SGC

For those that cant get ether to make diesel fuel through the normal channels (chemist/industrial supplies) John Deer starting fluid is 80% ether and works ok as a direct replacement just calculate the 20% as kero. The JD fluid is not wxpensive either , I purchased 3 X 7oz cans for A$12.60 from my local JD agent, so should be available in most areas of oz.

HaveBlue, Not all diesels are limited to slow slugging of largeish props, there are motors quite capable of 20,000RPM plus, its just they show there great fuel ecconomy at the higher loads/lower RPMs
Stewart

johnvb-RCU

My Feedback: (1)

That's for sure! I just came back from the Muswellbrook meeting where there were a number of team race and combat control-liners flown. These had 2.5cc Cyclon diesels (among others probably) and sounded fair dinkum like mosquitoes. Must have been getting towards 30k rpm, 2 seconds a lap by my rough count.

HaveBlue

Hi , in regards to the speed or rpm I didnt say they are slow, I know some diesels can turn, I said they are percieved as slow turning engines

AndyW

My Feedback: (1)

I have been operating model airplane engines since the days of carbon-zinc dry batteries and spark ignition (my first was a Fleetwind 60). I like fooling around with engines. I have enjoyed playing with the PAW and can even see myself buying another diesel in the future. However, barring some drastic new development in diesel technology, I believe they will always remain a niche product. The current two-stroke glow ignition engine is powerful, dependable, simple to operate, durable, and cheap. Until something comes along that is significantly better it will remain the choice of most modellers.

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Lou,

You've made some excellent points. What the problem with diesels, in my opinion, is this. In discussing diesel COMBUSTION, I think that we're confusing the issue with diesel ENGINES. Among diesel engines, there are many types. Traditional (outdated) designs like the PAW you mention in your post. And diesel conversions that take a very highly developed, light, modern, rugged, CHEAP glow engine and make them run on stinky fuel. It WOULD be cheap, that is, if you didn't have to go out and buy a special head for it. So now, to get a MODERN diesel, you have to pay more. Yes, MVVS and a few others make modern diesels but there aren't many. In addition, modern diesels and conversions also do the throttling thing quite well. Something you can't say about many traditional diesels. In part, it's due to bad throttle design such as no means to adjust the mixture at idle, as is the case with my PAW .06. Adding the feature made all the difference in the world. In part, it's due to bypass port design and timing.

In any event, there IS a drastic new development in engine technology that takes diesel operation to a level of simplicity and trouble free operation that parallels glow. I'm referring to Norvels converted to diesel. The following link will illustrate what I mean.

http://www.youtube.com/watch?v=af4dQNa60_w

Notice that the engine would not fire with the first few cranks of the spring. Note that it did with only one crank with the muffler blocked. And only a few tries got it running. This is on a spring starter (safe), the CP did not need to be changed from its running position to a start setting and the engine came up to top RPMs almost immediately, no long warm up required as with a traditional diesel. As well, adjustments are immediate, you don't have to wait till things stabilize to see where you've got to.

THIS IS CHARACTERISTIC OF ALL NORVELS.

I've done conversions up to the .15 and while the .15 hasn't flown, it behaves the same as my .074s and .061s. I have a brand new Norvel .40 for which I'm designing a diesel head. A standard button can't be made to fit so an entirely new approach is in the works. Will be posting the results at a much later date.

This appears not to be a fluke. I've installed the innards of a Norvel, (Revlite) .06 into the new CS/Brodak. 049 and it makes a wonderful diesel that starts with the use a small starter with no muss or fuss. You can see it here.

http://www.youtube.com/watch?v=Eu1ucHl9SXc

Note that this Revlite hybrid started without any attention being paid to the CP. It did require a bit of tweaking once running, but it did start. On the other hand, a stock (steel/iron)Brodak .049, with a diesel head, needs to be overcompressed a quarter turn, just to start. It WILL NOT START, even with the electric starter. The same happened with an odd conversion I made a good number of years ago. I was deathly afraid to apply an electric starter to Norvels because everybody always said, NEVER use one on a diesel. So, none of my Norvel conversions would start. That led me to the notion that I'd have to convert a Norvel to early steel/iron tech to get a light, modern, 1/2A diesel. Success was assured, I thought but no way. Well, not at first. That engine is pictured below. I had guesstimated, incorrectly, the size of the combustion volume needed to start and run and no matter what, even with an electric starter, it would not run. Years later, with a little more experience, I realized what the fix was and proceeded. But, the engine STILL would not start, again, even with the use of an electric starter. In the end, I found that I had to seriously overcompress for a start and a full minute or more of warm-up was required before any adjustments should be made. This appears to be a characteristic of steel/iron diesel engines.

None of these troublesome characteristics are evident with Norvel Revlite engines. Revlite refers to a hard anodized cylinder along with a nickel plated piston. This gives you a very hard/hard combination. Anodize is a form of aluminum oxide. The surface has a honeycomb structure and this works to provide excellent compression seal. Why Norvel/Revlite engines behave just like their glow counterparts, I think, may be due to the thermally insulating qualities of the anodized layer, both on the outside AND the inside of the cylinder.

