RCV 4S Engines

[Avaiojet]

Anyone have experience with the RCV 4S engines?

Charles

[Avaiojet]

For those that don't know what this engine looks like, here's a photo.

My interest is for a scale project.

Charles

[Andrew Tinsley]

They work, although the sound of the gearing is quite loud. I don't have one myself, but have seen them flying. They really are intended for scale R/C models as you can do a great nacelle design on a twin and you can't see the engine cylinder sticking out! Not brilliant in the power stakes but adequate. Not recommended for C/L stunt!

Regards,

Andrew.

[Paul Wood]

Charles,

I have the 1.20 in a 1/5 scale Pica WACO (RC).  This engine is more of a conversation piece than anything else.  It turns a huge prop, which is great for scale appearance, but the rpm of the prop is 1/2 the engine rpm.  So I have found the performance is about the same as a normal 1.20 with a standard size prop.  It is unique and I love it, but it's very heavy.  VERY HEAVY!  Great for conversation, but not at all practicle for any C/L application.  Maybe scale, but the weight is going to be a problem.  Oh yea, the torque and prop "P" factor are also huge.  It will actually walk the nose of my WACO to the left on a hard surface at full power while holding the tail.  Weird!

Paul 

[Avaiojet]

Charles,

I have the 1.20 in a 1/5 scale Pica WACO (RC).  This engine is more of a conversation piece than anything else.  It turns a huge prop, which is great for scale appearance, but the rpm of the prop is 1/2 the engine rpm.  So I have found the performance is about the same as a normal 1.20 with a standard size prop.  It is unique and I love it, but it's very heavy.  VERY HEAVY!  Great for conversation, but not at all practicle for any C/L application.  Maybe scale, but the weight is going to be a problem.  Oh yea, the torque and prop "P" factor are also huge.  It will actually walk the nose of my WACO to the left on a hard surface at full power while holding the tail.  Weird!Paul 

Paul,

Thanks for the reply. Conversation piece? Guys in the UK have them in many scale model swinging large scale props. Do a search and you'll see.

Yes, the engine "is designed" to swing a huge prop. My guess is, it'll swing a 4 blade scale prop at 5K. Just what I need.

Heavy? Compaired to what? It's light for a 120 4 stroke.

You have a Waco? My favorite bi-plane. I built the Pica Waco in the 70's, still have it. It's CFC Graphics' flag ship. It's going CL.

How long did it take to brake that engine in?

Thanks for the reply.

Charles

[Chris Wilson]

Heavy? Compaired to what? It's light for a 120 4 stroke.

What other 120 4 stroke is heavier?

An RCV120-SP weighs in at 36.4 oz.
AN  O.S. FS-120 with pump weighs in at 35.3oz.
A Saito FA-120S is 31.75oz.
The larger Enya R155-4C is 33.86oz.

Yet the comparable Saito FA-115 weighs in at 20.6 oz.

I think that you will find that the RCV's represent the heaviest of their kind.

[Avaiojet]

What other 120 4 stroke is heavier?

An RCV120-SP weighs in at 36.4 oz.
AN  O.S. FS-120 with pump weighs in at 35.3oz.
A Saito FA-120S is 31.75oz.
The larger Enya R155-4C is 33.86oz.

Yet the comparable Saito FA-115 weighs in at 20.6 oz.

I think that you will find that the RCV's represent the heaviest of their kind.

Chris,

OK, OK, ya got me!   

Now you know you're my second favorite CL guy, so bear with me. Lets take a look at this with different more practical math. 

The RCV 120 SP actually weighs 38.18 oz. with the muffler. I don't need the muffler because I'm designing an aluminum radial muffler.

Now the RCV 120 SP, also has other added built it design features and necessary parts, which will enable this engine to turn a 16.5" diam. 4 blade scale prop at 9,000 RPM. I expect to turn a 18.5" diam. 4 Blade scale prop at 6,800 RPM.

So, exactly what do you have to bolt onto, or have made, for the engines listed above, to enable them to turn a 18.5" diam. 4 blade prop at 6,800 RPM? Decided what is needed then add the weight.

"Ya got it!" A line from the movie Galaxyquest.

BTW. Your engine is in the mail! And you did real good! 

