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  1. #226

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    RE: Jetlegend Mig 29 Fulcrum

    Rob,
    I had 18 flights before I grounded it due to the unreliable undercarriage. It fly's good and has no tendancy to snap. It will operate in a wide speed range from some slow high alpha stuff to fast low passes. I use a Merlin 160. I started with the CG as stated and at this position it fly's OK but is nose heavy and requires quite a push inverted. I was gradually moving the cg back and dialling a mix for knife edge flight when I stopped flying.



    John
    CRASHING IS NOT AN OPTION.

  2. #227
    Jim Cattanach's Avatar
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    RE: Jetlegend Mig 29 Fulcrum


    ORIGINAL: JohnMac

    Hey Jeff,
    Any news on mine??
    Or mine. Jet legend do not respond to my e-mails asking about a delivery date.
    JET FLYING:- Resistance is futile. You will be assimilated.

  3. #228

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    RE: Jetlegend Mig 29 Fulcrum

    i just ran a short simple test of the landing gear - and when air is in the system the landing gear is extremely smooth and locks positively both up and down with the fimiliar "click" sound, but if the gear is down and i drain all the air from the tank (i.e. in the event of a pressure leak) - i can get the mains to retract only from applying a little forward pressure on the tire with my hand.
    since the main gearss are angled towards the nose of the aircraft, im not sure if after loss of pressure (gear fail safe) one will be able to land safely with no damage (due to the rear "pull" on the LG when the plane is rotating forward) or they will retract back in once the pressure of the weight of the plane is applied upon landing.
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  4. #229
    Jim Cattanach's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    How long did your Mig 29 take from order to delivery?
    JET FLYING:- Resistance is futile. You will be assimilated.

  5. #230
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    RE: Jetlegend Mig 29 Fulcrum

    Edgar, Ian,

    I called the supplier in Florida and learned that the connectors are not in stock as indicated in Edgar's post. I then called Shepherd controls in TX and increased the check valve order to 9. The check valves are in stock and will be shipped next week. The connectors are scheduled to be received by the NY distributor and are supposed to be shipped around 1/13/11. So, parts are on order and I'll distribute them to you when received. In the meantime, would you please PM your shipping address to me? Also, Dreamworks has the 4mm to 3mm reducers as well as the 3mm tees we'll need to complete the plumbing ( 6 of each ). They also have the 3mm tubing needed.

    JL has definitely changed the gear mechanism in the Mig. I expect they've removed the piston and replaced it with a solid piston without the ball bearings. I'll post details when my upgrade is received.

    regards,
    Rob
    Don't look back, they may be gaining on you!

  6. #231
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    RE: Jetlegend Mig 29 Fulcrum

    Wow mate that looks great. No wonder you have a big cheesy grin
    I must say JL models seem to get better and better. Can't wait to get mine now.
    Regards,

    John

  7. #232

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    RE: Jetlegend Mig 29 Fulcrum

    Guys,

    I havent taken my LG out of the plane, so i have no idea what is inside to be honest. is anyone recieves an upgrade it, i suspect it would be much easier to tell the difference once everything is outside of the model. the difference that IS visible is the outer locker on the mains. that wasnt there before. perhaps this is because there is now no internal lock ?? im not sure.

    Here is a short clip of the Landing gears retracting and opening. i was using a tiny air tank so it was only good for one run:

    [youtube]http://www.youtube.com/watch?v=iVpQkZfJTuI[/youtube]
    www.liorzahavi.com
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  8. #233
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    RE: Jetlegend Mig 29 Fulcrum

    Wasn't the problem that the gear ceased to work after 4-5 flights, not that it wouldn't work at all?
    Tom Perry
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  9. #234
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    RE: Jetlegend Mig 29 Fulcrum

    John,

    What pneumatic system for the doors are you using? Satisfied with it or would you do it differently? Thanks for the flying characteristics and suggestions.

    Regards,
    Rob
    Don't look back, they may be gaining on you!

  10. #235

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    RE: Jetlegend Mig 29 Fulcrum

    Rob,
    I have fitted a simple JL retract valve servo operated and controlled via a delay programmed through my Futaba 14MZ tx. It is just a matter of getting the timing right.




    John
    CRASHING IS NOT AN OPTION.

  11. #236
    Aussie Bart's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    That's interesting what they had to do to try and get the gear to lock, considering JL claimed there was nothing wrong with the other design, guess I will have to keep an eye on my mailbox to see if the upgraded parts magically appear.....

    But on a serious note, I see that they have not changed the nose leg locks. On my last flight at the Temora meeting, I actually had the nose leg collapse under heavy braking to the point (!) that the probe out the front of fuse has ground down (along with the front knuckle on the nose leg), as soon as I got off the brakes the leg popped back up. Now I can't tell you if the leg was fully locked down but my air tanks were full.

    As for your questions Rob, I am not sure of number of flights total but like John I stopped flying her when the gear was bad as I just got sick of flying with at least 1 leg hanging, since the upgrade I have only had a handfull of flights but each one of them has been magic, I am now not ashamed to take it to the feild.

