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 Post subject: The Taube has a new engine
PostPosted: Thu Oct 13, 2011 8:55 pm 
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Joined: Sun Sep 09, 2007 7:04 am
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Location: Indianapolis, IN
The Jeannin Stahltaube has a new engine installed. The original OS FS91 SII-P engine would not reliably put out the power that I thought it should at full throttle. It would top out at 9,000 RPM one day and 7,000 the next day!

After crashing the Taube at the NATS because of low power a friend, Jim Fruit, sent me a replacement engine. The replacement engine is a brand new in the box OS FS91 S engine. It will be broken in in the airplane. First 10 minutes will be at less than 4,000 RPM with full throttle running very rich. Then I will start leaning it out with intermittant rev ups and cool down periods. This is the way the owners manual says to do it. I checked the valves and they are set in the middle of the recommended gap.
Clancy

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Clancy Arnold
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 Post subject: Re: The Taube has a new engine
PostPosted: Fri Oct 14, 2011 9:44 pm 
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Posts: 300
Location: St. Paul MN
So how badly was the Taube damaged? such a shame...

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 Post subject: Re: The Taube has a new engine
PostPosted: Fri Oct 14, 2011 11:25 pm 
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Location: Indianapolis, IN
Ray
If it had 5 more feet of altitude it might have made a good landing. It did a three point landing, two mains and the nose. The glass filled motor mounts broke right behind the engine and that saved the airframe from much damage. It knocked the firewall loose on one side and I had to replace the balsa sheet wood on the top and bottom of the nose.

It is all repaired and ready to go as soon as I get the new engine through break in. One other thing that was knocked loose were the batteries under the engine that powered the U/Tronics. 4 each 2.2 AH NiCad cells (2/3 D size) weigh 11.7 Oz. I have replaced them with 4 each 3AH NiMH cells (AA size) weigh 2.8 Oz. There is now 11.7 Oz additional lead in the nose to go with the 4 Oz that were already there.

YES, almost 1 pound of lead to move the CG from 33 % of root cord to 20 % of root cord. The root cord of the wing is 19 inches! 1500 Sq. In./ 10.4 Sq. Ft. of wing area.
Clancy

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 Post subject: Re: The Taube has a new engine
PostPosted: Sat Apr 28, 2012 7:09 pm 
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Joined: Sun Sep 09, 2007 7:04 am
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Location: Indianapolis, IN
I have the new engine mounted in the Taube but as it does not have a fuel pump I have built a new fuel tank 4 W x 2 1/2 L x 1 1/2 H inches that should hold about 7.5 ounces of fuel. The tank is about one inch behind the engine and the top of the tank is about one inch below the carb. I plan on using muffler pressure to give it a steady fuel feed. At an empty fuel tank the engine will need 2 1/2 inches of draw offest by the mufler pressure.

the new metal tank is lighter than the original plastic tank as it is built out of .005 Phospher Bronze sheet stock.
Clancy


Attachments:
File comment: Tank lines (L-R) Overflow, Engine feed, Muffler pressure / Fill line.
Taube Fuel Tank 002 (525 x 394).jpg
Taube Fuel Tank 002 (525 x 394).jpg [ 47.04 KiB | Viewed 4595 times ]

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 Post subject: Re: The Taube has a new engine
PostPosted: Mon Apr 30, 2012 9:22 am 
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Location: detroit
Looking real good Clancy.......................you're very good at this.

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 Post subject: Re: The Taube has a new engine
PostPosted: Mon May 07, 2012 4:45 pm 
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Location: Indianapolis, IN
The weather cooperated today and I got to run the new engine in my Taube. I put 6 ounces of four stroke fuel in the new tank and fired up the brand new OS FS91 Surpass engine. The instruction sheet said to open the needle valve 3 to 4 turns if using an open vent on the fuel tank or 2 to 2 1/2 turns if running muffler pressure. The first run was for 3 minutes and I had to partly close the throttle to keep the RPM down where I wanted it even swinging an APC 14 x 6 prop. The second run was for4 minutes, samw as first run. Ifrew out the remaining fuel from the tank which was less than 1/2 ounce.

