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Old Oct 03, 2012, 04:47 AM
Sticks, Tissue & old Diesels
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Originally Posted by Twin-Stack View Post
Brian, Obviously someone wanted them, and was willing to pay 629,88 Euro's for the privilige.......
Too bad, I'll just have to make do with the engines I have...
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Old Oct 03, 2012, 05:08 AM
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Originally Posted by bogbeagle View Post
With the engine disassembled, can you slide the prop driver along the crankshaft?

Does the prop driver bear on the shoulder which is formed at the base of the crankshaft thread?
1. The spline top is the same as the rear of the shaft (5 mm), i.e. the propriver will stop (kind of) at the rear end of the groove, but further tightening of the prop nut, would chew the alu splines off at the propdriver inner...luckily no one has done this (the crankcase stops the movement before this happens)

2. The propdriver is splined right thru, i.e. the shoulder does not provide a stop.
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Old Oct 03, 2012, 08:24 AM
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Originally Posted by Twin-Stack View Post
mchandrayan, I don't know about the Taplin but did you see this one ? An Indian FROG !
http://www.ebay.com/itm/NEW-AURORA-2...item3a7a3a9d7d
Would be interesting to watch, what it sells for. But sure I am not interested in that one
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Old Oct 03, 2012, 10:44 AM
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Originally Posted by Gluehand View Post
1. The spline top is the same as the rear of the shaft (5 mm), i.e. the propriver will stop (kind of) at the rear end of the groove, but further tightening of the prop nut, would chew the alu splines off at the propdriver inner...luckily no one has done this (the crankcase stops the movement before this happens)

2. The propdriver is splined right thru, i.e. the shoulder does not provide a stop.


Well, if it were mine, I'd be tempted to get some soft-ish wire and form it such that it fits into that groove, thus preventing the prop driver from moving back along the crankshaft. Seizing wire or even copper wire should do the trick. As you suggest, the prop driver will prevent the wire from "popping out" of the groove.
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Old Oct 03, 2012, 12:34 PM
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Originally Posted by bogbeagle View Post
Well, if it were mine, I'd be tempted to get some soft-ish wire and form it such that it fits into that groove, thus preventing the prop driver from moving back along the crankshaft. Seizing wire or even copper wire should do the trick. As you suggest, the prop driver will prevent the wire from "popping out" of the groove.
Do not know about those elder types of wire circlips like used on Ohlson piston axles and on their car wheel retainers (quite hard to remove) but a large good quality spring steel circlip should do the trick no ?
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Old Oct 03, 2012, 02:03 PM
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Sure, a good steel circlip will do nicely ... but, if you don't have one to hand, maybe a bit of old wire will do just as well.
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Old Oct 03, 2012, 02:18 PM
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I had one of the Aurora 2.5s as pictured. I bought it at a swap meet. It started and ran fine. One thing I like is to be able to start a diesel (using starter sometimes) at the running settings. The engine should then run undercompressed until, in a few seconds, it warms up and runs to suit. The Aurora 2.5 would start OK, at the running setting, but would then run out a 2 oz tank without ever warming up. I sold it on ebay and made a small profit.
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Old Oct 03, 2012, 02:46 PM
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Originally Posted by Jim Thomerson View Post
One thing I like is to be able to start a diesel (using starter sometimes) at the running settings.
Brokenenglish and several other died in the wool diesel operators have just had to be carted off to intensive care in a state of collapse!!!
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Old Oct 03, 2012, 03:24 PM
Sticks, Tissue & old Diesels
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George, there are plenty of old diesels that start first flick most times, and never more than 2 or 3. Not to mention any team race diesel.
Using a starter just takes longer, is more complicated and is unkind to the engine.
I just don't mess with engines that don't start easily, that's all.
I took a short video a few weeks ago, of about 20 consecutive first flick starts on a 1949 ED Mk IV, with the intention of posting it in this kind of context, but I haven't got around to opening a youtube account yet...
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Old Oct 03, 2012, 09:50 PM
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Brokenenglish,
yes, if the engine (glow or diesel) does not start in few flicks there is something else wrong.
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Old Oct 04, 2012, 02:23 AM
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My Russian ELFIN 149 ABC will not hand start.

It starts first touch of an electric starter (Sullivan Hornet) and runs smoothly. It is also quite powerful for a 1950 design.

Russian Elfin 149 ABC Reproduction (2) (1 min 13 sec)


