GMA diesel articles?

But if I can help, I'd be happy. I've been flying diesels since 1956

I'm not exactly sure exactly what you want to know, so I'll put down pretty well everything - some you may already know.

1) Fuel. "Basic" fuel for small diesels is 1 part ether, 1 part kersone, 1 part oil. The oil can be ordinary multigrade motor oil.

A more advanced fuel is: 35% ether, 25% oil (castor oil is nice, but mineral will do) and 40% kerosene. To this can be added about 2 1/2% amyl nitrate, amyl nitrite, iso-propyl nitrate or diesel ignition improver (DII) This last makes the motor run smoother, but is not essential. Every flier has his favourite recipe, but the above is a good general purpose brew.

2) Starting. NEVER use an electric starter on a diesel! (OK I do sometimes, but I have 50 years experience).

a) Back the compression off about half a turn.
b) Finger choke and draw fuel into the motor. Usually 2 to 5 turns of the prop.
c) The engine should be a bit "wet". You can sometimes put in a small exhaust prime.
d) To protect your flicking finger, wrap two turns of "elastoplast" (Is it called that in the US?) around the end. This protects your finger from backfires and from being cut on sharp props.
e) Flick it over FAST. And again. SLOWLY increase the compression if it fires and stops, until it runs.
f) Let it settle a moment and then adjust the needle for a faster run. Needle is about 2 1/2 turns open on most motors.
g) Now adjust the compression. You may have to back this off as the engine warms up. And over-compressed motor runs "hard" and is not a happy motor!
h) Most find it best to run with the compression slightly backed off from max speed, and also the needle slightly richer than max speed. This should give you a nice consistent motor run.
i) Having two controls they need a bit more "feel" than glo motors, but that comes quickly

Diesels are great! If you have any other questions, I'll try and help.

Excellent synopsis, pretty well covers it all. I use a neoprene work glove with leather "armor" on the finger and palm back. The index finger is enough on the little ones- on something like a Drone .29- use two.

Once well run in, I found my PAW 19 would run happily on a lot less ether, and could often be started without varying the compression at all. Typically I would back off a quarter turn on the compression, and half turn on the needle for the first start of the day. From there on, it was just a matter of fuel, choke, flick and go with no further adjustments.

Really? You'd back off the compression to start? I'm no expert by any means but I always have to screw in the compression (more) for the first start. I just can't get it to start on the running setting.

Am I missing a trick?

Is your engine run in yet? What I describe below is for a well broken in PAW 19DS. For a new engine, like my barely run PAW 80DS (.049) it probably won't work. A new diesel, particularly one where you haven't established the running settings yet, can be a very frustrating engine. IMHO, getting those initial runs to happen is what puts many people off diesels. Once run in, and procedures are established, a diesel can be a true pleasure to fly - all you take to the circle is your fueled plane, no extraneous equipment.

A broken in diesel will fire across a fairly wide range of compressions either side of the optimal running compression. It can actually be harder to start if overcompressed, because the tendency to pre-ignite at high compression will cause it to kick back, whereas at lower compression it will fire a bit later and try to run forwards.

With my PAW 19, I found that I got a much easier start, with less kicking and ragged running on start, by backing up between a quarter and a half turn of the tommy bar.

For the first start of the day:

If the engine had been left at its running settings from the previous flying day, first start of the day would be:

1. Turn the compression back about a quarter turn.
2. Turn the engine so the piston covers the exhaust port.
3. Apply a small prime of fuel to the side of the piston.
4. Rock the prop back & forth a couple of times so the prime gets into the engine.
5. A couple of vigorous flips should give a burst.
6. Fill . Note - I was running my engine inverted. If mounted upright it would be wise to close the needle valve or disconnect the fuel line so you don't flood the engine. With an inverted mount any fuel that came up the fuel line would just drip out onto the ground.
7. Return needle valve to the last running setting if you closed it for fueling. Then choke the venturi with a thumb and gently turn over a couple of times to draw fuel up.
8. A couple of sharp flicks should lighter her off. Let run for 30 seconds to warm up, then adjust compression and needle valve until the engine peaks, then back off compression a fraction and richen the mixture a fraction (maybe an eighth of a turn of each - you'll find the right setting for your engine by experimenting). This slightly undercompress rich running is insurance against overcompressing and leaning out causing a 'hard run' once in the air. With the settings right, the castor oil ejected from the engine would be about the colour of honey. Too dark or carbonised points to over lean or over compressed running.

Subsequent flights just fuel, choke and start.

The above procedure would start my PAW 19, mounted inverted, very reliably without having to flip the plane over. The slightly rich and undercompressed setting worked out well in the air - that engine would purr to the last drop of fuel and often used to surprise me by cutting out cleanly with no warning.

The climate I lived in was fairly consistent, so there didn't tend to be a huge variation of running settings from one flying day to the next.

