Model Diesel Engines - Page 122 - RC Groups
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Mar 22, 2011, 10:14 PM
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I like the look of that French Micron 5 cc Fixed comp diesel in the Drone article

Looks like a powerful sturdy Controline piece

I was wondering where the first controline engines came from,,,,, and I could not imagine anyone flying one of those big ignition jobs in Controline
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Mar 22, 2011, 10:52 PM
Size Matters!
RocketRob's Avatar
Thanks JMP!
Mar 22, 2011, 11:58 PM
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TLyttle's Avatar
Why not? We had a few guys with big 60s flying on 70' lines, talk about a rock on a string! With all that weight, even wingovers were a hazard.
Mar 23, 2011, 12:23 AM
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The French are good

Micron Diesel ,,,,,, Renault F1 engine,,,,,,, Citroen AX,,,,,,best car in the World according to James May
Mar 23, 2011, 11:04 AM
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OS 40 diesel

Earlwb has a really nice engine mount for his .40 OS diesel.
See the following link for what he has to say about this engine.
Is anyone else running one of these conversions?
Mar 23, 2011, 05:03 PM
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I am thinking about starting a thread in the engines category as the modern model diesel engines with ABC, ball bearings et cetera may not quite be considered vintage in this thread. I also have a Fox .15 diesel conversion I want to play with, as well as a Fox .45 diesel conversion too. Now some folks had used the Fox .15 engines, but they had put in some plugs in the bypass ports to reduce or plug them up to improve the engine's performance. I was thinking that maybe something to reduce the intake might work better, but that is another thread.

I found and bought a couple of different 20-25 size carbs, but I am waiting for them to arrive to try on the 40LA to see how that works or not.

Someone found that the early high compression Saito FA-80 engines worked running as a diesel too. You just don't worry about the glow plug or put in a bad glow plug. So I want to have a go at it myself on my old well used FA-80 and see if it'll run OK or not.

Then I have a Russian 2.5cc Marz engine that had two of the head bolts strip out on it while running, so I was going to fix that and see if it works better or not. I have it apart, I just need to drill and tap it for slightly larger screws.

Anyway, I was waiting for the weekend to see how many engines I can get going to mess around with.
Mar 23, 2011, 05:47 PM
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Earl, have you considered Helicoils for that Marz? I saved a Webra T4-40 crankcase that way. The crankcase hardness was somewhere between cream cheese and mozzarella.

Mar 23, 2011, 06:13 PM
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yes I am concerned about that myself. I am going to try to tap for 4/40 screws first and see what happens. If they strip out again, then the metal alloy on the crankcase is really too soft. But one screw did hold up OK and was still tight. So I am thinking they did a poor job drilling and tapping the other two screw holes. or they overtightened the screws and stripped them out when it was assembled.

Unfortunately there isn't a lot of room left for heli-coils. I might have to resort to trying to machine slots for nuts below where the threads are exposed. But it depends on if there is room to notch the cylinder or not there. Of course maybe a little JB-weld is the fix for that too. Another thought was to drill out the hole slightly, maybe for a 3.5mm screw, if there is material for it, thread it and screw in a threaded aluminum plug (better alloy of course, or even a brass plug) using red locktite. Then let it set up good for a couple of days, and then drill and tap that for 3mm screws like they used originally.

Someone else in Australia noticed that on a Marz engine he got, and he pre-empted it by redrilling and tapping the holes for 4/40 screws before he ran the engine. It worked OK then.

I also have to double check the bearings on it. Earlier after removing the cylinder and head, I was turning the crank a little, and it sort of felt a little rough with the bearings, so I need to double check that as I might be replacing the bearings too.
I have another Marz 2.5 and the bearings are bad on it as they have about a 1/32 of a inch forward and backward movement to them right out of the bag.

Plus I haven't addressed the crankshafts either. Some people were advocating stabilizing the cranks so they don't break in some cases. Questionable hardening practices from wherever the cranks were made. But then if it breaks I have something I can copy to make one myself.
Last edited by earlwb; Mar 23, 2011 at 06:22 PM.
Mar 23, 2011, 07:48 PM
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Im not surprised little diesels existed back before WW2,
If you read about the availability of ether, you could buy it over the bar , a lot of people were drinking it , in one place its rate of smuggling was higher than Alcohol ,it was cheaper than Vodka , and you needed less of it to get intoxicated
Earl , the best thing you can do to increase the fatigue life of a crank is to remove all the sharp edges around the rotary port with fine emery paper around 1200 grade

You can retemper it to a lower harness value but that would surely bend the crank and ruin it , and you need a temperature controlled, inert atmosphere , furnace to know just how hot your getting the crank
Last edited by NX-687; Mar 23, 2011 at 07:55 PM. Reason: Add
Mar 24, 2011, 12:09 AM
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When I took my Marz 2.5 apart to redo the head screws, I discovered that the two screws I thought had stripped out, had in fact broke off. I didn't think that the cylinder and head were one piece at the time.

With my micro-drill press, I used a small drill bit to drill a hole into the two stubs (I used a center punch too), and then I tapped in a small hex driver and unscrewed the stubs. The threads look OK, but I'll chase them with a tap later. The screws were really too easy to drill into, which means they are made from a really soft steel alloy of some type. Definitely worth replacing the screws before you ever run one of these engines.

The bearings were horrid, rough and scratchy feeling and they were more or less new. One really needs to replace them too.
It looks like the front bearing is a OD=15mm, ID=6mm, width=5mm. The rear bearing is OD=19mm, ID=7mm, width=6mm.
Boca Bearings closest bearing matches look to be MR696-ZZ and MR607-ZZ.

Before the head screws broke off:

Screws broken off in the crankcase top.

Drilling small holes in the screw and using a hex wrench driver to unscrew the stubs

Broken screws

Marz 2.5 engine disassembled
Last edited by earlwb; Mar 24, 2011 at 12:16 AM.
Mar 24, 2011, 12:29 AM
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looks like 3 soft screws are not up to the running pressures of the engine or the bearings , nice pictures , thanks
Mar 24, 2011, 01:23 AM
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Engine test of Frog 50 Mk. 1 & photo's of a Mk. 2 BOB

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