i3dm

My Feedback: (51)

I agree with every word. well put !

mafrasca

For cheap jet kits see this link

http://www.injetdesigns.com

Enjoy!!!

knobby1

I'm affraid "Ducted Fans" just don't do it for most of the people on this thread, mind you some of them do get up and go pretty well.

Cheers,
Smithy.

Boomerang1

Is the Tigerjet a variant of the Skyburner? Could have Wren 44 potential. - John.

knobby1

Hi all,
Just an update on the afterburning JJ1800, as you may know, I was having some minor dramas getting the A/B to light-off reliably, well, after a great tip from somebody who shall remain nameless, (you know who you are!), many thanks to him! The A/B lights-off every time now, no matter what the rpm, kinda gave me a little fright when it "cracked" the first time at higher rpms.....just like the real jet cars, those that have witnessed a jet car in person will know what I mean..... absolutely awesome!!

I'll have to do some more thinking as to the pipe exit diameter, at the higher rpm ranges for the 1800, 75k+, where the engine starts to make some serious noise, the temps are getting up toward the 680+ range, which makes me a little uncomfortable as I like to have plenty of temp margin to play with...... my guess is that the tail pipe exit and/or flame holder is a little too restrictive and the air flow isn't quite what it should or could be. I may even redesign the flame holder to make it a little more "aerodynamically friendly" which may help some.

I'm also going to have to rethink my A/B fuel supply system, the normal "tygon" type fuel line just isn't up to the heat and starts to melt, which is not a good thing[X(] .....methinks a small stainless steel supply line is in order for this job. All in the fun of doing it I'll keep you all updated as to how it goes.

Cheers,
Smithy.

Strykaas

STOP TEASING WE NEED A VID !

rorrock

Knobby,
In terms of heat and heat dispersion for your fuel supply.. have you thought of creating a stainless steel piping that runs the cool/cold fuel around the hotter portion connecting to the feed point on the AB. I think this would do 2 things for you..

1. Remove heat from the pipe prior to the fuel tank..
2. Heat the fuel before entering the AB making it combust easier..

Rob

knobby1

You're quite right of course, I am teasing you, my appologies.... The vid should happen hopefully on Sunday my time here in sunny Sydney, a friend and I will get it all set up and I hope to take some nice stills and a video as well. I'd just like to get it running as nicely as possible before I make a complete idot of myself on camera!! Patience grasshopper

The thrust of the thing seems quite good too, gives quite a decent "kick" when the burner is lit in the higher rpm range, I might have to beef up my engine mounting to handle the extra, wouldn't want it shooting off into my neighbors yard or into the street, I don't think that would go down too well with the local constabulary

There's also the question of compressor surge if the burner can pressure starts to override the compressor/diffuser pressures and starts to disturb the airflow, but at this stage of proceedings I don't think it will be too much of an issue....I hope! There's lots of little things to think about, it's not just a matter of bolting the afterburner on and going for it, I have to be mindfull of the bearing lube system which relies the pressure differential between the back of the compressor wheel and the shaft tunnel, if I back the pressure up too much downstream it may effect the lube flows...time will tell. Stay tuned.....

Cheers,
Smithy.

knobby1

Hey Rorrock,
Many thanks for the ideas, I'm open to all suggestions, I have some 1/8" stainless piping running into the the can, it then travels to a "T" piece and is then formed into a circle and is directly in the exhaust flow, so I think/hope it gets plenty hot before the fuel exits the spray ring nozzles.

Combustion of the fuel is not a problem at this point, I have a small, "hot streak" system just downstream of the turbine wheel, this small fitting is the one which melts the tygon tubing attached to it, I think I've got it sorted though, my flexible tygon fuel tubing from the A/B pump was just too close to the jet pipe, I've just made it a little longer to get the tygon tube a little further away from the heat . I have a "T" piece in the A/B fuel line from the pump which distributes the fuel to the "hot streak" and the A/B spray ring, there's a small 0.015" restrictor in the hot streak supply line which limits the amount of fuel at this point.

Cheers,
Smithy.

Ed

Is there any way to check and verify that the bearings are receiving an adequate supply of lubrication ?

> Jim

fw190pilot

Easy take cowl off and blow through lube line if it is open bearings are getting oiled.

Ed

I think that's only an assumption that they are getting enough oil.

> Jim

KC36330

the only way to know if they are getting lubed with the turbine/afterburner running is with time if the brgs fail, they aren't getting adequate lube/heat dissipation, if they hold up, they are.

Ed

" if the brgs fail, they aren't getting adequate lube/heat dissipation, if they hold up, they are. " ........ .......... .........

That's exactly what I am trying to avoid. There has got to be a better way ?

KC36330

well you could disassemble the turbine, use layout dye to dye the brg surfaces and then reassemble, run the turbine, and take it back apart and check for signs of wear. it would show clearly on the dyed surface.

fw190pilot

All of the manufactures of our turbines have the lube system well sorted out already so no real reason to worry. Use clean fuel good fuel filters with the right oil and oil mix go fly and enjoy yourself.

