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Author Topic: I am new to four strokes.  (Read 3475 times)
Clancy Arnold
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I am 5 Ft. 8 In., the Taube is 7 Ft. 4 In.


« on: July 22, 2010, 07:00:29 PM »

Guidance please!
I bought a kit and engine for a new CL Sport Scale model.  The Model was designed for RC but I will build it for CL.  I plan on using 70 ft .027 lines and my U/Tronics control system.

The model is Nick Ziroli's WWI Taube.  88 inch WS and 1500 sq. inch wing area.

I bought an OS 91 Surpass pumped engine to power it.  First question what kind of test stand should I use to run in the engine?
Clancy
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« Reply #1 on: July 23, 2010, 08:37:12 AM »

Clancy, remember to forget every thing you know about 2 strokes.  If instructions came with the engine read them thoroughly.  I have  a .70 four stroke that is slated to go in a fun scale plane.  I bought one of the ready made mounts and boltd it to a peice of 2X4.  It is clamped to a saw horse.  It is amazing how much power these 4S's have with the low rpm.  Guess it must be the higher pitch in the props or could be the diameter which is larger.  Hae a good strong starter or do like I do.  Turn it backwards until you feel compression.  Pull forward a bit and then smack it hard backwards.  Sometimes when I feel a kick I go ahead and flip the prop.  Do use a heavy glove until you are used to it.   Hoff
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Clancy Arnold
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I am 5 Ft. 8 In., the Taube is 7 Ft. 4 In.


« Reply #2 on: July 23, 2010, 07:35:50 PM »

Thanks Doc
I read the instructions:
Spin the engine with a starter and slowly open the throttle until it starts.  Sounds easy!(?)

The instructions call for a 15 x 6 or 16 x 6 wood prop.  I asked for a 16 x 6 prop but the salesman at the RC Hobby Shop sold me a 15 x 6 that I did not catch until I drove 20 miles back home.  So that is what I will use first.

I have some metal motor mounts that I could drill for the OS 91 FS to mount on.  They are cut from 1/4 inch aluminum plate.  I will mount them on a BIG board to support the engine and hopefully it will stay in one place. LOL  I originally had them for the HP 40's in my C-7A Caribou.



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« Reply #3 on: July 24, 2010, 08:42:14 AM »

Make sure what ever you anchor it too will stay put.  First time I fired the .70 I had to sit on the saw horse.   Hoff
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« Reply #4 on: July 24, 2010, 04:13:01 PM »

Make sure what ever you anchor it too will stay put.  First time I fired the .70 I had to sit on the saw horse.   Hoff

Yes, anchor the engine VERY firmly. 4 strokes are very strong. Mine started to pull my test stand over, but I was able to catch it and anchor it with 2 extra masonry blocks. Big difference between an ST 46 and a Saito 72!!
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Clancy Arnold
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I am 5 Ft. 8 In., the Taube is 7 Ft. 4 In.


« Reply #5 on: July 24, 2010, 05:12:25 PM »

I normally test run engines under the tree in the front yard.  It has a 10 inch dia. trunk that I will tie the stand to.  That might hold it! LOL

Thanks,
Clancy
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Clancy Arnold
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« Reply #6 on: July 27, 2010, 07:17:18 AM »

Now don't blame us when the tree comes up by the roots. Layingdown Layingdown LL~I have a cast iron vise I clamp to my saw horse and the 70 with a 13 inch prop was pulling the saw horse. Hugh Hoff
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« Reply #7 on: July 27, 2010, 03:02:17 PM »

Clancy,

Please, please don't stand in front of the engine while it's running.  Four strokes often kick back, especially when new, and will throw a prop completely off the prop shaft.  This can also happen when you're starting it, but at least the engine isn't running.  Until the engine is broken in, the valves seated and the carb adjusted, be careful!  I've seen some very close calls, including myself, at the R/C field.  Also, be aware that the larger mass vibration can loosen anything in you're mounting rig that's not secure (i.e. C-clamps).  Have fun, they are great engines, but very strong.

Paul

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« Reply #8 on: July 27, 2010, 08:04:55 PM »

Thanks Paul
I normally try to set a new record in getting BEHIND an engine when it is running in a test stand.

