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What size conversion engine for a Dynaflite SE5a?

Old 09-23-2007, 08:48 AM
  #1  
JIMARRINGTON
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Default What size conversion engine for a Dynaflite SE5a?

I am building a Dynaflite SE5a WWI bipe. It has a 64" wing span and called for a 90-120 4 stroke engine. I had originally planned on using an OS 91 FX 2 stroke but am leaning heavily into getting away from glow. The airplane has a flat bottom airfoil so it will not be an aerobatic aircraft. I want maybe a little bit better than scale performance out of it. Ie I want loops from level, stall turns, etc. AUW should be aound 12-14 lbs. The engine compartment is roughly 5" x 7". Would like to use a conversion engine. Any recomendations as this would be my first gas.

Thanks
Jim
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Old 09-23-2007, 10:25 AM
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davewallace
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Default RE: What size conversion engine for a Dynaflite SE5a?

Jim,
Your plane would work well with a 25 to 32cc trimmer conversion, swinging a 16 to 18 inch prop. A Ryobi 31 would fit completly inside the cowl and use a 18" prop. A Homelite 25cc would be a good choice also, but the carb would stick out of the side of the cowl. This might make adjustment easier. The The four pound weight of a flywheel equiped engine would help balance the plane, since the nose is short. The Clark Y, flat bottomed airfoil will carry the extra weight fine.

Dave
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Old 09-23-2007, 12:01 PM
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Default RE: What size conversion engine for a Dynaflite SE5a?

First things first.

How much weight will it take to balance the plane?

There are lots of conversion engines to choose from.
The Ryobi 31 is pretty heavy comparatively.
A 25cc Toro weighs less and has more power, but if you need the weight the Ryobi
would still be a good choice.

Get the wings on it, and put it on the balance machine to see where you are.
Then you will be looking for an engine by weight.

A couple of friends have the smaller SE5a and they all needed extra nose weight,
even with a Saito 90. So a gasser should work out great for you.

This will be a fun flyer
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Old 09-23-2007, 12:26 PM
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Default RE: What size conversion engine for a Dynaflite SE5a?

I like the idea of the Ryobi fully cowled. On Wackerengines.com, they sell a conversion kit including the engine. Does anyone have an experience with this kit?

I would think that this airplane would fly best with a big prop with a lower pitch at a moderate rpm.


Thanks
Jim
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Old 09-23-2007, 12:32 PM
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Default RE: What size conversion engine for a Dynaflite SE5a?

BTW, I have a Quadra 35 with a spring starter. Would this engine be too big? It will fit inside the cowling but the carb will stick out.

Jim
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Old 09-23-2007, 04:14 PM
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Default RE: What size conversion engine for a Dynaflite SE5a?

I purchased the conversion kit from wackerengines. I think it is well worth the $$. The owner is very polite and helpful. Call him before you order so you don't get the wrong prop adapter. I can't tell you much more. I have an issue with the carb and I am waiting for parts. It started very easy before I ran into problems. I am no expert. I am sure I will be asking the experts here for help once I get the thing running again. The conversion is easy. Read all the web pages you find on the subject. I was told not to worry about opening up the carburetor throat..................

I had so much fun messing around with the conversion that I bought 5 more engines...another 31cc ryobi and 4 25cc engines that seem to be troybuilt blower engines. Lots to do this winter.
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Old 09-23-2007, 10:06 PM
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Default RE: What size conversion engine for a Dynaflite SE5a?

I see your in new boston.I would talk to Ken Lambert(lambertsrc),hes also in new boston and has been doing conversions for years.i would drive over and talk to him,see what he thinks,give him your specs ect..ive delt with him for 3-4 years now.he can help in many ways including pitts style mufflers wich i only buy from him.ill send you a pm also so be looking.
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Old 09-24-2007, 08:44 PM
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Default RE: What size conversion engine for a Dynaflite SE5a?

Hi Buck,

Yes I know Ken. Unfortunatley, he sold his house last week and moved. Real nice guy.

This morning when I got to work, waiting for me at the door was a customer who owned a lawnmower repair shop. We got to talking and come to find out he had some engines that he could give me. Later today he brought them to me. One was a featherlite 18cc that looks like a right off but maybe ok for practice. The other was a Troy Bilt power head that he said was thrown away because the shaft was messed up. I started taking it apart this evening and it looks to me like it has a Ryobi 31cc engine on it. It has a rear carb and muffler. The carb is a Zama. Right now I am stuck as I cant figur out how to get the clutch for the trimmer shaft off. Anyone know how to remove it? I started a thread on it.

Do you guys think this might be a good conversion engine? It still seems to have good compression. Just looking at it though, it seems like it might be too big for the SE5. What do yall think?

Jim
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Old 09-25-2007, 10:38 AM
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Default RE: What size conversion engine for a Dynaflite SE5a?

Jim,
The clutch drum is held on by a screw going into the end of the crank stud. Stick a allen wrench in the end of the drum where the flex shaft is normally inserted. Remove the allen screw and the drum wll slip off. Then clamp the flywheel in a vise and turn off the clutch shoe assembly. I beleive that it is left hand thread. You can reduce the engine weight and size by converting it ti gas/glow ignition. This is discussed else where in the conversion forum. Good luck.

Dave
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Old 09-25-2007, 05:16 PM
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Default RE: What size conversion engine for a Dynaflite SE5a?

Since it looks like I will be converting the Ryobi 31cc for this project, I will close out this thread and move to my conversion thread. It is titled what motor on a Troy Bilt weedeater.


Jim
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