Four-Strokers, Look at This!

If you're interested in another way to skin the four stroke cat, check out this http://www.rcvengines.com/model_home_page_full.htm
Just a little different than your average four-stroke. I'd be interested in hearing what four stroke users thoughts are on it. Looking at the specs they seem to be a little lower in published horsepower (whatever that means) and a little higher in published weight than corresponding Saito and OS models. It seems like a lot metal flailing around but then it's all rotary motion, nothing reciprocating like the push rods and rocker arms on a conventional 4-stroke. Anyway, I open the floor to the pros on this subject. Bob Z? Crusher of Cities? Dougie M?

Best, Hoovie

I like the prop sizes. Maybe Al could do a Rare Bear variant where he would have to take off in a three point attitude.

Now this looks interesting. The conventional layout looks very attractive.

So, who goes first?

Randy,

Exactly my question.

Best, Hoovie

Actually the 58 should be quite good. Look at the drawing and see how little piston mass you will have to deal with, shades of YS. Also while a rotary valve has traditionally not been a high rev it has an abundance of torque. The low profile should be an asset in cowling in the motor. Clarence Lee will be reviewing one in RCM in a few months.
As to the opther motors I really don't see any PA ship capable of using 16/10 or 20/12 or any of the other high pitch props that these are capable of turning. But they really are a great concept in a motor. These have been reviewed in RCM which incidentally is reviewing the 90 this month. Dennis

The way this engine works it's not surprising it can put out gobs of torque for its size. Essentially it is a 4-stroke engine geared two to one as a result of it's basic design. Gearing a stroker is going to mean the necessity of using huge props as RCV indicates. Even if it didn't have a weight penalty over regular 4-strokes there aren't too many PA ships that can handle a 16" prop without gear legs that would put a stork to shame. And if I read the info correctly recommended pitch is 10 to 12. 4-blade props sound like the path to taming this beast. Luck to the brave guinea pig that takes it on.---Mark

Yes. We looked at these engines in a Japanese mag that Steve had. Very interesting.

Not simple though.

KISS that's my thing. The Saito is KISS.

The only thing that bothers me about these engines is FloydC hasn't weighed in on them yet. THAT out to be a riot.

Come on Floyd, we're waiting on the shoe to drop!

Dear Professor Crusher of Cities:

Please elucidate my fuzzufucation. In your extremely suscint response you stated that the RCV was interesting but not simple and the Saito was simple. The last time I looked at the Saito cut-away I saw, in addition to the usual case, crank, cylinder and head, a pair of gears, a cam shaft, two push rods, two rocker arms, two valves, two springs - 11 pieces not counting assorted retainers etc. When I look at the RCV cut-away (I'm looking at the convention layout not the funky axial arangement) I see a pair of gears and a funky shaped cylinder which really performs the same function as the sleeve in a conventional engine. Now I'm not trying to start a fight, and I know you have researched this at great length and have a significant amount of air time with four-strokes which I do notm but I'm having a difficult time understanding how 11 pieces is simpler than 3 pieces.

I started this thread with the hope that the four-stroke gurus would weigh in on this with some constructive, insightful, illuminating comments for my own education as well as others who may be interested. "Saito is simple, RCV isn't", doesn't quite fill that expectation. A little more verbiage would be most helpful.

If you don't think it's worthwhile taking up forum space with it, email me directly because I'm very curious about your very short, blunt response.

Best, Hoovie

>If you don't think it's worthwhile
>taking up forum space with
>it, email me directly because
>I'm very curious about your
>very short, blunt response.

No, actually, I was at my brother-in-law's house on his cable line and we were about to play golf so I had to cut my response short.

Actually, I think this engine is really kind of cool, but I have no first hand knowledge of its performance. If one were donated to me, I would be more than happy to donate my time to evaluating it's performance.

The Saito is simple TO ME. It may not be simple to everyone else.

Brad,

I agree. The Saito is at least simple to operate. The RCV58-CD (the sorta conventional arrangement) isn't available until next month. I'm thinking about it.

I saw a posting on RCO if I remember correctly, where someone was so impressed with the inline RCV engines that he was selling all his conventional engines.

I will try one!! The conventional design, that is. I don't have a plane that will handle a 16" prop
Seriously, there was (is?) a rotary valve 4S engine on the market - the HP VT series. Only the valve rotates - not the sleeve. I have a VT .21 that is smooth, quiet, economical and GUTLESS. I doubt that it makes the power or torque of a good .15.
Maybe this new approach will be more efficient. I have a birthday coming up so I know what to ask for!
Bob

Bob, your right the 21 was a puny performer,it was neat running though and sounded like a sewing machine, also was one of the most miserly fuel drinkers ever made. The 49 is a little better but they were both way too heavy.
The Webra belt driven Aspen valve motors were not bad, we used then for awhile.
Strange when we bought the first OS 60 four cycle in 1976 it was just for a sedate fun type plane, The motor wasn't too powerful but was a really pleasent thing to run. However, knowledgeable modellers thought it was a step backwards.