The first success I had with any sort of diesel conversion never happened with Cox engines. I could never really get them started,,, the compression seal was just too poor even with a new engine. What DID work for me was a conversion I did that used a mix and match P/L set made of Wasp and Norvel AAN parts. A piston was found that was nearly an impossibly tight fit. This engine was started by using a heat gun on the cylinder to allow it to be turned over. It was carefully broken in using glow fuel at first and interestingly, the needle setting was very close when I converted to diesel. Once I had it running as diesel, I found that it would hand start without touching the CP setting. Two to three drops of prime into the intake and a couple of quick flips had the prime fire off. Two or three of these got the cylinder up to a temperature where the engine caught and kept running with that wonderful burrp, burrp sound we're so fond of. A minute of this and the engine transitioned into a beautiful, solid, max RPM. And, just like its glow version, throttling was VERY good. This, of course, required a throttle with an adjustable airbleed. That engine was sent off to Singapore and ever since then, I've never been able to find a mix and match P/L combo tight enough to replicate the experiment. Maybe someday.

As an aside, I added an MP Jets throttle to a Mills replica for Tom Anderson some years ago and it worked great. At the same time, out of mutual curiosity, I converted one of his Mills diesels to glow using a turned down Cox glow head. As I recall, the engine ran as well, or better and throttling was just as reliable on glow as it was as a diesel. Someday I'll do a PAW, just for fun. Yeah, sacrilege, I know. [:'(]

My experience with electric starters on Norvels prompted me to try one on my one and only RC diesel and that's a PAW .06. This one was started by hand first and adjusted at the needle and at the CP. Then, after allowing it to cool thoroughly, I applied three drops of prime into the intake, hit it with the starter and off she went, with no problems. I have no doubt that a spring starter would have worked as well.

All of this leads me to wonder if spring starters for diesel engines might be a right good idea, even up to .60 sizes,, or more. No chance of breaking anything and a lot easier on the shoulder joint. I guess, that's going to have to go on my to do list this summer.

In my opinion, there's really no difference between the two fuels as far as how they might respond to ENGINE DESIGN. Easy handling and throttling has as much to do with engine design as good throttle design.

AndyW

My Feedback: (1)

Early in my diesel adventures, I commented that diesels were more suited to running larger props than glow. I got properly corrected and running glow sized props showed me the error of my assumptions. However, I can only wonder, if a diesel on a small prop will run as fast as glow, what's the advantage of doing it the diesel way? Why not just run glow for these fast events?

Jim Thomerson

The FAI team race event has a tank size restriction, something like three drops of fuel, I think. So diesel it is. In the early days, there was talk of glows like the Cox Special 15 being competitive, but it did not happen, and the fuel tank size has been reduced twice or maybe three times over the years. Maybe the combat event specified diesels. There is a D-bat event flown in Canada and elsewhere, also Vintage combat and Oliver combat and etc. The British have several specific diesel racing events as well.

AndyW

My Feedback: (1)

Thanks Jim,

The versatility of diesel and its benefits ought to be better known.

on pipe

I didn't read every single post and it's just my two cents but, a lot of people have trouble with one component to adjust, (carburetor) let alone two. (carb AND compression) Maybe this causes people to think twice... Ross

AndyW

My Feedback: (1)

Ross,

You're right but that applies more heavily to traditional diesel engines. A glow conversion can be run as glow and all the throttle/carb adjustments can be made in this much more friendly and familiar environment. Then, with the diesel head installed but with NO fuel in the tank, the compression setting can be found. Once that's done, you can fill the tank and start the engine using just drops of prime into the intake and an electric starter. Once the engine gets running, you just tweak the CP screw for max rpm, go back to the needle, back to the CP, back and forth a few times, and you easily find that just right setting. Once set, you rarely have to adjust anything as long as your fuel formula or the weather doesn't change drastically.

And if you rig your tanks with neoprene tubing, as I've done, you can switch back and forth with just a change of the head and prop.

johnvb-RCU

My Feedback: (1)

That's true, but they quite often have more trouble NOT adjusting anything....

AndyW

My Feedback: (1)

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QUOTE:

Notice that the engine would not fire with the first few cranks of the spring. Note that it did with only one crank with the muffler blocked. And only a few tries got it running. This is on a spring starter (safe), the CP did not need to be changed from its running position to a start setting and the engine came up to top RPMs almost immediately, no long warm up required as with a traditional diesel. As well, adjustments are immediate, you don't have to wait till things stabilize to see where you've got to.

THIS IS CHARACTERISTIC OF ALL NORVELS.

I've done conversions up to the .15 and while the .15 hasn't flown, it behaves the same as my .074s and .061s. I have a brand new Norvel .40 for which I'm designing a diesel head. A standard button can't be made to fit so an entirely new approach is in the works. Will be posting the results at a much later date.

This appears not to be a fluke. I've installed the innards of a Norvel, (Revlite) .06 into the new CS/Brodak. 049 and it makes a wonderful diesel that starts with the use a small starter with no muss or fuss.

QUOTE:

++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++++


Further work on the remaining line of Norvels has revealed some interesting developments. The characteristic I'm referring to seems not to apply to the larger engines, the .15, the .25 and the .40.

As related, in the recent posts, the greater mass of the larger engines requires some slight overcompression to start. The .074 and smaller engines seem to come up to temp almost immediately so instant, glow like starts are possible.

The .15 behaved as described but for some inexplicable reason, only with the muffler removed.

The latest on YouTube can be seen here.

http://www.youtube.com/profile_videos?user=hopeso