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OS Gemini Twin Rear Walbro Gas Conversion

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OS Gemini Twin Rear Walbro Gas Conversion

Old 08-21-2022, 07:05 PM
  #176  
RadialWacko
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Originally Posted by mitchilito View Post
The Rascal is a perfect choice for that engine- even at that altitude IMHO.

I LOVE mine.
Ooo, I love this idea. The sig four star was my first ever nitro plane over a decade ago. I think I might just do this.
Old 08-23-2022, 11:20 AM
  #177  
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Originally Posted by 1967brutus View Post
TBH, I do not expect any problems...a 160 on gas more or less equals a 120 on output, not a 110. And a plane designed for a 120 will with near 100% certainty fly with an engine that equals a 120 glow, at 5500' altitude.
I fly one of my planes at a corrected 4500 altitude (2100' asl and another 2500 due tropical conditions) and I do not notice any significant loss of performance. The engine appears to be able to handle a slightly larger prop under those conditions but nothing exceptional.
The plane is a 5,5 lbs 60" ws trainer with an engine that at sealevel puts out 0,5 hp, so never overly powered to begin with.

Pretty sure you'll be fine with that FT160 running gas, in planes up to roughly 120 size, unless the plane is a high strung fast and aerobatic plane, then things might get critical. Otherwise I do not expect problems.
The FT160 is a rather bulky and weighty engine, you don't want it in a plane that does not have the wing area to carry weight or in an airframe that tends to be nose heavy on itself. That Rascal that Mitch is using really would not have issues with it.
We get density altitudes of 8-9000+ feet almost daily in the summer. Your reasoning makes sense on paper but I think you would be surprised how drastic of a difference it is here.
Old 08-23-2022, 12:23 PM
  #178  
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Originally Posted by RadialWacko View Post
We get density altitudes of 8-9000+ feet almost daily in the summer. Your reasoning makes sense on paper but I think you would be surprised how drastic of a difference it is here.
I have to honestly admit that I have no hands-on experience with the density altitudes you mention, but I still would be surprised if that Twin would not fly that Rascal at your locale. It might perform a bit different, that I readily believe.
My reasoning bases on how horribly overpowered RC planes generally are. The plane I told you about, the one that I fly in indonesia? In its last iteration by the manufacturer, a .40 2-stroke was advised, which is well over 1 hp.
I have a spare one that is still at home, and the plane is perfectly fine with 0.25 hp. I use it as clubtrainer even, and it is not critical in take off or corrective manouvres as happen frequently when instructing.
I am not claiming that tiny engine will fly it at your locale, just indicating how badly overpowered manufacturers recommendations generally can be.
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Old 08-23-2022, 04:44 PM
  #179  
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I one hundred percent agree with all of that. I learned and grew up at a field at 1/5 the elevation I am at now. I will never forget trying to fly a plane that I brought with me at my new location. I knew it was going to be a performance decrease, but it didn't even get off the ground... This engine would certainly fly the Rascal, I'm not saying that. But I do think it would struggle with even a .91 aerobatic plane, it's that significant. But with that said, I agree that most planes are way over powered. For the most part, I enjoy scale flying a lot more so I think it will work out well. Indonesia sounds like a nice place to fly, and that's cool that you are involved in the club training program. Good on you!
Old 08-24-2022, 03:44 AM
  #180  
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RW,
If you look at the flying vids of my Rascal with the gas twin in this thread you'll see that at sea level where I fly it has lots of power. But with the reduction in performance you are describing it's quite possible that you would not be satisified with it's performance where you fly. However, there are things you could do to mitigate that loss. If it was me I might consider continuing to run methanol which would negate a large portion of your density altitude power loss. I, personally wouldn't run nitro tho - its just too corrosive.

With that said, you would have to change some of the seals/diaphrams in your walbro carb to accommodate alcohol. The Moris conversion comes with a WT962 carb (or at least did when he filmed the vid I posted earlier in this thread - and then purchased for my conversion) and works GREAT with gasoline. I'm not sure how it would work with alcohol, since you have to pass more than twice the volume of fuel while running methanol. I'll bet it would work tho.

I'll bet Jesse OPEN would know that answer tho. He described a background in this exact area.

Jesse?

Old 11-29-2022, 02:18 AM
  #181  
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Hello world!!

It took three months for something worth mentioning to happen with regard to my wonderful Rascal/Gemini. The norm is I go out, gas her up and fly fly fly. But yesterday after starting her up I noticed an aileron twitching badly on taxi out. It seemed worse at different (lower) throttle settings. Then I noticed that ALL the controls were twitching. Badly. What the heck?? I taxied in and shut her down.

I come from the days of 72mhz radios where this kind of behavior was an every day occurrence but I've NEVER experienced this with 2.4ghz. The communication link is just too good. Or so I thought.

I could only think of one thing that could possibly cause this: an ignition leak. So I wiggled the spark plug caps and reseated them firmly. They did seem a little loose - one in particular reseated inward about a millimeter or two - not much really. But that did it: no more twitching.

Like I said, I've never had an interference problem of any kind with modern radios - but it can happen. So be sure to check your plug caps from time to time. . . .

Hope you all have the best of the holiday season! Till next time. . . . . .



