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need help with diesel rc engine!! help asap!!

Old 11-22-2010, 12:44 PM
  #51  
AndyW
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ORIGINAL: locktite401

ORIGINAL: Recycled Flyer

Hi Ray,
Got nothing against Oliver porting but in the Mills its vastly different. The Mills piston seems to have a step machined out of it that acts as a deflector and pretty much works like running into a brick wall as far as gas flow is concerned and the term 'smashing' here is very accurate. And how much 'separation' is achieved with both of those ports being side by side and very close together?

Obviously the Oliver has no such step or deflector, nor does it need one as radial porting would prohibit this.

Spiral fluting ground into the crank web and emanating from the central hole out to the periphery I have seen before - it looks very purposeful indeed!

Is this pic what you mean Ray?
No I don't think so, it's far more asymmetric than that. There's a pic of my PAW 09 TBR Team Race motor below. That's the best I can find right now although I have a pic of a better example somewhere. By the way notice it's non-standard bushed rectangular section rod. It's about the fifth or sixth that motor had.

My point about the Oliver porting was that the streams of gas collide as well.

Don't laugh at Mills porting, it's still used I suspect in the modern MPjet sideport diesels. Also the Mills is an absolutely delightful sports Free Flight diesel because of it's porting.

Andy, I mentioned in your previous post that you hadn't discovered anything new! An oldtimer in my club used to start his Mills .75 on a prime with an ether based brew, and while it run that out he would quickly fill the tank with a brew containing just oil and kero. It ran just the same, but then it's long been known that a mills will run on just about anything. By the way the one's that Carlson has are rather poor replica's of the Mills. The best are Doonside or Irvine which often turn up on Ebay.

Pics: LHS PAW 09 TBR diesel. RHS Brodak 25 for B Class Team Race, standard and modified ''Turbo'' cranks

Ray
Ray,

Yes, there's a lot that's gone on in the diesel world for the last, what, 80 years? But when I first started working with stinky fuel, I asked why the ether was necessary. Would a diesel engine run without it? Why? Because buying commercial, diesel fuel was close to impossible. Mixing your own by getting ether from the Pharmacy was also impossible. There was also that elusive, amyl nitrate. Since those very early days, I discovered ether in spray cans, then MEKP and finally, Amsoil cetane booster, octyl nitrate.

But the question persisted and I just had to find out,,, on my own. What I found out, at least for me, is that a diesel will run just fine without ether. It's getting the *^%$#*& things started without ether that was the problem. Once started, they ran. But without ether, they were sometimes not very responsive to good throttling. The high compression required to run on no ether came back to bite you when you throttled back. The higher temperature swing between high and low throttle was the culprit. Ether smoothed that out perfectly.

Also, in the early days, I was told to be very careful that you didn't lose any of that magical pixy dust known as ether. Somehow, your fuel could go stale and you would never, ever be able to start your engine on that fuel again. Never ever. You had to bless it with the addition of the ether that was obviously lost. But how MUCH was lost? How could you tell? How much did you need to add? This made the care and feeding of diesels some kind of Sorcerer's Apprentice exercise. It was mysterious, magical, spooky. You had to mumble certain old, VERY old, incantations that the elders of Dieseldom deemed necessary. You were forbidden to use electric starters. You were never told why. JUST DON'T DO IT !!! YOU'LL BE S-O-O-O-RY !! You were told that even the wise old men of the Diesel Brotherhood would in frustration haul out the starter only to break their diesels EVERY SINGLE TIME.

So just like why not eliminate ether, I wanted to know WHY NOT use a starter. Well, what I found out was that all diesels are not created equal. Look at the thin crankweb of the Mills diesel. How 'bout that dinky rod? No wonder they broke. Shoot, I had a Mills break a crankpin off just by hand flipping. And I flipped that flipping thing till my shoulder screamed bloody murder. I once asked, why not make up a high ether prime? I was severely admonished. Not till I went to a 40% ether mix did I ever get a small diesel to start and run. And I found that a 60% ether prime mix helped a whole lot.

I eventually found out WHY electric starters broke engines, even modern diesels. Too often, SOME instructions would tell you to fill up your tank, take out the needle to the recommended, average setting, back off the contra, apply prime to the exhaust, (oh the humanity) and start flipping. Imagine, here we're talking about vapourizing, raw liquid fuel as an essential component and we then go and tell people to dump raw liquid fuel directly into the combustion chamber. Then we flip and flip while messing with the contra lever. At some point, by sheer luck, some ether vapours ignite under compression. But boy oh boy, buddy, you'd better have that contra backed WAY out. So most often, you get a bit of a burrp. So you apply MORE, raw, liquid prime into that all holy of holeys, the combustion chamber. But now, the engine has warmed up a bit from that first, prime burst so you now your perfect compression ratio has changed and you muck about more with that compression screw. Then you get another prime burst and you repeat. Finally, you get close. finally, you get a long enough prime burst to draw fuel into the carb and your OFF. And if you're lucky that the instructions were good, the needle was close and you could now play with the mixture and the compression ratio and settle down to a nice, pleasing run of your thoroughbred.

But even the old hands could become frustrated with their beloved little devices and too often hauled out the starter and promptly broke their little backs. But no one could explain WHY? WHY, I asked? JUST DON"T DO IT !! I was told.

