earlwb

I didn't want to jinx it, so I breathlessly kept quiet until I had the engine in hand before I told anyone.
Many thanks to Wolfgang for selling me one of his extra radial diesel engines. I love it. I cannot wait until I run it to see how it works so I can decide which plane to put it on. I think I have just the plane for it too. I think he saw where I had lost the auction and was disappointed, so he offered to sell me his extra engine. I had to buy it for sure. I really appreciate him making one available to me too.
I am still somewhat speechless about getting the engine today and touching, holding it and fondling it of course.
Model airplane engine porn.

I am the proud owner of a WOHM 10cc RC Radial Diesel Engine and it is now an American Immigrant too.

earlwb

earlwb

fiery

My Feedback: (2)

Thank you posting this Earl.

Very alluring.

I am sure Wolfgang will be receiving orders.

batdog

My Feedback: (1)

I will be interested to know what plane you will put this on? Pictures? Good luck! Batdog

NM2K

My Feedback: (14)

You have once again topped everyone by getting such a beautiful engine. Good for you, Earl!

And I would like to know how much I would have to pay for such an engine. Approximate range, of course.


Ed Cregger

Hobbsy

My Feedback: (102)

Congrats Earl, that is beautiful and then some, like some of the modern TV ads say, "priceless".

AMB

Earl quite lucky you got it a rare priceless piece of suburb skill and engineering a true collectors item made by a vanishing few
masters of the art martin ( and it runs not just a display piece ) maybe a WACO bipe ?? martin
\\

earlwb

Thanks guys. Yeah I am still admiring it too.

I observed that he didn't just use a length of aluminum hex stock for the crankcase. He had machined in a round cylinder base for each cylinder in the crankcase as well. So he either used a really large size hex bar stock and machined it down a few sizes, or he used a large chunk of aluminum to machine in the hex shape and round cylinder bases. It is very impressive and I am sure it left a huge pile of leftover swarf too.

Here is a link to a older thread where we were discussing the diesel radial engines.
http://www.rcuniverse.com/forum/m_10...m.htm#10432008
or the printable version
http://www.rcuniverse.com/forum/m_10.../printable.htm

Some YouTube Videos of earlier WOHM engines. You can see how the engine design has been evolving over time.
[youtube]http://www.youtube.com/watch?v=AI1XMnUxso0[/youtube]

[youtube]http://www.youtube.com/watch?v=KO0NJCkOQSk[/youtube]

[youtube]http://www.youtube.com/watch?v=xBMJKZd9r0k&NR=1[/youtube]

A single cylinder 3.5cc version:
[youtube]http://www.youtube.com/watch?v=gOnDEKImPEE[/youtube]

and another radial version:
[youtube]http://www.youtube.com/watch?v=sUj1ly51-5U&feature=related[/youtube]

earlwb

If someone is interested Wolfgang has a "Black Devil" diesel radial engine built and ready to sell.
PM me and I'll give you his email address so you can contact him about it.
He black anodized the engine instead of using blue anodizing like on my engine.

iskandar taib

My Feedback: (5)

Interesting - this is a two stroke pumping via the crankcase, no? So how does it work? The only thing I can think of is all the cylinders hit BDC at the same time and TDC at the same time, which means all cylinders fire together. Is this true? It'd be interesting to see the crankshaft, in that case - and if so, it can't be a traditional radial with one "master rod" and one crankpin.

Actually.. Just noticed - the cylinders are not all in the same plane, so I suppose I'm right..

Iskandar

earlwb

Yes you are correct. it has all the pistons moving up and down in unison. They all fire at the same time.
It uses a reed valve on the carburetor for the intake, no rotary valve setup.

earlwb

I went ahead and fabricated a engine test mount for the WOHM engine. The prop shaft on the engine is setup for a 12mm size hole. I managed to trash two props before I got one reamed out close enough to be acceptable to use on the test bench. I would suggest sticking to wood props for this as the 12mm hole is too big for most plastic props.

earlwb

I got to test run the engine for several tanks of fuel. I had to fiddle with it some as a couple of the compression screws came loose on me, but no big deal. I used a Master Airscrew Scimitar 12x8 prop for my tests. But since you have to ream out the props for 12mm hole size, it is best to use wood, unless the prop has a solid hub to it. I trashed a couple of props before I got one reamed out acceptably to use for the test runs. it is still a bit off, but not too much for test purposes.

The engine still vibrated some but it was very smooth though in comparison to a single cylinder 10cc engine. The fuel tank didn't bounce around or foam up like you would see with a single cylinder engine in this size range.

The best RPMs I got after several tanks of fuel was about 6200 RPMs with the 12x8 prop. it ought to do a little better but I wasn't trying to push it and left it on the rich side more. As expected, with a multi-cylinder engine like this, the cylinders tend to run at different temperatures from the air and fuel flow differences. Standing from the rear, the top cylinder tends to run a little on the lean side, the right cylinder runs just right, and the left cylinder tends to run on the rich side. Measuring the cylinder temperatures had the top cylinder running the hottest at around 180 to 185 degrees F, the right cylinder at around 170-175 degrees F and the left cylinder at around 160 to 165 degrees F. The temps were likely higher, but the shininess of the cylinder heads tends to skew the measurments using a IR digital thermometer.

