Diesel Noob

While the oil % is higher, the fuel consumption is generally less, so I guess the "mess" is relative. Small diesels seem to do great in free-flight stuff. You can run a bigger prop than a glow, which will help with your "draggy airframe". The big issue these days with diesels is the practicality or otherwise of fuel.

The diesel engines are not so picky in terms of mufflers and muffler-extension (like a rubber hose) so it is easier to keep the exhaust residues (is that the "mess"...?) away from the plane.

Power output is fairly equal to glow but you can use a lower rpm, so therefore a larger prop and more static/low speed thrust.

It is getting harder and harder to find the fuel here, and the smell tends to linger in clothes etc, but otherwise there are only advantages with diesel engines.

Gentlemen:
Thank you very much for contributing to my meager diesel knowledge.
Actually, reading your prior posts is pretty much what pushed me over the edge.
I understand the difficulty obtaining fuel. I'm willing to mix my own using ingredients according to the recipes found here.
Surfer Kris' work with the diesel powered .074 Cox queen Bee kind of clinched it.
Great work. Thank you.  
My plan is to order a diesel head for one of my Cox .049s.
Will try running it in my shop so as to get use to adjustments.
Any suggestions toward other items that I may need is certainly welcome and appreciated.
Scratch...

The fuel is very important, even more so than i glow engines, as there is no glow element that can help with the combustion. I would strongly suggest to first get some commercial fuel, just to get a feel for how a diesel engine should behave on proper fuel. I have not managed to get any good performance from my home brew attempts, sure the engine "runs" but it doesn't run well. The main problem is to get pure ether, using starter fluids have not worked for me, there is too much of the propellant remaining in the liquid (that is my conclusion at least).

Below is another very smooth runner, here running on a commercial fuel mix that was blended to my specifications (25% castor, 34% ether and 1.5% DII, if I remember correctly). The pick-up from idle is very impressive for a diesel engines, this is perhaps the most difficult/demanding part. Usually the optimum compression ratio at full throttle is lower than the optimum one at lower throttle settings, and it is very hard to find a good compromise between the two. Here is where a proper fuel blend is very important. If you check any youtube videos of 4-stroke diesels, for instance, they never ever have a good acceleration from idle...

Here is an MVVS .09 engine (plain bearing with the stock airbleed carb, and the optional muffler), the exhaust note felt even softer in person:

Scratch here is another thread i had stared some time back https://www.coxengineforum.com/t12373-diesel-fuel-purchase-or-mix-ur-own?highlight=diesel

Surfer_kris wrote:I have not managed to get any good performance from my home brew attempts

I searched all over the net and could not find a model diesel fuel supplier in this country.
Did find one in England.
This is disturbing.  
Thanks for the link Getback.
Read through it and did find that Johnson Starting Fluid contains 50% ether.
I can get it locally.
Being a bit stubborn, I intend to research this further to see what I come up with.
I still intend to order a diesel head for one of my Bee's.
If all else fails, I can always go back to glow.
Scratch...

Scratch049 wrote:
I still intend to order a diesel head for one of my Bee's.

Just be sure to get one that doesn't use that silly teflon gasket stuff, that just doesn't work, been there done that...

The RJL one is much better (it seals with an o-ring):

Thank you Kris.
I believe that MECOA have the correct heads.
https://www.mecoa.biz/shopdisplayproducts.asp?catalogid=1650
Pretty engine.

Yes , get the head with the O-ring . Teflon head is more pain than it is worth . I have made heads for many diesels and the O-ring works great . Don't know why some people think that you need a cast iron contra or a Teflon seal , the O-ring works great and is easy to make a head for it .

Mike1484

Scratch049 wrote:
Read through it and did find that Johnson Starting Fluid contains 50% ether.
I can get it locally.
Scratch...

What you need to be careful of is, what's left behind once the propellant is bled off? Check out their Safety Data Sheet first which should have quantities of ingredients. When the propellant's gone you will have more that 50% ether. The rest will most likely be Heptane. From what I've learned, this pretty much is considered kerosene in your final mix.

John Deere fluid isn't available here as far as I know, due to our climate. It's pretty much 100% ether once the propellant is gone. Best I can find is "Master" 50%, which is probably the same stuff as your Johnson. Haven't tried it yet, but I'm confident that I could calculate out the right ratios to get the 1/3, 1/3, 1/3 mixture, considering the Heptane as part of the kero component.

Rod.

