fastpat

I did a search on this engine and found some very good information, but there is one question I've not seen asked nor answered.

I know about the fuel consumption issue, and the other issues with this engine.

This Wankel, the second version, has the exhaust coming out of one side of the cylinder housing, and the carb as well. Since I will be using two of them on a Duellist kit, I'd like to reverse the cylinder housing so that the exhaust exits from the opposite side on one of the engines. Anyone know if that's possible with this engine? I own one and am ordering another, but the one that I have is packed away in storage, so I can't look at it, or disassemble it to check the feasibility of this change. From looking at photos this could be done, changing not only the exhaust exit location, but the direction of rotation as well.

Pat

William Robison

My Feedback: (3)

Pat:

In theory a symmetric assembly should work, and give reversed rotation. You may find OS has put some alignment pins in to prevent this being done accidentally, careful machine work will fix that.

My biggest question: are you sure two of the Wankel engines will give enough power to haul their weight?

Bill.

fastpat

I read an evaluation of this engine, and one of the two evaulators recommended not disassembling the engine for reasons he couldn't explain or didn't know. Curious. I reckon I'll find out about this, on one engine at least.

According to O.S. the engine weighs 11.8 OZ and puts out 1.27 hp at a screaming 17,000 rpm. The weight is probably without what passes for a muffler.
http://www.osengines.com/engines/osmg1400.html So, in comparison with most .40-.45 engines, it's in the ball park for power to weight ratio.

William Robison

My Feedback: (3)

Pat:

If that approx 12 ounces is correct I withdraw my objection. I always had the impression that 22 or even 32 ounces was more correct.

Bill.

fastpat

When I get the engine I have out of storage, soon I hope, I'll solve this issue by putting it on a scale.

We should do that will all engines anyway, factory specs can be optimistic sometimes.

Pat

jrf

My Feedback: (551)

The second generation OS Wankle is roughly equivilent to a ball-bearing .25 in useable power. We used to put them on Quickee 500's and use them for sport flying. They weren't fast enough to race. You will have to run a 9x4 or 9x5 prop to get decent thrust from them.

Several people have used them on the Great Planes DC3, with limited success.

If you are looking for something that will fit in a round cowl, you would be far better off with a pair of RCV 60SP's.

Jim

fastpat

Perhaps so, but they produce about the same power that most sport .40's being used in Duellist 2/40's with a couple of exceptions I've seen. The one with the tuned pipes and RE engines undoubtedly is a powerful airplane.

Mostly, I want to use the wankels "because they're there", so to speak. If they were too heavy, or grossly underpowered, then I'd move on.

jrf

My Feedback: (551)

If you are basing that statement on the published hp figures, you are in for a rude awakening. Do yourself a big favor and try out the one you already have on a single before you spend big bucks for a second one.

Jim

The Ghost

fastpat,
I would clean up the motor that you have and use it for a paper weight. People say that it has the same power as a 40 sized motor. HA. I have several that have been given to me over the years as well as my own. They have usable power of about a 15 with the fuel consumption of about a 90. They have a great sound though. I would not take them apart, as the rotor seals and springs are easly lost. Yes you can reverse the rotor housing, but the engine does not run as well. (all ready be tried) I would look at 2 or 4st engines and leave the wankles as a talking piece.

Cheers

fastpat

Thanks for the info. Looks like I'll have to find out why it won't run well in the opposite direction. That would be expected if the combustion chamber in the rotor, where it's supposed to be, isn't symetrical.

PE2fan

My Feedback: (8)

The timing of the port openings is very important on wankels. It should be symetrical on the inside. Trust me you do not want to mess with the seals. Very easy to mess up and not forgiving(read as he messed up his RX-7) I would guess it would work turned around but not sure how well.

Micheal

JohnBuckner

My Feedback: (1)

I bought a pair about 15 years ago, I,ve no idea what version they were other than the fact that they were advertized with new and and improved seals and ran cooler than those prior to that.

My intent was also for some of my earlier multi bashing projects. This thread got my curiosity up so I went out and weighted one of mine which I,ve not used in quite a few years. With the muffler, carb (which by the way is a bleeder type), spinner nut and the special required mount ring it is 14.75 ounces.

