Author Topic: 12,6cc engine..  (Read 1184 times)

Offline Lauri

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12,6cc engine..
« on: June 23, 2019, 04:28:51 PM »
Hi.

I don't know if this is the right place to post these, but here is some pictures of my engines. They are for category F2B, control line aerobatics.
I make as much as I can at home, and Robbie Metkemeijer helps with barstock case, (I have only manual machines) and with some operations with pistons, like spark erosion of piston inside shapes and finishing my raw piston to final size.
We ended up with integral AAC construction, with Dykes ring, as it gives an excellent thermal stability.

Lauri

Offline Allen Smithee

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Re: 12,6cc engine..
« Reply #1 on: June 23, 2019, 06:00:39 PM »
Nice work! Say Hi to Rob from me (my actual name is Pete Rieden) I knew him and Robby Van den Bosch when I competed in the european and world champs in F3d in the 1990s.

AS
Quidquid latine dictum sit altum sonatur

Offline Ramon

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Re: 12,6cc engine..
« Reply #2 on: June 23, 2019, 07:03:44 PM »
Hello Lauri - welcome to the forum  :hi:

That's certainly some impressive machining you've accomplished there and two very nice looking stunt motors along with all the ancillaries as a result. I thought I had some pics of something very similar that Roger Ladds put in my hands last time I went to a Nats - around 4-5 years ago maybe? I took quite a few of it in the back of my car (usual thing, Barkston living up to it's windy reputation) If I'm right I think Rob Met had something to do with that particular engine too. I do have the drawings for that engine somewhere also from Roger.

I too have only home kit but nowhere near so lucky to have access to spark erosion and CNC - nice situation to be in.

I think we met at the last Nats I entered  - that would be 2006 but I was flying in Classic not F2b - I have a vague recollection your model won the Concours that year.  That was the last year I flew anything anywhere and haven't picked up a handle since.

Good to see you bringing your engine knowledge here - maybe you should put an introductory post up to introduce yourself

Looking forwards to hearing more about your engine building

Regards - Tug
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline Lauri

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Re: 12,6cc engine..
« Reply #3 on: June 23, 2019, 08:48:26 PM »
Thank you, Tug.

Roger has an early version, with Robbies original silly scavenging and screw-on head. I just did the fittings and ring to it.
My latest versions are with a proper 6-port Schnuerle.
Yes I was in 06 Nats as I was living in Peterborough back then. Don't remember about concource d'elegance, though. L

Offline Ramon

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Re: 12,6cc engine..
« Reply #4 on: June 23, 2019, 10:16:48 PM »
Ah, it was a vague recollection of a conversation at the time with John Benzing - I had thought perhaps my Thunderbird was in with a chance but it was for F2b comp models only - I thought he said it was going to you. (BTW sold the T'Bird last year to Gerben Wassenar, also a friend of Rob I believe)

I can't find the images of the engine but the drawings are here - wonder how old Roger is? Guess he's still judging? Haven't spoken to him for quite a while - last time I saw him was when he came and bought my Arca - wonder if he ever finished it. Probably not knowing Roger  :Lol:


Regards - Tug



"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline Art K

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Re: 12,6cc engine..
« Reply #5 on: June 24, 2019, 02:17:07 AM »
Lauri,
I don't have any history in RC or aircraft anything but, I do recognize a great piece of work when I see one. Welcome to the forum.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Lauri

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Re: 12,6cc engine..
« Reply #6 on: June 25, 2019, 06:18:36 PM »
Me neither, Art. This is for control line aerobatics, F2B.
Here is some pictures of my scavenging and making of it.
Robbie supplies me with chunks of Mahle #124, with a chromed and pre-honed hole.
I then machine the outside shape, fuel passages and ports. I machine the ports through chrome, so far zero problems with chipping.
We use 100% piston scavenging, everything passes through piston windows to by-passes, that gives an excellent cooling & lubrication, and may be one reason why I have zero problems with my piston rings (dykes-).
But with my museum machines, they are a pain in a** to make. I'm about to get a nice digital divider for my little Aciera mill, hopefully it makes the work easier.
The latest 6-port Schnuerle works quite well. At the moment I'm making 2 new ones, one with basically same layout but with smaller port area & opening°, and another with loop scavenging & deflector piston.

