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Post  ian1954 Tue Dec 30, 2014 4:45 pm

I like 5 Cylinder Radials!

G-Mark 5 Cylinder Radial .030 G-mark11
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Post  ian1954 Tue Dec 30, 2014 4:46 pm

Especially small ones!

G-Mark 5 Cylinder Radial .030 G-mark12
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Post  GallopingGhostler Tue Dec 30, 2014 9:23 pm

Nice. The smaller ones are your handiwork, Ian? Babe Bee
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Post  ian1954 Wed Dec 31, 2014 3:58 am

@GallopingGhostler wrote:Nice. The smaller ones are your handiwork, Ian? Babe Bee

Afraid not!. I have never gone beyond a twin. These are more of Ronald Valentine's creations. I fully expect, following his other creations, that we will be seeing even smaller versions.
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Post  balogh Wed Dec 31, 2014 9:03 am

@ian1954 wrote:
@GallopingGhostler wrote:Nice. The smaller ones are your handiwork, Ian? Babe Bee

Afraid not!. I have never gone beyond a twin. These are more of Ronald Valentine's creations. I fully expect, following his other creations, that we will be seeing even smaller versions.

I wonder how these multi-cylinder gems work sharing a common crankcase..I mean I suppose all pistons must move up and down simultaneously otherwise the suction from a shared carb and filling the cylinders with fresh charge would not possible...Do you happen to have a pic with the backplate removed so that the crankshaft and conrod configuration could be seen? (Just do not remove it for my sake..)
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Post  Surfer_kris Wed Dec 31, 2014 9:13 am

The G-mark is geared, so while the cylinders share the same carb they don't actually share the same crank-case. Here is a rather low resolution picture I had on my computer;

G-Mark 5 Cylinder Radial .030 G-mark10
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Post  TDbandit Wed Dec 31, 2014 9:53 am

Wow I've always wondered how they did it. Being an A&P mechanic it hurt my head wondering how a two stroke radial ran with the standard master/link rod setup (shouldn't be possible) now after seeing this "multiple cranks geared to a common shaft" makes a whole lot more sense. I've seen one of these run in a steerman a long time ago (G-mark) and they have a weird sound to them.
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Post  balogh Wed Dec 31, 2014 10:15 am

Gas engines are not famous for their compression, at least not in the sense of a nitro engine that has much thicker fuel containing 20% or so lubricant. Gas engines run on 1:50 gas/oil blend i.e. 2% oil content only. It means the cylinder walls are certainly pretty dry now, and you may want to check if the valve timing is properly set, the valve seats burred etc.

But it may simply have been used up to its duty life and worn as well.
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Post  TDbandit Wed Dec 31, 2014 10:30 am

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Post  GallopingGhostler Wed Dec 31, 2014 11:21 pm

The 2 stroke G-Mark 5 cylinder, do all the cylinders fire simultaneously or sequentially? Huh...
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Post  Surfer_kris Thu Jan 01, 2015 3:54 am

I don't have any of these engines myself, but from the construction I believe they fire sequentially. There is a rotating valve in the center that feeds the individual crank-volumes.

I have one of the twin engines though, and they fire simultaneously.

Here is a video (not mine) of the 5-cylinder engine when running. While the engine ran "fine" it didn't have much power and he never flew with it because of its weight;

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Post  GWILLIEFOX Thu Jan 01, 2015 7:33 am

@GallopingGhostler wrote:The 2 stroke G-Mark 5 cylinder, do all the cylinders fire simultaneously or sequentially? Huh...
They fire sequentially. Each fires for one revolution of the propeller so there are five exhaust notes per revolution of the prop.

The 5 cylinders exhaust into the front cavity of the case thus lubricating the gears. Finally, there is a single exhaust stack at the bottom front of the case.

