jason

My Feedback: (1)

It's about 30mm tapering to 20mm at the outlet.

jason

menzapsi

Hi knobby1, nick and jason
How much oil do you have in your fuel for the junior?
On the first time my junior last 6 starts and take 0,5 liter of fuel with 5,5% oil (the same fuel I use on my JJ1200) before it break.
When I get it back from Joe, it last only 1 start and after 3 min it was out, this time I have new blend with 3% oil (joe recomendation).
So I have just send it back to Joe.
Regards
jean

jason

My Feedback: (1)

I'm using 5% oil. Due to the lack of any instructions I'm not sure what JJ recommends.

Jason

knobby1

Hi Jean,
Initially Jet-Joe recommended the normal 5%, however, during my testing I found this to cause a little too much carbon build-up within the combustion chamber, fuel ring and around the rear bearing support, I have since reduced this to 2.5-3% with much better results. I have since passed this onto Joe and hopefully this information will be going out to customers.

My "test/development engine" has 171 cycles and just over 700 minutes showing on the total timer, this can be a little misleading though as the timer starts as soon as the ECU is switched on, I'd suggest the engine has possibly 75% of this as actual running time....still a goodly amount of time though, the bearings are the originals and will probably need replacing very soon.

Jean, does your engine "buzz" at all during running? If so I would tend to think the balance is not good enough and may be the primary cause of the failures you are having...as with all turbines, correct balance is vital to these little engines and is quite difficult to do due to the small size of the rotative. Readings in excess of 5mg-in will cause problems.

Those of you with Juniors, please make sure the tiny brass bearing lube line which exits near the front bearing behind the compressor wheel is clear, I've had one case of a blocked lube line, the ID of this line is only ~0.005" and can block very easily... needless to say the result is not good.

A quick check is to remove the front engine cover, detach the lube line (with restrictor) from the inlet "T" fitting and lightly blow through the line, if there is flow, the line is ok.....if not, firstly check the restrictor in the line to make sure it's clear, if it is then more than likely the brass tube is blocked, normally a quick blast with some low pressure compressed air will clear it, give it a quick blast from both ends if possible!!

Attached are a couple of photos of the offending tube.

Cheers,
Smithy.

knobby1

Hi Anthony,
The internal diameter of the exhaust pipe at the mount flange is 35.10mm, the exit diameter for a "stock" pipe is 21.75mm. I suggest opening the exit to an internal diameter of 24.50mm which means removing ~2mm from the total length of the pipe.

Total length of the stock pipe is 27.70mm.

Hope this helps you with your project.

Cheers,
Smithy.

jason

My Feedback: (1)

Smithy

No wonder I have a hot engine, my outlet measured 21.6mm and I increased it to 22.5mm.

jason

menzapsi

Hi knobby1
The turbine was a little sticky from new to the first time it break. I start the turbine and every thing seems normal, I go to max RPM still OK, I came back to Idle, when I want max RPM again, at 140.000rpm I have the message SPEED LOW and the noise from the crashing compressor.
From what I have read, the best balance have to be done without disassembling the turbine.
I supose Joe balance the turbine before he send it.
Please can you tell me if I can do it with the JJ balancer and and how to proceed
Regards
Jean

knobby1

Hi Jason,
My guess is that the pipes delivered with every engine are not all exactly the same, I've found an exit diameter of 24.50-25.00mm gives a good result without reducing the thrust by a huge amount.

Cheers,
Smithy.

knobby1

Hi Jean,
Definitely sounds like an out of balance compressor condition. The Jet-Joe balancer machine is not accurate enough to balance to the limits required, it will only get you somewhere in the ballpark and is only good to ~50mg sensitivity. A "core" balance is the most accurate method and is similar to how a turbocharger is balanced, as an assembly.

Cheers,
Smithy.

Xairflyer

My Feedback: (1)

Hi Smithy

How did you get the pictures showing as thumbnails, every time recently I post to RCU they are full size in the post, wondering if some of my settings are wrong.

