Author Topic: 1/4 Scale Cirrus MkI  (Read 30044 times)

Offline zeeprogrammer

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Re: 1/4 Scale Cirrus MkI
« Reply #105 on: April 05, 2018, 06:19:11 PM »
Just finished going through the thread. Wow. That's a beautiful engine.
I learned a lot going through this...mainly how much I don't know and need to learn.  :Lol:
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline cwelkie

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Re: 1/4 Scale Cirrus MkI
« Reply #106 on: April 06, 2018, 01:39:55 PM »
Thanks Carl
I reckon your comment applies each and every one of us; "...mainly how much I don't know and need to learn.", regardless of what we think we know  ;D
Charlie

Offline cwelkie

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Re: 1/4 Scale Cirrus MkI
« Reply #107 on: July 21, 2020, 05:55:28 PM »
Well, it’s been over 2 years since the last posting on this project but I felt it important to “wrap it up” with an update ...
It short I have a runner!  Frankly, I did something uncharacteristic for me and shelved the Cirrus while I worked on a number of other engines and shop bits when I couldn’t get it to run.

There were two main issues:
1. Poor ring fit.   The steel rings must have been over stressed when installed. On disassembly it was obvious that the rings were not sealing around the full circumference.  I remade the rings in cast iron to slightly wider and thicker dimensions.  Same “cold process” described earlier in the thread.

2. Poor valve seat seal.  For some unknown reason other than “incompetent machinist”  :D the valve guides when pressed in place were not perpendicular to the valve seats.  This combined with a seat cutter pilot that was just that much to small lead to seats that were wider on one side that the other.  The more I lapped them the worse it got.  I came to dislike stainless valves because they seemed to be ground as much or more than the aluminium seats.  In the end I made new valves from 12L14 and a new seater cutter to George Britnell’s design. Recutting the seats and a light lapping with extremely fine compound and final touch up with brasso did the trick.  Each cylinder was tested once I thought it was good to be sure. At least I didn’t have to revise the head to use one-piece cages!

In the end, running out of other projects provided the incentive and I’m very pleased with the result.  The brief video shows the Cirrus running on straight Coleman fuel (which provides the white coloured exhaust ... I think).

[youtube1] <a href="https://www.youtube.com/watch?v=hKGQQ0GrvpA" target="_blank">http://www.youtube.com/watch?v=hKGQQ0GrvpA</a>

 ... as a good friend said, “It’s now an engine, not just a model engine!”
Charlie
« Last Edit: November 02, 2021, 10:47:24 PM by cwelkie »

Online Dave Otto

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Re: 1/4 Scale Cirrus MkI
« Reply #108 on: July 21, 2020, 06:31:46 PM »
That sounds great!
Congrats on having a runner!

Dave

Offline Roger B

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Re: 1/4 Scale Cirrus MkI
« Reply #109 on: July 21, 2020, 07:05:25 PM »
Looks and sounds great  :praise2:  :praise2:  :wine1: Propellers  still scare me  :paranoia:

Your experience confirms mine, if the compression is good the engine will run, if it is not good messing with carbs and ignition will get you nowhere  :(
Best regards

Roger

Offline Admiral_dk

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Re: 1/4 Scale Cirrus MkI
« Reply #110 on: July 21, 2020, 09:09:57 PM »
Now that's more like it  :whoohoo:   Great that you solved the issues  :ThumbsUp:

Looks and runs great - you should be pleased  :cheers:

Per

Online Vixen

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Re: 1/4 Scale Cirrus MkI
« Reply #111 on: July 21, 2020, 09:39:53 PM »
Hi Charlie,

A great reward for all your effort and perseverance. Nice engine, nice sound, great result   :ThumbsUp: :ThumbsUp:

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline chucketn

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Re: 1/4 Scale Cirrus MkI
« Reply #112 on: July 21, 2020, 10:04:36 PM »
Video of running engine does not appear. Am I missing something?

Offline crueby

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Re: 1/4 Scale Cirrus MkI
« Reply #113 on: July 21, 2020, 10:28:50 PM »
Video of running engine does not appear. Am I missing something?
Are you using the secure connection to the forum website, with an 's' after the 'http'? If so, take the 's' off, its a known issue with videos on this forum.

Offline chucketn

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Re: 1/4 Scale Cirrus MkI
« Reply #114 on: July 21, 2020, 10:44:07 PM »
Are you using the secure connection to the forum website, with an 's' after the 'http'? If so, take the 's' off, its a known issue with videos on this forum.
[/quote]

That fixed it, thanks.

Offline nj111

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Re: 1/4 Scale Cirrus MkI
« Reply #115 on: July 22, 2020, 10:31:41 AM »
Looks and sounds fabulous. Very well done!
Nick

Offline cnr6400

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Re: 1/4 Scale Cirrus MkI
« Reply #116 on: July 22, 2020, 11:47:50 AM »
Great engine! well done!  :ThumbsUp: :ThumbsUp: :ThumbsUp:
"I've cut that stock three times, and it's still too short!"

Offline awake

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Re: 1/4 Scale Cirrus MkI
« Reply #117 on: July 22, 2020, 06:32:29 PM »
Sounds great! Will this go in an RC plane?
Andy

Offline cwelkie

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Re: 1/4 Scale Cirrus MkI
« Reply #118 on: July 22, 2020, 11:00:13 PM »
Thanks all ...
I certain agree with you Roger - without compression everything else is just "decoration".

Now that I've got it running I'm not completely happy with the carburetor.  It is based on an earlier 2-needle design of Jerry Howell that was published in SIC magazine.  Trouble is that the engine seems to be happiest with the high speed needle closed off and mixture controlled by the low-speed needle.  Don't know what I messed up in the build but it does bear looking into because I'm certain the engine will reliably idle slower than it is now if I can get away from such a compromised mixture.

BTW I didn't use the original design from the drawings due to what I perceived were challenges in fabricating.  If memory serves, trying to keep things concentric and two 0.005" slits in the spraybar (that's right 5 thou!).

Andy - Although another interest of mine is in scale RC models of vintage aircraft I don't think this one will fly as much as I'd like to put a DH Moth around it.  Certainly not until the carburetor is sorted ...


Offline Art K

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Re: 1/4 Scale Cirrus MkI
« Reply #119 on: July 23, 2020, 01:32:23 AM »
Just wanted to add my voice to the choir of voices, sounds and runs great. Good luck with sorting the carb out.
Art
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