heliweb

Someone could explain or show a picture of bearing preload system used by JetJoe engines

gregmax

On my JJ1400 the shaft tunnel contains 2 groves that house O rings at either end where the bearing seat is. These O rings rest against the bearing quite tightly and dampen their movement fore and aft.
At the front of the shaft tunnel there is a spring retained by a circlip seated in a groove just after the rear of the front bearing, this circlip also presumably stops the front bearing being pushed too far down the shaft tunnel. Next is a thin walled tube that sits inside the shaft tunnel and rest against the spring at the front bearing end and sits against the rear face of the rear bearing.
When the shaft is inserted into the shaft tunnel and the spinner nut tightened this compresses the spring inside the shaft tunnel thus producing the bearing preload.
Exactly the same system as used by other manufactures but the other manufactures do not use the O ring anymore as the O ring can cause problems.
Hope this explains it to you?

Greg

rcdriver22

My Feedback: (1)

In 1999? some homebuilders found a preload helped the bearings and the expensive ceramic bearings contain concentric and misalignment on shaft with expensive ceramic ungaged bearings live long with the shaft a 120k revs i,e very high revs.

See gregs photo
http://www.rcuniverse.com/forum/upfi...66/Ys49507.jpg

i.e. 1200 low life,
JJ1400 pre load bearings long life. OK

turn and burn

andy will be at the blackpool jet meet tomorrow with his jj if any one wants to see one .i will not be there wife is due to have our babby any day now

angturbines

Hi All,
The cc is located on the NGV but not a tight fit , the only real means of keeping the cc in the correct position is with the plug. If the fuel and gas lines are not quite set in the correct form when the plug is removed then the cc will move slightly , If you are building your engine from a kit then you need to make sure that the fuel and gas lines are not stretched or they will cause the cc to move when the plug is removed.Two plugs would give a positive location but it is not usully a problem,

J. Campbell

My Feedback: (31)

You can retrofit the pre-load to the 1200, when you order one, ask and it will be factory supplied with a pre-load. Russ

rcdriver22

My Feedback: (1)

Cheers Russ

Forgot it is readily available as either a retro fit or as an order item for the pre-load. Just about mandatory for any constant use. No other commercial manufacturer, as far as I know, offers any turbines without a pre load today.

It is raining and hailstones so I'm grounded till it clears in the UK. So no test flight of the jets today. I'll get the Hawk moved on and start some jobs in the workshop.

Paul

angturbines

Hi All,
The o ring is not to dampen the for and aft movement so much as to stop the outer cage rotating, the bearing should have a nice sliding fit in the tunnel and should not be tight,lf any tightness exists then the bearing will stick.

ltdorn1

My Feedback: (39)

where can i buy a JJ or at least see a price list?

rcdriver22

My Feedback: (1)

www.jetjoe.com

j_rc_heliman

hey guys i need some help. I accidentally reset my startup parameters in my GB Hobbies ECU and I am trying to do some more test runs on my jj-1200. When i try and start the turbine it spools up to about 18000 rpm and then hangs there running on both propane and kero until it over temps. I set my idle rps to 32k so it just sitts there in startup ramping mode. I think maybe my start ramp value may be causing this. Or perhaps the krappy JJ pump may be giving out on me. does anybody have any ideas?

thanks

turn and burn

my setting are you may need to play a little with this .
full power speed 160.000
idle speed 47.ooo
stop speed 21.ooo
start temp 100c
max temp 800c
acceleration delay020
stability delay 015
pump start point auto+1
pump start ramp004
that is with my jj pump hope this helps

J. Campbell

My Feedback: (31)

In my personal experience when or if the JJ pump goes out, it will always obtain Idle but not full power. You Kero ramp is probably not fast enough thus causing the engine not to obtain idle. Russ

j_rc_heliman

thanks for the input guys.. is there a easy way to check whether to use 1 or 2 pulses per rev? i had thought that jj-1200 had a magnet for 2 pulses per rev, but maybe i am mistaken. I have the remote hall sensor that i bought seperate from Moores Turbines that usually comes with the espiell fadec (although im using a GB Hobbies Fadec).

causeitflies

IR uses 2 pulses and magnet uses 1 pulse/rev.

rcdriver22

My Feedback: (1)