Note: it is some time since I have flown any of my diesels. I suspect when I actually get some diesel fuel, I may find I can't replicate the above advice as easily as I used to. It is definitely an acquired skill - one which can be quite frustrating to someone used to the easy handling of most modern glow engines.

Alternatively, follow the advice on this site:
http://www.antiquemodeler.org/diesels.htm

cheers,
Colin

Sorry about that.

Now hook up the fuel line, open the needle a couple of turns and suck fuel up to the venturi. Prime and flip. See previous instructions above.

A flooded diesel will not start. Generally running compression is less than easy starting compression, and running needle is a little on the lean side for easy starting. I like leaving settings alone, so I usualy use a starter once I am flying and the engine is sorted out. Diesels are more sensitive to compression than to the needle. A little rich won't hurt anything if compression is right.

If the engine slows in maneuvers it is overcompressed. If it misses in maneuvers it is a hair lean. The engine should run steadily in level flight. It should be warmed up and running good about the time you get the safety thong on and are ready for a launch. Diesels are idiosyncratic. The proceedure which works for one will need a little modification for another, perhaps.

Not trying to hi-jack this thread either, but George Aldrich did write about diesels on several ocassions. However, in searching through my records, his articles did not provide any more useful information that what has been provided here.

But to answer the question if George Aldrich ever published anything more on diesel operation, here is what I found.

George wrote a column for Model Airplane News starting in March 1980 until March 1985 ca;;ed "For Engine Lovers". In May 1980, he talked about diesel conversions. In May 1983, he talked about fuel formulas for diesels. In June 1984 he made some general comments about diesels and throttles. Pictures of some OT diesels in his last collumn in March 1985.

In May 1978, George wrote another column in Model Builder magazine with Dale Kirn and Otto Bernhardt ca;;ed "Fuel Lines". In the November 1979 issue, he talked about fuel and conversions to diesels.

Then, in the February 1980 issue of that magazine, Henry Nelson took over for Aldrich's contribution with the introduction as a kiesel expert. Henry wrote about diesels almost every month after that until July 1980.

It is unfortunate that the model magazines do not have anything comparable to those columns any more.

George used an Oliver Tiger Mk3 in the Peacemaker published in Aeromodeller.
The engine was not 2.5cc, but a .19 special.

Dave

Dave

Dave, you have me puzzled. My Mk-3 OT is a 2.5cc. At that time John Oliver also put out a modified (tuned) version but it was also a .15. I never heard of an OT Mk-3 in a .19 size, please enlighten me.

There was however I believe a 3.5cc Oliver Tiger Major if my very distant memory serves me correctly. But it certainly wasn't around for long (if ever there was one). I also read somewhere that GMA flew a Nobler with an OT 15! I THINK that was in his Peacemaker article in February '58 Aeromodeller.

I agree with Jim that yes, put a bigger prop than normal on when learning to handle your diesel. A 10x4 or even 10x6 is quite OK for a 15 while you are getting the knack of it.

You only go to tiny props and 23,000+ rpm when you are quite an expert!

I agree, having flown many Peacemakers. I "tame" mine with vintage PAW 2.49 by using a 9x4 prop and an extra home-made muffler. It really flies well - as they all have. The fastest I flew was with a Rossi 15D - too fast. And one of the nicest handling was with a Cox Olympic 15 on an 8x4, those were really sweet plane to fly.

It's a very pretty airplane, not much appreciated outside the UK (unfortunately!). I still have the set of Aeromodeller plans George got for me from a UK contact before he passed on.

Peace,

http://www.vicstunt.com/Plans/PeterWhite.htm

cheers,
Colin

There certainly was an Oliver Tiger Major 3.5cc diesel. I've posted some pics of a mates in his "Small Fry" OT stunt model. The motor has as the brits say "adequate power". The last pic is a modern Oliver Tiger replica, a Rothwell R250 in a Peacemaker for vintage combat. The r250 pulls the model around at about 90mph. Previously Steve had the motor in a full size RTF Flitestreak and it was only moderately slower.

The OT major was produced well into the 1980s according to Clanford's book. I seem to remember them being available in the 1960s but thats not reliable. Probably not used a lot in controline. There was a r/c version.

...and 0.199 cu in is about 3.25 cc.

Just for reference; no engine mfr would get away with calling a 0.199/3.25 engine a 3.5, eh?

3.5 cc comes to almost 0.214 cu in.

Isn't the PAW .19 closer to 3cc than it is to 3.2?

Just asking, regards Ray

Some of the early PAW 19s were even smaller, just a bit over .18 / 3cc

PAW had for several years offered repair/rebuild services at the factory, where I seem to remember the word "rebore" appeared as an overhaul action. Building below an engine-class boundary allows this, without forcing your mill 'over the line.'

Other than events where engine displacement defines the equipment, it seems we are less concerned with actual displacement these days.