Wellll,,, what I found out was this. The problem was, in fact, the caveat against using an electric starter in the first place. Yup, that's what I found out. Here's what's happening. Applying prime to the exhaust puts liquid into a sealed chamber that now tries to compress an incompressible medium. Only when enough liquid fuel is expelled by flipping and some gets vapourized by the activity do we get a burst. But it all has to go so perfectly and purely by guess and by gosh and by hope and sweat and tears. And if you don't get a prime burst after several tries, what happens is that that very volatile ether goes away to ether heaven and that low volatility kerosene and OIL stays in hell,,, the bottom of your crankcase. And thats about when that innocent starter gets hauled out. That starter that's "just following orders", does its job and flings all that EXCESS liquid up from the case and into the combustion chamber. All that uncompressable liquid. BANG goes your crankpin. CREAK goes your connecting rod.

So, if you had used the starter in the FIRST place, and NOT filled the tank in the FIRST place and NOT opened the needle in the FIRST place, that starter would have allowed you to find the compression setting pretty quick. But ONLY if you had primed into the INTAKE. That's where the fuel goes. You feed a cow where the TEETH are located, not the OTHER end. And if your compression setting isn't just right, that small bit of prime will be vapourized and go out the BACK end, just as nature had intended. The starter assures that. Virtually none will remain IN the engine. So now you cinch up the compression a bit and feed your device, once again, at the intake end. You repeat this until you get a nice, prime burst. You can do this forever and no harm will be done. Here, http://www.youtube.com/watch?v=ZmdlIRI1RNg I spent an entire afternoon, doing just that. Sure ran good on the prime. But as it was spinning backwards, fuel wasn't being drawn into the engine.

So now, you open the needle, but only open it say one full turn if your instructions say 1 1/2 turn. Why? A diesel will run, if too lean, a glow will not. So if you get a start and the engine is lean, it'll run till you get on that needle and back it out. Where a lean setting can pay dividends is where you get no instructions or they happen to be wrong, or your particular engine is funny that way. OR, when you have no way to really tell if your fuel is up the line to the carb. Most times, we use neoprene because that plastic, see through stuff is stiff and gets brittle. So most times you choke the engine and flip a few times and hope the fuel is up the line just right and also hope that you didn't flip one or two many times and you get some serious, excess fuel into your engine. Then you ADD more fuel when you prime and then despite your best efforts, you can't get a start and now that starter gets hauled out and bites you out of spite. So, I never choke my engines to get fuel up the line. I let a small number of prime bursts do that for me. Shoot sometimes I don't even need to prime. http://www.youtube.com/user/hopeso#p/u/104/af4dQNa60_w Along with a leaner needle setting, you'll never overload your poor diesel engine with that horrible, uncompressable, liquid dynamite.

Finding out why starters broke diesel engines and why ether really was required has led me to the conclusion that diesel engines are no more difficult nor more delicate than glow or gasoline engines. Here, http://www.youtube.com/user/hopeso#p/u/67/FJb7aZFMVwY I start a PAW cold without touching the compression screw. Note the ice cube. Also note the prime boiling in the intake. That's because it's mostly ether with a bit of oil. It's a traditional, PAW engine, the one that you are never, ever to use a starter on. The neat thing is that when you use an electric starter, you really don't have to play with the compression screw. That's because you're priming into the intake and not the outake. Here, http://www.youtube.com/user/hopeso#p/u/65/zkNb63u1tHo I start the same PAW on a NO ether fuel WITH starter WITHOUT touching the compression screw OR the needle. Note the very high ether prime just POURS out of the bottle into the intake. That's some serious, overprime, but that's what a starter can do for you if you do it right AND if your starter is sized for the job. Note that it stalls, initially. That's not because of hydraulic lock, the engine hasn't even turned over yet. That's because of the high compression that's needed to run a no ether fuel and the starter is sized just right. Both the needle and compression were found earlier, the engine was stopped and allowed to cool. Using a starter and a high ether prime allowed prime bursts to warm up the engine to the point that the engine eventually caught, warmed up some more and transitioned into a run. Applying a heat gun would accomplish the same thing. Heat, heat heat, it's all about heat with diesels. Your old timer was on to something but he could have accomplished the same thing my just heating up the engine either with a small torch or a bunch of prime runs.

And mentioned elsewhere, I had made up a VERY tight, Norvel, AAN engine that would start by hand, also without touching the compression or needle. That this was possible leads me to believe that Norvel got it very right as far as effectively vapourizing the fuel into the compression chamber. Perfect compression seal a big factor here too. And this is where a long stroke can help. Piston speeds are relatively higher and this slows compression leak as you flip. I had converted a Mills to glow and found it VERY easy to start by hand, often on the first flip and this I attribute to higher piston speeds holding the compression better. A starter does that automatically.

Hope that doesn't come across as a rant but,,, [sm=bananahead.gif][sm=punching.gif][sm=bananahead.gif] what the heck.

Old 11-22-2010, 03:16 PM
  #52  
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Default RE: need help with diesel rc engine!! help asap!!


ORIGINAL: Recycled Flyer

So if the rod is not fully eclipsing the intake journal then what is the cutaway in the crank web for then?
This thing has been bugging me a bit. Had a closer look today and there is another purpose that it might have. On the downstroke, the slot gives a larger opening between the inner part of the crank and the volume of gas that should now go up through the transfer channels. So instead of having just the small gap between crank web and the backplate for the gas in the inner part of the crank, there is now an opening pointing straight up in the crank web. This would then help to use more of the total crank volume, as the inner part of the crank is actually a rather large amount of the total crank volume in a racing engine with a large crank bore. A cambered leading edge of the crank web could then serve a similar purpose of not closing the volume at the crank web cutout.

I don't know if this is understandable, or even makes any sense, or not, but the bottom line is that the crank design could be mainly for the downstroke, when there is compression in the crank and gas should flow up through the transfer channels. As opposed to a special design for the upstroke as I had assumed before.
Old 11-22-2010, 05:34 PM
  #53  
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Default RE: need help with diesel rc engine!! help asap!!


