Author Topic: Green G30 Sleeve Valve Engine  (Read 3471 times)

Offline Laurentic

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Green G30 Sleeve Valve Engine
« on: May 21, 2018, 09:47:48 PM »
Has anyone out there built the Green G30 Sleeve Valve engine?  The plans date from 1988.  Casting kits were available - one was offered for sale not long ago so presumably some were built.  Would be interested to hear if anyone did build one how they got the thing to run and what compression pressure was achieved.

Chris

Offline dieselpilot

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Re: Green G30 Sleeve Valve Engine
« Reply #1 on: May 22, 2018, 02:17:03 PM »
Did you build one? Are you having trouble with it? I have a plan set.

Offline Laurentic

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Re: Green G30 Sleeve Valve Engine
« Reply #2 on: May 22, 2018, 02:52:32 PM »
Hi - yes I built one, won't start but as it has very low compression I'm not surprised.  I have a set of imperial plans from 1988 from which I built the engine.  A friend 'Down Under" built one before me and he couldn'y start his either.  Did you build one yourself?  Did it run?
Chris

Online Jo

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Re: Green G30 Sleeve Valve Engine
« Reply #3 on: May 22, 2018, 03:17:58 PM »
They run very well. All they need is a good fit between the lapped piston/cylinder and a slightly wider fit with just enough space for some oil between the Liner and the Cylinder  ;)

Jo
Enjoyment is more important than achievement.

Offline kvom

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Offline Laurentic

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Re: Green G30 Sleeve Valve Engine
« Reply #5 on: May 22, 2018, 04:12:10 PM »
Jo - glad to hear they run very well, only wish mine did.  The sleeve bore was lapped so as the piston just slid in.  I fitted 2 piston rings to mine.  The drawing calls for a sliding fit for the sleeve liner interface, and that's what it is, a close sliding fit.  Have oiled sleeve to liner interface and piston to sleeve interface.  Still getting very low compression.  Suspect that the compression air is leaking by through the sleeve port before it seals against the junk head ring and out via inlet and exhaust ports, when I test it on low pressure air this is the impression I am getting.  Were the ones that run built as per the drawings or were their any mods, does anybody know? 
Chris

Online Roger B

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Re: Green G30 Sleeve Valve Engine
« Reply #6 on: May 22, 2018, 06:48:00 PM »
I think that I can picture this but can you post a drawing of the cylinder/sleeve/piston layout?
Best regards

Roger

Offline dieselpilot

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Re: Green G30 Sleeve Valve Engine
« Reply #7 on: May 22, 2018, 06:59:50 PM »
How many degrees after BDC does intake close?

Online Jo

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Re: Green G30 Sleeve Valve Engine
« Reply #8 on: May 22, 2018, 07:08:39 PM »
« Last Edit: May 22, 2018, 07:14:13 PM by Jo »
Enjoyment is more important than achievement.

Online Roger B

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Re: Green G30 Sleeve Valve Engine
« Reply #9 on: May 22, 2018, 08:35:20 PM »
This looks to me that the top (junk head) piston ring is critical. I will read the rest of the German description tomorrow and comment on that.
Best regards

Roger

Offline Laurentic

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Re: Green G30 Sleeve Valve Engine
« Reply #10 on: May 22, 2018, 09:42:00 PM »
dieselpilot - inlet closes 64 degrees after BDC .

Jo - nice engine, quite sophisticated, have looked at that one before, but it's not the Green G30 sleeve valve engine.  Have you seen one (a G30) running?  If so, am envious!!

Roger - I agree that the junk head ring is critical.  I feel on my engine that the junk head ring only just closes off the sleeve port as the sleeve gets to TDC.  I think it should shut off earlier.  That's why I feel compression pressure is being lost via the sleeve port on the compression stroke.  To try and minimise this loos I am thinking that sleeve/liner interface should be lapped (I feel a new liner coming on here)- and hope that the heat doesn't seize things up.  Always assuming the damn thing runs of course.

Chris
« Last Edit: May 22, 2018, 10:07:20 PM by Laurentic »

Offline Laurentic

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Re: Green G30 Sleeve Valve Engine
« Reply #11 on: May 22, 2018, 09:46:49 PM »
Roger - to answer your first question, I will try and post a photo of the GA tomorrow. 

Chris

Offline Art K

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Re: Green G30 Sleeve Valve Engine
« Reply #12 on: May 23, 2018, 02:36:27 AM »
Chris,
I have always been fascinated by the sleeve valve engine. Can't say I've every heard of the Green G30 before today though. I recognize the difficulty with the timing cant just bump the cam forward or back to fix the timing. Looks great.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Online Roger B

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Re: Green G30 Sleeve Valve Engine
« Reply #13 on: May 23, 2018, 02:11:33 PM »
I have had a quick look through the metallmodellbau build. I know its a different engine but there are a few points that may help:

-He states that the sleeve is made from a special steel, ETG100, that doesn't distort much with temperature.

-The sleeve is lapped inside and out to +/- 0.005mm of the nominal size.

-The shape and position of the ports is critical to the timing. He made a second sleeve to correct the timing errors after he carried out a timing check with the engine assembled.

I also wonder how important the sealing of the space in the junk piston above the sleeve is? When the ports pass by the junk piston ring there will be some leakage into this space. If it is sealed it should reach some form of equilibrium  :headscratch:
« Last Edit: May 23, 2018, 02:20:50 PM by Roger B »
Best regards

Roger

Offline dieselpilot

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Re: Green G30 Sleeve Valve Engine
« Reply #14 on: May 23, 2018, 02:39:22 PM »
64° is about what my CAD model shows. It isn't excessive, many production RC engines are ~60°ABDC. The port sealing by the ring only really matters for static compression. At running speed, face of the junk head will determine timing. It's no different than porting in a two stroke engine. The sleeve port passes the junk head ring at ~90°BTDC. Geometric compression ratio as designed is quite high. I considered fitting a dyke's ring in the junk head when I build mine, but don't feel it should be necessary.

There was a collector who had several Green engines on one of the RC forums. These were built by Green and sold complete. Very few were supplied complete, I've only ever seen a few for sale. He said he ran all of them and that they ran well.

Most glow engines don't need very good compression sealing to run, but often engines in this condition will be difficult to start and by hand sometimes impossible.