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What's the attraction of diesel plane engines?

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Old 04-28-2018, 05:24 PM
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N99JH
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Originally Posted by 1QwkSport2.5r View Post
Ringed engines should NEVER EVER be used as Diesel conversions in the air. IMVHAIO. Ringless pistons are the proper way to go as is the proper fuel. Synthetic oils have NO place in model diesel fuels. Set the engine right and you shouldn’t have to do much to it for a long time. Carbon buildup in a short period of time causing the engine to not run properly leads me to believe either improper engine settings or incorrect fuels being used. IMO.
And how much actual flying experience do you have if you don't mind me asking?
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Old 04-28-2018, 05:38 PM
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Originally Posted by N99JH View Post
And how much actual flying experience do you have if you don't mind me asking?
Enough to know ringed engines suck as Diesels.
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Old 04-30-2018, 10:46 AM
  #28  
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Back in the 60's diesels up to .15 (or 2.5cc) rarely had problems other than to those who didn't like the smell. At the time we thought bigger engines like 3.5cc upwards would not be very suitable due to the vibrations that came with increased size. The really big engines that came to use later on, often with a piston ring, is yet another matter.

So for smaller CL engines, I think diesels are really good fun. No carbon problems that I know of. The combat and team race diesel powered models have shown us how powerful these little engines can be.

Maybe the diesel concept is best suited for the smaller engines?
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Old 04-30-2018, 12:37 PM
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I spoke at length with Dave Platt about his diesel experience. He grew up flying diesels (mostly Oliver/Tiger) in Great Britain and it is my impression he is/was quite well-versed in them. Back when he was competing at the highest levels of RC Scale, he was campaigning a T-28 in which he had installed a Moki 1.8 2 stroke glow. However, he wanted to spin a large 3 blade prop and also to have the engine fully enclosed and was worried about over-heating a regular glow engine under these conditions... So he converted the big Moki to diesel. In our conversation he told me he could never get the engine to run well enough to use in this application; he tried different fuel mixes and carburetion and finally gave up, converting back to glow.
It seems some engines just make bad diesel engines.
My experience has been that you probably cannot go wrong with a P.A.W.
They may not be the most modern powerplant, but they are designed from the ground up as diesels, and have many years of successful diesel experience behind their construction.
Picking the correct type of model and flying style is also integral to "success" with a diesel.
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Old 05-01-2018, 02:06 AM
  #30  
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All of my experience is with Davis Diesel conversions and I used his fuel. I adjusted the engines per his instructions and never ran them over-compressed. Simply put - no matter what I tried, it did not work. Plain and simple!
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Old 05-01-2018, 03:11 AM
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I used Davis conversions as well. I did not adjust the engines his way nor did I use his fuel. I mixed my own fuel and used tuning advice from a friend. I run my conversions slightly rich of peak and adjust the compression accordingly.

My fuel was 31% ether, 23% castor oil, 2% Amsoil cetane boost, balance JetA or Kerosene. Works every time without any poor habits or side effects. Davis fuel has synthetic oil in it which IMO is not a good choice to make. Model engine synthetics do not have the pressure properties that castor does and likely why more of the oil burned than blowing out the exhaust. IMO based on speculation and no pictures.
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Old 05-01-2018, 09:01 AM
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Originally Posted by 1QwkSport2.5r View Post
I used Davis conversions as well. I did not adjust the engines his way nor did I use his fuel. I mixed my own fuel and used tuning advice from a friend. I run my conversions slightly rich of peak and adjust the compression accordingly.

My fuel was 31% ether, 23% castor oil, 2% Amsoil cetane boost, balance JetA or Kerosene. Works every time without any poor habits or side effects. Davis fuel has synthetic oil in it which IMO is not a good choice to make. Model engine synthetics do not have the pressure properties that castor does and likely why more of the oil burned than blowing out the exhaust. IMO based on speculation and no pictures.
Any idea where we can acquire the ingredients for model diesel fuel? Amyl Nitrate and Ether are the real challenges. Have you ever substituted an auto diesel Cetane booster and John Deere Staring fluid, respectively?
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Old 05-01-2018, 10:54 AM
  #33  
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The best is to get ready-made fuel, rather than experimenting with different blends. What has worked well for 70 years will still work well....

Doesn't Davis Diesel Development provide fuel in the US for instance?
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Old 05-01-2018, 11:02 AM
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Originally Posted by Mr Cox View Post
The best is to get ready-made fuel, rather than experimenting with different blends. What has worked well for 70 years will still work well....

Doesn't Davis Diesel Development provide fuel in the US for instance?
The only source for Davis fuel is Tower Hobbies...where is it perpetually on back-order.
FHS (Red Max) was another source - not any longer.
Aerodyne (British I think?) also not available.
Home brew seems to be the only option; ether and amyl nitrate are impossible to obtain in many places.
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Old 05-01-2018, 11:36 AM
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I use John Deere starting fluid and Amsoil Cetane Boost for my fuel and it works identically to Davis fuel as far as power and starting/handling goes. I do not have excessive carbon build-up either.

I mix my own diesel fuel because it’s about 60% cheaper to do so as well as the fuel has exactly what I want in it at the proportions I want. Davis fuel costs about $15 per quart plus shipping. My fuel costs me about $6-7 per quart to make myself.
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Old 05-01-2018, 08:36 PM
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A big 10 c.c. Russian Zeus and a big fan up front ... a Bolly Clubman 13.5 x 6. Old OS .25 FSR carb. Conversions are great if the base engine is built to take the extra strain and the conversion head is properly engineered.


