# 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

### 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

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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

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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

### PTAirco

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I am GREEN with envy at your CNC facilities!

5. May 24, 2010

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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

### 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

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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.

Shannon.

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17. May 28, 2010

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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

### 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

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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 lighteronder:

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

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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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