I have other ABC diesels I can hand start. It's reluctance to start when hand flicked is puzzling.
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Old Oct 04, 2012, 04:14 AM
Sticks, Tissue & old Diesels
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Derek, That's exactly the point we were making. As a diesel, there's something wrong with your engine!
In 99% of cases, the problem is bore taper. Any engine, to be hand started, needs good crankcase compression to blow the mixture up the transfer ports. On the "quality" early diesels, any bore taper was very slight, machining was precise and they were all hand lapped (only a few seconds is needed), to obtain perfect compression at the top with good crankcase compression at the bottom. People like David Owen, Jon Fletcher, Mike Crisp and Tom Crompton are still doing that today, it's the only way.
Unfortunately, engines like the one you mention are made on modern "glow" principles, with excessive bore taper, so that the bore fit is very tight at the top (which passes for good compression!) and is far too loose at the bottom, and the engine is left to "sort itself out" somewhere between. The result is insufficient (or no) crankcase compression, so that hand starting is impossible. This is certainly the case with your engine. However, using a starter, the high rpm generates enough crankcase pressure to start the engine which, again, is your case I think. But the fact remains that for old traditional diesel lovers like myself, the engine ain't the way it should be! Your engine is a good example. I possess four original Elfin 1.49s and they all start in a couple of flicks... The implications are obvious!
The most frustrating thing for me on diesel-related forums is that many people, unfamiliar with the super old diesels, naturally assume that "modern must be better" (NC and all that), whereas, in reality, most modern diesels aren't a patch on the late forties, fifties and sixties diesels, most of which are still great for flying today!
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Old Oct 04, 2012, 05:54 AM
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Originally Posted by brokenenglish View Post
Derek, That's exactly the point we were making. As a diesel, there's something wrong with your engine!
In 99% of cases, the problem is bore taper. Any engine, to be hand started, needs good crankcase compression to blow the mixture up the transfer ports. On the "quality" early diesels, any bore taper was very slight, machining was precise and they were all hand lapped (only a few seconds is needed), to obtain perfect compression at the top with good crankcase compression at the bottom. People like David Owen, Jon Fletcher, Mike Crisp and Tom Crompton are still doing that today, it's the only way.
Unfortunately, engines like the one you mention are made on modern "glow" principles, with excessive bore taper, so that the bore fit is very tight at the top (which passes for good compression!) and is far too loose at the bottom, and the engine is left to "sort itself out" somewhere between. The result is insufficient (or no) crankcase compression, so that hand starting is impossible. This is certainly the case with your engine. However, using a starter, the high rpm generates enough crankcase pressure to start the engine which, again, is your case I think. But the fact remains that for old traditional diesel lovers like myself, the engine ain't the way it should be! Your engine is a good example. I possess four original Elfin 1.49s and they all start in a couple of flicks... The implications are obvious!
The most frustrating thing for me on diesel-related forums is that many people, unfamiliar with the super old diesels, naturally assume that "modern must be better" (NC and all that), whereas, in reality, most modern diesels aren't a patch on the late forties, fifties and sixties diesels, most of which are still great for flying today!
Brian, I feel I must really take you to task here, mainly on the multitude of generalisations you expound. There is NO doubt in my mind that an engine produced by a CNC machine is vastly superior to the "super old diesels" (a misnomer if ever there was one !) that you talk about. If there is a problem there with cylinder taper or whatever, its only because the CNC machine (which is computer controlled) has had the incorrect data fed into it, which basically means that the guy who programmed the thing didn't know much about model Diesels and their requirements. Your statement that "whereas, in reality, most modern diesels aren't a patch on the late forties, fifties and sixties diesels" is only true up to a point, that being that design has not progressed that much in the last 60 years, BUT execution, I'm afraid, is now light years ahead of what it was. You are simply not taking into account the advances in metalurgy and quality control which is now available to model engine manufacturers. If, through total ignorance, they type in the wrong co-ordinates on their wizz-bang electronic metal shaver (as in the case of the Russian Elfins), then yes - the modern Diesel will be dis-advantaged. Don't forget though, all those great designs of half a century ago,which looked great on paper but wouldn't even run due to poor workmanship or execution. The late Monty Tyrrell (a great Aussie modeller) spoke of the days when he worked for Hearns Hobbies in Melbourne during the 1950's - one of his jobs was to test each and every FROG engine in every shipment they received. The ones he couldn't get to run were returned to the factory in England. And what of the immortal MILLS Diesels ? Pronounced variations, especially in such basic things as cylinder timing, was well known and just accepted as "how it was". When you speak of piston / cylinder fit, two model engine manufacturers stand head and shoulders above all others with regard to quality and consistency. No 1 is COX due to ultra-precision machinery, and No 2 is ENYA due to accurate initial machining and then hand lapping. Of your "super old diesels" only the basically hand made Oliver Tiger comes close.
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Old Oct 04, 2012, 06:31 AM
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Brian,

Thanks for those words...!...you're hitting a very important point, little spoken about these days....
There is indeed a noteable difference between the old school "liner/piston philosophy" and the more "modern" thinking....
By feeling a decent crankcase compression, you can, even before run, tell that this is one of the "good" diesels, which will start easily...or vice versa...

My 2 C's:
Lately, I have dismantled-cleaned-assembled a number of engines, which thus has provided the opportunity to compare the "feel" of the piston/liner fit when assembling/oiling, all in a fairly short time, i.e. they are all in fresh memory. (fun, really...) Also, I have compared the "feel" when pressing the contra-piston out/in....
All in all, my experience confirms Brian's words....the old diesels all have a very slight taper of the bore, of which a few were close to insignificant...

For a diesel manufacturer, the importance of this should be essential knowledge.
By applying "modern" standards, we've simply got...er....something different...!

The old diesels, with all gaskets intact, are all easy hand starters....with very few exceptions...

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Old Oct 04, 2012, 06:53 AM
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If there is a problem there with cylinder taper or whatever, its only because the CNC machine (which is computer controlled) has had the incorrect data fed into it, which basically means that the guy who programmed the thing didn't know much about model Diesels and their requirements. .
This is also true...!....let's not mix up the old discussion of hand craft vs CNC manufacturing, with the main issue, i.e. the bore taper "philosophy"...
If the CNC guys knew what parameters it takes to make a good diesel, they would obviously set the program accordingly, making perfect easy-starting diesels with constant quality, forever....

What we see here is more like a "historical gap", where "modern" knowledge is allowed to overshadow the "old school" ditto......which isn't always the best way to go...


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