Old 11-30-2022, 09:36 AM
  #182  
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So fly fly fly and periodic maintenance.
Great pic!
Thanks for the update.
Happy holidays
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Old 12-02-2022, 01:00 AM
  #183  
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Originally Posted by mitchilito View Post
Hello world!!

It took three months for something worth mentioning to happen with regard to my wonderful Rascal/Gemini. The norm is I go out, gas her up and fly fly fly. But yesterday after starting her up I noticed an aileron twitching badly on taxi out. It seemed worse at different (lower) throttle settings. Then I noticed that ALL the controls were twitching. Badly. What the heck?? I taxied in and shut her down.

I come from the days of 72mhz radios where this kind of behavior was an every day occurrence but I've NEVER experienced this with 2.4ghz. The communication link is just too good. Or so I thought.

I could only think of one thing that could possibly cause this: an ignition leak. So I wiggled the spark plug caps and reseated them firmly. They did seem a little loose - one in particular reseated inward about a millimeter or two - not much really. But that did it: no more twitching.

Like I said, I've never had an interference problem of any kind with modern radios - but it can happen. So be sure to check your plug caps from time to time. . . .

Hope you all have the best of the holiday season! Till next time. . . . . .
If you still have the same ignition you had in the beginning of this thread, if you ONLY pushed the plugcaps down, that issue will re-occur, and sooner or later cost you that pretty Rascal... And that is preventable...

You have the twistlock plugcaps, they should lock 100% by pushing down hard on them, then twisting them about 30 degrees (half of a hex) clockwise, and releasing them should be "pushing down hard, twist 30 degrees counterclockwise and release"

Also, this specific type of plugcaps should come with contactsprings that go into the cap to ensure a good electrical connection between plugbase and cap-shell. They are thin gauge conical springs and go in with the small end facing the engine.
Old 12-02-2022, 01:41 AM
  #184  
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No, I don't have the "twist lock" plug caps anymore. I'm now running the RC excel style caps that are just a force fit. Not sure what the friction mechanism is but they are generally VERY hard to remove (just like on my Saito FG-60 radial).

I actually made a nifty little slide hammer to remove these style plug caps. Very handy!


When used carefully this baby is also much less abusive to the equipment

Last edited by mitchilito; 12-02-2022 at 01:43 AM.
Old 12-02-2022, 02:05 AM
  #185  
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Originally Posted by mitchilito View Post
No, I don't have the "twist lock" plug caps anymore. I'm now running the RC excel style caps that are just a force fit. Not sure what the friction mechanism is but they are generally VERY hard to remove (just like on my Saito FG-60 radial).

I actually made a nifty little slide hammer to remove these style plug caps. Very handy!


When used carefully this baby is also much less abusive to the equipment
Ah, OK, I did not know that of course.
I have so far not yet had one of those new styple caps come loose, but I do not trust them as much as I do the twistlock caps, with which I have never had a single problem (once I discovered that they were twist-locks... before that I thought they were the worst possible design )

EDIT and PS: That slide hammer is a good one, Going to steal that from you

Last edited by 1967brutus; 12-02-2022 at 03:27 AM.
Old 12-02-2022, 09:13 AM
  #186  
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I believe that a flat screwdriver at the base prying up with a twist while wiggling and a slight pull upward is in my opinion the least likely to cause any damage.
Seeing your tool gives me the idea that a purpose built tool is a better way to go (can you see the smoke coming out my ears?).
Old 12-02-2022, 05:44 PM
  #187  
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Originally Posted by 1967brutus View Post
Ah, OK, I did not know that of course.
I have so far not yet had one of those new styple caps come loose, but I do not trust them as much as I do the twistlock caps, with which I have never had a single problem (once I discovered that they were twist-locks... before that I thought they were the worst possible design )

EDIT and PS: That slide hammer is a good one, Going to steal that from you
I LOVED the ease of installation/removal of the twist locks but could never get them clocked right i.e. one was always noticeably higher than the other. Just bugged me.

Then I got the Saito FG 60 with the push locks and had a hell of of time trying to get the caps off. The slide hammer is a MUST. Maybe I should manufacture a couple hundred ☺️
Old 12-03-2022, 12:21 AM
  #188  
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Originally Posted by mitchilito View Post
I LOVED the ease of installation/removal of the twist locks but could never get them clocked right i.e. one was always noticeably higher than the other. Just bugged me.

Then I got the Saito FG 60 with the push locks and had a hell of of time trying to get the caps off. The slide hammer is a MUST. Maybe I should manufacture a couple hundred ☺️
I have basically the same with my ASP radial.
For the twistlock caps, I have always "indexed" the plugs (more like "index the hex") so the caps would be on in more or less proper alignment, has never been an issue. Most of the times it was no more than tightening one plug a bit stronger, very rarely I had to flatten the washer a bit.
Nowadays the single and twin ignitions from RcExl all come with the pushlocks and I do not particularly like them. But what can we do?

I have so far managed without a cap pulling tool, but I am going to try it.
Old 12-03-2022, 02:58 AM
  #189  
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Originally Posted by 1967brutus View Post
I have basically the same with my ASP radial.
I have so far managed without a cap pulling tool, but I am going to try it.
I think you'll find you really like the ease of removal with the slide hammer. One just has to be careful using it. Wouldn't want to yank on the leads. . . .


Old 12-03-2022, 05:58 AM
  #190  
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I am gonna find out when I am home again (at sea till early January)

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