Charles

[Mark Scarborough]

Charles, have you calculated what kind of pitch you will need to have in yoru prop to run at 6800 rpm? in order to get usable airspeed anyway,, and I think you will see in all likely hood that you wont be turning that 16.5  inprop in the pitch you need. I have heard a couple people who say they have run these motors and they state they are not really very powerfull,,
however , maybe you can unleash the magic,,

OBTW in order to get 55 mph at 6800 rpm, you will likely need something like a 10 inch pitch prop minimum,, and if this is a typical scale airplane, you will likely need more than 55 mph to maintain any kind of authoratative flight properties... I am guessing your going to need to see closer to 12 inch pitch,,, and MY GUESS is that you will end up swinging something more like a 13 inch diameter prop at that diameter,, but then time will tell, I know the Saito 4 strokes are animals for power,, but all I have read on these is that while they are cool, they are not very powerfull,,
I look at what others do, If these were capable of swinging a scale diamter prop on a scale airplane,, effectivly,, I dare say you would see them much more prevelant in Scale,,,, and I just dont see that happening,,

I wish you the best,, just throwing an opinion in there,,

[Avaiojet]

Mark,

Thanks for the reply and the input.

For CL flying I have no idea how fast the model will fly or need to fly. Tests will be with standard props.

You may be correct about the pitch.

Here's what I do know by talking to a modeler who has a H9 Corsair with a RCV 90 4S, set up for R/C.

He flew this model with a 18" diam. 3 Blade scale prop. His engine turned 4500 RPM.

He said he could continue to fly the model with this setup, but the engine is overworked. He's going to downsize to a 16" diam. 3 blade scale prop. He said he'll get back to me with the results.

Should keep in mind, I'll have no needed R/C gear on board, so I expect a model of some lesser weight.

Plus I have the 120.

Thanks for the reply.

Charles

[Chris Wilson]

Just going by the web site here -

6000rpm  - two blade 17x13, 18x12, 20x12
                - Three blade 15.75x13
                - Four blade 15.5x12
These are the quoted absolute maximums for that motor but the manual warns of using only coarse pitched props at no more than 5150 rpm in normal use, and never more than 5500 anyway.

Mark , perhaps some of the British sites might shed some light on exactly how these engines work in practice.

Charles, thanks again for the Super Tigre X 45 - I will see what it can (or can't do ) when a tuned pipe is attached.

Thanks.

P.S. And here is a gallery of pics with models using the RCV 120SP -
http://www.rcvengines.com/gallery/rcv_gallery_120sp.htm

Those pics are further linked to "model aircraft, performance specifications and customer comments.  "

[Avaiojet]

Here ya go!

http://www.rcvengines.com/rcv120sp.htm

Charles

[Chris Wilson]

Anyone have experience with the RCV 4S engines?

Charles

http://www.rcvengines.com/gallery/rcv_gallery_120sp.htm

(Bump.)

[Douglas Ames]

Truly an engine designed to wear itself out. Reciprocating piston and rotating cylinder combined? What fuel/ lube % do these engines req.?

[Avaiojet]

Truly an engine designed to wear itself out. Reciprocating piston and rotating cylinder combined? What fuel/ lube % do these engines req.?

Douglas,

That was my observation also. The engines have been around for 10 years and are popular across the pond.

So, I'm guessing they have the engineering down by now. You would think.

However, a really good point. Not to mention compression, or by design, the lack of it.

Thanks for the reply.

Charles

[Chris Wilson]

Truly an engine designed to wear itself out. Reciprocating piston and rotating cylinder combined? What fuel/ lube % do these engines req.?

Hi Doug,
              its all on their web site mate -
10% Nitro / 15% Oil including max 6% Castor.

And what makes you think that it is 'designed to wear out?'  Consider that the there are no hot spots on the liner so it has extremely even thermal expansion, no fixed thrust face on which to constantly wear on and it is wholly ball raced construction.

Do you think that because the liner has radial movement along with linear that it is going to wear out all the sooner?
The talk that I hear states the opposite and runs along the lines of the wear pattern creating a self regenerating cross hatch pattern that holds the oil extremely well.

Thanks.

[Avaiojet]

For what it's worth.

I didn't jump into this engine choice blind.

I've had e-mail communication with a half dozen owners.

I couldn't find one second hand, no one will part with them.

Charles

[Douglas Ames]

I would think the heat from friction would be double or at least noticeably higher, making the lube all the more critical.
I had a 2nd Gen. OS Wankel that was sensitive to mixture and would cook castor like sauce on your Barbie.
The RCV is an interesting design though. 

