CriCri MC-15 in NZ

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

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  1. May 23, 2010 #161

    mz-

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    Whoa! That saw sure has a good battery if you can cut slabs of 2024 just like that. Your work is inspiration to everyone! Also, I'm sceptical that both of your engines are mockups, the silvery one must be real!
     
  2. May 23, 2010 #162

    MadRocketScientist

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    Its just a makita lithium-ion saw, the trick is to use aluminium cutting blades and cut slowly. I also use a wax stick on the blade to stop things getting jammed up. The 2024 cuts really nicely (when I keep the saw stfraight):gig::gig: I also clamp the part being cut behind the saw as I had one piece grab and remove most of the teeth from the saw blade:depressed.

    Both engines are mockups, they fool people in real life too.

    Shannon.
     
  3. May 24, 2010 #163

    MadRocketScientist

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    I am guessing you mean two and three bladed propellers? I think I will use a three bladed as they are smoother than a two blade. The CriCri already has a lot of vibration so any little reduction will help.

    Shannon.
     
  4. May 24, 2010 #164

    PTAirco

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    I am GREEN with envy at your CNC facilities!
     
  5. May 24, 2010 #165

    MadRocketScientist

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    Hmm sure beats doing things by hand....:gig::gig:

    Made a couple more clamps, the cut finish isn't a lot better. I think its pretty close to the limits with a gantry router.

    Also sorted out the lower bungee pin for the nose gear, I made the flared end a while ago but only just made the locking clip and drilled the hole. The blue zip tie is a placeholder for the bungee.

    Also started on the threaded end for the elevator linkage. Not quite perfect so I may make another one:gig::gig:. I need to purchase a tap and die for cutting the threads.

    Shannon.
     

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  6. May 24, 2010 #166

    nathj

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    wow well done, iv just finished reading the thread and am very impressed with the cnc work.:)

    im about to start a cri cri but after reading this thread im definatly going to build in composite. i havent found any on the net yet but im sure it will work fine,

    i always thought of doing a composite cri cri for the main reason of minimal tools and less work, man i couldnt imagine cutting all those parts by hand.:tired:
     
  7. May 24, 2010 #167

    MadRocketScientist

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    There aren't any plans for a composite CriCri but the Iranians (of all people) have made one. If you Google search 'Faez Light twin' you should be able to find some pictures on it. Also check out here...
    EAA News - Identical Twin?

    There has been the odd discussion about doing the CriCri in composite by others on the Yahoo groups but it would need a full redesign and you are still left with the engine issue.

    I am also seriously looking at kitting the CriCri but I would prefer that I have all the parts made and checked for fit before any release. Pricing is still to be determined but I do have a close pricing for the sheet metal parts, its all the brackets etc.. that are hard to calculate without actually making them. I can make the engine mounts for around NZD$120 a pair, for example. Multiply that by the many small parts and the cost is hard to estimate.

    Shannon.
     
  8. May 24, 2010 #168

    mz-

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    You could build an MC-30 Luciole instead - a few carbon fibre spars and rest is wood and fabric. I don't know how the work compares with Cri-Cri, but I'd imagine it is less. Probably the performance a lot less as well.
     
  9. May 25, 2010 #169

    MadRocketScientist

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    It is interesting to note that the MC-30 has been designed to a similar set of design goals as the CriCri was in the 70's. A low cost small aircraft. Granted that the MC-30 isn't as aerobatic as the CriCri it is a lot cheaper to build. The MC-30 also has lot going for it in the form of a reliable engine.

    Shannon.
     