ORIGINAL: AndyW


ORIGINAL: locktite401

ORIGINAL: Recycled Flyer

Hi Ray,
Got nothing against Oliver porting but in the Mills its vastly different. The Mills piston seems to have a step machined out of it that acts as a deflector and pretty much works like running into a brick wall as far as gas flow is concerned and the term 'smashing' here is very accurate. And how much 'separation' is achieved with both of those ports being side by side and very close together?

Obviously the Oliver has no such step or deflector, nor does it need one as radial porting would prohibit this.

Spiral fluting ground into the crank web and emanating from the central hole out to the periphery I have seen before - it looks very purposeful indeed!

Is this pic what you mean Ray?
No I don't think so, it's far more asymmetric than that. There's a pic of my PAW 09 TBR Team Race motor below. That's the best I can find right now although I have a pic of a better example somewhere. By the way notice it's non-standard bushed rectangular section rod. It's about the fifth or sixth that motor had.

My point about the Oliver porting was that the streams of gas collide as well.

Don't laugh at Mills porting, it's still used I suspect in the modern MPjet sideport diesels. Also the Mills is an absolutely delightful sports Free Flight diesel because of it's porting.

Andy, I mentioned in your previous post that you hadn't discovered anything new! An oldtimer in my club used to start his Mills .75 on a prime with an ether based brew, and while it run that out he would quickly fill the tank with a brew containing just oil and kero. It ran just the same, but then it's long been known that a mills will run on just about anything. By the way the one's that Carlson has are rather poor replica's of the Mills. The best are Doonside or Irvine which often turn up on Ebay.

Pics: LHS PAW 09 TBR diesel. RHS Brodak 25 for B Class Team Race, standard and modified ''Turbo'' cranks

Ray
Ray,

Yes, there's a lot that's gone on in the diesel world for the last, what, 80 years? But when I first started working with stinky fuel, I asked why the ether was necessary. Would a diesel engine run without it? Why? Because buying commercial, diesel fuel was close to impossible. Mixing your own by getting ether from the Pharmacy was also impossible. There was also that elusive, amyl nitrate. Since those very early days, I discovered ether in spray cans, then MEKP and finally, Amsoil cetane booster, octyl nitrate.

But the question persisted and I just had to find out,,, on my own. What I found out, at least for me, is that a diesel will run just fine without ether. It's getting the *^%$#*& things started without ether that was the problem. Once started, they ran. But without ether, they were sometimes not very responsive to good throttling. The high compression required to run on no ether came back to bite you when you throttled back. The higher temperature swing between high and low throttle was the culprit. Ether smoothed that out perfectly.

Also, in the early days, I was told to be very careful that you didn't lose any of that magical pixy dust known as ether. Somehow, your fuel could go stale and you would never, ever be able to start your engine on that fuel again. Never ever. You had to bless it with the addition of the ether that was obviously lost. But how MUCH was lost? How could you tell? How much did you need to add? This made the care and feeding of diesels some kind of Sorcerer's Apprentice exercise. It was mysterious, magical, spooky. You had to mumble certain old, VERY old, incantations that the elders of Dieseldom deemed necessary. You were forbidden to use electric starters. You were never told why. JUST DON'T DO IT !!! YOU'LL BE S-O-O-O-RY !! You were told that even the wise old men of the Diesel Brotherhood would in frustration haul out the starter only to break their diesels EVERY SINGLE TIME.

So just like why not eliminate ether, I wanted to know WHY NOT use a starter. Well, what I found out was that all diesels are not created equal. Look at the thin crankweb of the Mills diesel. How 'bout that dinky rod? No wonder they broke. Shoot, I had a Mills break a crankpin off just by hand flipping. And I flipped that flipping thing till my shoulder screamed bloody murder. I once asked, why not make up a high ether prime? I was severely admonished. Not till I went to a 40% ether mix did I ever get a small diesel to start and run. And I found that a 60% ether prime mix helped a whole lot.

I eventually found out WHY electric starters broke engines, even modern diesels. Too often, SOME instructions would tell you to fill up your tank, take out the needle to the recommended, average setting, back off the contra, apply prime to the exhaust, (oh the humanity) and start flipping. Imagine, here we're talking about vapourizing, raw liquid fuel as an essential component and we then go and tell people to dump raw liquid fuel directly into the combustion chamber. Then we flip and flip while messing with the contra lever. At some point, by sheer luck, some ether vapours ignite under compression. But boy oh boy, buddy, you'd better have that contra backed WAY out. So most often, you get a bit of a burrp. So you apply MORE, raw, liquid prime into that all holy of holeys, the combustion chamber. But now, the engine has warmed up a bit from that first, prime burst so you now your perfect compression ratio has changed and you muck about more with that compression screw. Then you get another prime burst and you repeat. Finally, you get close. finally, you get a long enough prime burst to draw fuel into the carb and your OFF. And if you're lucky that the instructions were good, the needle was close and you could now play with the mixture and the compression ratio and settle down to a nice, pleasing run of your thoroughbred.

But even the old hands could become frustrated with their beloved little devices and too often hauled out the starter and promptly broke their little backs. But no one could explain WHY? WHY, I asked? JUST DON"T DO IT !! I was told.