KC36330

obviously you haven't read and paid attention to why the concern.

Gerald Rutten

I wouldn't be too worried about the oil supply to the bearings. As you all know the oil/air mist distribution within the core-engine works ok already, if the afterburner would cause too much back-pressure to disturb this I reckon the entire engine operation would stall. The whole engine operation principle depends on small pressure variations between impeller, diffuser, combuster outer area and hence into the combustor. (Not by mass-flow as some might think....although you need that as well for power...) Outside the bearing shaft tunnel there is a little over pressure to keep the cooling air going inside the tunnel together with the supllied fuel/oil pressure, would this fail due to back-pressure, the entire engine wouldn't work at all as the other factors mentioned would stop their operation as well. I would be more worried about the EGT rise which would occur, that has to be monitored at all times as the rear bearing is housed directly below the hot section of the engine.

Following this with great interest, keep it going Smithy!

Rgds,
gerald

monkeyking

Hi to all!

I have two JJ1400 that I bought from the chilean dealer.
I have had problems with the two turbines.
I cant reach the max rpms.
I bought one the last year and the other one a few days ago...
Its very rare, because the new one is in a YA Stingray and I saw it flying and it was working very well, but when I bought it it started to fail
I thought that the problem was the fuel...but I went to the local airport and bought JP1...the problem continue...
It takes more than one minute to reach 140K rpms...when it has to take only 6 seconds and the pump only reach a value of PW=300....
I am using Motul 600 oil...I dont know if that can cause the problem.
I didnt change the parameters of the ECU..

What do you think?

Hope you can help me and sorry for my bad english!
Mauro.-

fw190pilot

Did you reset the ECU to your transmitter? Are you using the JetJoe pump or the Flight Works pump? How far is the thermocouple stuck in the tail cone? If the turbine was working well and now it isn't something has changed. Maybe your dealer can help.

monkeyking

Hi!
I will try moving the thermocouple...I think that the problem is there, because its working at 780°C at full stick
The turbine works fine...my dealer is my friend, he is helping me, but I wanted to try here..

How do I reset the ECU?
I am using a Flight Works 200A

Thanks for your help!!!

snir2001

My Feedback: (1)

Hi monkeyking

What type of ECU do you have ?

monkeyking

Hi!
The problem was the thermocouple!!!

I have one NADES and on REGAL.

Thanks!

snir2001

My Feedback: (1)

Great News.

It's good to know that most of the problems are small things...

knobby1

Hey Gerald and anyone else who may be interested,

Thanks for the interest...Well, I ran my afterburning JJ1800 over the weekend, we had a long weekend here in Aus due to "Australia Day", and I'm happy to report no major dramas, I changed the flame holder assembly as I wasn't happy with the restriction it was causing, I believe it's now a lot more "air flow friendly", (As Gerald has mentioned, and rightly so, I've been religiously keeping an eagle eye on the EGT's during running) ...I can confirm this by the resulting lower EGT's which have dropped by some 50c to an average of ~618-624c when running without the A/B and ~640-650c with the A/B running, I'm losing about 1500 rpm on the hit of the A/B also which is to be expected, the same thing happens with our real jet dragster engine, but it soon recovers nicely within a second or two.... so I'm a happy chappy I'm quite comfortable with the engine running at these temps, when she was approaching 680+ I was getting a little nervous[] I was probably worrying needlessly but I belive the cooler I can get it the better, as long as there is plenty of temp margin to play with, i'll be reasonably happy.

One thing I do know for sure, she certainly likes to drink fuel, an educated guess would say she uses close to 1.5lt/min, and that's just through the afterburner[X(] plus what the engine itself uses!!

I was able to do a few runs over the weekend with the A/B at various rpms, the system seems to work very nicely at low to moderate rpms, my mods to the flame holder have given a better exhaust flow throught the A/B can which seems to be causing the A/B to not like to light at higher rpms.., with the older "restrictive" flame holder it would light off ok..... but if I hold my tongue in the right spot, i'll get it sorted

The A/B can pressure at the higher rpm's is forcing the fuel back through the lines and pump into the separate tank when the A/B isn't running, which means I will have to fit a small check valve in the line.... It guess it takes time to sort these thing out.

All in all the A/B system doesn't seem to upset the normal internal pressures within the engine or the lube flow much, if at all, the engine seems to run normally as if the A/B system wasn't even there, the bearings are still nice and smooth, I've had no temp problems that I'm aware of, all seems good at this point, I have close to 30mins running with the A/B system fitted so far, I think a few hours of running will give us a clearer understanding of what's going on.....but at this point, so far...so good.

My friend and I were able to take a video of the engine running, with some A/B action too, when I edit out all the useless junk i'll post it here, hopefully in the next day or two.

Cheers,
Smithy.