    I fly mine with a P160 SX and use the centre of the front spar as my CG point (thanks John) and it now needs less elevator in the hard turns. I built a new pipe for her with a bigger bifrucation junction and bigger legs which resulted in 65mm outlets, this has certainly added more power to the flight as the old 55mm outlets were just too restrictive in my view.

    As for doors, I use a jectronic valve and an Airpower sequencer. The sequencer controls the doors and the hydraulic system. All the doors are left open when the gear is down, from what I could see during research this is the same for full scale.

    One last point, and not wanting to put a dampner on things, but keep an eye on the "new" JL locking system, those legs are very long and the lock is soooo close to the pivot point that the lever ratio is very large. 1 kg of force pushed forward on the leg will be like 20 kgs of load on the lock. The leg sits at only a few degrees of angle when the plane is on the ground but when you come in at 15 degrees of alpha and you put that 15 kgs (plus g load) of plane onto the legs, I think the locks will be under a lot of stress.
    I only say this because of the work we have all done on the hydraulic conversion, and looking at how far out from the pivot the main cylinder attaches, and we still got a lot of movement (sponginess) on the legs hence why the pilot check valves have to be fitted. I just hope Yang backs up this mod properly.
    Bart

  12. #237
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    RE: Jetlegend Mig 29 Fulcrum

    Rob

    I was talking to a friend last night who was setting up a UMS system for a different project and he made an off hand comment about how stiff the control valve was to move, just like yours. After a bit more dicussion, we came up with the thought (which I had not warned any of you guys about) that the valve may not be mounted on a sufficiently flat surface or that the screws he used to bolt it down are too long.

    The threads in the valve are rather shallow and are directly in line with the spool, and if you put in screws too long they WILL deform the aluminium and bind the spool, same goes if you mount it to a plate that is not truly flat, that is why I use carbon fibre plates (sheet from Hobby King).

    From my experiance, without the valve mounted you shouild be able to shift the spool quite easily once the seals "break free" (stiction on the o rings), when you mount the valve it should be exactly the same. If you get a chance, back off your screws a bit and see if you can move it by hand.

    If not, pop the E clip off one end of the spool and pull the spool out, have a look on the spool for any shiny spots, this indicates that the spool is rubbing, if so you may need to wrap a bit of 2000 grit wet & dry paper around a bit of rod just smaller than the bore and try and lap the high spot out of the valve body, just don't get over zelous.

    As I mentioned before, the load on the valve spool hardly changes whether fully pressurized or not as the spool is pressure balanced design.
    Bart

  13. #238

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    RE: Jetlegend Mig 29 Fulcrum

    question for those with the old style landing gear - if you leave the LG open and drain all air pressure - does the gear remain locked or can you retract it by applying pressure to push the main wheel forward ?
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  14. #239
    Aussie Bart's Avatar
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    RE: Jetlegend Mig 29 Fulcrum


    ORIGINAL: i3dm

    question for those with the old style landing gear - if you leave the LG open and drain all air pressure - does the gear remain locked or can you retract it by applying pressure to push the main wheel forward ?
    The original system had the locks inside the cylinders and once the gear was down it would stay locked indefinitely until the retract side was pressurised, this was great for the first 20 times............
    Bart

  15. #240

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    RE: Jetlegend Mig 29 Fulcrum

    Then i suspect that the new system has better locks once pressured, but might expirience a problem with loss of pressure.
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  16. #241
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    RE: Jetlegend Mig 29 Fulcrum

    Well it appears the locking system is now like a standard retract built into the trunion. I bet they got rid of the cylinder locks all together. Just remove one of your cylinders Lior and unscrew one end. Should only take about 5 minutes to check

  17. #242
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    RE: Jetlegend Mig 29 Fulcrum


    ORIGINAL: i3dm

    Then i suspect that the new system has better locks once pressured, but might expirience a problem with loss of pressure.
    Not much fun if you have an air leak!! even if you have a low pressure fail safe system like a Tam Jets or a 42% unit. At least with the old system it stayed locked (which was why it would not retract when it was supposed to) like a conventional retract unit.
    Bart

  18. #243

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    RE: Jetlegend Mig 29 Fulcrum


    ORIGINAL: ianober

    Well it appears the locking system is now like a standard retract built into the trunion. I bet they got rid of the cylinder locks all together. Just remove one of your cylinders Lior and unscrew one end. Should only take about 5 minutes to check
    the long cylinder still has air inlets on both of its sides, so it should still have a shuttle of some sort inside, ill pull one out and have a look.
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  19. #244

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    RE: Jetlegend Mig 29 Fulcrum

    OK guys so i took the long cylinder apart, and the new shuttle is basically a tube with 2 O rings on its OD to seal it to the ID of the outer tube. it does not have any ball bearings or any lock mechnism. the lock of the mains comes from the new Trunion block assembly.
    The problem is, as mentioned before, that these struts are huge for the size of the retract base, and therefore when no air is in the system, it is fairly easy to get them to retract when pulling the wheel forward.
    Once pressure above 20PSI or so is in the system, it seems to work well and lock positively.

