and cooked it (just don't ask) . I sent it back to brett and he repaired it and sent it back, new fuel ring and rear bearing.[img][/img] He did run it on his test bench and said it ran perfectly with all my gear.

I mounted the engine on a test bench and tried to run it to no avail. the starter motor failed, then the ECU failed ( the circuit board melted) so I repaired it and now it will run.

My problem is the temps durning the startup run around the 800's and sometimes it will slow down durning start up to cool down from the "over temp" then climb to an idle, but the idle is set to 45K but it sits at 50-55 odd K and will settle at 45K (+ -) 5K fluctuating but idles with a temp of 630 odd degrease.. then when i do the learning function up down 3 times 10-15 seconds up 10-15 down 3 times it is all over the place, at top end the temp is at 800 + and will sometimes shut down ?

The thermo couple is only 0.5mm in (any further it just over temps even at idle) I have tried another thermocouple (from another one of my turbines) but the same result.

I have a single cone tailpipe and have read that using the 2 piece pipe will fix the problem or even shaving 5mm from the length of the tailpipe will fix this is it true ? why did brett get it to run and I cant ?

I am using futaba 14 MZ and my fadec is setup, I have also tried using a 2 ch standard hitec radio but to no avail.

Full 160.000
Idle 45.000
Stop30.000
Start min temp 100
Max temp 800
Acceleration Delay30
Deceleration Delay 30
Stability delay 60
Pump start point Auto + 2
Pump start ramp 005
Glow power 020

trim down stick down 0889 @ 00 %
trim up stick down 1060 @ 13 %
trim up stick up 2178 @ 100 %

V.B reads 7.1V (using a top fuel 2 cell 2100 MAH LIPO
Firmware 4.03

I have tried with the accell and de cell at 20 and at 25 also with both at stability delay of 50 but the current values allow it to run (just)

I am stumped I am an experienced turbine user and am just baffled at it. the bendix is dis engaging and I am disconnecting the gas (3 seconds into fuel ramp)

I would love some help as I have now purchased a jetcat P60 to fill the shoes of this engine but I will not let this engine beat me. I will buy a falcon 120 airframe for it and "tinker" with Below are some pics of the inners of my engine.

ok how do I post images ?

Here we go figured it out.

Its a pitty they dont do the right thing and use a genuine fadec had me thinking about my atj fadec but got it from xicoy that thay had purchesed 30 fadecs for the first year of production and they are doing the right thing good to see.

Anyone ?

Hi.

Do you know if the shaft tunnel has an o-ring on the bearing? Looking at the combustion chamber pics,there is definately overheating present. Was there a flame(s) present during the start-up process? The NGV has a white "powder-like" residue on it and thats not normal.

If the shaft was turning freely,then I don`t believe that the o-ring could have been effecting the preload on the bearings. I had the same effect,once where the starter was not able to achieve the required Rpm and it caused the engine to overheat during start-up. When the bendix dissengaged,the fuel ramp was too powerful and was supplying fuel at a too low Rpm.

Assemble the engine,but leave the starter off it. Used compressed air instead,during the start-up phase and be careful not to blow the flame out,by spinning it too fast. This method should prove,whether its a starter,fuel ramp or preload problem.

Give it a go and see what happens.

Regards

Craig

Hi Craig thanks for the reply,

I moved the thermocouple 180 degrease today ( other side of engine ) and temps where better high 500's idle and just over 700 on slam and settling down to 700 at 160,000. ( I know this does not rectify the situation )

My engine does not have the o ring on the shaft tunnel. I have not seen one on a jet joe engine but would love to see a picture just to see what it looks like, I have heard of them but not seen one. Does the o ring present a problem. is it better to have one or not ?

The starter motor is not the problem as I have tried starting with air but no difference,

Preload how much should I have ? I can push the turbine wheel towards the compressor wheel about .5mm with good spring back. What is the best method to adjust pre load and how much should I have ?

the white powder I believe is the butane start gas, I remove the gas completely after the ramp has started and fuel is flowing. yes there are flames durning start up not big ones but they are there.

I am stumped as to why this is happening.

Hi

When you view your turbine from the rear end,position the EGT probe between the 4 o`clock and 5 o`clock position. This is a good starting point,as the "Hydrostatic pressure differential" between the upper and lower halves of the combustion chamber,causes more fuel to tend to be in the lower area of the casing. The EGT probe should protrude not more than 4mm into the exhaust flow. 0,5 mm is too little and won`t achieve an accurate reading. Your ECU is tyring to control the fuel flow,according to the exh. temperature. Do a manual start and not full auto-start,so that the ECU can learn the parameters and then do a full auto-start.

The o-ring could be in a groove at the front end of the shaft tunnel. This is supposd to prevent the bearing`s outer casing from rotating in its bore. Better not having an o-ring - just better tolerances in clearances. If it has an o-ring and you cooked the engine,maybe this o-ring is damaged?

I used to use a "pull-scale" and attatch it to the compressor end,with my own nut. I pull on the scale and when the compressor wheel stops at its furthest point,I read the amount on the scale. Approximately 40 Nm. See the photo of the shaft tunnel from the JJ1800. It had broken and I`m not using an o-ring again. Just making a new shaft tunnel with better clearances.

Regards

Craig