Wellll,,, what I found out was this. The problem was, in fact, the caveat against using an electric starter in the first place. Yup, that's what I found out. Here's what's happening. Applying prime to the exhaust puts liquid into a sealed chamber that now tries to compress an incompressible medium.
Only when enough liquid fuel is expelled by flipping and some gets vapourized by the activity do we get a burst. But it all has to go so perfectly and purely by guess and by gosh and by hope and sweat and tears. And if you don't get a prime burst after several tries, what happens is that that very volatile ether goes away to ether heaven and that low volatility kerosene and OIL stays in hell,,, the bottom of your crankcase. And thats about when that innocent starter gets hauled out. That starter that's "just following orders", does its job and flings all that EXCESS liquid up from the case and into the combustion chamber. All that uncompressable liquid. BANG goes your crankpin. CREAK goes your connecting rod.

So, if you had used the starter in the FIRST place, and NOT filled the tank in the FIRST place and NOT opened the needle in the FIRST place, that starter would have allowed you to find the compression setting pretty quick. But ONLY if you had primed into the INTAKE. That's where the fuel goes. You feed a cow where the TEETH are located, not the OTHER end. And if your compression setting isn't just right, that small bit of prime will be vapourized and go out the BACK end, just as nature had intended. The starter assures that. Virtually none will remain IN the engine. So now you cinch up the compression a bit and feed your device, once again, at the intake end. You repeat this until you get a nice, prime burst. You can do this forever and no harm will be done. Here, http://www.youtube.com/watch?v=ZmdlIRI1RNg I spent an entire afternoon, doing just that. Sure ran good on the prime. But as it was spinning backwards, fuel wasn't being drawn into the engine.

So now, you open the needle, but only open it say one full turn if your instructions say 1 1/2 turn. Why? A diesel will run, if too lean, a glow will not. So if you get a start and the engine is lean, it'll run till you get on that needle and back it out. Where a lean setting can pay dividends is where you get no instructions or they happen to be wrong, or your particular engine is funny that way. OR, when you have no way to really tell if your fuel is up the line to the carb. Most times, we use neoprene because that plastic, see through stuff is stiff and gets brittle. So most times you choke the engine and flip a few times and hope the fuel is up the line just right and also hope that you didn't flip one or two many times and you get some serious, excess fuel into your engine. Then you ADD more fuel when you prime and then despite your best efforts, you can't get a sart and now that starter gets hauled out and bites you out of spite. So, I never choke my engines to get fuel up the line. I let a small number of prime bursts do that for me. Shoot sometims I don't even need to prime. http://www.youtube.com/user/hopeso#p/u/104/af4dQNa60_w Along with a leaner needle setting, you'll never overload your poor diesel engine with that horrible, uncompressable, liquid dynamite.

Finding out why starters broke diesel engines and why ether really was required has led me to the conclusion that diesel engines are no more difficult nor more delicate than glow or gasoline engines. Here, http://www.youtube.com/user/hopeso#p/u/67/FJb7aZFMVwY I start a PAW cold without touching the compression screw. Note the ice cube. Also note the prime boiling in the intake. That's because it's mostly ether with a bit of oil. It's a traditional, PAW engine, the one that you are never, ever to use a starter on. The neat thing is that when you use an electric starter, you really don't have to play with the compression screw. That's because you're priming into the intake and not the outake. Here, http://www.youtube.com/user/hopeso#p/u/65/zkNb63u1tHo I start the same PAW on a NO ether fuel WITH starter WITHOUT touching the compression screw OR the needle. Note the very high ether prime just POURS out of the bottle into the intake. That's some serious, overprime, but that's what a starter can do for you if you do it right AND if your starter is sized for the job. Note that it stalls, initially. That's not because of hydraulic lock, the engine hasn't even turned over yet. That's because of the high compression that's needed to run a no ether fuel and the starter is sized just right. Both the needle and compression were found earlier, the engine was stopped and allowed to cool. Using a starter and a high ether prime allowed prime bursts to warm up the engine to the point that the engine eventually caught, warmed up some more and transitioned into a run. Applying a heat gun would accomplish the same thing. Heat, heat heat, it's all about heat with diesels. Your old timer was on to something but he could have accomplished the same thing my just heating up the engine either with a small torch or a bunch of prime runs.

And mentioned elsewhere, I had made up a VERY tight, Norvel, AAN engine that would start by hand, also without touching the compression or needle. That this was possible leads me to believe that Norvel got it very right as far as effectively vapourizing the fuel into the compression chamber. Perfect compression seal a big factor here too. And this is where a long stroke can help. Piston speeds are relatively higher and this slows compression leak as you flip. I had converted a Mills to glow and found it VERY easy to start by hand, often on the first flip and this I attribute to higher piston speeds holding the compression better. A starter does that automatcally.

Hope that doesn't come across as a rant but,,, [sm=bananahead.gif][sm=punching.gif][sm=bananahead.gif] what the heck.

And first prize for the world's longest post goes to ................ Andy!

But seriously mate I see a fatal flaw in the above, you seem to be exhaust priming with an OPEN port and no wonder its flooding. Do the prime against a CLOSED port with the piston sealing up the gap in the liner, this will introduce the correct amount of fume into the combustion chamber the next time the port opens.

The method I was shown for my PAW's was to draw the fuel to the spray bar via finger choking (do not draw raw fuel actually into the venturi), closed exhaust prime and hand flip away.
If this fails repeat those steps and to date I have had little issue with starting.

The only drama is with muffled engines that proclude access to the enclosed exhaust port but this is very easily solved with a pressure nipple added to the muffler that points towards the port.
But even without the exhaust prime the hand flipping is enough to draw the fuel air mix past the spray bar to make it fire.

Cheers.