I hope that 91 4stroke puts out a lot of power because of the size of the model and the amount of air drag all of those bracing wires will create.  I bought a 15 x 6 wood prop to try it with.  They could have made two 10 x 6 props out of the wood in this one prop.
Clancy
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« Reply #9 on: July 28, 2010, 09:11:17 AM »

If there is enough threads, go to your local hardware and pick up a nut that has the nylon insert.  Did that both of my 4S.  If the propcame loose it stayed with the engine.   Hoff
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« Reply #10 on: July 28, 2010, 11:07:20 AM »

Doc
Thanks for the suggestion.  I think I have some 1/4 28 nylok nuts in stock.  The engine came with a double nut system that looks like it would be hard to loosen.  The second nut goes into a tapered hole in the first nut and is castelated to compress onto the threaded shaft.

Clancy
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Clancy Arnold
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« Reply #11 on: July 29, 2010, 08:52:10 AM »

You sure that is not a 5/16th shaft on that big engine?
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Clancy Arnold
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« Reply #12 on: July 29, 2010, 09:05:06 AM »

Doc
You are right!!
I should have remembered since I just bought a prop reamer to make the new prop fit the shaft.  Now I will have to take the current prop nut to a hardware store and match the threads.

I ordered a new set of the biggest motor mounts SIG sells to use to mount the engine to the test stand and later to the model. 
Clancy
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Clancy Arnold
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« Reply #13 on: July 30, 2010, 10:38:03 AM »

I usually take the whole engine to the hardware store when looking for screws and nuts.  You should see the looks I get when I tell them I needed parts. Hoff
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« Reply #14 on: July 30, 2010, 10:45:47 AM »

Forget the nylon lock nut or any lock nut except the ones that came with the engine. You won't be able to turn it as you have no way to hold the shaft. All the stock nuts take is two wrenches.
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« Reply #15 on: July 30, 2010, 06:32:58 PM »

Doc
I will take the engine with me and see how they react.  LOL


Bob
I can handle two wrenches but the wrench supplied has the correct sizes on opposite ends.  A standard double ended open end wrench.  I will use some of my 50 year old Craftsman wrenches for the first time.  Oops, I need to buy new METRIC 12 and 14 mm wrenches.

Clancy
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Clancy Arnold
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« Reply #16 on: August 02, 2010, 12:17:21 AM »

Now that I think about, you can hit up Han Xing Ping for 4 stroke info-in fact, you can hit up the whole Chinese team!!!
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« Reply #17 on: June 24, 2011, 04:32:09 PM »

Well I now have gotten 2 flights on the OS 91FS.  Very confusing!!
The first flight the engine fired right up and ran fine.  .the second flight was at the Brodak Fly-In.  The engine would start fine but idled rough and when I had walked out to the center of the circle I would move the throttle to high power but the engine would not pick up speed and shortly would die.  Last attempt so I started it again and kept it at mid throttle while I walked to the center of the circle.  Before I signaled to release it I checked that it would follow the throttle.  Go for launch.

After the contest was over two friends Denis Lipsett and Johnny Recker fired it up in the motel parking lot and Dennis adjusted the carb. 

The owners manual said to move the idle screw less than 1/8 turn at a time.  This engine required turning it in over half a turn!  Now it starts, idles and then follows the Throttle. 
Clancy

http://www.youtube.com/user/frankcarlisle#p/a/u/1/h7iml6TUTo4
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Clancy Arnold
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« Reply #18 on: June 24, 2011, 05:01:02 PM »

Carburetors are the same whether the engine is four stroke or two.  It sounds like you got some dried castor or dirt in a needle valve.

How much time between flights?  If weeks or months -- think dried oil.
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« Reply #19 on: June 25, 2011, 11:45:55 AM »

Tim
Time between flights was 3 weeks.
Test ran it in the front yard today, new fuel and it idles at 2100  - 2200 RPM and at full power on a 15 x 6 - 10 prop it turns 6500 RPM.  Way more power than I wll ever need on the Taube.
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« Reply #20 on: June 26, 2011, 02:52:09 PM »

Question?

I have noticed that the engine idles smoother with the glo igniter attached but roughens up and seems to miss fire after it is removed.  Engine has a brand new OS F-8 plug.  Should I add an onboard plug igniter to switch on at idle?

During yesterdays test run it idles at 2100 - 2200 RPM on my digital tach.  Full power with a 15 x 6 - 10 Zinger wood prop is 6500 RPM.  Does this sound about right?