The pistons, rods, and cylinders are the same as used on G-Mark's single cylinder .060 (1 cc) and opposed .12 twin.
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Post  gcb Thu Jan 01, 2015 4:53 pm

@crankbndr wrote:This really cool Morton 5 is currently on eBay, I would like to own it but you got to wonder why there is no compression.
G-Mark 5 Cylinder Radial .030 5_tiff10


The Morton M-5 (also known as the Burgess M-5...I don't remember who sold to whom) is/was a much sought-after engine and the price will probably go several times the present price.

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Post  GallopingGhostler Thu Jan 01, 2015 5:37 pm

@GWILLIEFOX wrote:They fire sequentially.  Each fires for one revolution of the propeller so there are five exhaust notes per revolution of the prop. The 5 cylinders exhaust into the front cavity of the case thus lubricating the gears.  Finally, there is a single exhaust stack at the bottom front of the case. The pistons, rods, and cylinders are the same as used on G-Mark's single cylinder .060 (1 cc) and opposed .12 twin.

That is interesting, then it must be a very smooth running engine. Due to the internal friction of the gearing, and as pointed out the glow plug head versus higher compression integral glow head and heavier weight, its lower power would make it more suited for a short nosed lightweight biplane like a sopwith 1-1/2 Strutter or triplane like the Fokker DR-1. That would have really been a sight to see it fly if properly mated to a matching airframe.

I heard that the last of the G-Mark parts were lost from heavy damage at sea and alas the line had a short lived time span. I gather that one could probably take 5 Cox standard Sure Start crankcases and cylinders, manufacture an external exposed gear front to drive a central prop shaft, build a choke tube manifold to a single carburetor, which would feed the 5 cylinders, to have a similar type experience.

This is more of an advanced topic that although unique, takes one out of the run of the mill sport experience that most would simply bolt on a modern .15 or .20 glow engine and be done with. Tired w/ Coffee Read Smile
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Post  Tabman Wed Sep 27, 2017 11:00 pm

Greetings from Sydney! Can anyone help me reassemble/time a G Mark .30 radial engine? Is there a manual available out there somewhere?
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Post  GWILLIEFOX Thu Sep 28, 2017 12:55 pm

@Tabman wrote:Greetings from Sydney! Can anyone help me reassemble/time a G Mark .30 radial engine? Is there a manual available out there somewhere?

The September 1980 Model Airplane News had a test report by Peter Chinn.  I have included the instructions for timing the gears to the main crankshaft.
G-Mark 5 Cylinder Radial .030 Man09811
G-Mark 5 Cylinder Radial .030 Man09810
G-Mark 5 Cylinder Radial .030 Gmark_10
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Post  GWILLIEFOX Thu Sep 28, 2017 1:00 pm

http://sceptreflight.net/Model%20Engine%20Tests/G-Mark%2030%20Radial.html

Above is a link to Peter's report in and English mag and the first pages of the MAN ad

G-Mark 5 Cylinder Radial .030 Man09815
G-Mark 5 Cylinder Radial .030 Man09812
G-Mark 5 Cylinder Radial .030 Man09814
G-Mark 5 Cylinder Radial .030 Man09813

If you get this together and running, you will love the sound!
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Post  Tabman Thu Sep 28, 2017 4:34 pm

Thank you so much! I tried to start the engine 25 years ago without success.... couldn't get enough power to the glow plugs... and then packed it away. The fuel left in the engine had gummed it up horribly, my son and I are determined to get it running, I'll let you know how I go. Thanks again for your help.
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Post  GWILLIEFOX Thu Sep 28, 2017 7:51 pm

Yes powering 5 plugs is a bit of a challenge.  I also have and OS Pegasus 4 cylinder and was thinking about it.  I got a couple of 2 cell pencilled boxes and attached leads with alligator clips to th3 boxes.  Th3 boxes were wir3d with thE cells in series.  Connecting a clip to the tops of th3 plugs on each of two cylinders puts two plugs in series with the two batteri3s in series and you get 1.2 v per plug.  I used nickel metal rechargeablespecially.  Our two of these boxes take care of 4 cylinders and a regular glow driver handles the 5th.
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