Posted a picture of my fuel needles (JJ1400) now all working as a test

Xairflyer

My Feedback: (1)

Just made a liar out of myself the picture above is a thumbnail !!
must be a setting problem on other threads as I have tried to post to the jetjoe thread and they are always fullsize ?

knobby1

Hey Xair,

I dunno mate, I just post the pics and up they pop as thumbnails, all done with smoke and mirrors if you ask me ;-))

Good to see your fuel needles are all doing the same thing, a rarity for some of the JJ fuel rings. As you mentioned over on RCGroups, giving the main ring a little squeeze with smooth pliers at 90 degrees to each needle will often help. I, like you, believe they push the needles in too far when brazing and they bottom out inside, I see it all too often.

Cheers,
Smithy.

tonyjms2005

Hi

Excellent! Thank you for your swift reply.

Antony




http://tributetothem.com

tonyjms2005

Hi

I have watching this thread and it seems to me that there are two majorproblems with this little turbine, but when they are addressed it should be a good little engine:

The pre-load is wrong, the bearings are either too tight, giving higher egt's, or in some too loose causing movement and therefore fretting damage to the bearings.

Pre load spring poor quality, the spring is obviously of poor quality causing the preload to fail and as a result the bearings to fail, get a tidy washer for this and the it should be much better.


http://www.swcbearing.com/technical/Preload01.asp

I hope this helps.

Antony



http://tributetothem.com

jamiechip

brett the warranty agent for ausjets has already adressed these problems and solved the issue's if you buy an engine from ausjets you wont go wrong for the best set up out there

littlepiston

My Feedback: (12)

post a web site were one can look up aus jets?[&:]

ThomasP

http://www.ausjets.com/

Alistair

shorty55

How the engine Jason?
Any updates?
Nick.

tonyjms2005

Hi

Can anyone recommend a supplier for an air blower/starter for a JJ Junior sized engine?


Kind regards

Antony



http://tributetothem.com

dw_crash

My Feedback: (6)

There is a fellow on E-Bay that sells 12 Vdc compressors for industrial use. They have a few gallon tank on them. I tried to buy one but shipping to Canada was more than the compressor. So, I went to the hardware store and bought, on sale, a regular 120 Vac compressor and a 12 Vdc small compressor. Then, put the 12 Vdc compressor on the tank from the 120 Vac compressor. I used it for awhile to start my JJ1400 till I converted to autostart.

Just an Idea or two,
DW_Crash

jason

My Feedback: (1)

Antony

camping shops sell them for blowing airbeds up or heres one on Amazon. [link=http://images.google.co.uk/imgres?imgurl=http://ecx.images-amazon.com/images/I/4147ZdG6XXL._SL500_AA280_.jpg&imgrefurl=http://www.amazon.co.uk/240V-HIGH-INFLATOR-AIRBED-MATTRESS/dp/B0013HDHB8&usg=__EaSQF5Wni8Lg2YhylLfDsjlprag=&h=280&w=280&sz=15&hl=en&start=19&um=1&tbnid=bFW9zij4REq8KM:&tbnh=114&tbnw=114&prev=/images%3Fq%3Dpyramid%2Bproducts%2Bair%2Bpump%26nds p%3D18%26hl%3Den%26sa%3DN%26start%3D18%26um%3D1]This will last longer than your JJJ :-)[/link]


Jason

tonyjms2005

Hi

Thanks, Its ok I haven't got a JJ, It for one of myown built ones.


cheers


Antony


http://tributetothem.com

jason

My Feedback: (1)

Antony

you have more of a chance then

Jason

tonyjms2005

Its a shame JJ dont do all their engines as a kit because then, as you build the engine you can iron out all the flaws, like the semi working fuel rings and bad soldering (maybe with one or two engines, but this is just an example), maybe even do one ortwo mods if you know what your are doing to prolong engine life.

That way you could have a decent engine that will last well.


Cheers

Antony


http://tributetothem.com

Xairflyer

My Feedback: (1)

Solution is to strip it when you buy, make it a kit [sm=idea.gif] we might have a JJJ stripdown thread added soon so you will have no excuses