Old 11-22-2010, 08:16 PM
  #54  
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Also, in the early days, I was told to be very careful that you didn't lose any of that magical pixy dust known as ether. Somehow, your fuel could go stale and you would never, ever be able to start your engine on that fuel again. Never ever. You had to bless it with the addition of the ether that was obviously lost.
This is an interesting one. I've always tried very hard to preserve my highly volatile magical pixy dust, just as Andy says. Yet recently, I was at a friend's place in Brisbane and dragged out a PAW 249DS-powered model that we'd been flying this the previous week. On the off-chance that there were some dregs left in the tank, I choked it through a couple of times and flicked it. It fired instantly, and ran out the dregs.

Now this was a small quantity of fuel which had been sitting for 8 days in an unsealed tank, in a location where the daytime temperatures were up around 30C. By rights, there should have been no ether left and nothing much should have happened when I flicked it. Yet it fired and ran as if the fuel was freshly made. Fuel for thought, eh (so to speak)!
Old 11-22-2010, 09:10 PM
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Good point, Recycled Flyer. But some traditional diesels have the piston top ride below the bottom of the exhaust port at BDC. So that raw, liquid fuel that's made that nice, fat fillet against the piston goes POURING into the combustion chamber in a gushing torrent causing havoc and mayhem. [X(]
Old 11-22-2010, 09:54 PM
  #56  
Recycled Flyer
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Good point, Recycled Flyer. But some traditional diesels have the piston top ride below the bottom of the exhaust port at BDC. So that raw, liquid fuel that's made that nice, fat fillet against the piston goes POURING into the combustion chamber in a gushing torrent causing havoc and mayhem. [X(]
How does that happen when the entire port is held closed with piston in place?

I am talking about rotating the crankshaft so that the piston sits mid stroke, TDC is no good due to it being very difficult to hold there and sub piston induction could cause lower crankcse flooding and BDC is obviously the worst place as the exhaust port is entirely open.

So with the exhaust port closed and sealed off, squirt some raw fuel against the closed off port, immediately the excess will drain off leaving a very thin wash only on part of the piston wall but fumes galore hanging around. Then flip the engine, the thin wash on the piston wall plus the fumes will be more than enough to support ignition causing a quick burst of life, this in turn will be enough to start the draw from the spraybar - assuming of course that you have finger choked the fuel to be drawn up the tubing to the spraybar in the first place.

I have found that putting drops of fuel down the throat of the venturi to result in flooding every time. You really need fumes to fire off a model diesel not drops of anything.

Talk soon, Chris.

Old 11-22-2010, 09:54 PM
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Default RE: need help with diesel rc engine!! help asap!!

ORIGINAL: AndyW

Good point, Recycled Flyer. But some traditional diesels have the piston top ride below the bottom of the exhaust port at BDC. So that raw, liquid fuel that's made that nice, fat fillet against the piston goes POURING into the combustion chamber in a gushing torrent causing havoc and mayhem. [X(]
Most diesels in sport controline models and even most racing engines are mounted "sidewinder" style. It is usually a simple matter to completely close the exhaust with the piston when priming, and the closed piston prime excess just follows gravity. Below is a picture of my Nelson 15 F2F diesel. Like most very high performance diesels it has an overflow priming system. The other pic is of my Parra Diesel in a Goodyear model with a home made version.

Both systems divert part of the tank overflow to the closed piston to (hopefully) deliver an instant one flick start during pitstops. Note the potential influence of gravity on the excess.
Old 11-22-2010, 10:12 PM
  #58  
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Some of my early attempts at starting diesels were with donated Frog and ED engines. They always had a tendency to bite you no matter how carefully you applied prime, even with the piston closing off the port. (I'm very much familiar with the technique, I've run Cox engines for 45 years). That, to me, was a result of excess, liquid prime, hard to precisely control, giving you a good measure of pre-ignition. Yes, you back off on the compression but then the fussy little beasties would refuse to light off. Only if you allowed it to bite you could you get them to run off a prime and then as they warmed up, they would behave more user friendly.

Both of you are correct though, and I agree that in experienced hands, starting a purpose built diesel, by hand, can be readily accomplished. But not all diesels are created equal. One might not embrace glow conversions but they ARE diesel engines if they run on diesel fuel. Small Norvels will not easily hand start on glow and are impossible to hand start on diesel fuel. Too much cylinder taper.

The point was, and I exaggerated for effect, using a starter in a diesel is not a problem and can make it all so much easier to the newbie, IF they use and understand the technique outlined.
Old 11-22-2010, 10:25 PM
  #59  
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Default RE: need help with diesel rc engine!! help asap!!

ORIGINAL: steve111

Also, in the early days, I was told to be very careful that you didn't lose any of that magical pixy dust known as ether. Somehow, your fuel could go stale and you would never, ever be able to start your engine on that fuel again. Never ever. You had to bless it with the addition of the ether that was obviously lost.
This is an interesting one. I've always tried very hard to preserve my highly volatile magical pixy dust, just as Andy says. Yet recently, I was at a friend's place in Brisbane and dragged out a PAW 249DS-powered model that we'd been flying this the previous week. On the off-chance that there were some dregs left in the tank, I choked it through a couple of times and flicked it. It fired instantly, and ran out the dregs.

Now this was a small quantity of fuel which had been sitting for 8 days in an unsealed tank, in a location where the daytime temperatures were up around 30C. By rights, there should have been no ether left and nothing much should have happened when I flicked it. Yet it fired and ran as if the fuel was freshly made. Fuel for thought, eh (so to speak)!

There's a phenomena with ether fuels that I've never seen mentioned on this forum. When you mix say 320 ml of ether with 200 ml of castor oil so as to make a Litre of diesel fuel you immediately lose 30-40 ml of the combined mix due (probably) to a partial solubility of the latter in the former. What actually happens is unknown but it seems to increase and decrease with changes in room temperature.

