CriCri MC-15 in NZ

Discussion in 'The light stuff area' started by MadRocketScientist, Jun 19, 2009.

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  1. Apr 14, 2010 #141

    MadRocketScientist

    MadRocketScientist

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    I think I can sort out the engine reliability issues. Two stroke engines need the correct cooling to make them reliable. This can be seen with the JPX CriCri engines and the head cooling mods done to direct the air in a controlled manner over the cylinder. The bore needs to be kept as round as possible by making sure the cooling is as even as possible on all sides of the head. Water cooled engines have the coolant channels in the head carefully designed (generally) to cool the hottest parts first and keep the head temperature as even as possible to promote roundness. If the cooling ducts/shrouds are properly designed the engine can be run leaner for the same CHT's due to less fuel being wasted in cooling the engine.

    To me an air cooled two stroke without shrouding is similar to just using spray from a hose to cool water cooled engine. The cylinder ends up very cold on one side and very hot on the other.

    A good article is here.
    http://www.x-jets.com/Design_for_optimum_cooling_efficiency.pdf

    Shannon.
     
    blane.c likes this.
  2. Apr 15, 2010 #142

    MadRocketScientist

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    Sneak preview;)
     

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  3. Apr 15, 2010 #143

    h_zwakenberg

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    I like your thinking - which is valid for aircooled four stroke engines as well...

    cheers
    Hans
     
  4. Apr 15, 2010 #144

    DaveK

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    Pardon my ignorance but what type of engine is that? Brand, size, etc?

    Thanks
    Dave
     
  5. Apr 17, 2010 #145

    MadRocketScientist

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    The engine is a ZDZ210 sorta.....

    Today I welded up the second nose gear outer (no pics), this time with the outer tube needing no machining. I am still waiting for the inner aluminium tube to come from aircraft spruce.

    I made the lower control stick (also for the second time) this one is as per plans. I had made it in three pieces but the lower area is really only the tube flattened out and drilled to suit. I think I have it right this time. Hopefully weld it up tomorrow. Must sand those nasty scratches out of the aluminium bearing holder:ponder:

    Shannon.
     

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  6. Apr 18, 2010 #146

    MadRocketScientist

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    Welded and painted the lower control column parts today. Although there isn't a lot of 4130 in the build there sure seems to be a lot when it comes to welding it up.


    Shannon.
     

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  7. Apr 23, 2010 #147

    MadRocketScientist

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    A few pictures of the pedal tray locking mechanism and the weld jig. The ends still need to be bent up so I can use my heels to release the tray for pedal adjustment. Pilots complain about the ends of the music wire digging into their ankles in flight. I have left the ends longer than needed so that I can bend them outwards to prevent getting 'spiked'. Hopefully my plan works.

    Shannon.
     

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  8. Apr 25, 2010 #148

    MadRocketScientist

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    Finished welding the engine mounts, sanded the scale off and painted with the green primer. There are 9 individual parts to align and weld correctly so it takes some time to do even with the jig. The welding isn't as cosmetically nice as I would like but I am sure it will be strong enough. Welding is one of those skills that takes practice to keep it in good form.

    A few tips for making the engine mounts for other builders. Use MIG wire for welding as it is thinner and gives a much neater and smaller weld with the 0.035" walled tubes. I started with welding rods but the MIG wire works much better. Another thing I would do next time is drill a small hole on the inner side of the outer engine mount bolt tubes (500 02) to allow for gas relief. The last weld on mine blew out on the tidy up reheat:dis:. I also normalized the welded areas by heating to a dull red and letting slowly air cool. Also it would be good to make sure the relief on the side mounting (501 02) has plenty of clearance where it isn't welded. If it is too small it is hard to see through a welding helmet. Mine had barely 1mm gap and I missed it on one side and welded it over.

    I can see why other builders complain about access to the internal nose area. I can barely get my hand through and around to tighten the engine mount bolts on the inside of F1 and the wiring and fuel lines will also need to go through the opening. I am glad I have the nose hatches in place, they already get used at this stage of the build.

    I still have a few 4130N parts left to weld. The canopy hinges, the axles and the main wing pin handles. I should be able weld the canopy hinges soon but the axles and wing pins need other parts made before I can weld them up.

    I am still enjoying building the CriCri, It is quite satisfying to sit back and see the progress so far. I would say it has been one of the more rewarding projects that I have built so far.

    Shannon.
     

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  9. Apr 29, 2010 #149

    MadRocketScientist

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    A photo of current progress, The mx-5 is a Blastolene special :gig::gig:(just kidding)

    Also spent some time bending the canopy hinges. I need to take the front fuselage section to the airfield to weld them up. The welding needs to be done when the parts are on the plane so the alignment is correct.

    Shannon.
     

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  10. May 15, 2010 #150

    MadRocketScientist

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    Not a lot of progress to report although I have temporarily fitted the lower elevator bellcrank to F11. The rudder pedals are close to finished too.

    I have the nose gear leg getting chrome plated The platers said it would be ready for last Friday, I called them this week and then they said this Friday (just been) but when I called them they hadn't even started on it. Hopefully it gets done for Monday. Not very impressed with the service:dis:, I won't be using that company again. Now I hope they don't stuff up the plating to boot:para:.

    Lots of things still to make, might work on parts for the aileron trim on the control column tomorrow.

    Shannon.
     

