Help please

Which conversion head are you using?
I've never had any luck with the teflon gasket, it just never seals. A thin sheet metal gasket works fine though. Prime only the side of the piston to get a feel for the compression setting before you even hook it up to a tank. You don't need to run in glow fuel but you do need a nice fit between piston and liner.

Check the comp with the glow head.
If it seems good then the problem I most likely the diesel head not sealing.
If It uses teflon discs check those, they break really easy so I just make them from Alu or Brass as Per Surfer_Kris' advice.

Can anyone post a sketch of a diesel? I'd like to know where the discs go, what the T-bar does, etc.

Here is the principle;

It's funny how things change with time. My father has never been very fond of glow engines, it is a pain to get them to run right when there is only one needle to tune on...

Surfer_kris wrote:It's funny how things change with time. My father has never been very fond of glow engines, it is a pain to get them to run right when there is only one needle to tune on...

I started glow and converted to diesel, despite having more things to tune they are so much less fussy, until you get smaller than .15cc then they can get a little finicky!
And no glow starters or electric stuff needed to run them!

Check out carlsonengineimports.net. Mr. Carlson always has a lot of good info on diesels. He is also a grerat guy to deal with.

Some folks may want a basic comparison between glow and diesel running, so here is an attempt:

Glow engines are set-up to perform well within a certain range of fuel mix, on a certain range of prop sizes, and with a certain glow plug. If you vary outside that range, you must compensate by adjusting other factors. For example, if you go to a larger prop, the engine will overheat because you need to retard firing timing a bit. This is done by adjusting head shims, adjusting nitro, or both. You may also need to decrease intake size to increase venturi velocity for adequate fuel draw.

With a diesel, firing timing is adjusted with the tommy bar as you vary compression to make iit run best for the particular fuel/prop combination you are using. Often the intake size is on the low end so you can use larger props.

Some folks fiddle with the tommy bar more than necessary. Once you have established a running position, it should be good for the rest of the day while you are using the same prop and fuel. Running characteristics of a diesel allow it to still achieve most of its power even if the settings are a little off.

Some engines require a starting adjustment that is different from the actual running setting. Often it is possible to adapt your starting procedure to compensate and start it in the actual running position.

George

Thanks for the lesson.

"Back when I were a lad, in't good ole days......."

Seriously though, in the 50's 60's early 70's in the UK, glow motors smaller than .35 were hardly ever seen, the diesel ruled the modelling skies, with a few exceptions ALL British made engines were diesel, I grew up with them, and if I had the chance I would happily swap all my glow engines for diesels! All you need for a days flying is the model and a tin of fuel, no wires to tangle or batteries to go flat at crucial times.
I can still start a diesel easier than I can a glow, after some practice you develop a "feel" for the compression screw and needle settings, the technique is, left hand holds the compression screw while the right flicks the prop, you move the compression up and down while flicking the prop until you can feel it's about right, and it will start.
The important thing to avoid with any diesel is what is known as "hydraulic lock" this is when the engine is flooded so badly that the piston won't go over compression, this can have some serious results, especially in small engines (and Cox conversions) you can bend the conrod or break the crankpin off the crankshaft, and also your finger will slide down a sharp prop edge, which is VERY painfull! So start with too little compression and work up!

Wilf

Being an engine new boy, haven't needed to run one since I was a schoolboy. You dont need engines in sailplanes.
And my current RC club is electric only Thankyou for helping me understand whats going on. I'll appreciate them even more now and want to run them.
Thanks

ebeneezer wrote:
The fuel I'm using is 30% ether 36% Kerosene 2% nitrate.

There's your problem - you're only using 68% fuel

dinsdale wrote:

ebeneezer wrote:
The fuel I'm using is 30% ether 36% Kerosene 2% nitrate.

There's your problem - you're only using 68% fuel

Assume what was not counted was castor oil

dinsdale wrote:

ebeneezer wrote:
The fuel I'm using is 30% ether 36% Kerosene 2% nitrate.

There's your problem - you're only using 68% fuel

And using that, you'll only get 68% of the revs!

Ivanhoe wrote:

dinsdale wrote:

ebeneezer wrote:
The fuel I'm using is 30% ether 36% Kerosene 2% nitrate.

There's your problem - you're only using 68% fuel

And using that, you'll only get 68% of the revs!

Nah you get 680% of the revs but 0.068% of the engine life!

ebeneezer wrote:Being an engine new boy, haven't needed to run one since I was a schoolboy. You dont need engines in sailplanes.
And my current RC club is electric only Thankyou for helping me understand whats going on. I'll appreciate them even more now and want to run them.
Thanks

We have been kidding a lot, but I would suggest:

Reinstall the glow plug and break-in the engine on a 5"x3" prop. After that, use the diesel head with a 6x3 or so prop and run it as a diesel. Use commercial diesel fuel at first if you can get it. That way you are not trying to jump over multiple hurdles at the same time. When stating diesel fuel ingredients, most commonly you name ether, lubricant, nitrate, with the assumption that the remainder is kerosene. That's why the teasing.

I hope you do take the time to learn engines, they are a lot of fun.

George

6x3 on a diesel is too small, that's what I use on my Pee Wee diesels and they spin it at around 10000rpm. For a .049 engine try something around 7x4 instead.

What's the nitrate you mention? All the articles I've ever read state a rule-of-thumb 40% kero, 35% ether an 25% oil (you can mix synthetic and castor oil).

These are good articles:-
http://coxengines.ca/files/FG.pdf
http://coxengines.ca/files/DEG.pdf
http://coxengines.ca/files/EOG.pdf

The nitrate referred to was in the old days amyl nitrate, or nitrite
and used to be available over the counter at the chemist but is now
unfortunately a controlled drug. It was added to model diesel fuel
as an ignition improver, usually at 2%.
Nowadays various substitutes are added by fuel vendors in about
the same percentage.
Not necessary if you are mixing your diesel fuel.
Your fuel will work almost as well without additives.
John

First off your ether content is way to low for a 1/2A engine. Basic fuel is 1/3/1/3./1/3. For 1/2a ether needs to be at 40%.

On inspection I now realise that the pressure diaphragm is missing. Can I get a replacement? or can I make one, and out of what? Second question, does anyone do a diesel conversion for a PeeWee?
I'm getting into the idea of diesel powered Cox engines. It must be the Brit in me

ebeneezer wrote:On inspection I now realise that the pressure diaphragm is missing. Can I get a replacement? or can I make one, and out of what? Second question, does anyone do a diesel conversion for a PeeWee?
I'm getting into the idea of diesel powered Cox engines. It must be the Brit in me

Assuming your engine has a DDD (Davis) or Cox International conversion, you can buy extra teflon discs. The reason teflon is used is so if you are running over-compressed (which raises engine temperature) the discs will melt and hopefully save your engine. Some folks prefer running "on the edge" and prefer a conversion that does not have that feature.

If you have a Cox reed engine, you should also get the Cox "Killer Bee or diesel" crankshaft because the standard crankshaft will break (there are probably a few exceptions). If you are using a COX TD, the crankshaft should be OK.

These parts can be found in some local hobby shops, and are also available from Davis Diesel Development or Cox International. Shipping is cheaper at CI.

George