It didn't want to idle much below 3,000 RPMs, but it had a up and over fuel draw from the fuel tank and the prop doesn't have much inertia to it either. But that isn't a problem when I mount the fuel tank in a airplane better and maybe run exhaust collectors and some muffler pressure as well as maybe a larger or heavier pitch prop.








Some videos of me messing around with it. Oops the top compression screw came loose at the beginning of this video.
[youtube]http://www.youtube.com/watch?v=7R6dbb45ax8[/youtube]

[youtube]http://www.youtube.com/watch?v=SVSbndZTT8M[/youtube]

[youtube]http://www.youtube.com/watch?v=qZM9ZH2eAAo[/youtube]

AMB

Awsome sounds nice and smooth whats your fuel mix?? martin

earlwb

Davis Diesel Development fuel. Nothing extra added.

AMB

Earl Be careful running 3 cylinders at a time , Bob might triple your fuel cost
( I just had to say that) Kidding aside, combustion on the money, very little
smoke running clean as a whistle, oil that I see light brown, and not much
speaks well of the engine and fuel
Drooling in Fl Martin

earlwb

It appears that only the top cylinder was running a little brown color for the residue. I think that was because it tended to be a little on the lean side compared to the other two cylinders, so it tends to run a little hotter than the other two.

Thanks, I am quite in love with it. If you back off the compression a little bit, it develops a bit of a miss to it that sorta sounds pretty cool like a old timey engine of a sorts.

I am studying what I can put it on to fly it. The heavier weight of the engine and its lower RPMs tends to mean it is used in maybe a vintage style free flight converted to RC, or maybe a 40 size large winged bipe like a Stearman, or Tiger Moth or something like that, or maybe a TopFlight Elder, or a Taube would look good too. A 12x8 prop turning 6200 RPMs yields a theoretical airspeed of around 47 mph. So one has to be careful what they put it on.

Hobbsy

My Feedback: (102)

Great runner and obvious quality.

DeviousDave

Watching the video of starting and adjusting this engine, the first thing that comes to mind is the price to pay for having an engine this different is having to adjust three compression screws...

Sort of like having more than one wife, with the penalty being more than one mother-in-law.

Recycled Flyer

Earl, bugger all counter weight on the crank?

I assume that the counter weights are in fact the other pistons.

Interesting about the running temperatures with upright verses inverted cylinders but makes sense when you consider the internal ballistics - fuel/air mixtures must be influenced by gravitational forces even though they are being thrashed around in the washing machine of a crankcase at many 1,000's of rpm's.

It's something that I have held to be the truth when considering control line stunt diesels and the burp one gets with an inverted or upright engine when changing flight orientation.

Cheers.

earlwb

Thanks

Yeah the three pistons and rods tend to balance each other out very nicely. When you watch the engine run, the little fuel bottle doesn't even jiggle, as there are no low frequency vibrations to set off the resonances with. It still has a fine higher frequency mode though as the tachometer won't stay on the table but slowly vibrates off. I assume there is a slight twisting motion with the crankshaft causing the slight vibration effects because of the triple throws making the crankshaft longer and unsupported in the middle.

It didn't take too long for people to figure out that the pistons and rods can balance each other out to reduce vibration.
The classic example was the Anzani 3 cylinder radial engine as used in the early Bleriot airplanes. Obviously it had vibration problems.
But later they came out with the improved version with all three cylinders spaced out 120 degrees apart and it was much better of course.

I first saw the effects of the air fuel flow characteristics in the Fox 1.20 twin engine years ago. The left cylinder tended to run more rich and cooler than the right cylinder, and both cylinders had their own carburetor and were isolated from each other and the pistons fired 180 degrees apart and the exhaust was reversed too. But the left cylinder was drastically affected by the crankshaft rotation trying to force the air fuel to flow in a direction that tended to be unnatural or against the flow so to speak. You had to run the left side more rich or the left side would lean out too far on you. So the engine had a tendency to flood out the left cylinder when you lowered the throttle quickly. Once fix was to block off the main port to prevent a slug of fuel from drowning out the glow plug. Another fix was to use a on board glow starter to turn on below 1/4 throttle if you needed maximum power. So you had to be careful tuning the carbs as the left side didn't want to lean out much and the right side would easily lean out like normal.

Recycled Flyer

Mate, I could have done with your experience as back up when I tried to say the same once on a different forum - no one would believe that the fuel/air mixture in the lower crankcase of a two stroke is so easily thrown around.

The mixture in the lower crank case volume seems to be far more 'solid' and substantial than it first appears, and the denser it becomes in a lean air mix system (like that in a model diesel) the more it will be effected when subject to G forces. In other words glow engines suffer far less from this due to their tolerance richer mixs.

earlwb

Sorry I missed your discussion about it. One has to have a multi-cylinder engine and a thermometer and take some measurements before they really see it.
Clarence Lee once did a article about the Fox 1.20 engine's flameout issues, but I can't find it now.

Recycled Flyer

Earl, back on topic mate, what is to stop a simultaneously firing multi-cylinder design from linking the combustion chambers via a thin copper pipe or similar to ensure that all the heads run at the same pressure?

Example 1,
Have one master cylinder with a comp screw in its head and link that left and then right to the other two ........... but perhaps its too much to ask just one head to have enough adjustment to cover off all three cylinders.

Example 2,
Have all cylinders with comp screws in their heads and link all three heads in a continuous circular fashion, each head having a left and right connection to the one next one to it.

That should make tuning the comp very much easier or I am dreaming here?