Juker008

I'm thinking pros:

[*]Fuel economy?[*]Low chance of detonation?[*]Tq[/list]Cons:
[*]Can't get high RPMs?[/list]

123Cat

Pro's are good smell

Good power

Right burping sound

No batteries

Unique

good bit of vibration ,,

Nice oily mess

No disadvantages

mike109

G'day

Pros.

1. Use about half the volume of fuel.

2. They just don't stop. Diesels rarely dead stick.

3. You can swing very large props because you have control over the ignition timing (compression).

4. Rust is not usually a problem though it does help to run them dry.

5. No one else will have one.

6. The smell of ether.

7. Simplicity. All you need is the engine and some fuel. No starters, no glow plugs, no glow starters. Fill, prime and flick.

8. Modern glow motors often make good conversion subjects. The OS LA engines are particularly good as diesels and run better than they do as glow engines.

Cons.

1. They usually cost more.

2. They are rarer.

3. The smell of burnt kero.

4. Getting ether is not easy but if you are in the US you have access to good commercial diesel fuel. Not so here in Australia.

5. The older iron/steel ones take a while to run in but this helps you to learn about the engine.

6. Some of the modern glow engines have carbys which are too large for use as a diesel. They work best with a smaller or sleeved carby. Not really a Con but something to be aware of.


I am currently running in a PAW 40. It was reasonably easy to start from new and is running quite well on my home brew to the makers instructions. So they must have something going for them.

Cheers

Mike in Oz

steve111

Pros:

What the previous posters said, plus I just plain like running the things.
I also find that being quieter than glows, I can run my diesels (up to .25 ci) without mufflers, so you've got a very good ratio of power to overall weight.

Cons:

Ether can be hard to come by for some people.
Messy - although I'm finding Benol-based fuel much better in that regard.

As far as not revving well, I've got an MP Jet 061 BB that spins a 7x3 at nearly 18000 (ie in Norvel 074 glow territory); I also saw a 2.8cc engine, designed and built by David Owen, turning an 8x5 at over 16000 the other day. Seems like enough revs to me!

fiery

My Feedback: (2)

Great replies chaps.

My Mecoa diesel head converted FP 40 with a hefty 10x6 composite prop spins 500 rpm harder on standard plain bearing (25% castor) diesel fuel, than on FAI glow fuel. It's on youtube.

http://www.youtube.com/watch?v=eFa407riGj8

http://www.youtube.com/watch?v=X7VlP...eature=related

So much for the myth of lower RPM's. Throttles like a beaut as well.

No need to lug these engines down, though they will cope with it much more happily as a diesel than as a glow.

My favourite benefit is simply the ability to adjust compression for any situation. And the deeper, less raspy, throatier sound they make.

Mr Cox

Most of the "pros" have been meantioned already, and there are only two "cons": i) getting the fuel and ii) getting the smell out of everything after a day at the field...

Juker008

Hold on. What you guys are telling me is that not only is more fuel efficient than petrol (or are you guys talking about glow), but also produces more rpms than glow?
Now what is this about no starter, or glow starter?Your telling me that they ignight simply by compression?
And what is this about smell, are we talking about the smell that get when you're at an airport, or are we talking about popcorn, cotton candy, and fried food (running on recycled cooking oil / ecofuel) .
Being that the engines are running diesel, do you still have to add oil to the mix?

So if it is a win / win , why aren't more USowners running diesel engines?

So what would it take to convert a gas to diesel?

Many thanks for the replies.

Mr Cox

These are model diesel engines, running on special fuel, and they have very little in common with your regular diesel engines in cars that you can run on cooking oils etc.

mike109

G'day

Model "diesel" engines are not really diesel engines at all but "compression ignition" engines. Real diesel engines compress air then at the point of ignition, fuel is injected at high pressure, combustion occurs and away we go. Model diesel engines are like glow or gas engines but do not have a glow plug or spark plug.

Their fuel is kerosene and their ignition source is diethyl ether or as it is usually known, ether, plus oil. The oil used to be castor oil and it is still used in older style engines with steel liners with iron pistons but in modern glow engines converted to diesel, other synthetic oils or mixtures are used.