This probably goes someway to explain why the fuel level seems to change in stored fuel.

A friend tells the story of his Mills 1.3 cc diesel stored in a model with a prop on for about five years. He picked it up one day and flicked it, and it ran out a burst from what was in the cylinder.

Ray
Old 11-22-2010, 10:35 PM
  #60  
qazimoto
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Default RE: need help with diesel rc engine!! help asap!!

At the risk of "flogging a dead horse" there is a slightly different technique for starting an inverted diesel.

The pics below show a Vintage A Team Racers (2.5cc engine with 15cc of fuel). The tank overflow is a tyre valve operated by one hand while the other aligns and squezzes the filler bottle. When the tank is full a prime is forced into the engine (via the fuel tubing) by closing the tyre valve but continuing to fill. Usually you turn the engine over twice and give one hard flick and it starts.

The other pic shows a glow engine in a team racer, with a screen over the venturi. The tank is filled via the same system, but the "overfill" prime is collected as well in the mesh. This give a vapour available to encourage starting. The same idea is used with diesels.

Ray
Old 11-22-2010, 10:57 PM
  #61  
Recycled Flyer
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Default RE: need help with diesel rc engine!! help asap!!

At the time of typing this there was 8270 views on this thread - that surely must be a new record?
Old 11-22-2010, 11:03 PM
  #62  
AndyW
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Default RE: need help with diesel rc engine!! help asap!!


ORIGINAL: locktite401


ORIGINAL: steve111

Also, in the early days, I was told to be very careful that you didn't lose any of that magical pixy dust known as ether. Somehow, your fuel could go stale and you would never, ever be able to start your engine on that fuel again. Never ever. You had to bless it with the addition of the ether that was obviously lost.
This is an interesting one. I've always tried very hard to preserve my highly volatile magical pixy dust, just as Andy says. Yet recently, I was at a friend's place in Brisbane and dragged out a PAW 249DS-powered model that we'd been flying this the previous week. On the off-chance that there were some dregs left in the tank, I choked it through a couple of times and flicked it. It fired instantly, and ran out the dregs.

Now this was a small quantity of fuel which had been sitting for 8 days in an unsealed tank, in a location where the daytime temperatures were up around 30C. By rights, there should have been no ether left and nothing much should have happened when I flicked it. Yet it fired and ran as if the fuel was freshly made. Fuel for thought, eh (so to speak)!

The's a phenomena with ether fuels that I've never seen mentioned on this forum. When you mix say 320 ml of ether with 200 ml of castor oil so as to make a Litre of diesel fuel you immediately lose 30-40 ml of the combined mix due (probably) to a partial solubility of the latter in the former. What actually happens is unknown but it seems to increase and decrease with changes in room temperature.

This probably goes someway to explain why the fuel level seems to change in stored fuel.

A friend tells the story of his Mills 1.3 cc diesel stored in a model with a prop on for about five years. He picked it up one day and flicked it, and it ran out a burst from what was in the cylinder.

Ray
That goes back to my question as to what happens when you mix ingredients. Especially ingredients that facilitate the mxing of a third ingredient, the kerosene. Do you get an entirely new molecule? Would that not generate heat if so? Or do you get a simple mixing of molecules. Or both?

Do racing diesels ever use synthetic oils? What's the result compared to Castor?
Old 11-23-2010, 12:17 AM
  #63  
qazimoto
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Default RE: need help with diesel rc engine!! help asap!!

ORIGINAL: AndyW


ORIGINAL: locktite401


ORIGINAL: steve111

Also, in the early days, I was told to be very careful that you didn't lose any of that magical pixy dust known as ether. Somehow, your fuel could go stale and you would never, ever be able to start your engine on that fuel again. Never ever. You had to bless it with the addition of the ether that was obviously lost.
This is an interesting one. I've always tried very hard to preserve my highly volatile magical pixy dust, just as Andy says. Yet recently, I was at a friend's place in Brisbane and dragged out a PAW 249DS-powered model that we'd been flying this the previous week. On the off-chance that there were some dregs left in the tank, I choked it through a couple of times and flicked it. It fired instantly, and ran out the dregs.

Now this was a small quantity of fuel which had been sitting for 8 days in an unsealed tank, in a location where the daytime temperatures were up around 30C. By rights, there should have been no ether left and nothing much should have happened when I flicked it. Yet it fired and ran as if the fuel was freshly made. Fuel for thought, eh (so to speak)!

The's a phenomena with ether fuels that I've never seen mentioned on this forum. When you mix say 320 ml of ether with 200 ml of castor oil so as to make a Litre of diesel fuel you immediately lose 30-40 ml of the combined mix due (probably) to a partial solubility of the latter in the former. What actually happens is unknown but it seems to increase and decrease with changes in room temperature.

This probably goes someway to explain why the fuel level seems to change in stored fuel.

A friend tells the story of his Mills 1.3 cc diesel stored in a model with a prop on for about five years. He picked it up one day and flicked it, and it ran out a burst from what was in the cylinder.

Ray
That goes back to my question as to what happens when you mix ingredients. Especially ingredients that facilitate the mxing of a third ingredient, the kerosene. Do you get an entirely new molecule? Would that not generate heat if so? Or do you get a simple mixing of molecules. Or both?

Do racing diesels ever use synthetic oils? What's the result compared to Castor?
Racing diesels use both synthetic and castor based oils. There's quite a few of these. I'll post some links when I find the discussions.

I'd guess that you get a disassociation and a mixing of all the liquids into their molecules and a little bit of chemical reaction occasionally but not regularly. I suspect that the latter would be unintentional. Some people were reporting it happening with (dud/new post9/11/Mcvaine) nitromethane in glow fuel recently.