Thanks Rod.
I called our local John Deere office and was advised that the Starting fluid isn't available, that I should look at an auto parts store.
It may be available on line but I have not checked yet.
Here's the info from the Johnsons starting fluid Safety Data Sheet.
Ethyl Ether  49-60%  400ppm
Heptane      20-30%  400ppm
Propane        5-15% 1000ppm
Iso Butane     2-10%
Lubricating Oil .5-15%
May be similar to your product?
Johnsons is fairly inexpensive here at $2.99 for a 7.2 ounce can.
Hi Mike.
Have you had any success with the Cox diesel conversions?
Scratch...

scratch , you may have to ck. some the JD dealers that sell LARGE COMBINE and other equip , or ebay ... https://www.ebay.com/itm/163817034391 About the same price as it in store at 7.00 -+ here in NC ..

Appreciate the link Getback.
The local Deere dealer does sell tractors and other large equipment.
It's fairly rural here.
It may be recreational drug problem related.
From other info on the web, I'll surely be careful handling this stuff. Outside mixing and careful storage in the outside shed.
Anyway, this is what a Safety Data Sheet said about the JD starting fluid.
Diethel ether              400ppm  80-90%
Liqued petroleum gas  1000ppm  10-20%
Propellant:
  Carbon dioxide      5000ppm
Looks like a higher ether content than Johnsons.
Scratch...

Scratch,

I always slip a small diesel engine in my pocket, when I visit a John Deere dealer. If they ask what you plan to use the starting fluid for, just show them the diesel engine.

My first visit to buy starting fluid (without a diesel engine in my pocket) they had me sign a form, but in the ten years since, have never asked again! I think the word has gotten around that some people actually run model diesel engines.

Bill

Great idea Bill.  
Will have to remember it if I run into the same situation.
I felt that the guy at my local JD dealer was kind of irritated.
They may have had a problem in the past.
No matter. As long as I have a source when I need it.
Scratch.

Scratch049 wrote:Thanks Rod.
I called our local John Deere office and was advised that the Starting fluid isn't available, that I should look at an auto parts store.
It may be available on line but I have not checked yet.
Here's the info from the Johnsons starting fluid Safety Data Sheet.
Ethyl Ether  49-60%  400ppm
Heptane      20-30%  400ppm
Propane        5-15% 1000ppm
Iso Butane     2-10%
Lubricating Oil .5-15%
May be similar to your product?
Johnsons is fairly inexpensive here at $2.99 for a 7.2 ounce can.
Hi Mike.
Have you had any success with the Cox diesel conversions?
Scratch...

Average out the Propane & Butane elements and remove them from the ingredients list as they are the propellants which will be bled off. You'll be left with Ether, Heptane (equivalent to kerosene) and a little oil (which can probably be included in the Heptane content.)

Ahh...
Good to know,Rod.
I"ll keep this info with the rest of my diesel file.
(slowly growing)
Many thanks.
Scratch...

Scratch ,

Never bought a reedy diesel conversion but made some heads for the .049 and .020 . Made some with O-rings and some with Teflon discs . Also have a Davis head ( Teflon disc ) for my Cox Tee Dee .09 . The Davis head ran nice on the .09 on an old timer . The .020 was not any fun or worth while but had some good results with the o-ring heads on .049's .25 and .35 O.S. and Super Tigres . Also have Davis heads for O. S. .10 , .25 and a S.T..40 . They all work fine . I have about 50 -60 diesels and enjoy running and messing with them and yes I fly them also . On the small .049 and smaller engies I think the best set up is the solid contra piston fitted to the inside of the cylinder bore . PAW motors and a lot of older English engines fit this category . I don't claim to be the almighty master of the diesels but after 60 years of messing and flying them I can say that I am comfortable around them except that SMELL . Some pictures of my diesels are on R/C groups in my attachments if you like to look at engines .

Mike 1484

The .020 work fine but there were some errors with the DDD head for them. On mine the counter piston was sitting too low in the head, I had to remove about 0.15 mm in order to get enough a low enough compression ration and a little bit of adjustments range around that. The Teflon disc are useless, but it is easy to cut a new one from a sheet of brass and will last for many runs.

I have one in J3 cub and it flies much better with the PeeWee on diesel, spinning a 6x3 prop at around 10000rpm rather than screaming at around 15000rpm on the stock glow prop. On diesel I get longer runs and no sudden stops, the diesel just tend to continue running even if the settings are a little off.

Here is the plane (I still need to mount the engine cowl):


A short bench run, it was set a little too rich here and you can hear it rev up as it empties the tank:

Hi kris ,
Funny but I never tried the metal disc , guess I had too many small diesels to play with other than the small Cox .020 - .049 's . Your .020 ran like mine but I think the metal disc is almost needed to get a good seal on the head . Small .020 was pretty touchy to set but these diesels even with a bad set like to keep on running .

Mike1484

Nice Cub Kris.
Really like the sound of that .020.
Mike:
Curious as to the kind of fuel that you used in your O.S. diesels.
Home brew ??
Thanks.
Scratch...