As for HP published figures in my opinion they are virtually useless as all the manufacturers for those tests use test clubs (propellors) of a completely impractical size and pitch to properly fly any airplane. These figures always result in inflated figures in the real world and of course these advertizeing figures cannot make any allowance for the design of the airframe. For example is it a nice sleek cowl like a mustang with most of the propellor out beyond the cowl or is it a radial cowl with only a small portion of the prop out in the working area outside of the cowl diameter. In a case like that what is needed is an engine that can effectively turn a large diameter prop.

Just making the point that depending on those advertizeing numbers is really not of much use. Particularly when you are dealing with an unusual engine which in this case requires a rather small diameter prop or an unusual airframe type like a twin.

Having said all that I agree with jrf totally This engine is pretty wimpy for its weight and requires rather short props. About the same power as a good .25/.30 engine but anything over a nine inch prop is not going to cut it and you will have some excessive heating.

I never ended up using them in a twin because of several additional reasons and used them in what at that time were called competition arrowshaft fun fly types Which normally used twenty fives and they were really no better than and in some case worse than the funflys with good .25's.

Out side of the wimpy performance for the weight for use in twins your biggest problem will without a doubt be fuel tankage. I cannot remember exact figure but consumption was close to twice that of a comparable power engine. An as you may already know with many nacelle mounted twins room for tankage is always severely lacking. Its likely your flight time will be restricted to far less than you are use to (not good in a twin).

Another problem especially for a twin is, I was never very successful in acheiveing a reasonable idle speed. Maybe others did but not I, This is a severe problem in a twin and will eliminate much taxi work on the ground.

This engine has a unique sound signature unlike any other and two of them are fantastic however this is the only plus in your application I can think off.



John

fastpat

Thanks, John, for taking the time to weigh your example.

Here's photo's of the two designs produced by OS.

The first design. Note tyhe carb position, what the exact flow path of the fuel/air mixture was is a mystery to me, but I imagine they were trying to keep the carb in a somewhat conventional location. This 1st design is where most of the overheating reputation comes from, as best as I can determine. The finning was insufficient and not integral with the cylinder casting.


The 2nd design. I think this performed better and carried heat away from the cylinder better.


I'd love to have examples of both to compare, and may acquire one of the older ones as a collectible, but that's for the future.

Ted M

Hi Folks;
I have a new model Wankel in a Balsa USA Taube. It flys the overweight plane fine. My problem is that it won't run out the tank. I run it rich and have the top of the tank even with the carb. Any ideas?

JohnBuckner

My Feedback: (1)

Your tank is to low. Center the tank height on the needle valve.

John

Ted M

John
Thanks for the tip. It will take some carving but I will try raising the tank as far as I can. I guess that the pressure line doesn't do much.
Ted

Michael211

My Feedback: (1)

Just out of curiousity... what would 4 of these things do for a '79" span B-17 bomber? I've already acquired 2 of the OS .25 SF engines for this project, but absolutely dread chopping up the spun aluminum engine cowls to get them to fit!

Earlier today it occurred to me that these Wankle engines would almost certainly fit better in the nacelle and given the "openess" of the cowlings they should get plenty of air for cooling, if 4 of them would run well together. Thoughts?

- Michael

The Ghost

Michael,
4 of them would work well together if you are ready to feed them. It would be like running 4 90size engines. Then there is the weight or 4 of them hanging off the wing.

Cheers

Ted M

The first problem would be the cost. I wouldn't feel right seeing that much money flying around.
I'd suggest the RCV engines for better cowling.
I raised the tank on my Taube and it helped a bit. Next I am going to make a (High Temp) plastic extension for the carb. It is possible that the fuel is vaporizing before it gets to the engine. It does run hot!

Parkerm

My Feedback: (6)

The Wankel performs best if you throw away the instruction book and feed it some high nitro high synthetic mix. I use Powermaster YS/Saito 20/20. That's right NO castor. My Wankels will turn a 10X6 prop 14K with that mix and I haven't had any problems so far.

I bought a Wankel off the internet that would not run well. I opened it up and found the apex seal springs broken. They are simple to replace. While I was at it I replaced those stupid 3mm phillips head screws with some socket heads. This engine outperforms any Wankel I have had now. It's in the strong .40 range turning the 10X6 14.4 K.

