RE: JetJoe OWNERS thread
 

I think I know what you mean, not sure if I want to start twisting them through 90deg though, is it important to try to make sure the end of the needles is not touching the vapor tube ?

RE: JetJoe OWNERS thread
 

On the opposite ;) It is very important that the end of each needle IS touchting the stick (vaporizing tube). There is a high airflow through the sticks and if the needle would be in the center of the stick the fuel could blow throug the stick and not being vaporised as soon as needed.

RE: JetJoe OWNERS thread
 

Yes makes sense when you think about it and why the ends are bent in the first place, I am learning all the time :D

RE: JetJoe OWNERS thread
 

The better the vaporizing is the faster the engine can accellerate.

RE: JetJoe OWNERS thread
 

OIC HK - I understand what you mean now. Thanks.

Install VMWARE on my current machine, and run up a WIN98 disk on this machine instead of installing it on a refreshed old hard disk?

Yah, I could do that. I'm trying to check an error Xair is getting regarding an OCX error some FADEC software is generating. I'm guessing it has something to do with the VB run-time files being from a wrong version or something. I'm just wondering if running it under a virutal machine will respond differently when compared it to running it on a native '98 machine though.

BJ:)

RE: JetJoe OWNERS thread
 

Hi BJ,

Yes, that is wat i mean. The VM is only different in hardware but software will responde exactly the same. You will need to install windows and partition the virtual HD exactly like a normal PC. The best thing is you can make a snapshot and revert to it to redo installations.

RE: JetJoe OWNERS thread
 

Kewl - thanks HK.

I might give that a try.

BJ:)

RE: JetJoe OWNERS thread
 

And thanks Xair and HK re the JJ1400 'service'.

I've put together a nice little document on 'How To Service a JJ' from your info, pics and advice. Thanks for that. :D

The info regarding the left-hand thread is invaluable - I've only just recently buggered up my electric Mitre-saw because I didn't have a manual and the blade-retaining bolt was left-hand thread. DOH! [&:] I soon found out when the bolt busted...

BJ:)

RE: JetJoe OWNERS thread
 

Xairflyer, thanks for posting the disassembly pics. While I'm not a fan of the JetJoe it was interesting to see how my Wren goes together. - John

RE: JetJoe OWNERS thread
 

The wren has a better way now of locating/securing the Combustion with standoff spacers from the diffusor like the KJ66, earlier wrens had two glow plugs which I believe was for giving a positive location for the combustion chamber, I might look at adding some standoffs to mine when putting back together as it is a pain when you remove the glow plug and the combustion chamber/plug hole moves.

RE: JetJoe OWNERS thread
 

I burned out the combustion chamber on my Ram 750P. Any chance of someone out there with some pics and dimensions of the JJ-1800 Combustion chamber?

For all the bad mouthing of JetJoe I have read, I have not seen any for sale on Ebay or RCU in the last month or so. Kind of makes me think either disgruntled owners must be tossing them into the trash or work through the teething pains.

Thanks in advance
Roy

RE: JetJoe OWNERS thread
 

Carlos at RTI in your neighborhood can help you out with genuine parts!

Dave

RE: JetJoe OWNERS thread
 

"...For all the bad mouthing of JetJoe I have read... ... either disgruntled owners must be tossing them into the trash or work through the teething pains..."

Or... they are just out there having fun and flying them ??

BJ:)

RE: JetJoe OWNERS thread
 

I have yet to see a cheap one for sale and they would have to be cheap as they are scrap, so only worth scrap metal prices :D

RE: JetJoe OWNERS thread
 

Lol....

My JJ is running smoother every time. I now have a max egt of 560c af 167.000!!! And to think i started with 800c at 160.000

RE: JetJoe OWNERS thread
 

To learn more about JetJoe turbines, and see why JetJoe has had such a bad wrap, I thought I would take a series of pictures of all the bits of my turbine before I rebuild it after its service and stick them up here and have each one scrutinised one by one.

First I want to say when I bought my Turbine I never heard of Jetjoe or its past, The Jet World Masters 2007 was coming to Enniskillen which is 45miles from me and an opertunity to take part arose, I had intended to fly a ducted fan, but was told about a turbine from Australia called a Model Jets 1400 the price tempted me to buy it, I never thought at that time I would own a gas turbine and if the JWM had'nt came here I would probably not be writting this.
I spoke to Model Jets in Australia the guy was friendly with our local JWM organisers, having meet at previous JWM so ordered it up.

It was only later on that I discovered that the MJ1400 and the JJ1400 were the same engine and it was being assembled in Aus by ModelJets and re branded, my turbine has a ModelJets stamping on the case.

Truth be told If I had of read the neggie stuff first then I probably would not have bought one, but I would not have bought anything else either, due to the cost, and second hand tubines were not as common as they are now.
I am glad now I did'nt know about all the problems, because I have been flying a turbine powered jet ever since. It could have blown up of course on the first runs and I would have been a neggie too!
Maybe I was lucky, after I learned how to get it running from a fellow flyer, it never failed to start, run or has ever flamed out.

My fellow jet flyers were all weary of it at the start but now just accept it like any other and all love the distinctive whistle it has in flight.

My gripe at the start was it not producing the claimed 14lb thrust, and cost me flying in the JWM with my JL T45 Hawk, problem was sorted aftwards however with a new single piece tailcone.

As I recently bought a S/H Boomerang with a MK2 Wren 54, I decided to strip my JJ1400 as I will still have something to fly.
The ECU shows 694mins, my Bobcat timer was set at 4mins 45secs due to the small tank, with startup and shut down time it is about 7mins so it has had a good few flights.

