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OS FT120 Gemini Mk1

Old 05-24-2018, 12:57 AM
  #1  
Godhelper
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Default OS FT120 Gemini Mk1

Hello Sirs,

I really have difficulties in getting the a m engine to run smoothly....
I bought it from new (second hand) some years back, broke it in with mixed results, mounted it in a plane and took flight 3-4 times and then the plane "died"...(pilot error).
Now I've mounted it in another plane and I simply cannot get it to run smoothly. It start very easily, but top rpm is different from each start and the transition from idle (when it does idle), is very hesitative.
I tried adjusting for hours but with no result (
I saw some pictures online of various airframes with the same engine, where I notised that the carb was mounted with the HS needle pointing to the left on one plane, and to the right on another plane.
Does the orientation of the carb have any influence on the running behaviour?

I do the following:
1# Starting the engine, advancing to full throttle and adjusting the HS needle to peak rpm and then backs up a few clicks to richen it a little...a small amount of smoke should be present.
2# Decreasing throttle to idle, making sure the barrel is not fully closed (by trim) and let it idle - ok.
3# Advancing throttle to max and it hesitates a lot, so I adjust the airscrew ccw in 1/4 turn increments (the manual for the Mk2 says 1/2 - 1/1 turn).

But it will not run smoothly!
Is it possible to mount another OS carb on this engine?

Can anyone help with the original instructions/manual/parts list for this engine or guide me to clarification of this erratic engine?

Any help and pointers a highly appreciated.

Have a nice flying time!

Regards Kim
Old 05-24-2018, 04:29 PM
  #2  
chris de jon
 
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Default

Try this link, most of the engines are listed
https://www.osengines.com/manuals/index.html

Cheers

CJ
Old 05-24-2018, 09:53 PM
  #3  
Godhelper
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Thanks mate,
But i've already been surfing these pages and the only thing coming up is for the Mk2...no info whatsoever for the Mk1.... (
Old 05-25-2018, 05:11 PM
  #4  
chris de jon
 
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Default OS Gemini FT 120 Gemini Mk1

Good day,

I found my Gemini 120 MK1 in its box all stored away for quite some time now.

I have scanned the manual for you. Here are the PDFs 20 pages.

I think this engine was the very first twin made by OS.

It was never a very powerful engine and was quickly superseded by the MK 2

I never ever have run nitro at all in any of my twins incl the 160s. I always use a glo plug igniter and a C Cell 5000MA battery

I mount a Micro switch in the plane with its springy lever being pushed in and out by the throttle servo arm. The lever is mounted so that the arm can be adjusted to switch on glow at 0 to throttle.

I also have in series a 2 way switch on the outside of the fuselage so that I am not relying on leaving the throttle on full when sitting in the pits. I place a charging jack on the Cell so that the batt can be charged while in the plane.

The MK1 was difficult to tune and running in took a long time, but once run in became a good running reliable engine.

Hope this helps you.



Cheers
Attached Files
File Type: pdf
Gemini 120 Note.pdf (480.5 KB, 268 views)
File Type: pdf
Gemini 120 Page 6.pdf (598.7 KB, 212 views)
File Type: pdf
Gemini 120 Page 4.pdf (973.0 KB, 175 views)
File Type: pdf
Gemini 120 Page 5.pdf (1,004.7 KB, 234 views)
File Type: pdf
Gemini 120 Page 3.pdf (1.25 MB, 237 views)
File Type: pdf
Gemini 120 Page 8.pdf (836.5 KB, 172 views)
File Type: pdf
Gemini 120 Page 10.pdf (889.4 KB, 205 views)
File Type: pdf
Gemini 120 page 13.pdf (1.17 MB, 228 views)
File Type: pdf
Gemini 120 Page 15.pdf (1.05 MB, 229 views)
File Type: pdf
Gemini 120 Page 16.pdf (693.3 KB, 194 views)
File Type: pdf
Gemini 120 Page 19.pdf (777.5 KB, 201 views)
File Type: pdf
Gemini 120 Page 18.pdf (697.3 KB, 180 views)
File Type: pdf
Gemini 120 Page 7.pdf (702.6 KB, 142 views)
File Type: pdf
Gemini 120 Page 14.pdf (525.5 KB, 165 views)
File Type: pdf
Gemini 120 Page 12.pdf (950.3 KB, 170 views)
File Type: pdf
Gemini 120 Page 9.pdf (938.3 KB, 186 views)
File Type: pdf
Gemini 120 Page 17.pdf (1.44 MB, 239 views)

Last edited by chris de jon; 05-25-2018 at 05:20 PM.
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Old 05-25-2018, 09:31 PM
  #5  
Godhelper
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Hello Chris,

This is absolutely great!
Thanks a lot for the manual - that is highly valuable for me. If You should stumble over page 11 some time, don't hesitate to upload it here )
I think there is good information about the mixture settings on that particular page?

For my glow solution, I just mounted a mini servo and a microswitch on two SUB C 1,2V 5400 mah NiMh's, so it's either on or off.
I wanted the engine to run without permanent current on the glow plugs, but if it's the only (or best) way to haveit reliable, I think I will opt in for the JustEngines one https://www.justengines.co.uk/acatal...oard_Glow.html
I got one already in a Top Flite DC-3 and it works great!

Thanks again for Your great help Chris and have a good week-end.

Regards Kim
Old 05-26-2018, 12:03 AM
  #6  
chris de jon
 
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Default OS Gemini FT 120 Gemini Mk1

Gee very sorry, I thought page 11 was uploaded.
Well here it is,
You have a good weekend as well.

Cheers
Attached Files
File Type: pdf
Gemini 120 Page 11.pdf (1,013.4 KB, 184 views)
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Old 05-26-2018, 08:29 AM
  #7  
Godhelper
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Fantastic Chris,

I really appreciate Your effort!

Grab a pint on me

Cheers

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