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  1. #101
    Aussie Bart's Avatar
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    RE: Jetlegend Mig 29 Fulcrum


    ORIGINAL: Alex48

    Very interesting mod Bart, thanks for posting. I've just ordered a load of stuff from UMS to have a play with and your thread will be a great reference. I presume all the gear doors are still air?

    Cheers, Alex
    Alex

    Yep the door cylinders remain as air and the gear and doors are still run off the same sequencer as before, just plug the hydraulic controller into the sequencer in place of the old gear air valve. You will need to Y lead the directional valve servo onto this and set the end points or servo throws to suit.
    Bart

  2. #102
    ianober's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    Here are some shots of my modified pistons for the hydraulic setup. They went pretty fast, a couple hours in the garage and I am set!! Now I am just waiting for the parts from UMS.
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  3. #103
    Edgar Perez's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    This may be obvious to you guys, but I was wondering why the pistons need to be modified. If the air does not leak, why we need to fiddle with the internals?
    Edgar Perez
    Puerto Rico

  4. #104

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    RE: Jetlegend Mig 29 Fulcrum

    The original pistons are hollow and have the offending shuttle mechanism in them. The shuttle is being discarded which leaves the vent holes open which would allow the hydraulic fluid to pass to the other side of the piston. The choice is to make a bung to plug up the holes or a new piston.



    John
    CRASHING IS NOT AN OPTION.

  5. #105
    Edgar Perez's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    Thanks. How critical is to remove the shuttle? Will the wear out of it allow the oil to leak? Will having the oil inside avoid the shuttle to wear out?
    It looks simple enough to remove the shuttle, but wanted to understand the options.
    Edgar Perez
    Puerto Rico

  6. #106
    ianober's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    Edgar, I think you should re-read this thread. The answers to all of your questions have been posted here already. Bart went through a lengthy description of how and why the units will fail. It is up to you to do the mod if you like, you dont have to, but personally I would like trouble free gear that will work every time I hit the switch.

  7. #107
    Aussie Bart's Avatar
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    RE: Jetlegend Mig 29 Fulcrum


    ORIGINAL: Edgar Perez

    Thanks. How critical is to remove the shuttle? Will the wear out of it allow the oil to leak? Will having the oil inside avoid the shuttle to wear out?
    It looks simple enough to remove the shuttle, but wanted to understand the options.
    Edgar

    Ian is right, I can assure you that if you leave the shuttles in they will jamb up and eventually groove out the cylinder walls. As I mentioned earlier, the design of the shuttles is wonderfull, but will not hold up over time cause of the dynamics.
    Bart

  8. #108
    Edgar Perez's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    Got it. Thanks!
    Edgar Perez
    Puerto Rico

  9. #109
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    RE: Jetlegend Mig 29 Fulcrum

    Bart,

    DHL delivered my Mig 29 today and I only had one minor piece of damage-the former that the nose door ram mounts to broke free from the fuse. This was either due to poor glue or failure to sand before gluing. Easily repaired. So, figured I would try to cycle the two main gear to see how the factory original worked. The long and short of it was, they didn't work. One gear stayed stuck down and the other finally came free and slammed into the fuse so hard I thought it would break something. It will definitely benefit from the hydraulic conversion.

    Ianober, would you consider machining a set of pistons for a fee? Your work looks really good. As I don't have access to a lathe, the Hysol option with plug seems my choice unless you're willing to run another set. Let me know please.

    My impression of the Mig 29 is that its not a home run ARF. The wood seems really light and the formers don't appear strong enough to withstand a hard landing. As easily as my one former separated from the fuse in shipment, I can't imagine the main gear formers withstanding a hard landing without reinforcement. I think I'll be adding fiberglass cloth on each side of the two main formers. The other odd feature of the Mig is the location of the twin fuel tanks. Their center looks to be at least 12" forward of the CG. This should make the Mig extremely nose heavy on takeoff. Bart, have you noticed this?

    More later as I play with it at greater length.

    Rob
    F15driver
    Don't look back, they may be gaining on you!