  10. May 25, 2010 #170

    nathj

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    Building a composite cri cri shouldnt be too hard i think. As long as i stick with the mesurments of the cri it should be fine. it would be as simple as copying the wing cross section for example and cutting the foam, and of course inserting a main spar. i was thinking of useing a fiberglass I beam as i couldnt sorce a carbon one big enough.

    but that iranian craft sure does look like a cri cri, wow and it was designed by there aerospace finest:gig::gig::gig:. I bet they bought a set of plans like us. i really like the part where they say it can be upgraded to a two seater.

    iv fallen in love with the jet cri cri and i think that with a composite air frame it could have performances never seen:ponder: but im just day dreaming again.

    maby that might be something you would like to look into shannon, unless you already have power plants, the non mdf type;). which i might add had me fooled and yet another master piece shannon.

    so im thinking that the jet engines would have less vibration, be more reliable ????:ermm:, better performance, and cheaper (if home made).

    any thoughts about model jet engines used in full sized craft???
     
  11. May 25, 2010 #171

    MadRocketScientist

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    A jet CriCri would rock, the downsides are a very short flight time (30 mins) and a short TBO on the engines. Apart from that it would be loads of fun.

    More progress tonight...

    ***Builders hint***
    After messing up the drilling of the steering tube (401 11) when using a V block in the drill press, I decided on another plan. I glued some scrap mdf onto the tube using a small amount of CA glue. the effectively gave me a right angle block as part of the tube. I then drilled both ends of the tube at the same angle using the mdf block as a reference. I could also rotate it 90 degrees and then drill the holes for the split pins near the center. All holes were spot on:ban:. If the holes for the split pins are drilled accurately before the nose bracket is installed (bit hard to do when its in the plane anyhow:gig:) the clamping action spreads the 'ears' when its installed. This tightens them against the split pins slightly and stops the steering bar from rattling around.

    I also made the bump stop washers for the steering cables out of some urethane instead of rubber. A sharpened brass tube from an old RC transmitter aerial made a good 10mm punch. I need to make some 10mm diameter washers with a 1/16 hole in the middle to go between the urethane and the stop on the end of the cable. I will also use nicopress cable end stops from aircraft spruce. I have had the pushbike cable ends fail on me before (when on a pushbike) and do NOT want it to happen in an aircraft;).

    Had some retail therapy today and purchased some quality taps and dies. I used the 5/16" die to cut the thread on the pushrod end and drilled the rivet holes (rivets to go in later). The clecos will stop it going AWOL.

    Shannon.
     

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  12. May 25, 2010 #172

    Mac790

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    So you can call me a fool :gig:, I thought that one of them is real (maybe I should look a little bit closer). Thanks for updates Shannon nice work.
    A week ago I was reading something, somewhere :) (sorry don't remember where was that)about a jet version of the Cri Cri, from what I remember one of the issues was, jet exhaust temperature, owner removed jet engines because he was worried about potential problems with delamination (is it correct word?) of the bond between ribs and wing skin.

    Seb
     
  13. May 26, 2010 #173

    MadRocketScientist

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    I should thank everyone for the kind comments, my focus isn't quite so good when posting late a night after spending ages making parts;);)

    Seb,
    I make a distinction between being fooled and being a fool :gig::gig:.

    The Turbine CriCri was the one on the AMT website, There was some concern about the hot and cold cycles affecting the bonding of the divinycell wing ribs to the aluminium skins. My guess is the the short flight times also had an bearing on the choice the change back to piston engines.

    Shannon.
     
  14. May 26, 2010 #174

    medo200039

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    I intend to do I provide my cri-cri plane such Turbine from AMT if not in use and operation in normal engines are better than this

    I hope my engagement Opinion
     
  15. May 27, 2010 #175

    MadRocketScientist

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    Formed the 'feel attach plate' today, its part of the artificial control force setup due the light stick forces involved. Rubber bands are connected to this plate to provide elevator stick forces and also the trim.

    The holes will get drilled out of 1/8" rivets but its safer to use 3/32" clecos for the meantime.

    Shannon.
     

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  16. May 27, 2010 #176

    MadRocketScientist

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    Not one for resting on my laurels (at least not in the evenings, and where does one get a laurel from these days anyway:ponder::gig:) I continued making some more parts.