Most model diesel engines have variable compression. The cylinder has the usual piston but there is a second "contra piston" in the top of the cylinder (or sometimes in the head) which can be moved up and down to increase or decrease the compression. This allows the user to adjust the timing and can allow a diesel to swing a very large prop if this is required. Old Timer Texaco is one typical use for this.

Diesel engines start and run on the heat generated by the compression and the fact that ether will explode at quite a low temperature. That is why you don't need a glow starter etc.

The fuel can be as simple as equal parts of ether, castor oil and kerosene. Or more usually, about 20% oil, 30% ether and 48% kero with 2% ignition improver such as isopropyl nitrate. The improver increases the Cetane rating of the fuel allowing the use of a lower compression setting.

Davis Diesel Developments in the US make diesel heads for many glow engines. They also supply fuel and are a good place to start. Traditional diesels like my English PAW (Progress Aero Works) 40 make a wide range of engines from very small to about .60 size. Then there are European manufacturers of competition engines and old time engines, like the Czech MPJet, for enthusiasts.

So why does everyone not use them? Well, the fuel can be difficult to find, the smell puts some people off and glow engines are so available and easy to use. But diesels still have a following and are great fun to play with. And with DDD in the US, you have a source of excellent diesel heads for common glow engines and also fuel. Look them up for more info.

Cheers

Mike in Oz

gkamysz

My Feedback: (19)

Fuel consumption rate is between glow and gasoline. There is no point in converting a gasoline engine to diesel, unless you're doing it as a curiosity.

378

My Feedback: (4)

I'm surprized nobody's mentioned the fiddlyness of having to tune the compression AND fuel mixture at once. 'Tis the main reason I don't run diesels myself, I don't even like tuning the fuel mix all that often and like to set my carbs so I don't have to touch them for months on end. Can't do that with diesels, I've NEVER seen or heard of anyone just putting fuel in it, flipping it and it going, always have to tinker a bit.

djlyon

Diesels are not boring like a good glow. If you like boring run glow or gas or go with the ultimate of boring, go electric.

Denis

378

My Feedback: (4)

Define boring.


I find tuning boring. I don't find running boring. I much prefer an engine I can fuel, flip and fly to one that I have to spend thirty minutes tinkering with for every five minutes of enjoying. The fun, for me, isn't in finding the perfect tune, but simply hearing it scream and watching the plane rocket through the sky, or my touring car to powerslide around the family cat while it stares back with a look of pure indifference. I want to hear the engine scream, watch the smoke pour out of the exhaust, watch the tires balloon and dirt fly. I want to hear the prop tips ripping, want to watch the plane zoom skyward with complete contempt for gravity. That puts a huge smile on my face. I don't want to slave over a hot cylinder head tinkering with compression and fuel mixture, that is just annoying busywork, a necessary evil I want to cut as much out of as possible.



Find me a diesel that is as fire-and-forget as an OS glow engine and I'll happily buy it. If I don't have to touch the carb or comp screw for months and can just fuel, flip and fly then I'll revel in the fuel savings. But if no such engine exists, I'll stick with glow on my own models and simply watch and admire others running theirs.

Hobbsy

My Feedback: (102)

You can set and forget the compression setting on a Davis conversion unless there was 50 degree or mare change in ambien temp. Only a fool would fly a plane without checking the HS needle first.

378

My Feedback: (4)

Hrm...I'll have to check to see if there's a DDD head for my 46AX then. Fuel costs are manageable with a .18 but the .46 is gonna drink quite a bit more.


As for not checking the HSN...Hah, it's pretty obvious whether or not that's happy when you jam the throttle open in the pits to warm it up. The engine will tell you if it wants to be adjusted when you do that. You don't need to reach in and tinker with the needle every time, just when the engine says it wants a tweak during the pre-flight warmup.

Mr Cox

I agree, there is no fiddling as such once you get to know the engine. You just adapt the engine to the current conditions, and adjusting the compression is much easier on a diesel than on glow where you have to undo the whole head just to alter the compression a tiny bit.