Last edited by fiery; 05-01-2018 at 08:50 PM. Reason: Correct propeller specs.
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Old 05-01-2018, 08:46 PM
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Ringed engines suck as a diesel? No-one told that to this nice Webra Speed .61.

Delay in starting was due to my not advancing compression. Once I did that it fired right up.

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Old 05-02-2018, 01:45 AM
  #38  
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I’ve run ringed Diesels too. They don’t hand start for beans, and seemed finnickier to adjust. The ringless engines seem 10X better and easier to handle, so I dumped the ringed ones or converted them to ABC. I recently converted a ringed ST .51 to ABC with a piston/liner from a Tiger Shark .52. I haven’t run it as a Diesel yet, but I intend to. My benchmark 7.5cc prop is an APC 13x6, which an ST GS.45 ABC can do around 10,800+. I’d think a 13.5x6 would be a little small for a .61?
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Old 05-05-2018, 02:30 PM
  #39  
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John Deere starting fluid is 80% ether. I believe it's the best you can get.
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Old 05-05-2018, 03:47 PM
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Originally Posted by ebeneezer3 View Post
John Deere starting fluid is 80% ether. I believe it's the best you can get.
It’s near 100% when you remove the propellant. It’s 80% ether and 20% propellant. I treat it as pure ether and my fuel matches Davis Diesels fuel in rpm from the same engine. I actually get more power in some cases.
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Old 05-05-2018, 03:53 PM
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My Fox .74 w/Davis head

Last edited by RichardGee; 05-05-2018 at 03:55 PM.
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Old 05-05-2018, 05:08 PM
  #42  
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Originally Posted by 1QwkSport2.5r View Post
I use John Deere starting fluid and Amsoil Cetane Boost for my fuel and it works identically to Davis fuel as far as power and starting/handling goes. I do not have excessive carbon build-up either.

I mix my own diesel fuel because it’s about 60% cheaper to do so as well as the fuel has exactly what I want in it at the proportions I want. Davis fuel costs about $15 per quart plus shipping. My fuel costs me about $6-7 per quart to make myself.
What percent of each are you using? Is the balance pump Kerosene? Can you please share your home brew formula? I would love to try it.
Thanks
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Old 05-08-2018, 10:22 AM
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Originally Posted by N99JH View Post
What percent of each are you using? Is the balance pump Kerosene? Can you please share your home brew formula? I would love to try it.
Thanks
31% John Deere ether, 23% castor oil, 2% Amsoil Cetane Boost, balance pump kerosene or Jet A.
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Old 05-12-2018, 11:24 AM
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Do you know if ANY Castor oil will work? For example, WalMart sells a 16 oz. bottle of cold pressed Castor oil. Will this work for mixing fuel?
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Old 05-12-2018, 03:30 PM
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Originally Posted by RichardGee View Post
Do you know if ANY Castor oil will work? For example, WalMart sells a 16 oz. bottle of cold pressed Castor oil. Will this work for mixing fuel?
As long as it contains no additives. Check the label. Larger quantities is cheaper though. I get a gallon for $17+shipping. Usually around $22-25 shipped. Last time I bought an 8oz bottle it costed $5 at Wally world. For mixing large amounts of fuel, it’s impractical to use such small quantities.
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Old 05-13-2018, 11:55 AM
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Great thread and have certainly enjoyed reading this. Not a lot of experience here, but years ago have run a 40FP w//DDD on stand. After a long break, and having accumulated numerous DDD heads for mostly K & B engines, have a MVVS .61 and factory diesel head which I'm hoping to install in a J3 Cub. Maybe a 16" prop will be about right. Tried to check for DDD fuel at TH, but unable to access it. All Things change, don't they!
Thanks again

Last edited by triumphman49; 05-13-2018 at 11:56 AM. Reason: misspell
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Old 05-14-2018, 05:32 AM
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Originally Posted by triumphman49 View Post
Great thread and have certainly enjoyed reading this. Not a lot of experience here, but years ago have run a 40FP w//DDD on stand. After a long break, and having accumulated numerous DDD heads for mostly K & B engines, have a MVVS .61 and factory diesel head which I'm hoping to install in a J3 Cub. Maybe a 16" prop will be about right. Tried to check for DDD fuel at TH, but unable to access it. All Things change, don't they!
Thanks again
Have you run the MVVS .61D yet?
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Old 05-14-2018, 03:04 PM
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No, Haven't run it yet. Just received the .61 last week and there is a strong push for hours on my construction job. Also will have to brew the fuel. Thanks for asking.
T-man 49
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Old 05-15-2018, 03:36 AM
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Originally Posted by RichardGee View Post







My Fox .74 w/Davis head
What paint is that O_O. I'm mesmerized.
Jim West
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Old 05-15-2018, 07:15 AM
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Originally Posted by controlliner View Post
What paint is that O_O. I'm mesmerized.
Jim West
I used VHT hi temperature (650 deg. F) "copper"

Mother's Mag Aluminum polish on the shiny areas.

Drilled a hole through the hex head of a longer compression adjustment screw and silver soldered a copper T bar. Hi temp black applied to the screw.
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