Hey all
I have been looking for a new engine for my plane and came across this site
Marcel
Within our club we have had 3 people using RCVs,
User 1: 2x RCV 60s in a Dakota, unreliable running from 1 engine, RCV exchanged the engine and this only partly solved the problem, general unreliable running and difficulty getting the two "new" engines to match rev's. he got so pissed off with them he sold them at rock bottom prices and sold the airframe separately.
User 2: RCV 90, used in scale warbird, found to be unreliable (repeated deadsticks), problems with overheating although plenty of enter & exit air holes. Said engine now sits happily on a shelf!
User 3: RCV 120, used in various 1/6 size warbirds, In a YT P-51 it repeatedly vibrated loose on it's mount, solved by using bigger nyloc bolts, it then vibrated the bulkhead away from the airframe while on the ground. Bulkhead fixed and test flown again, still lots of vibration, engine departed from airframe while flying straight and level, airframe destroyed, engine survived to be sent back to RCV. RCV admit "balance" problem and replace with a new engine. Replacement new RCV 120 placed in a Flair FW190, constant overheating problems despite "half" the cowl being cut away for ventilation (note direction of cooling fins on engine), still suffering constant vibration, difficult to start, fiddly to get to run smooth, repeated deadsticks with the longest flight being about a 1½ minutes, whilst trying to get the engine to run reliably in the pit area the engine vibrates off the engine mount destroying the cowl and causing (exhaust) burns to the modeller when he tries to stop the engine totally breaking free. Engine returned to RCV who give a full refund (one good thing about RCV). Said FW190 now flies regularly and happily with an SC120 at 70 ukp cheaper.
I'm now about to buy 120 sized warbird, guess which make four-stroke engine I won't be using? IMHO, don't buy RCV, they're a pain and unreliable, spend your hard earned cash on the tried and tested four-strokes!
HTH
-=Plane Mad=-
Mmm. That is pretty much what i'd heard as well - that they were sufficiently 'different' to need special treament as against conventional, and the fore and aft piston movement resulted ina a mode of vibration that most airframes were not designed to take.
Some people seem to get them to work Ok tho, but 'fit and forget' they ain't.
When you use an RCV, you need to make cooling ducts in the cowl because of the way the fins are situated on the motor - otherwise you will not get enough air flow to cool the engine - Unless you fly your plane sideways!
Mike
Seems like that should have been properly designed in the first place.
As for cooling the RCV engines.
Air is a fluid that will always take the path with the least resistance.
That means it will flow around (not in between) the cooling fins of an air-cooled engine, regardless of the direction of the cooling fins.
If you want to make the air passing by do more than just pass by, you will need to make a ducting to force the air to pass in between the cooling fins.
Just take a look inside the cowling on any Lycoming-powered aircraft.
The reason that the RCV engines runs hotter than most engines is simply that there is less metal to take up the heat.
In a conventional engine you have the hot cylinder separate from the crank, allowing the heat to dissipate from the cylinder throughout the entire engine.
The RCV engines doesn't have that possibility, causing the entire engine to heat up.
Kjell Aanvik
Oslo.
"Paul McIntosh" skrev i melding news:bnelu2$8hp$ snipped-for-privacy@titan.btinternet.com...
Are yo saying that ALL air-cooled engine designers got it wrong? That all the fins on air cooled engines are just so much window dressing? Why not save a bunch of weight then and remove all the fins?
No, the fins are needed to dissipate the heat into the flowing air. However unless the fins are like those of a Husquavarna dirt bike, one STILL needs to tightly control the flow of air. One hard thing to do is to make sure that there is at least 2 (preferably 3) to one exit to entrance ratio. The other think is to provide baffling to channel the air through the fins, like Lycoming and Continental.do. Apparently on the RCV engines it is a bit of a challenge.
Look at taking a little air in on the top and exiting it on the bottom.
FWIW
It does make you wonder why they didn't position the fins so the air would flow through them as the aircraft was flying???
Mike
Rider scale birds use DOWNDRAFT cooling air flow.
overheating
The RCV-58 is a conventional layour according to the web site. The larger ones are the other way.
I asked the RCV people about the direction of the cooling fins when they were exhibiting at one of the major shows a few years ago. They claimed that it made very little difference.
I'd say they were probably right. Unless you have very high airflow through the fins, just replacing the hot stale air in the cowl is usually 90% of the potantial cooling gains
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