It appears that the FADEC sensors in use are virtually identical using the magnet within the compressor nut to pick up the speed, so it should not be part of the problem. It is difficult at a distance to pin point and you may have thought of these, but substitution is the fastest eliminator. You mention spooling to 18K but with a 6-7 cell pack the starter should be turning well over 10+k anyway, on most of mine when the fuel very first starts, it is at 20+k then spools quickly up to 50k. Sometimes too much fuel is a problem holds the turbine back, so if like the Gasper FADEC setup, follow the start/ minimal pump alignment. Then try

a) disconnect the fuel line and take it to a spare can, run the pump at idle it is steady few drops of fuel and at full a long stream of fuel.
b) Depending on (a) use an exchange pump or borrow a friends pump.
c) Using spare line, blow into the fuel line into the jj1200 there should be a little resistance but you hear the air entering (or use the propane bottle for higher pressure test). I also filter my fuel at four points prior to the fuel getting to the pump, it amazing the gunge and crud that is trapped on intitial runs.

T+Bs Fadec settings with mine in brackets if different for initial setup runs

full power speed 160.000 (not sure of top rpm for early JJ1200s)
idle speed 47.ooo (45K)
stop speed 21.ooo
start temp 100c
max temp 800c
acceleration delay020 (accel ramp 25)
stability delay 015 ( this will depend on your unit.)
pump start point auto+1 (auto +0)
pump start ramp004 (start ramp +5 (+3 with flightworks pump)

Hope this gets you up to 50K idle and then on to full power.

Paul

rcdriver22

My Feedback: (1)

Blue devil with two JJ1400s (previously used J66). Available thrust 28lbs, take off probably needs only 20lbs from full brakes for 2/3 rotation off the strip. Obviously, 14 lbs thrust for our grass strip wasn't viable with this model, but two JJs is just slightly overkil for powerl then again it validates the twin setup arrangements. Gone flying.......

Paul

j_rc_heliman

ok guys. thank you for all the help! Im going to test out the new setttings this afternoon and then ill let you know how it went.

turn and burn

paul how is the jet with twin jj

JohnVH

My Feedback: (38)

Im curious, how many people out there own these engines, and how many are having good, and how many having bad luck.

Maybe we need a poll?

rcdriver22

My Feedback: (1)

T+B

Two JJ1400s were mounted and tested on the Blue Devil and I was going to the field on Friday to fly but had to wait in once again for a delivery of jet Hawk parts. The problem I have is that the BD needs a perfect setup as I have NO Rudders, so if one turbine goes out the plane may well just spiral in[] if I don't close down the other quickly enough, though the parallel high fins will help. While stopping is extremely unlikely to occur as since any air in the fuel line would knock out both turbines together, I need to be confident in all areas when going dead on one turbine.

Also I try not to experiment or maiden (too often) at the weekends, as it completely stops lots of people flying while I monopolize the flight strip. So I expect to go this Wednesday as I promised a potential JJ user I'd go when he was available to act as crew for the CO2. I'll report back when she flys.

Paul

gregmax

Paul,
What plane is the Blue Devil?
Who makes it and where can one buy one from etc?

Cheers

Greg

rcdriver22

My Feedback: (1)

I placed Wanted Adverts here and in five other NGs asking for any non operational Jetjoes as I'd buy them. Got zero replies.
I guess people don't have them or simply they got them fixed by return to the factory. Most who built theirs know the score and got them running. Those who ordered recent MKs have them running out of the box. So no bargains for me[&o]

Better to ask "Anyone still not got their JJ running?? post here with its JJ number"

gregmax

My JJ1400 bought direct from Joe in China worked fine out of the box. I supplied my own fuel pump (from a KJ66) Fadec and ancillaries. For the price it cant be beaten and as has been said before you get to a certain extent what you pay for. With a little refinement and extra care from the manufacturers it will be an even greater bargain
All in I am very pleased with the JJ1400 so far

I got my rotating parts back from Andy (JJ UK rep) the other day as I sent them off to be rebalanced, it needed quite a bit of rebalancing judging by the photo's below compared to the photo's I posted previously, Andy also replaced two of the fuel ring needles!

rcdriver22

My Feedback: (1)

Greg

This is a really nice model called the Black Shark/ Blue Devil, mine is black underneath and it really looks a bit 'vulcanized' in the sky. It is made by http://www.jetwelt.de/2-jetwelt_1.html. There is cavanous huge capacity for fuel load near the c of g with maybe upto 18 minutes depending on the stick position and turbine setup. Not a bad price, great for grass strip flying with the usual high AOA landings possible.

Paul