Clancy
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« Reply #21 on: June 27, 2011, 09:34:01 AM »

Yes Clancy. That sounds about right. I have run OS 4 strokes for years, and they all drop when the glow ignitor is removed. If you set them any leaner on idle to keep it from doing that, then they are slow to idle down, and will stay at around 3,000 rpm for a little bit. They like to have that miss fire idle and are very consistant with that. I have never had the need for glow heat at idle, but it sure would not hurt anything.

Saito's on the other hand, like to be a bit leaner, and will not do the miss thing at idle. Just a difference in the way the engines are set up. I kind of like the way the OS engines idle, but that is just me.

Back to running on a test stand, I run mine on this one all the time with out problems. I made this about 30 years ago, and it will run a 90 four stroke just fine.
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« Reply #22 on: June 27, 2011, 05:39:43 PM »

Jim
That is a nice looking test stand.  Do you add extra weight to it for the big four strokers?

Here is my test stand. LOL
That is a 17 Inch diameter Ash tree.
Clancy
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« Reply #23 on: June 27, 2011, 07:17:40 PM »

I either hold it down by hand, or use a cement block to hold it down. I usually run my engines in the back yard, and after I get them started I sometimes sit in a chair with my foot on one of the side rails to hold it down. Never had a problem with an engine coming loose or anything else. I do have a switch on my ignition box so that if anything does happen when running those, I can just switch it off.

I have also used a test stand similar to yours, but mine is tied to a swing. No matter how well you get an engine set on the test stand it will always need tweeking when you get it in the plane. I really enjoyed the video of your plane at Brodaks. It is magnificent.
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« Reply #24 on: June 28, 2011, 08:38:30 PM »

Jim
Today I bought a molded 15 x 6 Evolution prop.  It is 1 1/2 ounces heaver than the Zinger 15 x 6-10 wood  that I have been flying.  It increased the top Speed to 7500 RPM and smoothed out the idle.  It actually set there at 1700 RPM.
Clancy
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« Reply #25 on: June 30, 2011, 03:47:51 PM »

Oh Yeah Clancy; A four stroke running at 1700 idle sounds like just a tick over. I know my old OS 90 will idle so slow it sounds like it is going to quit, but just keeps running. That is usually at the end of a flight when it is good and warmed up, and the fuel level is low. A heavier prop really helps with the flywheel action on idle.
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« Reply #26 on: July 06, 2011, 07:58:00 PM »

I had engine problems at the Control Line Scale NATS.  The engine would not turn up and I should not have even tried to fly in the wind on Saturday.  After kocking the engine out of my 1914 Jeannin Stahltaube I only found one thing wrong with the engine.  The Crankcase breather nipple was loose.
 
Today I verified the loose nipple was the problem.    A month ago my oldest son's table saw died.  I asked for the steel stand it was on.  Today I was up in the attic and found the Easy Just motor test stand I bought while a teenager.  Price on the bottom was $1.30.  It is made of hard maple wood.  I have never ran any thing bigger than a 35 in it.  The FS91 fit and by starting it at low throttle, and immediately getting behind the prop, I thought it would be worth a try.  I bolted it to the table saw stand and lashed the stand to a 17 inch Ash tree.
 
I had tightened the loose nipple about a full turn.
First run - Evolution 15 x 6 prop - 7500 RPM.  Last time it peaked at 7000 RPM. Did not touch the needle valve.  Loosened the nipple 1/2 turn.
Second run - 7000 RPM.  Re tightened the vent nipple.
Third run 14 x 6 APC prop - 9,100 RPM.  Saturday on a 14 x 6 APC prop It could not power through the wind like I needed  it to.  There was no 9000+ RPM available!!  This is the highest RPM I have seen on the Tach on this engine.  Started to adjust the needle to see how much more was available when it started to die, the two ounces of fuel in the test stand tank were gone.  End of testing.

It is important to understand the key definition of how this engine operates to visualize the problem I was having.  Note: there are TWO nipples connected directly to the crankcase.  The first is the common breather vent which on this engine is plumbed to the intake manifold.  The second one is mounted in the center of the backplate and is connected to the Fuel Pump.

"The varying pressure in the lower crankcase actuates the diaphragm in the Fuel  Pump allowing it to providing sufficient fuel, under pressure, to the Pressure Regulator to allow it to provide the required amount of fuel, at a constant pressure, to the Carb."  

The loose crankcase vent nipple was causing a  loss of varying crankcase pressure preventing the Fuel Pump from providing sufficient fuel to the Pressure Regulator to feed the engine at high power settings.  It was acting like a Governor!!.
Clancy

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Clancy Arnold
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