  10. #110
    Edgar Perez's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    I will also be interested in the machining from Bart if available
    Edgar Perez
    Puerto Rico

  11. #111

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    RE: Jetlegend Mig 29 Fulcrum

    Rob, I had similar concerns regarding the location of the fuel tanks on the CG. As Shane(Aussie Bart) was the first that I knew to fly the Mig I emailed him prior to my first flight and he reassured me it is OK. Prior to me grounding my Mig due to the undercarriage issues, I had had 18 flights and the fuel tank location is not a problem. The leading edge extensions produce lift right up to the nose, in fact on the real sized aircraft 40% of the total lift is from the body. With the Mig's CG as per the plan the model rotates effortlessly and landings are superb, the nose can be held in a nose high attitude for a realistic touchdown. I haven't had any issues with my undercarriage formers and I have not strengthened anything. I fly from tarmac, but usually in some stiff crosswinds, Shane, I know fly's mainly from grass. I was starting to move my CG back and I ended up at 12mm behind the stated position. At this point inverted light was better and I could do point and very slow rolls satisfactory. Having said all this my Mig was ordered in January, so there is a possibility construction methods could have changed, but I doubt it.
    Here is a link to a very poor video of the first flight (CG as per plan), you can get the idea of the takeoff and landing qualities. http://www.youtube.com/watch?v=GpJpQUdAY0k


    John
    CRASHING IS NOT AN OPTION.

  12. #112
    ianober's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    Rob, it should be no problem to machine up another set. I may have to have you send me one of your pistons or give me the measurements to compare to mine just to be sure. I am pretty sure that the Mig has the same size cylinders as the SU-27 but I am not certain as I do not have one. So if you want you can just send me your 3 pistons and I will swap it all out for you, just remove them via the pins and e-clips and send the whole things to me. That should be no problem.

  13. #113
    Aussie Bart's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    Ok guys, I finally got a chance to finish it off and get some video of it as below. This was run with a 2 cell Lipo but you can set your speed slower by using a 2 cell life or even a single cell lipo (like I do on my T45) however you need to consider the sequencer timing. In the video I am using an Airpower sequencer that has the same time lag from gear up/door close to door open/gear down. I taxied her around for quite a while after the video (mainly to test my new "Big Bore" pipe) and she rode over really rough rocks and lumpy ground with no signs of collapsing. I am away with work again for a few weeks so hope to test fly when I get back.

    http://www.youtube.com/watch?v=mMZTKeYmXsc

    Bart

  14. #114
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    RE: Jetlegend Mig 29 Fulcrum

    Well I must say Bart, you have me convinced. I think I will go with this system from the outset. Not only is the operation solid but scale too.
    I may also fit the system to my F14 in due course.
    Regards,

    John

  15. #115
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    RE: Jetlegend Mig 29 Fulcrum

    Bart,
    Cool! Like the scale speed. Good job.
    Rob
    F15driver
    Don't look back, they may be gaining on you!

  16. #116
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    RE: Jetlegend Mig 29 Fulcrum

    iabober,

    Much appreciated. I'll disassemble the gear over this weekend and remove the pistons. Would you email me your mailing address to the following: rpuetz@att.net. Thanks loads and good luck with your Mig.

    Regards,
    Rob
    F15driver
    Don't look back, they may be gaining on you!

  17. #117
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    RE: Jetlegend Mig 29 Fulcrum

    John,
    Very nice flight and landing. You satisfied my concern about the tank location and their effect on takeoff and landing. If all my landings were as smooth as yours in the video, I wouldn't need to strengthen the formers either! Good job.

    Rob
    F15driver
    Don't look back, they may be gaining on you!

  18. #118
    JohnMac's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    I have just one descision to make now. Which colour scheme?
    What do you guys think?
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  19. #119

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    RE: Jetlegend Mig 29 Fulcrum

    Definitely the camo version on the left. For info John, the UMS hydraulic conversion kit was a little more expensive than I led you to believe. I've just had a bill from customs for Β£28.00 still its good value.



    John
    CRASHING IS NOT AN OPTION.

  20. #120
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    RE: Jetlegend Mig 29 Fulcrum

    The UMS hydraulic system looks to work great, but do they offer self sealing valves to close the system off if the UMS were implemented on a retract setup where the mains are in the removable wings.