[Chris Wilson]

I would think the heat from friction would be double or at least noticeably higher, making the lube all the more critical.
I had a 2nd Gen. OS Wankel that was sensitive to mixture and would cook castor like sauce on your Barbie.
The RCV is an interesting design though. 

Hi Doug,
              yes it is am interesting design and perhaps more could be gleaned from this link. Its all about RCV's.

http://www.rcuniverse.com/forum/m_9054094/tm.htm

[Paul Wood]

Charles,

Did you say you already have the engine?  If not, you might consider the RCV CD series.  I have the .91 CD and it is very small and light.  I originally had it mounted on the WACO, but the small prop was just silly looking.  I have found the flight performance of the WACO to be the same with either the .91 CD or the 1.20 SP.  I'm using a 20x10 prop.  The pitch MUST be large or the plane will not go anywhere.  The prop is only turning 1/2 the engine speed and you will get very little thrust at 5500 prop rpm.

Another consideration not mentioned in the literature is the amount of oil blown out the crankcase port.  It is unbelievable.  I had to mount a 2 oz. fuel tank plumbed to the crank port to collect the oil.  After 3-4 flights, it's full and I have to suck out the tank with a fuel bulb.  But, almost no oil in the exhaust.  Easy clean up after several flights.

In spite of everything said about starting the engine, I found the starter shaft method unacceptable.  You can use an electric starter spinning the prop hub while holding your finger over the exhaust.  When the engine starts to fire remove your finger and it will run fine.  (Of course there's that 20" prop trying to eat your forearm!).  It must be very wet to start.  Also needs an on board glow battery.  Can't get a glow stick to the glow plug because of the prop.  Conversation piece?  Yep!  Have fun.

Paul

[Avaiojet]

Paul,

Thanks for the reply.

I spent a bit of time researching before I chose this engine.

I mention above that a modeler flew a H9 Corsair, set up for R/C, with a RCV 90 SP and a 18" three blade prop.

The model flew fine but some strain on the engine because all he could get out of it was 4200RPM. He's downsizing to a 16" three blade.

Yes I already have the engine. For my project, actually a fine choice.

The entire model will be a conversation piece! 

Thanks again for the reply.

Charles

[Chris Wilson]

Technical questions are answered here -
http://www.rcvengines.com/corporate/rcv_technology.htm

Down load the SAE paper and have a read.

[Chris Wilson]

Charles,

In spite of everything said about starting the engine, I found the starter shaft method unacceptable.  You can use an electric starter spinning the prop hub while holding your finger over the exhaust.  When the engine starts to fire remove your finger and it will run fine.  (Of course there's that 20" prop trying to eat your forearm!).  It must be very wet to start.  Also needs an on board glow battery.  Can't get a glow stick to the glow plug because of the prop.  Conversation piece?  Yep!  Have fun.

Paul

Paul, have you seen the extended ball end starter shaft that enables you significantly angle your forearm away from said 20" Meat grinder?

And the glow stick is best avoided mate, use a remote plug setup instead with your normal battery in the flight box.

Cheers.

[Paul Wood]

Chris,

I have not seen the ball end shaft extension, but I actually made a similar extension myself.  The problem with the starter shaft is keeping it in the recepticle as the engine begins to wind up.  I have to push so hard on the starter that I am afraid of damaging the airplane if it pops out.  Plus, by turning the prop hub as I do, I actually spin the engine at double the RPM of the starter.  Makes fuel draw and engine starting much easier for me.  Regarding the thumb over the exhaust, I now use a helper to "thumb" the exhaust.  Just too dangerous to do it myself.

Paul

[Chris Wilson]

Hey Paul,
               there is a review in the June 2011' Aviation Modeller International' magazine all about the RCV 60 SP.

Interesting stuff and it heavily alludes to the 10 year development of the engine, apparently improvements abound over the original engine!

Gear noise down, power is significantly up, much improved muffler now available, firewall mount now has a backing plate and the carbies are flow tested on every engine before sale.

Much of the negative press must relate to the earlier versions of this engine as the latest incarnation seems to be quite good.

The starting issue is addressed in that article and it too prefers hand staring at the front rather than 'leaning on the jack hammer' at the back.

Almost makes me want to buy one now.

[Avaiojet]

U-Tube has guys starting this engine using the "allen head bolt" with absolutely no issues.

Take a look!

Charles 

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