Lauri

Offline Neil-Lickfold

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Re: 12,6cc engine..
« Reply #7 on: June 25, 2019, 08:35:23 PM »
Hi Lauri, It is so good that you have joined the forum, taking photo's of the exquisite work you do.
Thanks,
Neil

Offline Lauri

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Re: 12,6cc engine..
« Reply #8 on: June 25, 2019, 08:44:02 PM »
Thank you, Neil. I hope you are doing well down there. L

Offline Lauri

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Re: 12,6cc engine..
« Reply #9 on: June 25, 2019, 09:20:39 PM »
I have tested lots of different combustion chambers, but lately settled to a simple dome without squish band, with a titanium plug shield. That kind of a head seems to be best for handling the thermal hysteresis issues. Please note that I am not interested in maximum power output, but stability.
Silencer is based on Robbies calculations, it has 2 expansion chambers and one side resonance chamber in the middle. It works ok, but I feel I could still have something quieter.
I don't use nitro, just 80% methanol and 20% oil (5% Racing castor #927, 15% Klotz #189). For fine tuning the run in differend weather conditions I mostly play with venturi size. It's the easiest way as I made a quick change system in backplate. Nominal vennturi (True venturi geometry) ø is 5mm, and I can change them in 0.1mm steps. L

Offline Admiral_dk

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Re: 12,6cc engine..
« Reply #10 on: June 25, 2019, 10:08:22 PM »
Fantastic machining and construction  :praise2:   :cheers:

That said - I'm surprised that you have such success with pistons that looks "like Swiss cheese"  :o
When I tuned 50cc's in my youth - ANY windows in the pistons where a recipe for disaster  :cussing:
Mind you, the engine in question was supposed to run all year round for many hours every day .... (my daily transport).
I never tried doing it in any off my racers (MotoX).

I'm also surprised about your success with the (very asymmetrical) head shape - but I guess that it has proved it self to you already.

Best wishes

Per

Offline Lauri

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Re: 12,6cc engine..
« Reply #11 on: June 25, 2019, 11:23:56 PM »
Thank you Per.
Maybe your 50cc has bigger clearances, or just wrong kind of holes :)? This one seals pretty well even without ring. And as I said earlier, the windows are necessary because of piston scavenging.
Of course I have tried normal, symmetrical heads too with many different squish areas. But as the whole scavenging + exhaust package is asymmetric, it would be weird to assume that head should be symmetric.
I spent lots of time with the asymmetrick squish heads and they work clearly better than symmetric head with same squish %. But I have later abandoned the squish heads for thermal stability reasons.
There is a classical reason for asymmetric squish (more at exhaust side), for cooling reasons, but I doubt it's important in such a small engine. My reason is a better control of the ballistics of gas flow, I don't want that the incoming mixture hits the squish band and looses velocity before reaching the glow plug. At least that's how I think about it, maybe I'm wrong.
So far everything I have made in order to keep gas flow speed high, and with minimal discontinuations, has been beneficial to the engine run. L

Offline 90LX_Notch

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Re: 12,6cc engine..
« Reply #12 on: June 26, 2019, 01:09:31 AM »
Impressive.  That piston is mind blowing.

-Bob
Proud Member of MEM

My Engine Videos on YouTube-
http://www.youtube.com/user/Notch90usa/videos

Offline Niels Abildgaard

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Re: 12,6cc engine..
« Reply #13 on: June 26, 2019, 09:37:34 AM »
What is the benefit/explanation of the glow plug shield and why titanium?
I have seen titanium pipes disolved by  methanol ?

Offline Lauri

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Re: 12,6cc engine..
« Reply #14 on: June 26, 2019, 10:43:39 AM »
Hi Niels,

The purpose of Ti umbrella is to protect glow plug from fuel droplets and perhaps to pre-heat/stabilize the combustion process. It’s not a new Idea; I copied it from the engines of my friend Yuriy Yatsenko.
It gets very hot during running, so it has to be corrosion resistant. It also needs to have a relatively low mass. Ti is ideal for that purpose.
So far there is hundreds of hours of running wih this system, and no problems with it. L