  21. #121
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    RE: Jetlegend Mig 29 Fulcrum

    Anyone have trouble signing in to the UMS site? I just keep getting refreshed back to the login page when I try.
    JET FLYING:- Resistance is futile. You will be assimilated.

  22. #122

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    RE: Jetlegend Mig 29 Fulcrum

    No no problems: http://umstech.in/index.php



    John
    CRASHING IS NOT AN OPTION.

  23. #123
    Aussie Bart's Avatar
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    RE: Jetlegend Mig 29 Fulcrum


    ORIGINAL: Countryboy

    The UMS hydraulic system looks to work great, but do they offer self sealing valves to close the system off if the UMS were implemented on a retract setup where the mains are in the removable wings.
    I use the same system on my JL T45 hawk which also has a removable wing. I use the same quick connect couplers as you would on an air system (different colours) on the lines that go through the fuse to the wing.

    The up line is fitted with blue couplers and the down with red. The up line from the fuse is a female couple and the down line from the fuse is a male coupler.

    After you retract your gear ready to strip the wings off, disconnect the retract pump battery and then cycle the gear at least once, this dumps any high pressure still trapped in the line but the gear stays locked up on its cam.

    Once that is done, disconnect the couplers from each other and the connect the male/female on the fuse together and the male/female on the wing together. Oil won't come out the line unless you shake it (surface tension of oil is too high) and by conncting together the oil stays looped even if you accidently start the pump with the wing off.

    You will still get a drip or two from between the couplers so keep a rag on hand and there is a small amount of thermal expansion of the oil trapped in the wing if its temperature is a fair bit higher when you assemble the wing onto the fuse.

    Every now and then, check your reservoir level and top up if required.
    Bart

  24. #124
    Aussie Bart's Avatar
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    RE: Jetlegend Mig 29 Fulcrum

    Just one last thing for the guys who are converting the JL Mig over. Because the legs don't have any positive locks in them anymore (never worked anyway) you will find the legs sort of like spongy if you put a fair bit of pressure on them, either up or down. I am not sure bit looking at the Skymaster version of these legs, I think they only lock the air in the cylinders which if this is the case would be far more spongy.

    This is simply the 3 mm airline expanding under the load and is about 1/2" on one leg or 1/4" if you push both, if it goes anymore than this you proberbly still have air in the cylinders or lines. Try sitting the plane inverted and cycling the gear a couple of times (reservoir has a clunk line so does not care which way is up).

    I really don't think the spongy reaction will cause any grief, it is more likely to work like another shock absorber. However if you dump the landing the those tubes will be under alot of stress so you must ensure that the 3 mm line length is kept to a minimum, always put a lock wire on the tubes that go onto the barbs (have a close look at the pic with the leg in it and the blue tube, you can just make out the lock wire) and all ather fittings need to be Festo type "Push In" fittings as these hold harder as the pressure rises.

    One last bit of advise, when first setting up the system, adjust the controller sensitivity down to the - end, the gear will cycle and once bottoms out will bring on the overload light and then time out. If the gear is not all trhe way home then wind the sensitivity towards the + until it is right, mine is set at about halfway. If this is set too high then the pump will keep running and potentially burn out.

    If you have you retract pump powered up and turn on your reciever, don't be surprised if your pump runs for a "cycle", this is because the controller has seen a change of signal.

    I use a 2 cell lipo on the Mig and 1000 Ma will give you about 30 cycles so no need to over power the system.
    Bart

  25. #125
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    RE: Jetlegend Mig 29 Fulcrum

    Boy This thread gets even more interesting. I have a very old unfinished Sabre. Unfinished because I just cannot get the gear to lift successfully. The retract units are very small for the size and weight of the model but the location does not allow bigger ones to be fitted. Even at 150 PSI I cannot guarantee the legs will lift. I thought of Hydraulics, but dismissed the idea as I imagined oil spurting everywhere and having to bleed the system every time.
    I thiink this might be worth a shot.
    Thanks Bart. Very illuminating.


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