Thread: Discussion Model Diesel Engines
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Old Oct 06, 2012, 12:05 PM
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Another two on the East European theme...

The 2.5 cc Alag X-3 is probably the best known of this family.
As it happens, I have an X-4 (1.5 cc) and an X-5 (1 cc) that have lived, fairly anonymously, in my box of bits, for lots of years....
Back then, in the late 50's, these engines were "cheapos", not sold by the "serious" hobby dealers. You could purchase them, mail order, from importers that didn't know a thing about the aeromodelling hobby.
Among "serious" aeromodellers, these engines were rated very low, and I figure most of them were bought by pure beginners, that either ruined them immediately, or, after failing to start them, threw them away. All in all, you didn't see many of these Alags actually running (I didn't, anyway...)

My 2 examples are "brand new", i.e. unrun, and recently I dismantled them to remove the "factory-gunk" and tidy them up.

A pleasant surprise
After dismantling, cleaning and adding some fresh oil, I fiddle around with the parts, and I get the obvious feel of GOOD engines...!
Nicely built crankcases, drillings centered. All threaded parts have a good & non-sloppy fit, indicating good manufacturing standards, and providing a pleasant feel when fiddling & fitting....
Cylinder/piston lapping seems just perfect....and, when I press the contra-pistons out, I feel just the "right" resistance, and they DON'T just fall down the sleeve, but I can "feel" a tapered bore, just a tad, all the way down...and the CP's are steel, NOT of alu, as sometimes seen on cheaply produced engines.
The prop driver taper is a perfect fit, on both....
The X-4 backplate is plastic though, but even "respectable" makers (like e.g. ED) have practised this, with no trouble.. The X-5 backplate is metal, the traditional way...


Junk engines...?...I'm no longer sure of that...!...so far these engines seem just great...! (I am not able to comment the metallurgic standards, though...)

Both engines are very compactly designed (small really, for their displacements)...and lightweight:
The X-4 weighs in at 68 grams...not bad for a .09..!
The X-5 weighs just 52 grams...about 2 grams (!) more than a British Mills P75...

It seems the Hungarian guys knew exactly what they were doing.......I get no "junk engine feel" at all, really....

Eventually I will run them in, carefully, to give them a fair chance to refute their bad old reputation....

BTW I think they look good too...
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Last edited by Gluehand; Oct 06, 2012 at 12:35 PM.
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