.20 Something Diesels
#27
Thread Starter
Aright Dave, I froze my fingers off and ran my Sportster .20 today. It was 29F outside.
APC 9x6 @ 11,280rpm
APC 10x6 @ 10,020rpm
MAS K 11x6 @ 8,790rpm
I don't know what size the carb is, I'll measure it later. I used the same fuel that I've been using, though I think these little bushing engines might need a little more oil. 25% oil would probably be better than the 20% I was using today. It idled down to 2,300rpm and throttled nicely. I think the eccentric screw doesn't allow it to go quite rich enough down low, but it would recover pretty good anyway.
Edit: added video. http://youtu.be/dSP-DnOP77Y
APC 9x6 @ 11,280rpm
APC 10x6 @ 10,020rpm
MAS K 11x6 @ 8,790rpm
I don't know what size the carb is, I'll measure it later. I used the same fuel that I've been using, though I think these little bushing engines might need a little more oil. 25% oil would probably be better than the 20% I was using today. It idled down to 2,300rpm and throttled nicely. I think the eccentric screw doesn't allow it to go quite rich enough down low, but it would recover pretty good anyway.
Edit: added video. http://youtu.be/dSP-DnOP77Y
Last edited by 1QwkSport2.5r; 11-20-2015 at 05:09 PM.
#28
Thread Starter
Earl - those Drone diesels having a fixed compression ratio must be a little finickier to run in regard to fuel/props? Or I should say you might have to adjust the ether content for different props or do you just have a narrow span of props you can use with them?
#30
Thread Starter
Would you be willing to do an Apples to Apples comparison? Do you have a good 9x6 and 10x6 you would be willing try? I realize Davis already ran a .20 on those prop sizes, but we all know no two engines run the same. It's just mere curiosity for me. If not, no worries. I know we do things differently.
Last edited by 1QwkSport2.5r; 11-21-2015 at 07:27 AM.
#31
Thus if you use our current model diesel engine fuel, you need to try some different propellers to get it to run OK. But even then it may not want to peak out with the needle valve setting and run with a bit of a miss to it. If you use a variable compression head then you don't have the problem. Some variable compression heads are more limited in the compression ratio range though than others.
There are some variable compression heads for them and there are even some glow heads too. The glow heads came out late when glow engines had taken over the USA market. I do have a copy of a old article about making a DIY variable compression head for the Drone engines too.
These two examples were made by someone in Italy of all places for a Drone .29 engine. Even way back in 1947 through 1949 the Drone engines had some international interest with people.
I am partial to the regular fixed compression heads as it confuses people a lot at the flying field.
Last edited by earlwb; 11-21-2015 at 09:06 AM. Reason: add more info
#33
they were made in Elisabeth NJ in the late 1940s and early 50s by Leon Shulman I went there and bought mine at the factory as a teenager martin
fuel 30% mineral oil and 70% ether from the drug store
the fuel mixes now are conventional of course with lower ether % kerosene and castor oil that was the original formula suggested by drone back then
Quite sure they would do fine on our newer blends
my drone is shot poor compression so a no run
fuel 30% mineral oil and 70% ether from the drug store
the fuel mixes now are conventional of course with lower ether % kerosene and castor oil that was the original formula suggested by drone back then
Quite sure they would do fine on our newer blends
my drone is shot poor compression so a no run
Last edited by AMB; 11-21-2015 at 01:36 PM.
#34
Thread Starter
Thanks for the info, Martin. They look pretty interesting - I can believe the funny looks one might get (that Earl mentioned) seeing the head has no compression adjustment or glow plug (typically).
The fuel mixture - Whew! That's a lot of ether.. It's too bad Ether is so hard to get in quantity. I've been using John Deere ether at a little over $4/can. That would get expensive real quick running those Drones.
The fuel mixture - Whew! That's a lot of ether.. It's too bad Ether is so hard to get in quantity. I've been using John Deere ether at a little over $4/can. That would get expensive real quick running those Drones.
#35
I have just been running my Drone engines using Davis Diesel development diesel fuel. I add a little extra castor oil to the mix though. They run Ok like that. I don't think that there is all that much difference between the suggested Drone fuel and the normal commercial diesel fuels we have today.
Way back then some of the control line flyers would fly their models enough to actually have the engine wear a oval shape into the main bearing (bushing) on the engines. All that ether would of course strain the engine during combustion and force the crankshaft down harder. That prompted the designer when he came out with the second model to add a large ball bearing to the engine to help minimize the wear. Now of course this was the competition flyers who could easily put in 20 hours or more flying during a week. So they were really racking up some serious time on their Drone engines. Thus the Drone engines were pretty tough when you think about it.
Way back then some of the control line flyers would fly their models enough to actually have the engine wear a oval shape into the main bearing (bushing) on the engines. All that ether would of course strain the engine during combustion and force the crankshaft down harder. That prompted the designer when he came out with the second model to add a large ball bearing to the engine to help minimize the wear. Now of course this was the competition flyers who could easily put in 20 hours or more flying during a week. So they were really racking up some serious time on their Drone engines. Thus the Drone engines were pretty tough when you think about it.