I dont like big long posts myself so I will start uploading the pics on another one and txt relating to each part.

RE: JetJoe OWNERS thread
 

The assembly of the engine is very important. If it is nicely assembled it will run cooler and have much a longer life. If it is (re)build by a company that puts more care in to the assembling then it is a much better engine. The main problem of jetjoe is their assembly level. It is very very very low. The basic engine is a good set of components. It needs carefully balancing and the right pretension on the bearings ect. Jetjoe just puts them together without checking and then ships them to customers. If you are lucky you get a good engine but a lot of them are not that great. You have a rebranded / build engine which is much better compared to the factory jetjoe's even though you can hardly see the difference if you put them together.

In europe the jetjoe's cannot be sold without modifications. There are some companies here which do the same but a few have stopped because it was to much work.

RE: JetJoe OWNERS thread
 

From my simple strip down and learning curve about this turbine, I can’t understand why there has been so many problems.
My engineering knowledge is fairly good in most areas, but I am no expert in gas turbines design or workings. But I can look at it component by component.
The gas turbine engine has a small amount of basic parts, where can the flaws be ?
I am not really interested for now in better design, efficiency etc just materials and mechanical build to give a reliable running turbine.

There are very few components in this type of turbine, forget about starter motors, FOD screens etc the layout of my 1400 is shown below.

Start with the simple stuff to get it out of the way.
The outer case is made from stainless steel and very well formed (spun) all the holes are on a perfect PCD.
Similarly the tail cones (single and twin shown) are well made and holes line up perfectly with the case. As mentioned tailcone design will effect thrust but for now I am only concerned with is it well enough made which it is.

RE: JetJoe OWNERS thread
 

At the front you have a compressor wheel - mass produced commercial item not sure who makes it, but it has a stamp on it which looks like a S, anyway it is a bought in commercial item probably from a turbocharger.
Balance on theback has been machined

Around that a Diffusor and front cover, these are multi axis CNC items from alum and both beautifully made, so so long as the CAD drawing was correct the first day it will be perfect every time.

Bolted to the diffusor is the shaft tunnel, again out of alum, this holds the bearings, very simple item which anyone with a lathe could make, dimensions need to be correct for the bearing outer case etc but no reason for it to be wrong.
Inside the shaft tunnel is the preload spring and spacer again once you know what the prelaod should be easy enough to duplicate and make each time.

Similar the main shaft simple machining part from tool steel ? bearing journals again must be correct to prevent early wear.

RE: JetJoe OWNERS thread
 

The basic problem is leakage. Check the casing on the inside where it sits against the NGV. In the 2 engines i had it wasn't flat, there was a small uneven ring of metal towards the inside of the casing. The NGV leaked there a it. Also the o ring between the ngv cover and the casing may leak if the casins is tightend to much because the casing is just a bit to large.

The next problem is the fuel ring. In a lot of cases some needles where blocked.

Fixing these issue's can reduce the egt alot.

RE: JetJoe OWNERS thread
 

Yes I believe the problems are in assembly, once I get all the bits uploaded and confirmed they are good or bad we can look at how it all goes together

RE: JetJoe OWNERS thread
 

Great info. Here's my JJ1800 powered Topgun Mig 29.
Steve[youtube][/youtube]http://www.youtube.com/watch?v=bHoZD1fBSf8

RE: JetJoe OWNERS thread
 

As you said, you don't have knowledge in gas turbines. They are very deceptive. The shaft tunnel for example. Looks fairly easy to make and it really isn't all that hard. You do, however, have to make sure that the faces are as concentric and parallel as possible. Get this wrong by 2-3 microns and the bearings might wear prematurely or even the turbine might not run at all. Looking at the pictures it seems that the holes in the rear of the diffuser which are designed to let cooling air through to the bearings are blocked. In the original Wren there was a fine mesh screen there. This could lead to insufficient lubrication and bearing failure. (hmmm.... do a lot of JJ's have bearing issues? :eek:)

There are other things that you can't see that may be of importance. For example the turbine is cast from Inconel 713c. At least it's supposed to be cast from Inconel 713c. The casting process is difficult and expensive. It's easy to use a different casting process that produces a different grade of Inconel. This reduces the already low margin of safety for these turbines. Some turbine mfg's x-ray their turbines to make sure that they don't explode on you. A failed test means that the whole batch of turbines is scrapped. *Expensive* (Ever wonder how JJ can produce low cost turbines? :eek:)


These are only a few issues that can be problematic. My point is that JJ's are inferior motors made to sub par specifications with little or no understanding of the real issues faced by turbines. The user pays for these with problems, lesser performance and reduced safety.


p.s. I have seen claims that the JJ turbines are x-rayed. Coming from a mfg with a history of copying and cutting corners I take these claims with more than a grain of salt.

RE: JetJoe OWNERS thread
 

There are no air holes in the diffusor??? I have seen different designes of those holes but it is only weight reduction. The bearing cooling is done by a 2mm hole in the front of the tunnel opposite of the lubrication line. It is fed with compressed air from the front of the engine.

RE: JetJoe OWNERS thread
 

I may not be an expert but I do understand engineering and yes I know it is important that surfaces are machined accuratly, I do own my own Lather mill and CNC. Would it surfice to say that my turbine which had no vibration had fairly good level of accurate machining ?

Which holes in the diffusor are you reffering to? none of the holes are blocked, and I hav'nt even wiped it from diss-assembly Looking at the wren diffusor I cant see any additional holes other than the three to mount the CC.

I believe early engines did have bearing failures but for one they were using sub standard bearings and balance from the factory was not always good.


Hav'nt got to the turbine wheel yet, hope to get more uploaded tonight.