    Does anyone have any ideas on how to make sure this gear stays locked even without air pressure ?
    Perhaps a hydraulic conversion is still in order ?
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  20. #245

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    RE: Jetlegend Mig 29 Fulcrum

    ORIGINAL: i3dm

    Guys,

    I havent taken my LG out of the plane, so i have no idea what is inside to be honest. is anyone recieves an upgrade it, i suspect it would be much easier to tell the difference once everything is outside of the model. the difference that IS visible is the outer locker on the mains. that wasnt there before. perhaps this is because there is now no internal lock ?? im not sure.

    Here is a short clip of the Landing gears retracting and opening. i was using a tiny air tank so it was only good for one run:

    [youtube]http://www.youtube.com/watch?v=iVpQkZfJTuI[/youtube]
    I had a problem with the landing gear on my f-22. I chose to replace the air cylinders. I purchased them from dreamworks and my gear works perfect now. I have also heard people are using teflon tape under the o-ring. Its most likely blowby. I can get 5 to 6 cycles on my landing gear now.

    Sincerely,

    Eddie

  21. #246

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    RE: Jetlegend Mig 29 Fulcrum

    So I've fitted the upgrade to my MIG and so far I'm quite pleased with the results. The mains units seem to work well and hold pressure and whilst I understand where Bart's coming from regarding the forces acting upon the new part I think it will be ok considering there is still the main cylinder providing force also. I'm not sure about the the nose unit though as there is no locking mechanism on the cylinder whatsoever. It just relies on the pressure so when at 100psi you can, albeit with some force, push the strut backwards. However, being the 'glass is half full' kind of guy that I am, I also think that this may be a good thing. I don't think that under normal landing forces it will go backwards but consider if there is a mishap and the model lands long, hits an obstruction etc. The fact that the nose strut can move backwards may save the nose leg and/or nose section. Ideally though, it would be better to have a proper locking mechanism...

    Jeff
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  22. #247

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    RE: Jetlegend Mig 29 Fulcrum

    Jeff,

    Im worried from what might happen in case of an air leak ?
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  23. #248
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    RE: Jetlegend Mig 29 Fulcrum


    ORIGINAL: jeff sewell

    So I've fitted the upgrade to my MIG and so far I'm quite pleased with the results. The mains units seem to work well and hold pressure and whilst I understand where Bart's coming from regarding the forces acting upon the new part I think it will be ok considering there is still the main cylinder providing force also. I'm not sure about the the nose unit though as there is no locking mechanism on the cylinder whatsoever. It just relies on the pressure so when at 100psi you can, albeit with some force, push the strut backwards. However, being the 'glass is half full' kind of guy that I am, I also think that this may be a good thing. I don't think that under normal landing forces it will go backwards but consider if there is a mishap and the model lands long, hits an obstruction etc. The fact that the nose strut can move backwards may save the nose leg and/or nose section. Ideally though, it would be better to have a proper locking mechanism...

    Jeff
    Hey Jeff

    Just for reference, these are some photo's of nose gear knuckle and probe and the damage from when the nose gear collapsed at Temora this year. It was the last flight with the original air & lock system and there was still over 90 psi in the tanks.
    I don't know what caused the collapse but the plane had all 3 down (only 2 had to come down cause 1 never went up). The landing was the usual mains first but as I had come in a bit hot and landed past the pilots box all I could see was the back of the plane. Interestingly though, the leg popped back up and I taxied off the tarmac without problems.

    Point being that these legs are soooo looong that there is alot of leverage.

    Look forward to the flight reports as I hope this issue is fixed, the JL stuff is just too nice to have this hiccup happening in the background.
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    Bart

  24. #249
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    RE: Jetlegend Mig 29 Fulcrum


    ORIGINAL: Aussie Bart

    Rob

    I was talking to a friend last night who was setting up a UMS system for a different project and he made an off hand comment about how stiff the control valve was to move, just like yours. After a bit more dicussion, we came up with the thought (which I had not warned any of you guys about) that the valve may not be mounted on a sufficiently flat surface or that the screws he used to bolt it down are too long.

    The threads in the valve are rather shallow and are directly in line with the spool, and if you put in screws too long they WILL deform the aluminium and bind the spool, same goes if you mount it to a plate that is not truly flat, that is why I use carbon fibre plates (sheet from Hobby King).

    From my experiance, without the valve mounted you shouild be able to shift the spool quite easily once the seals ''break free'' (stiction on the o rings), when you mount the valve it should be exactly the same. If you get a chance, back off your screws a bit and see if you can move it by hand.

    If not, pop the E clip off one end of the spool and pull the spool out, have a look on the spool for any shiny spots, this indicates that the spool is rubbing, if so you may need to wrap a bit of 2000 grit wet & dry paper around a bit of rod just smaller than the bore and try and lap the high spot out of the valve body, just don't get over zelous.

    As I mentioned before, the load on the valve spool hardly changes whether fully pressurized or not as the spool is pressure balanced design.
    Bart, did as we discussed and backed out the screws, still tight to cycle the valve.

    Any ideas???[]
    Retired

  25. #250
    Aussie Bart's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    Does the valve move smoothly with little effort when you take it out of the circuit?? if not send to me and I will fix it for you.
    Bart


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