I'll get you some contacts with a proper chemist.

Ray
Old 11-23-2010, 12:18 AM
  #64  
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Default RE: need help with diesel rc engine!! help asap!!


ORIGINAL: Recycled Flyer

At the time of typing this there was 8270 views on this thread - that surely must be a new record?
Actually, the record might be for, "Substitute for Ether" at 56,734 views. http://www.rcuniverse.com/forum/foru...smode_1/tt.htm Scroll down to the bottom.
Old 11-23-2010, 12:34 AM
  #65  
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Default RE: need help with diesel rc engine!! help asap!!

And this might illustrate all my points. http://www.youtube.com/watch?v=zkNb6...eature=channel A traditional diesel starting, using a starter, no adjustments to the compression OR the main needle and utilizing a high ether prime.

Later work showed that the PAW would light off first try and keep running if the engine were heated to near running temps with a heat gun.

That's a lot of struggle to get an engine running but WITH ether in the fuel, this PAW will start with the starter, first crack, without the need to play with the compression or main needle.
Old 11-23-2010, 05:32 PM
  #66  
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Default RE: need help with diesel rc engine!! help asap!!

Andy, whilst I applaude your lateral thinking here I just can't see the point since you either have to prime an etherless fuel with ether anyway or you have to carry around a heat gun and its power source in order to get the engine to start, and then still need the starter anyway!

Wouldn't it just be simpler to use an ether based fuel mix and be done with it?

I accept that far less ether has to be used when using an etherless fuel run but Istill harbour doubts that the oil will be totally miscible in the kerosene without it.
This excellent link provides good reading concerning model fuels and in part states that a vegetable based oil like castor will NOTblend with a parrafin based fuel.

http://modelenginenews.org/faq/fuels.html

So perhaps Klotz Benoil has some additive that would assist here?

Cheers.
Old 11-23-2010, 11:22 PM
  #67  
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Default RE: need help with diesel rc engine!! help asap!!

Some process is performed on the castor to help it blend with petroleum. Some castor oils do have additives. As we discussed in the etherless thread years ago, most castor oil blends with kerosene above 5°C or so. I had some castor that wouldn't blend even with ether in the mix. In my four stroke conversions I've been running synthetic oils to avoid the issue.
Old 11-24-2010, 12:53 AM
  #68  
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Default RE: need help with diesel rc engine!! help asap!!

For me, running no ether was just a way of trying to understand the why and the how. Of course, I wouldn't advocate making that standard practice, we need ether for a number of reasons. Lower compression ratios, easier starting, starter or no and better throttling. That last is a biggie for me.

In Europe, nitro is very expensive. So much so that they developed glow engines that ran well on very little or no nitro. Problems arose when those engines were imported to North America. No nitro meant higher compression ratios and when nitro fuels WERE used, all kinds of problems surfaced. That the manufacturers and importers didn't anticipate this is beyond me.

So consider a day that ether becomes so expensive that everyone just packs away their beloved, little engines. For no reason. Our diesel engines WILL run without ether and the problems associated with that will likely be solved by regular guys like you and me.
Old 11-24-2010, 01:04 AM
  #69  
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Default RE: need help with diesel rc engine!! help asap!!


ORIGINAL: AndyW

In Europe, nitro is very expensive. So much so that they developed glow engines that ran well on very little or no nitro. Problems arose when those engines were imported to North America. No nitro meant higher compression ratios and when nitro fuels WERE used, all kinds of problems surfaced. That the manufacturers and importers didn't anticipate this is beyond me.

So consider a day that ether becomes so expensive that everyone just packs away their beloved, little engines. For no reason. Our diesel engines WILL run without ether and the problems associated with that will likely be solved by regular guys like you and me.
Andy,

nitro was very expensive and rare outside the USA in the 1960's but that is no longer the case and hasn't been for decades. Diethyl Ether is available as an industrial solvent and is used in large quantities in various chemical processes. It's not expensive in bulk and is not likely to become so.

Ray
Old 11-24-2010, 01:48 AM
  #70  
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Default RE: need help with diesel rc engine!! help asap!!

You are correct in principle than nitro is not hard to find here anymore, but I do think that it is still expensive. As an example I would pay around $9 for one litre of 80/20 fuel (pure castor, no nitro) and about $16 for 10% nitro (still 20% castor) and this is from the same manufacturer, so about twice the price in order to get 10% nitro in the fuel. I sometimes buy nitro on its own to blend my own fuel, and if I remeber correctly it is something around $50 for a litre. So most of us here still regard nitro as an additive, best used in small amounts only.

The best no nitro engine I've seen so far (or own that is) is the Webra 1.8cc speedy, runs beautifully completely stock on 80/20 fuel.
Old 11-24-2010, 02:02 AM
  #71  
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Default RE: need help with diesel rc engine!! help asap!!


ORIGINAL: Mr Cox

You are correct in principle than nitro is not hard to find here anymore, but I do think that it is still expensive. As an example I would pay around $9 for one litre of 80/20 fuel (pure castor, no nitro) and about $16 for 10% nitro (still 20% castor) and this is from the same manufacturer, so about twice the price in order to get 10% nitro in the fuel. I sometimes buy nitro on its own to blend my own fuel, and if I remeber correctly it is something around $50 for a litre. So most of us here still regard nitro as an additive, best used in small amounts only.

The best no nitro engine I've seen so far (or own that is) is the Webra 1.8cc speedy, runs beautifully completely stock on 80/20 fuel.
Nitro here is $15-$30 per litre depending where and how you buy it. You don't have Nitro Drag Racers in Northern Europe?

