Glad your turbine is running well on the bench and otherwise than the exhaust all is well. Mounting the temp probe is better when there is no metal to metal contact. I have seen people thread through the joint between the two strap halves but better to get a plastic strap around the thick end of the probe and affix it to one of bolts hold the mounting straps together. The probe is pushed as far forward as possible, this means you have too much length, however, you then make either a 'U' loop or circle which also assists the probe remaining fixed in position 2-3 mm into the exhaust and the main NGV gas exhaust flow.

Paul

rcdriver, thanks i will look into that.

I think the two piece cone is little more efficient but the one piece is easier to produce. Two piece cones were known for coming apart so the small gain may not be worth it.

I think the efflux area was reduced on the one piece at the cost of sightly higher temps but with an increase in thrust. That might also be why the gas turbine builders assocation members found that there was no benefit to smoothing the efflux jet in the rear centre of the turbine wheel on small turbines. Cost was never a consideration to home grown metal bashers but it was amazing how things were done in one way just because thats the way everyone had done it for years. I'll ask the GTBA guys for verification but I know my turbines Chinese or British when upgraded lost the two piece.

Paul

Sounds right to me Paul.
But then there are still a lot of two piece cone makers out there, unless by small you mean smaller than the P-70 size. Otherwise it seems everyone would go this route.

"I think the two piece cone is little more efficient but the one piece is easier to produce."

That's about right, Mark. A two-piece cone has the potential to give most thrust, but the two parts have to be matched carefully for the best effect and that takes time and knowledge. The single, straight-sided cone gives the least thrust but is easy to make. The machined version we currently use on the 44s and 54s (not straight-sided but with a curve to it), is almost as good as a two-piece one - but the very best of the two-part ones might exceed it.

Sara Parish
Wren Turbines

Mark

Yes there certainly are many many manufacturers worldwide with twin cones and I've got three types in the workshop TT66, JP66 and a JG100 that I would not change or make a single cone for. On the smaller types, its attempting to wring the max thrust from these miniature turbojets that's the driver. I'll have a surf tonight and look at the minute Lamberts and the Bee.

Paul

Hi Sara

Hows the new place? Don't see you on this thread rarely. Mark you was right, I'll go to the foot of our stairs! Still rereading the GTBA back newsletters if it was simply a matter of throwing away the centre cone piece, with no effect, for costs saving, why then reduce the efflux area.

Paul

The area should be about the same following the area rule. The center cone takes up some space so the outer cone must make up for it with a larger diameter opening. You can squeeze the area on either type and get more thrust and higher temps.

Thanks Sara for making it appear I know what I'm talking about

You know more about it than me Paul. I just have a little knack for understanding SOME things

I don't know if it is applicable here but in real aircraft engines the inner cone does something more.
It stops hot gases from touching the turbine wheel center were the mounting bolts and the last bearing (from the inside) is located.
Chris

Thanks, guys! I've never posted on this thread before because it's for JetJoe OWNERS and there is no way that I would EVER be one of them.
However, I've always followed the thread and this seemed to be a sensible bit of discussion between knowledgeable people so I thought I'd add to it. Mark, you are certainly right about the area-ruling - in the days when the MW44 had a two part cone (the only one it would run with) the guys would be there with calipers and calculators, measuring, mixing and matching tailcone inners and outers to get the best permutations. There were always some left over, it was very time-consuming and uneconomical, so it was a relief when Mike Murphy developed the engine to a stage where it would take the machined one-piece cone.

Sara Parish
Wren Turbines

Cheers Mark

Lambert 15N (1.5kp) at 243,000 RPM is twin cone also a twin.

Paul

Here is the reply from China:
----
The two pcs tail cone is the latest and upgraded parts for JJ-1400.
Unless you have any special instruction asking for a one pc tail cone, we'll send only teo pcs tail cone.

B.rgds
Joe
----

I admit it.. im confused now.. [&:]

Hi to all!!
Somebody has the complete list of the 31 parameters of the hidden menu of the JJ1400 Full Auto Regal Fadec to know what is each one?

I couldn´t start my turbine yet!
It only spins the motor one time for one second and the RPMs in the displays are crazy!


Thanks!

go to http://www.espiell.com/users1.htm, click on your fadec version and save a copy of the manual, there you will find all parameters..

Try the link minus the commar, I don't think the hidden parameters are given out (though I maybe mistaken) only data on the open parameters. If the fadec's fuzzy logic shows high rpms on screen when the starter engages then eliminate any electrical noise. Keep the hall pickup clear of stray magnetic sources such as fuel pump, solenoid valves, glow plug wire, or servo’s, as the magnetic field generated can upset the rpm reading and abort the start up. Gasper may shortly be pulling the above link and nades.net. I tried his jets-munt.com site for the new 'help forum' but the link was missing.

OK the tail cone issue has been resolved, here is what JetJoe china said:

----
Gabe want all his turbine ship to USA with one pc tail as his special request.

Any way we can ship you one pc tail pls re cfm your address again.
---

This would explain why all US engines have one piece cones, and would also say something about JJ's support - sending me a new cone with no questions asked.
BTW - when i first got the motor a few months ago, one of the solenoids was stuck, i emailed JJ and 2 days after it was in the mail, no questions asked.

Seems like JJ is trying hard to give the best possible service, i appriciate it.

guys,

any idea if the bolts on the tail cone are just standard 3mm bolts ? i would like to change them over to my own liked hardware (black steel 3mm bolts) but these bolts are silver colored and so i wonder if they are made of a different material due to the heat ?

can standrad black steel 3mm bolts be used ?

...not a good idea, the rear rings are made out of some degree of stainless steel, and so are the bolts. Replacing them by the black steel ones will cause corrosion in long therm, has other temp./expansion coefficients and so a possibillity the bolts got seized up in the holes, breaking off at removal......you don't want that. Stainless steel bolts are howerer everywere to obtain, not very rare so I wouldn't tamper with that! (Been there, my home built engines has all ss bolts where I tried others in the past.)

Good luck,
Gerald

Might somebody help me. Would like to know what type (name/number) of compressor wheel is used on the JJ 1400 sice would like to upgrade a homebuilt one if possible?

Go to post 773 for the details on the compressor used

Paul

Thanks Paul,

But I think the Garrett 446335-09 and 446335-10 are the 10 bladed and not the new 12 bladed.

Regards

Orl

Orl

You might order from JJ a 12 blade unmachined compressor and then balance and profile to your intake cover. JJ orders hundreds and you will not beat bulk discount by ordering just one from garret.

Paul

Thanks again Paul,

Do you think reprofiling will reduce thrust or better make a new intake cover.

Regards

Orl

Orl

The profile of a Wren 54 and JJ is slightly different and also to outside smaller front face diameter. More important thouigh is reducing any gap losses that was ignored by the Chinese machining early on.

Paul