AMB

Running and set issues with diesel?? nil, Just look at the glow site, fuels nitro% 0 to 5, 10, 15.20.25% requires different heat glow plugs, PULL HEAD TO ADD OR REMOVE SHIMS for different fuels , prop loads. one lean high speed run and engine can be toast, diesel lean, just misses, slows down if really lean stops, the power increase and fuel economy over glow a given, a little time learning the set up worth the effort, folks have spent more time setting up 4 strk glows
Hobbsy is so right , it is flip and go or a quick shot with a starter, and minor quick needle adjustment or minor one on the compression screw once set either
Davis conversions or the classics such as PAW, Tiapans, same deal, corrosion issues with bearing on diesel, not aware of any martin

378 the OS 46 with the davis head a winner all the way around ( yes I have one) use the ABCDavis fuel

KeroPower

OS .46 AX runs perfectly on glow fuel. Maybe the most popular .46 two stroke glow. Why you want to convert it to 'diesel'? It will not run on $4 a gallon diesel. Instead it runs on $12 a quart model diesel fuel that will stink up your entire house. Your clothes, coat, basement, door knobs, car interior, etc will stink of kerosene. The you will have headache. You would have more fun converting it to spark ignition if you really wanted to converting it to something.

Hobbsy

My Feedback: (102)

Here is a shot of one of my OS LA .46 trurning a Graupner 12x7. It won't give you a head ache, I promise. It turns the 12x7 at 9,450. I have two gas engines I converted from gas to Diesel, a Maloney 1.25 and a tartan 1.34. The Maloney turns a 15x8 two blade at 7,200 as a gas engine and a 15x8 three blade at 7,200 as a Diesel.

AMB

Keropower. As far as kero smell I have transported and planes in fuel in my Rodeo SUV the fuel is in metal cans, the vehicle does not smell, I keep the fuel in my bathroom closet , no smell in the bathroom, the planes do not smell (exhaust piped to to rear or down landing gear leg, any little bit that gets on the plane
wiped with windex on paper towel tossed in trash can , once or twice yes have spilled fuel several times on my pants in the last 15 years or so, all my planes stored in
a back room of house about 20 , 17 are diesel 3 are 4 strk glow no smell in the room, any remaining fuel in planes after flying just put back in the fuel can
so I have not had the "odor issue" martin

Note if you are running without a muffler yes the stuff will get all over the plane and every little corner will get it and it will smell , if glow you have oil all over it
but of course no odor after cleanup
also after flying I drain the muffler of any remaining oil and just use a little of paper towel stuffed in the muffler outlet so no oil stains in the vehicle, the planes are stored nose down in the room (paper plug removed from muffler)

Recycled Flyer

That would be Dave's side port engine Steve? Impressive ain't it!

Recycled Flyer

My turn -
Pros:

[*]Fuel economy - yes but its not something I would dwell on since the higher initial price erodes any perceived benefit.[*]Low chance of detonation? No chance of detonationas far as Iam aware.[*]Gives the tinker a chance to 'tink,' and all options are good.[*]Actually teaches you to listen to your engine and appreciate what is going far more.[*]Much more control over the ignition advance and therefore prop selection.[/list]Cons:
[*]Can't get high RPMs? Partly true, the best diesels will rev out slightly less than the best glows but its very marginal.[*]Can get frustrating if you get a bad batch of fuel, spelt 'low ether content.'[*]Timing the length of a run can be problematical, especially with control line stunt.[/list]

AMB

More pros Since my planes are sport, and scale ,mild acrobatics usually running 9000-10000 max, hence not a lot of noise, diesels have a more mellow sound anyhow thus flying similar to my 4 strk glows ( these are the only glow I fly) all my 2 cycles, classics or conversions are diesel and of course no glow plugs or battery to mess with (on the diesels) laid back flying martin

A few years back at a small field that was electric , had my ripmax coyote electric and my J-3 cub with on OS 10 Davis head had exhaust piped to back, flew the
coyote a few times then hauled out the cub fuel flip go, the electric crowd were amazed 100 ft out could not hear it, thought I had lost the engine hit the throttle
and yes it was running fine, quieter than the electrics flew it many times there till a shopping center built there, great while it lasted always at least 20 guys
flying their electrics weekends

Hobbsy

My Feedback: (102)

Martin, this is my favorite Diesel picture. The K&B 1.00 really smokes, it may be the box muffler/engine mount. I the picture it is turning a Graupner 14x7 three blade at 8,500. Also Fox .74 with Bisson Sport Muffler.

AMB

HOBBSY.. just 2 words sums them up stump pullers martin