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What's the attraction of diesel plane engines?

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Old 09-04-2018, 09:06 AM
  #76  
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I mix my own. Much much cheaper and it runs as well as commercial fuel. Having control over what lubricants and how much is an extra bonus.

Last edited by 1QwkSport2.5r; 09-04-2018 at 09:38 AM.
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Old 09-07-2018, 09:42 AM
  #77  
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We seem to have lost the person who started this thread, was he just trolling...?
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Old 09-07-2018, 02:19 PM
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Originally Posted by Mr Cox View Post
We seem to have lost the person who started this thread, was he just trolling...?
NO, not at all!
was an ardent believer in diesel engines and flew them extensively. After 4 crashes and numerous close calls due to rapid carbon build up in the combustion chamber and between the compression rings and pistons - I came to the sad realization that this concept is not working.
I also suspect that most people who are enamored with diesels, do most of the flying "on the bench" and not in actual airplanes. My experience is limited to Davis Diesel Conversions.
If you or anybody else still want to try it, I have about 15 diesel heads ranging in size from 25 up to ST 4500 and 60 CC twin engines. I also have 12 gallons of fuel. Will be more than happy to sell all for a reasonable, fair price.
Contact me if interested.
Joshua
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Old 09-07-2018, 02:41 PM
  #79  
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Hi Josh,
I sent you a PM about the fuel.
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Old 09-07-2018, 02:45 PM
  #80  
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Hi, would love to have an OS 60FP head and a gallon of fuel. Not sure what it would cost to ship thou.
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Old 09-08-2018, 09:40 AM
  #81  
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Originally Posted by N99JH View Post
NO, not at all!
was an ardent believer in diesel engines and flew them extensively. After 4 crashes and numerous close calls due to rapid carbon build up in the combustion chamber and between the compression rings and pistons - I came to the sad realization that this concept is not working.
I also suspect that most people who are enamored with diesels, do most of the flying "on the bench" and not in actual airplanes. My experience is limited to Davis Diesel Conversions.
I'm the opposite, I don't have any conversions from DDD (apart from one or two for Cox engines) and only use dedicated diesel engines. I fly them regularly, but the fuel is getting harder to find here, so for everyday flying I'm using glow engines.

Perhaps you would have had a better experience if you had tried dedicated, non-ringed, diesel engines. These are every bit as easy to use as glow engines. In fact even easier to start and tune actually, and you never have to worry about any deadsticks from a poor tuning, the diesel engines will just continue to run even if they miss a little.

Here is a short example using a Modela/MVVS 2cc engine. This is one of the first outings with the engine and didn't want to push it too hard. The compression setting is therefore set a little low and you can hear it missing, but it will never accidentally quit on you.


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Old 09-08-2018, 11:50 AM
  #82  
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I didn’t like ringed Diesel conversion engines, but conventional ringless designs have proven to be fantastic (lapped meehanite and ABC technologies). I have only used conversion engines myself, but at some point want to venture into purpose built Diesels. I suspect I’ll need to for my 1/2a trainer as the engine I want to use will be a bit of a quagmire to find a Diesel head for.
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Old 09-09-2018, 03:19 AM
  #83  
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Originally Posted by Mr Cox View Post
I'm the opposite, I don't have any conversions from DDD (apart from one or two for Cox engines) and only use dedicated diesel engines. I fly them regularly, but the fuel is getting harder to find here, so for everyday flying I'm using glow engines.

Perhaps you would have had a better experience if you had tried dedicated, non-ringed, diesel engines. These are every bit as easy to use as glow engines. In fact even easier to start and tune actually, and you never have to worry about any deadsticks from a poor tuning, the diesel engines will just continue to run even if they miss a little.

Here is a short example using a Modela/MVVS 2cc engine. This is one of the first outings with the engine and didn't want to push it too hard. The compression setting is therefore set a little low and you can hear it missing, but it will never accidentally quit on you.

https://youtu.be/hlaPw71z9Mk
Since the smallest engines I use are 40 and 60 size, the number of dedicated diesels available is limited. I have an OS 40FSR ABC which I can easily convert but the issue of carbon build up in the combustion chamber will still be there. I am not about to experiment with brewing my own fuel, too many other exciting projects take priority and life is getting shorter by the minute.
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Old 09-09-2018, 10:39 AM
  #84  
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PAW engines are available all the way up to .60, so that would be something to try.

I have never had any problem with carbon buildup in the engines. The piston gets black on the top but that is about it, it doesn't grow beyond a thin black layer, in my experience.
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Old 09-09-2018, 02:33 PM
  #85  
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Originally Posted by H5487 View Post
Please don't shoot me for asking but I don't understand the attraction of diesel engines in model airplanes. What am I missing?

Thanks,

Harvey
Getting back to the original question of what attracts people to diesel engines in model airplanes.
I can see three major advantages that diesels have that would attract niche modellers.
  1. You can entirely build or manufacture a model diesel engine in your own garage with a lathe and a mill, not so with spark or glow as I have yet to see anyone make a glow plug or spark plug in their own home.
  2. A model diesel with variable compression allows the user to change the ignition point at will, and here you might quip "So what?" But consider something as simple as altitude changes, the thinner the air the more blade area a model needs for comparable performance to sea level and here a diesel excels as its not as fuel/air hungry as other systems and will happily pull helicopter size blades around in a slightly decompressed state. I have seen a pylon racer with a diesel head conversion on it at a meeting here called the "Oily Hand" and the pilot said it was slightly down on straight line speed but he was curious to see when the engine would quit if he went vertical for as long as possible. (Apparently this 'test' was done quite a few times just for the heck of it.) The model went straight up and was barely in sight when he commented that "right about now the glow engine would quit but the diesel just kept on going up, and up and up. It simply would not quit. And after speaking with a competition control line stunt flyer from South Africa who has to contend with massive altitude changes that vary with venue he settled on an MVVS 49 with a diesel head with the reasoning that altitude changes needed blade area changes, and guess what - the diesel out performed the glow when tasked with this issue. The venier screw changes the ignition advance or point, as does oil content or any other non compressable fluid.
  3. Fuel economy and hot engine restarts, specifically F2C events or indeed or other fun fly event that requires the same.
What I don't see is a claimed 'maximum' torque advantage as a petrol or methanol engine with a tuned exhaust will easily out perform a model (non turbo) diesel. And what I dont see is that simply bolting on a diesel head onto a glow engine equals a guarantee of success.

