CriCri MC-15 in NZ

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Kenneth Higdon

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Apr 12, 2020
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Shannon -
What is the advantages over the 3W engine. Weight, HP, rpm, cost, dependability ?

Kenneth Higdon - Alabama Beach builder
 

MadRocketScientist

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Canterbury, New Zealand, Earth, Milky Way Galaxy.
Shannon -
What is the advantages over the 3W engine. Weight, HP, rpm, cost, dependability ?

Kenneth Higdon - Alabama Beach builder
Hi Kenneth, I am assuming you mean compared to the ZDZ210/250?

The ZDZ is around half the cost of a similar 3W engine. A plus for 3W is that many of the 3W engines have dual sparkplug heads. What sold it for me though was that the RC pylon racers were running the ZDZ210's at 9000rpm and 40+hp on methanol and they hold together just fine, ground impacts aside. There have been also some issues with the 3W crankshafts and prop hubs in the past, quite a few failures talked about over at the Flying Giants forum. I had a good hunt around the internet for failures in the ZDZ210's and didn't really come up with much, there are a few that got overheated and seized but that is an installation/operation issue. Good CHT and EGT will help stop a lot of overheating/ lean run issues.

Do you have any progress pictures? Feel free to poet some here!:cool:
Shannon.
 

proppastie

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but I have plenty of 1/16" stainless steel cable.
do you recommend 7x19 or 7x7 I can mill spec. with extra lubrication from Mcmaster...choices choices.....helps to get other opinions. Do you need end caps, Boden cable do not have them.
 

MadRocketScientist

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do you recommend 7x19 or 7x7 I can mill spec. with extra lubrication from Mcmaster...choices choices.....helps to get other opinions. Do you need end caps, Boden cable do not have them.
I think all the 1/16 cable I have is 7x7, in that small cable the strand size for 7x19 is pretty thin! Some of my 1/16 cable is generic bycycle cable and some is aircraft cable.
 

MadRocketScientist

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Another 'little' job almost sorted, this one took me all afternoon and its still not finished!

I dug out the canopy latches and after checking that they worked okay I took them apart and gave them a good working over with the scotchbrite pad. When I was happy with the finish I alodined them.
I was thinking of painting these red all over but the other day in the shower I had the idea to paint the insides red and the outside white to match the other control knobs. The red should be easily visible to see when they are unlatched.
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I masked off the outsides and painted the red on. Once that was dry I masked out the inside and painted on the white. I painted the top coat directly over the alodine finish and some of the red paint still lifted in places. I tried leaving the paint a while and letting it bake in the sun but it didn't seem to help. Maybe I should have used primer.
I needed to remake some of the pivot pins as the previous ones I made were a little too short. They were quite quick to make in the lathe. I peened over one end before putting the pins in the latches. I will let the paint harden up some more before peening over the other ends and locking the pins in place.
The last two pictures are taken here at home where the lighting isnt the best but the red contrasts nicely with the white.
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ALPER SARISAN

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May 13, 2019
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362/5000



Hello to everyone .
I started cri cri construction 3 years ago. Your manufacturing know-how has been very useful to me. you can see my construction stages on my page below
I have a question for you.
Where can I get cri cri's canopy bobble flour?
I would be very glad if you could help me with this ...
 

MadRocketScientist

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Canterbury, New Zealand, Earth, Milky Way Galaxy.
After waiting for over two months, the shipment with the ball lock pins finally arrived from china!

The quality is actually alright. The push button springs do have a slight variation in the pressure required to release them but still not bad for under NZD$10 each. I think I will cut all the cables off to keep weight down. ;)

The other thing is, I had completely overlooked that the holes that these go into will need to be reamed to fit, but do you think I can find a 6mm reamer around anywhere? I will have to order one and wait for it to arrive, so until then I can't fit these secondary pins to hold the wings in place.
 

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proppastie

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those pins from China....Slightly hollow? How hard/strong???? If the plans called out for AN hardware or equal for the wing attach bolts I am not sure I would trust Chinese hardware without testing and certainly a hollow shaft of the same diameter and hardness as solid shaft will not be as strong.
 

MadRocketScientist

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those pins from China....Slightly hollow? How hard/strong???? If the plans called out for AN hardware or equal for the wing attach bolts I am not sure I would trust Chinese hardware without testing and certainly a hollow shaft of the same diameter and hardness as solid shaft will not be as strong.
The plans have two versions, you can make your own pins from 4130 tubing or use off the shelf pins. The China pins are stainless and there is a mechanism through the middle that locks and unlocks the balls. They should be plenty strong enough.
 

Jim_MC15

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Oct 30, 2018
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The plans have two versions, you can make your own pins from 4130 tubing or use off the shelf pins. The China pins are stainless and there is a mechanism through the middle that locks and unlocks the balls. They should be plenty strong enough.
Wait... What? You didn't make your own??? Probably easier than say, dual spark plug cylinder heads, wheels, formed wing tips, canopy latches.... LOL :)
 

MadRocketScientist

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So the 6mm reamers that I ordered on Ebay arrived finally. Shipping is still hit and miss, with some things never turning up, at least these arrived in reasonable time.

I rummaged around in my drills and found a 5.7mm drill bit to pre-bore the holes. The first attempt at reaming showed that there was a fair amount of slop when the pins were in the holes. The pins vary in diameter somewhat from around 5.96mm to right on 6,00mm so I decided to adjust the reamer slightly smaller ;) I can linish the larger diameter pins to the same smaller size in the lathe.

First up I mounted the reamer in a 6 sided collet block and clamped it down the bed of the cnc
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I used a diamond file to carefully remove an equal amount of material off the top of each of the cutter flutes. The six sided block made it really easy to index the reamer. I stacked up some wood blocks to hold the diamond file in the same orientation while I slid it back and forward, removing material off the cutting edges. It took a few tries to get the size just right, with testing the finished hole size each time, but with careful honing I got a good sliding fit on the smaller diameter pins.
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I polished the shank of the adjusted reamer so I could tell which one is undersize. I used an offcut of 2024 to sneak up on the correct finished hole size.
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A neat fit.
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Now to line up the holes in the wing attachments!
 

MadRocketScientist

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I took my spinner mold into a local metal spinner that other day and asked what I needed to change to mount it to their spinning lathe. Turns out that it needed a 1"BSW thread for the lathe adapter.
While they do have a tap to suit, I made the most of the challenge and cut the thread with the cnc using a single point threading tool, custom made from another cutter of course! Being an obsolete thread, it has a unusual thread form with a 55 deg thread angle instead of the more usual 60 deg.

I ran some tests with the new cutter, first in extruded polystyrene and then in MDF. I cut these test cuts in half the check the size of the thread and adjusted the CNC code to suit. I don't have any 1"BSW thread around so hopefully it fits the lathe adapter when I take it in to the metal spinner.

Once I had the thread cutting to what I assume is the correct size, I made up a new backing plate for the spinner mold from some Meranti ply. I chucked the backing plate in the lathe and adjusted the mold for minimum runout. It only needed a few pieces of masking tape as packing.

Next time I am in town I will drop this off and get some spinners spun, I will get a few extra sets of spinners made in case anyone else needs them.

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MadRocketScientist

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Spent some time today fitting a couple of wing pins, I got two pins installed and then spent the rest of the afternoon tweaking the spar fit. The spar is still a little tight in the spar box and I am chasing down a sliding fit by filing the tight spots on the spar. Once I have that sorted I will install the pins for the left wing.
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