Ray
Old 11-24-2010, 02:26 AM
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Default RE: need help with diesel rc engine!! help asap!!

Recycled Flyer,

Just read through the link you provided and found it most enlightening. Now I can put numbers to what I discovered experimentally. It's dated 1950 and 95% of the material is still relevant. Modern, castor formulations being the exception, of course, and no discussion is made about the qualities or grades of castor available at the time. Would that have been pharmaceutical castor?

What I find MOST interesting is that despite the advice, (given in 1950) that too much oil is detrimental and that 20% should be adequate, we STILL hear about the 1/3rd blend being a starting point. I made up a bored, MP Jets, ABC engine utilizing AP .09 parts. http://www.youtube.com/user/hopeso#p/u/69/E8_aLl_eAzI This gave me about an .074 over the original .06. I used the 1/3rd mix and no amount of flipping would get that little b*gger started. This was in the fall and over the winter, on the Smallnet forum one fellow suggested that small diesels need more ether than larger. By the Spring I came upon information that kerosene had lubricating properties all on its own. So why so much castor?? So I made up a mix of 20% castor, 39% ether, 39% kerosene and 2% MEKP. First warm day in April, I took out that little beast, filled the tank, left the fuel line off and flipped while blocking the muffler. When the line showed fuel dripping out, I hooked it up and proceeded. I swear on any stack of holy books, I primed into the intake, gave ONE healthy flip and that impossible to start engine lit off and RAN. I didn't touch the compression OR the main needle from the previous attempts in the Fall. It just sat there, running as pretty as you please.

Wonder of wonders. From there, I never looked back.
Old 11-24-2010, 04:00 AM
  #73  
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Default RE: need help with diesel rc engine!! help asap!!

Diesel fuel is a simple mixture with the following ingredients:
Ether*
Kerosene**
Oil***
Dope**** amyl nitate, amyl nitrite, hexyl nitrate, isopropyl nitrate are suitable.
*Ether is used in the range of 20-30% by volume and its SOLE purpose is to lower the self ignition temperature (SIT) of the fuel mix to facilitate starting.
**Kerosene is used in the range of 33-50% by volume and it is this that gives the fuel mix its energy of combustion.
***Oil is used at 20-33% by volume and lubricates the engine. You can use virgin extra pressed castor oil or synthetic oil containing about 10% castor.
****Dope is used at 1-2% by volume and this can help in promoting smoother running or extracting more power in the case of racing engines.
I mix my own fuel and my basic recipe is 25% ether, 43.5% kerosene, 30% oil and 1.5% amyl nitrate.
Only mix as much as you need for a week or two, typically 100-250mL and keep in a well sealed container and protect from direct light.
If you do have access to ether, keep no more than 500mL in your workshop or wherever you do your modelling. It is very volatile and seriously explosive when in vapour form. Flash point is -35C and 4% vapour in air will cause a big bang if ignited.
I am an experienced "diesel head" and have learnt what I have written over a long time.
Enjoy your diesels and have patience with them especially if you are starting out.
Old 11-24-2010, 04:44 PM
  #74  
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Default RE: need help with diesel rc engine!! help asap!!


ORIGINAL: AndyW

Recycled Flyer,

Just read through the link you provided and found it most enlightening. Now I can put numbers to what I discovered experimentally. It's dated 1950 and 95% of the material is still relevant. Modern, castor formulations being the exception, of course, and no discussion is made about the qualities or grades of castor available at the time. Would that have been pharmaceutical castor?

What I find MOST interesting is that despite the advice, (given in 1950) that too much oil is detrimental and that 20% should be adequate, we STILL hear about the 1/3rd blend being a starting point. I made up a bored, MP Jets, ABC engine utilizing AP .09 parts. http://www.youtube.com/user/hopeso#p/u/69/E8_aLl_eAzI This gave me about an .074 over the original .06. I used the 1/3rd mix and no amount of flipping would get that little b*gger started. This was in the fall and over the winter, on the Smallnet forum one fellow suggested that small diesels need more ether than larger. By the Spring I came upon information that kerosene had lubricating properties all on its own. So why so much castor?? So I made up a mix of 20% castor, 39% ether, 39% kerosene and 2% MEKP. First warm day in April, I took out that little beast, filled the tank, left the fuel line off and flipped while blocking the muffler. When the line showed fuel dripping out, I hooked it up and proceeded. I swear on any stack of holy books, I primed into the intake, gave ONE healthy flip and that impossible to start engine lit off and RAN. I didn't touch the compression OR the main needle from the previous attempts in the Fall. It just sat there, running as pretty as you please.

Wonder of wonders. From there, I never looked back.
Hi again Andy,
I am glad that you found that link good reading, some of those older authors seem to talk relaxed to you and I take in what they say much better than modern science talkers!

Pharmaceutical (medical) castor has a higher purity and I assume that it would be the prefered oil to use, and again that is the one specified on the PAWweb site -

Med. Castor Oil

Paraffin

Ether

Iso Propyl Nitrate or
similar ignition improver

Running in

30%

35%

33%

2%

Fully run in

25%

40%

33%

2%

Fully run in
- BR Models

20%

48%

30%

2%

Fully run in
- TBR only
(Racing and Speed)

15%

50%

32-33%

2-3%



The one third brew is very old fashioned and was designed to take up the manufacturing slack if poor tolerances were evident in an engine and it kept the power down to a very safe level in the public consumption arena. Basically if you ever ruined an engine using the old one third brew then you should look at an another hobby!

And I don't see that 20% castor is a problem in a fully run in engine as long as it has nice tight fits on its running parts.

Cheers.

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