For the third run I connected the muffler pressure, put 6 ounces of fuel in the tank and closed the needle valve to 3 turns open and it again pulled real hard. I still did not go to full open throttle but am sure I could fly the Taube right now! I plan on running at least four more tanks of fuel through the engine before flying it. The engine exhaust was a white ckoud so I am sure there now are no bugs in our neighborhood!
Clancy

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 Post subject: Re: The Taube has a new engine
PostPosted: Mon May 07, 2012 8:32 pm 
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Joined: Sat Oct 27, 2007 3:44 pm
Posts: 376
Generally OS makes engines that really don't benefit from protracted run ins. I usually run them once on the ground and then fly them in keeping it on the rich side, In 5/6 flights your ready to go. Clancy, with throttle control you have no problem keeping that engine fumigating the whole county.
Dennis


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 Post subject: Re: The Taube has a new engine
PostPosted: Mon May 07, 2012 9:08 pm 
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Location: Indianapolis, IN
Dennis
I was running it so rich that it was using almost an ounce a minute of fuel. There was a big white cloud beside the model.

After some more running I will start leaning it out and open it up. Then I plan on trying different props to see which gives me the most static thrust. I have a digital scale ready to check it with. The scale only goes to 88 lbs.
Clancy


Attachments:
File comment: Digital Scale, 10G - 40 KG.
Digital hanging scale.jpg
Digital hanging scale.jpg [ 35.15 KiB | Viewed 4533 times ]

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 Post subject: Re: The Taube has a new engine
PostPosted: Sun May 13, 2012 9:45 am 
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Joined: Tue Sep 11, 2007 8:36 pm
Posts: 133
Location: Harsens Island, MI
Clancy

Best way to set the high speed needle on a 4 stroke seems to be to use a tach. Its really tough to tell the proper end point because it doesn't enter a 2 cycle like a 2 cycle motor does (dah). What I have found works well is to slowly... cause the needle doesn't respond as quickly as with a 2 stroke... lean the needle in and when you reach peak rpm go back a quarter turn or so. That should pretty well be it. You should see a white smoke trail at full song. If not, richen it up a bit more. 4 strokes really don't give much indication of going lean till they stop other than the smoke trail disappearing. If I loose the smoke trail I land and make it richer, I don't finish the tank.

When you adjust the low speed needle you will need to reset the high speed, but the high speed has to come first. Also changing props will of course change things too. You would not set the high speed needle to a lower power setting than full throttle however. The low speed should be set for a smooth consistent idle and a smooth clean transition as you increase throttle quickly. If the transition stumbles, you are most likely too rich on the low speed needle. Changes to the low speed needle btw are extremely sensitive. Select a given amount of change and use it each change so you can sneak up on the right setting. 1/16th of a turn at a time is about right.

Sorry I could not get back on this sooner but I have not been able to log in until today.

bob branch


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 Post subject: Re: The Taube has a new engine
PostPosted: Mon May 14, 2012 4:10 pm 
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Location: Indianapolis, IN
Thanks Bob
The problem I had at the Brodak Fly-In was the low speed needle needed turned in over 1/2 turn. When I would idle the engine while I walked out to the center of the circle the engine wold load up and die. Dennis Lipsit adjusted it in the motel parking lot after the contest was over. Then when I tried to fly it at the NATS the Crankcase breather nipple had come loose loosing the pressure to actuate the fuel pump properly. RPM was down several hundred and thrust was missing in action. Jim Fruit gave me the NIB OS FS91 Surpass engine he had bought for a model he never got around to building and then he converted to all electric power.

I have a tach but too much smoke to get a good reading yet! I will also need help to do the measured thrust testing.
Clancy

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 Post subject: Re: The Taube has a new engine
PostPosted: Tue May 22, 2012 3:51 pm 
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Location: Indianapolis, IN
More break in time on the new OS FS91 Surpass engine.

Two runs today. First run used 6 oz of fuel and ran 8 1/2 Min. Second run I filled the tank, which held 8 1/4 oz of fuel and it ran 10 1/2 Min. I kept varying the throttle and it keeps getting stronger!

I am using an APC 14 x 6 prop for break in. With the throttle at about 3/4 The Luggage scale read 89 oz. Near the end of the last run I opened the throttle full but did not lean out the engine and the pull was 118 oz. As you can see in the pictures I am running it in the shade of a large Ash tree so the optical tachometer will not give a steady reading.

I have posted a couple of pictures of my engine run in stand. The table is 39 x 48 inches.

It is getting there.
Clancy


Attachments:
File comment: The engine is at half throttle. note the landing gear are tied to each side to prevent it walking off the 39 x 48 inch table.
OS FS91 004 (450 x 338).jpg
OS FS91 004 (450 x 338).jpg [ 45.44 KiB | Viewed 4470 times ]
File comment: TheTaube is restrained with 50 lb test nylon cord.
OS FS91 003 (550 x 413).jpg
OS FS91 003 (550 x 413).jpg [ 46.1 KiB | Viewed 4472 times ]

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