Last edited by earlwb; 11-21-2015 at 07:43 PM. Reason: add more info
#36
Thread Starter
Good to know Earl. Thanks so much (and everyone else) for contributing to this thread. I'm a new diesel guy and the bug bit me hard. Got all conversion engines so far, but I'll surely get a purpose-built diesel soon enough. I have 7 engines that I can run with conversion heads. I'm still learning, but it's been fun so far. No failures as of yet. I plan to keep it that way if I can.
The easiest starters are AAC or ABC construction. The one lapped engine is a beat up basketcase that's been through some tough runs.
The easiest starters are AAC or ABC construction. The one lapped engine is a beat up basketcase that's been through some tough runs.
#37
Thread Starter
I had a little time and some fuel to finish using up before winter, so I ran the Sportster .20 Davis conversion again. I ran two props to see what happened. It ran well, throttled nicely (I still think I may need to modify the idle disc to allow slightly richer idle mixture) and overall did well I think.
APC 13x4W - idled at 1,800rpm and peaked at 6,600rpm
APC 10x5 - idled down to 2,200rpm and peaked at 10,800rpm. This one seems a bit small since the compression adjustment had to be within 1/2 turn of bottomed out.
APC 13x4W - idled at 1,800rpm and peaked at 6,600rpm
APC 10x5 - idled down to 2,200rpm and peaked at 10,800rpm. This one seems a bit small since the compression adjustment had to be within 1/2 turn of bottomed out.
#38
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I have just been running my Drone engines using Davis Diesel development diesel fuel. I add a little extra castor oil to the mix though. They run Ok like that. I don't think that there is all that much difference between the suggested Drone fuel and the normal commercial diesel fuels we have today.
"The first point to bear in mind is that a conventional diesel fuel with kerosene and ignition improver should not be used in these engines—quite apart from the starting difficulties which will be experienced, serious damage will result if this advice is ignored."
I dunno Earl, perhaps the extra calorific value of kerosene would over stress the engine?
#39
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I have just been running my Drone engines using Davis Diesel development diesel fuel. I add a little extra castor oil to the mix though. They run Ok like that. I don't think that there is all that much difference between the suggested Drone fuel and the normal commercial diesel fuels we have today.
"The first point to bear in mind is that a conventional diesel fuel with kerosene and ignition improver should not be used in these engines—quite apart from the starting difficulties which will be experienced, serious damage will result if this advice is ignored."
http://modelenginenews.org/faq/fc_diesel_ops.html
"However, we can turn some of the characteristics of ether to our advantage when looking at fixed-compression operation. One factor in model diesel operation that often gives rise to a need for a reduction in compression during running is that of over-heating. Since we can't respond in this manner to any overheating issues with our fixed-compression diesel, we need to do everything that we can to prevent an overheating situation from arising in the first place. This means that the use of hot-burning fuels is definitely out—do not attempt to run a fixed-compression diesel on conventional modern diesel fuel!! If you do, damage will likely result.
To keep temperatures under control, fixed-compression diesels are generally run on a fuel consisting of straight ether and mineral oil, with no power-enhancing additives such as kerosene (which burns far hotter than ether) or ignition improvers such as amyl nitrate. Ether has a high latent heat of evaporation, and the fuel mixture with an ether-based fuel thus enters the working parts of the engine at a very low temperature and does much to promote cooling of those parts. And the relatively low calorific value of ether reduces the tendency for the engine to run hot, although it also reduces the power potential of the fuel. But the imperative is to prevent overheating, and fixed-compression diesels run very cool on an all-ether fuel, so there is little chance of the overheating problem occurring. "
I dunno Earl, perhaps the extra calorific value (and heat) of kerosene would over stress the engine?
#41
http://modelenginenews.org/ad/drone.html
I dunno Earl, perhaps the extra calorific value (and heat) of kerosene would over stress the engine?
I dunno Earl, perhaps the extra calorific value (and heat) of kerosene would over stress the engine?
The problem with the modern fuels is oil content. You need to add more oil to it. But I see your point though. it is something to think about. I was watching my engines closely to ensure they weren't running too hot or getting pre-ignition going too. Thus when I ran them, fixed compression, they tended to be a little bit on the undercompressed side. But in any case your concerns are duly noted.
Last edited by earlwb; 11-26-2015 at 07:01 AM. Reason: add more info
#44
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She is a delight, mostly, she can sing soprano with the best of them. I have two sleeves and two pistons for the Irvine .20, the best choice is not the best choice because it's too tight a fit.
#45
Thread Starter
Are these Irvine .20s converted glow engines or purpose built diesel? Is it a new engine? Generally, a tight fitting piston is a good thing, though too tight is too tight. I had to use a heat gun to start my Jett .35 the first time because it was so tight, but after a few runs it loosened up a bit. I can see an ABC/AAC with a tight fit being problematic for use with diesel since the diesel doesn't run as hot.
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Finally, I have some Irvine .20 numbers with a wide blade 10x6, too big, I think.
Irvine .20 with Irvine Diesel Head
Fuel===Davis Plane Fuel
Max rpm====8,330, 8,000 to 8,100 more comfortable
Prop Robbe Dynamic 10x6.
Expelled oil, black a s coal.
Irvine .20 with Irvine Diesel Head
Fuel===Davis Plane Fuel
Max rpm====8,330, 8,000 to 8,100 more comfortable
Prop Robbe Dynamic 10x6.
Expelled oil, black a s coal.