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  11. May 16, 2010 #151

    MadRocketScientist

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    Fitted the upper control column and the aileron trim system tonight. The washers that hold the rubber bands are usually made out of two separate parts, a washer and a bushing. I decided to integrate the two into one and machined them out of 3/4" diameter 2024 bar in the lathe. I also threaded the inside so that a nut is no longer needed. There is about 1/4" of thread engagement into the aluminium, plenty for a solid joint. I will use threadlock on final assembly.

    I had to temporarily add a spacer to the lower trim lever as my last 1/4" bolt was too long. I will head over to the airfield shop and get a correct length bolt this week. I also fitted the lower aileron stop to the lower control column (not shown in the pics). There are still a few parts to add yet, brake lever, brake cable stop plate, stick grip and more. The holes for the locking pin to hold the stick centered when setting up control surfaces also needs to be drilled.

    The last two pics show the trim set to one side and then centered.

    The parts bin is getting emptier.:):):)

    Shannon.
     

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  12. May 18, 2010 #152

    MadRocketScientist

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    I picked up the nose legs from the chrome platers. Cost quite a bit and way late on the stated finish time. The finish seems to be good but I will find out how smooth when I machine the slider block. I now have two nose gear legs:ermm::ponder::nervous:. I need to CNC the upper clamp out of 2024T3 now that I have the nose legs back and can machine them for a good fit. Something to do in the next few days anyhow.

    **Builders note on nose gear leg**
    After much machining and pondering... The best way to deal with the imperial conversion seems to be to use a 7/8"x0.035" 4130N tube for the outer (p/n 401 04) and machine the inner (p/n 401 05) from a 7/8"x0.120" 6061T6 tube. The inner tube ends up slightly heavier (20grams or so). Interestingly the plans allow for use of a 2mm wall tube for the inner. Changing from a 1.5mm wall 2024 tube to a 2.0mm wall (after machining) 6061 tube shouldn't create any issues IMHO.

    I should also come clean about the engines I don't really have... I was waiting until someone asked but since no-one has it might be for the next post to reveal all.....

    Shannon.
     

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  13. May 18, 2010 #153

    MadRocketScientist

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    Had a bit of fun with these 'engines'.... I decided since I wasn't going to purchase the real ones for a while, and needing some mass wood engines. Having worked on the sets of the Avatar movie you soon learn what can be done. Had great fun with the engines out at the airfield with quite a few people being taken in:gig::gig:. Looks like a real engine sitting on the floor or a few feet away but once you pick them up you realize that they are only wood.

    I did cop a bit of flak about having too much time to waste. My reply was that I have just as much as anyone else but I just choose to waste it in different ways to normal people.:gig::gig: All good fun. Also got a few suggestions to sell them on ebay.....as real engines....:ermm:;):) Not sure if I am up to that, but maybe I could try selling a 'rotax' to those that suggested it :gig::gig::gig:
    Also suggested was to use the mdf ones as casting patterns and manufacture my own engines.

    I did really enjoy putting these together, A bit of PVA glooo and a couple of evenings and voila, a few wooden motors. Its a bit like a puzzle only I end up with something way better. There is a 3 view on the internet of the ZDZ210 that has been drawn in CAD but its only a bitmap image. I used that and some dimensions as a starting point to do the CAD files for cutting all the parts on the CNC. They are just lots of slices stacked to give it shape. I also put some threaded 8mm rod and skateboard bearings inside so the propellers rotate.
    They do a good job of keeping the nose wheel on the ground (beats using a big hunk of wood as a weight). Should also come in handy when designing the engine mounts and cowlings.

    BTW, if anyone wants a larger version of any of the pictures in the thread, PM or email me and I can send you them. I take most of them at 3MP but reduce them to save space when posting.

    Shannon.
     

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  14. May 18, 2010 #154

    MadRocketScientist

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    I should also mention there is something else CriCri related that I am working on...that's all I am saying though. More details later (when I can get around to taking photos...:gig::gig::gig:)

    Shannon.
     
  15. May 18, 2010 #155

    addaon

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    Very cool.
     
  16. May 18, 2010 #156

    danmcgee

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    OK Shannon now that is way to much time on your hands but very cool. Now just do them out of alum and you made your own engines.

    Dan
     
  17. May 22, 2010 #157

    MadRocketScientist

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    This is also a small airplane...:gig::gig:

    1/3 scale RC. Similar amount of progress to the slightly bigger one but a lot less time invested. Will be mounting the electrics before closing up the fuselage. Hoping this one flies first.

    Shannon.
     

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  18. May 22, 2010 #158

    MadRocketScientist

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    Now for some 'real' stuff.

    Made a jig and machined the hole in the nose gear slide block this afternoon.
    Hopefully get a start on the upper clamp tonight.

    Shannon.
     

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  19. May 22, 2010 #159

    MadRocketScientist

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    Burnt a bit of midnight oil... no make that a lot, it's almost 2am:tired::gig:
    Used the cordless skill-saw and cut a sliver off one of my 2024 slabs and made it into a nose gear clamp.

    Pretty straightforward to cut, machine it on its side then stand up to do the next passes.
    I need to sort out a better toolpath strategy as the finish quality is a bit lacking. I think the part will still be usable but I will make another one anyway (because I can :gig:)

    A bit of attacking with the band-saw and a file cuts it off the block and cleans up any leftovers.

    Shannon.
     

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  20. May 23, 2010 #160

    medo200039

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    Thank you for all this information and wonderful pictures and I want to know if you are a fan plane binary blade or blade three and which one
    is best

    :):):)
    :):)
    :)
     

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