Fuel is an issue, my current consumption is 1 oz/minute at WOT.[&o]

Another note. The OS support people tell me this engine cannot be reversed. (would of been cool for a twin huh).

twinman

My Feedback: (2)

IF "'79" span B-17 bomber" is the Cedar Hobbies. The fuel tank capacity would be a problem. Four ounce due to width with the in nacell servos is about the max. Also the inner nacelles are a bit longer due to the landing gear, but you cannot have smaller tanks on the outer engines. If you do a search, you will find that I did build one of the first Cedar prototypes with on tank, but it took $200 in pumps and I do not know if the Perry pump will work for a wankel. If it will, you can put a large tank in the middle fuse and use the nacell tanks as header tanks like the helicopters. Muffler pressure WILL NOT WORK!! You would also have to modify..OK to scale appearance the cowls for better airflow. If you remove the in nacell servos and mount on the wing,,which you CAN do, a square tank could fit, but not sure the size available. You could contact Niel over at Cedar and get him to measure the tank area.
Good Luck,
Twinman

Parkerm

My Feedback: (6)

The Wankel is about 2" shorther than any similarly sized piston engine and has a radial type engine mount. Therefore, you must use standoffs (as I did on my PBY) or move the firewall forward. On my PBY 4 oz tanks were what the nacelles were sized for. I used Sullivan 10 oz round tanks, which are about the same as a 4 oz cross sectionally and about 2" longer. By cutting a round hole in the firewall to accept the tank and standing off the Wankel to the edges of the firewall I was able to match the cowl and shoehorn in 10 oz of fuel. The Wankel has virtually no vibration so tank padding was minimal. I doubt a vibration actuated pump would work and the Wankel has no provision for muffler pressure. Keep the tank even with the engine and the carb pointing down and it will run consistently, I've never had one quit.
It will also siphon all the fuel through the carbuerator when the engine is stopped.[&o]

jaka

Hi!
It is my personal experience that the OS wankel engine is a real good performer. Nearly in comparence to a .40 sport engine.

25 years ago I helped a friend who had built a high winged scale (semiscale so to speak) highwinged airplane, a Nomad. span was around 210cm and weight was over 5kg and it was powered by two OS.30 wankels (the old version with cowling).
We ran 10% nitro/20% Castor oil and used 10x6 props (make I don't remember) and those wankels flew that bird nicely. I don't remember any RPM findings though but rpm was nearly as good as those .40 engines we had in those days, if I remember correctly

The new model OS .30 wankel is even more powerfull and I think it will power most .40 size birds easily.
Putting 4 of these in a "small" 79 " (200cm) size B-17 bomber is perhaps no good because I think they will be to powerful for it and weight (wing loading )will be a little high. I would go up to at leat 220-240cm in span and aim for a weight of 7-8kg ready to fly.
For a 200cm B-17 I would go for .25 engines...no more! Otherwise it will fly like a pattern plane.

Regards!
Jan K
Sweden

Michael211

My Feedback: (1)

Ok a B-17 that fly's like a pattern ship is NOT my objective here... LOL! So the Wankles would be overkill and probably suck too hard on my fuel budget for this sized plane.

I have already acquired 2 OS .25 SF ABC engines NIB from Ebay and it sounds like I'm going to end up having to get 2 more in the coming months for this bird. I'd prefer to mount them inverted however as I've had good experiences with inverted OS .40 SF ABC engines on single engine models.

And if I have to cut a hole in the cowls I INSIST the hole be carved out of the underside!!! :-|

Any thoughts on alternative muffling systems that wouldn't stand out like the factory mufflers do?

Oh and this bomber is the old Royal kit. Purchased off of Ebay last fall partialle framed up with original box and plans and all. There's a few areas that I have to redo on the fuse where the tail section got off square as it was being frames up originally but nothing I can't fix.

Lastly, I have an old RCM magazine with a construction article for a .40 sized floatplane that the author fitted with one of the early OS Wankles and he speaks of it having a factory nipple on the engine casing (but no provision for a nipple on the muffler!). When he put the fuel tank pressure line on this nipple the engine ran slobbering rich. But without pressurizing the tank he said the Wankle ran just fine... and the floatplane used a mere 6 oz tank! The article makes no mention of fuel consuption issues. He does however comment that the Wankle seemed to be "a highly efficient fuel pump all by itself". Perhaps it wasn't meant to have pressurized fuel and by doing so people are causing these engines to "over-eat"? :-/

- Michael

William Robison

My Feedback: (3)

Michael:

I think when he said “…the Wankel seemed to be `a highly efficient fuel pump all by itself’ " he was saying it emptied the tank much faster than he liked.

Bill.