Bob,

I got an email back from the RCV folks. I had asked a bunch of questions about both the SP (inline) and CD (conventional) engines. On the CD, they claim the torque and HP are comparable to the Saito and OS. They don't claim fuel efficency, but say it is also comparable. The CD has 1to1 gearing from the crank to the Prop. The SP is 2to1. They also claim that the usable torque in the SP is pretty stiff. That's why the recommend such a large prop. But that (they say) can be gotten around by using more blades. They have tested the SP with 4 and 5 blade props and with 3 blade, very large area props (ala Rare Bear, I assume) and have gotten very good results. I don't know, a 16x10, 4 blade in stunt. Hmm, maybe not.

Certainly something to look at, though. I wonder how the CD would do running at the advertised 11,000 RPM (middle of the range) with a 3 blade, low pitch prop. Hmm...

But I'm not at all sure I want to be the one to spend a thousand hours testing the beast (either the CD or SP) to come up with a workable set up. Call me a coward...

LAST EDITED ON Aug-21-02 AT 10:08 AM (CDT)

LAST EDITED ON Aug-21-02 AT 09:53 AM (CDT)

Looking at the specs of the 58. It is said to turn the props of the Saito 56 and just a bit longer than the props of the os 52. The rpm range is the os 52s exact range. However my 52 has never seen a tick above 9800. Remember the number goes way down as the diameter goes up. Also hooking up to a set of lines steals about 35% of its power. This motor looks to be a great equal of the Saito 56 from the numbers only a bit heavier and that helps no one.

However maybe the rotating valve will allow the high pitch setup without a pipe. That would eliminate the valve floating you see in the Saito and OS motors at high RPM.

The RCV inline. 20oz for a 60, without the muffler I think. Unconventional mounting. This is going to be tough to get an inline tank behind it and far enough back so it will turn. I saw these about a year ago. The concept is AWESOME! The added weight and overall length really bites for stunt. The plane for this motor is going to have to be BIG! That right there means heavier everything. Making the advantage one sided. It can fly bigger planes. I mean this because the nose is going to be long for the motor and tank. That tail is really going to have to be long. Not only are you turning a 20oz motor but also it's 16" prop on top of that. This wont be a conventional 60 size stunter. Unless it uses a really small tank. Retro fitting this motor into something like Cardinal would be next impossible. There is going to have to be a stunt plane built just for this motor just to know if it will work or not. That is a big chance right there. Because you cant refit it with a conventional motor. Well I gess you could RC mount it later if it didnt work out. I have been wanting one for about year. I would have to get it on a venturi before I flew it. We are already running into excessive yaw problems with 14" props, well Brad is. I dont know what would happen with a 16" prop!

By the way Brad says the saito is simple. Well maybe it is now but it wasnt in the beggining. I remeber a day when I flew 19 flights while we worked on a stupid Saito 56 that never did run worth a crap. Blasted metal tank! Stupid Carburator! We went round and round(no pun intened) with that motor. It took hundreds of flights. Many many different props. One Heck of a Saturn test bed and The Zone and The Shear Panic and The Unassuming(which now holds a YS 63). I have seen a bag of 20 props or more sitting in his box many times. Dont let him fool you he worked hard to get that setup running. Real hard! I remember calling him the mad scientest because he always had some contraption full of fuel and making new mixes all the time all different %s of castor no castor and nitro nitro nitro. Now he has tried all the fuels you can think of to come back to Powermaster YS20/20. Spike it to 30/20 when it gets real hot, say over 95. Now I am going to steal that setup from him and beat him with it! Cant wait! It took a while but he has made it simple now. All his hard work is going to payoff for me. Thanks ahead of time Brad. There is no question in my mind it is going to take something big to change him from the Saito camp. He watches the best PA in the country run in Bob Gieseke's plane but still wouldnt run one himself. He says the Saito is to easy now. Why change? Good argument all the way. I feel the same way about PAs. The toughest part is propping it. But that is true with all motors. You have to go through this learning curve and figure out where the "pocket" is for that motor. Then you can get some practice in.

I am still really interested in the Inline. Not so much in the standard. Did you see how spread those lug holes were? That right there will stink going into a stunt plane. I wish they were more weight friendly on the inline.

LAST EDITED ON Aug-21-02 AT 11:37 AM (CDT)

LAST EDITED ON Aug-21-02 AT 11:37 AM (CDT)

Doug,

I agree completely. I think the inline engine would take way too much work just to see if you had anything. Like Brad, I'm pretty much a Saito guy. But I may try the conventional RCV engine just to see if you can avoid the valve float problem at higher rpm. I really haven't had a problem with that with my Saito, even though I run it at a higher rpm than most. But as you noted, you experiment until you get a setup that works for you. Then stick with it. After all the work I put into getting the Saito to run the way I want it to, I'm not too sure I want to start the same process with the RCV.

We'll see, I guess.

Bob,

Have a really happy birthday. We'll all be looking forward to your report.

Best, Hoovie