    I was not really looking forward to making these rod ends as I wasn't too sure how to go about them. I decided to make a start and see where things ended up. I put some 3/4" round 2024 bar in the lathe and bored the hole for the rod end. Then I turned down the outer diameter to give a 1mm wall thickness. Flipping the part around in the lathe and wrapping some tape around the previously turned end I put a radius on the remaining blank. CNC'ed out a block and clamped the previously turned parts in this to CNC mill them as shown in the pictures. The holes for the rivets need drilling and the ones for the bolts need to be drilled out to final size. I should have drilled the rivet holes on the CNC when I had everything in the jig but didn't think of it until I had everything finished. Better luck next time..DOH:emb:

    In the end they turned out well (except for the leftover one) and weren't such a pain to make as I though they would be. I didn't get a close up of them once they were de-burred and the tooling marks sanded off but they do look good.

    I may have to remake the pushrod tubes as I flattened a bit too much of them when fitting the plates on the opposite end (shown in last pic) Not huge loss as they only use a few $ worth of aluminium.

    Shannon.
     

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  17. May 28, 2010 #177

    MadRocketScientist

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    Turned and CNC'ed another rod end tonight, I made a small change in the form of a check hole. The thread has to have at least 10mm of engagement. If a piece of wire can be pushed right through the check hole the thread needs to be screwed in more. I found the idea in one of my aviation maintenance manuals.

    I also cut a few spare locking tabs for locking the nut, shouldn't be needing any more for a while.:gig: Alodined them while the metal was fresh.

    Attached is a .dxf file for the lockwasher as there isn't a layout for it in the plans.

    Shannon.
     

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  18. May 28, 2010 #178

    PTAirco

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    Odd- on those pushrods you have a complex machined fork on one end and a pair of simple flat plates on the other. What was the designer thinking when he did this? Why not have those forks at both ends or simple plates on both ? I'm sure there is a reason....
     

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  19. May 29, 2010 #179

    MadRocketScientist

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    I was thinking the same thing as I was making these....

    I 'think' the flat plates at one end are for ease of building and the fork is to make it easier to align the ends when installing them. These pushrods need to be aligned when installed due to the slight angle they have to be set at.
    The Elevator pushrods are straightforward to make due to the alignment (parallel or 90 degrees) and all use flat plates on both ends. I think it would look better having the forks all around but would take much longer to make for the general builder.
    With the right setup the CNC could make the forked pieces much faster.

    I might also weigh them and see which is lighter:ponder:

    I think if I went through the aircraft with the proper analysis and optimized the parts for CNC cutting I could reduce the overall weight somewhat. The designer has said the the elevator brackets only need to be 1mm thick to handle the forces involved (they are 4mm tee section to support the spherical bearings)

    Shannon.
     
  20. May 29, 2010 #180

    MadRocketScientist

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    Made the other side for the control stick support tonight. Took three tries to get one to bend without cracking. Builders should take note, as shown in the plans the bends are way too tight to bend consistently. I think I will redraw it and try to allow for reasonable bend allowance. This one is usable but by the time I got to folding it I was starting to get pretty annoyed :mad2:. This sort of carryon would have some people throwing parts around the workshop for sure:gig::gig:.

    The plans state to bend up the bracket out of a larger piece of aluminium and them cut it out. I 'could' have done that but cutting most of it with the CNC works well when the bend radius is correct, although the drawings do have to be spot on for it to work. The extra 'tabs' on the blank are to allow the bends to form properly but also minimizing the waste that needs cutting off after folding. This makes it much easier to get accurate parts without too much working it by hand. I also changed the mounting somewhat and decided to install another spherical bearing. The plans call for reamed aluminium for the control column base to turn in, I prefer the spherical bearing for longer life.

    I will make another one with a more relaxed bend radius.

    Live and learn I guess.

    Shannon.
     

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