And I will make a controversial statement here "I predict that when electric engines totally eclipse IC engines as a viably commercial powerplant and they cease to be made, the diesels will still be around long after that point."

Cheers.

Last edited by Chris W; 09-09-2018 at 03:17 PM.
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Old 10-29-2018, 07:19 AM
  #86  
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From a flying point of view the diesel has the least catastrophic failure points. By that I mean failure points that will end in a possible crash. In spark operation the weak point is the ignition points and spark plug, these can get dirt in the points stopping reliable spark or the spark plug can foul again stopping reliable spark. If this happens during a critical point in a maneuver you could lose the plane. With glow operation the critical weak point is the glow plug. The plug can out right fail (as in broken element or blown out element) or foul causing erratic runs or just full stop. Electric also has weak points such as the timer (for control line), ESP itself just stopping or lose/broken wires and lastly a battery pack failure.

With diesel these items don't exist. The main failure for diesel (once running) would be trash plugging the fuel line or a broken fuel line. These are pretty low risk and in the case of trash in the fuel line would lean the engine before cutting out so there is likely some warning. Flex tubing failure is also low risk and with a little care in the selection of the tubing material and installation to avoid sharp edges is also low risk.

Once you have a diesel running and correctly set not much will out right stop it. For control line it is the ultimate electric style power package. As for starting once you get the hang of starting (avoid flooding) and setting (for those with variable compression heads) it is pretty much fuel and go. The one down side to current diesel operation is the residual aromatic smell left on the ship and on you. I believe this is caused by the Kerosene. If we can eliminate this smell (not the ether smell of the raw fuel as that evaporates quickly) diesel would be more popular.

Best, DennisT
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Old 10-29-2018, 10:25 AM
  #87  
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I have always wondered why more diesels aren't used in Control Line flying where steady engine run is so important. Not being a U/C guy, I am wondering if it's that diesels don't exhibit the 4/2 break? Is it the fuel and mess?
I see more electric line control models than diesels, by far. Anyone know why?
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Old 10-30-2018, 01:42 PM
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Originally Posted by Stuntguy13 View Post
Once you have a diesel running and correctly set not much will out right stop it.
Best, DennisT
So how does one time a run then? I have flown diesel stunt and had the engine burp around running on fumes for many laps after a schedule and the temperature greatly effecting the length of the run.
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Old 10-30-2018, 02:07 PM
  #89  
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Originally Posted by RichardGee View Post
I have always wondered why more diesels aren't used in Control Line flying where steady engine run is so important. Not being a U/C guy, I am wondering if it's that diesels don't exhibit the 4/2 break? Is it the fuel and mess?
I see more electric line control models than diesels, by far. Anyone know why?
1. Engine Choice.
I assume that you mean that a 'steady run' equates to F2B stunt?
To my knowledge there has been no model diesel engine specifically made for F2B, ever.

This includes the still in production PAW 40, bought straight off the shelf they are simply a fixed venturi engine that fills the role of general free flight or sport control line flying.
Ordered specifically for F2B ( and thats if you want to pay quite a bit extra for the mods and the factory will oblige) they become a little known 'one off' engine.

2. Fuel.
Temperature greatly effects the length of the run and without a timer or a stable weather pattern how do you time a run accurately?
Smell, it does get some getting used to and in competition no one wants diesel fumes blown all over the other models etc.
Ether is increasingly more difficult to obtain.

3. Model Choice.
A 'gear change' moment is horribly present with either an upright or invert mount model as the internal ballistics of the fuel muck with the run, leaving you with the only sensible option of going side mount.

So it becomes a very speciallised pursuit indeed.

Cheers.
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Old 10-30-2018, 04:39 PM
  #90  
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I have found that substituting white spirit (aka mineral spirit) (not 'white gas', such as coleman camp stove fuel or shellite) for kerosene/paraffin virtually eliminates the residual odour of burnt diesel fuel.
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Old 11-01-2018, 07:36 PM
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Chris,
Timing the run is per the rule book, from when the signal is given to the judges to start the engine until the model comes to a full stop on the ground, 7 min for PA stunt and 8 min for OTS. I have flown OTS and PA with PAW engines. If the fuel has enough ether and the compression/needle is set so as not to be to lean my engines gave a clean run and cutoff at the end of the fuel load. For me diesel is very much in line with the current thinking in stunt of constant power. It runs very much like electric power.

Rich,
Having flown diesel in competition I can say the main resistance to diesel is not the aroma of the ether but the lingering smell of the residual exhaust residue as this is mixed with the oil and lingers. Control line competition flyers are always looking for any kind of edge they can get. The problem is the lingering smell of the residue and the touchiness of the compression/needle setting with the current fuel formulations make it more than most are willing to lean when glow or electric is workable.

What we need is fuel that has no residual smell. I believe this is from the kero. The idea of using the
white spirit as suggested by Fier above is encouraging and worth doing more work on. I think using this in combination with higher ether levels (around 50%) with mineral oil as the lubricant with a little castor added would give less sensitive needle settings and cleaner cut off. This would work well in stunt.

Best, DennisT

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