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OS gemeni 120 connecting rods

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Old 10-15-2008, 11:22 AM
  #1
donkey doctor
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Default OS gemeni 120 connecting rods

Hello; I (vaugely) remember Brian Winch talking (writing really) about early FT 120's coming out with connecting rods that would break after a few uses. I think it was in RC Report magazine a few months ago. I have come into an old FT 120 that has aluminum die cast rods with OS cast into them, and I'm pretty sure that those are the rods he was mentioning.

This particular engine suffered a crank failure, the web between the two crank throws fractured, but has been welded up and balanced, so now all I have to do is polish the mains (to get a bit of welding spatter off) and re-assemble it, to try it out.

I don't want to finish the job if there's a chance that the rods aren't up to the job. I will post pictures if it'll help.

Any body remember that? Brian are you on?
t
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Old 10-15-2008, 07:31 PM
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Default RE: OS gemeni 120 connecting rods

T,
I remember OS had listed the serial numbers of these older engines. Might check their website.
I have it copied down somewhere in my file.
I have one of these old 120 twins on a cub...which dosen't do any full power dives.
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Old 10-15-2008, 08:40 PM
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Default RE: OS gemeni 120 connecting rods

The welded crank needs to be normalized to relieve the stresses caused by the welding or they may crack again at the edge of the weld
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Old 10-15-2008, 09:35 PM
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Default RE: OS gemeni 120 connecting rods

I would use the rods you have. I am sure they will out last that welded crank by a long way. Not many people around that have the skills to weld a crank and if they have the skill they would definitly cover the journals.
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Old 10-17-2008, 11:28 AM
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Default RE: OS gemeni 120 connecting rods

Does the Gemeni 160 have the same problem?
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Old 10-17-2008, 12:23 PM
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Default RE: OS gemeni 120 connecting rods

As far as I know the OS 160 is OK.
I haven't heard of any problems of this kind with the 160.
I have one and it is a very good twin.
Jim
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Old 10-17-2008, 03:27 PM
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Default RE: OS gemeni 120 connecting rods

The 120 II and 160 are almost the same engine. The early 120 twin is a different animal and is only similar in its looks.
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Old 10-17-2008, 07:52 PM
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Default RE: OS gemeni 120 connecting rods

The 160 twin is a great engine, no problems with rods.
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Old 10-24-2008, 06:20 PM
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Default RE: OS gemeni 120 connecting rods

Jim,
I've got one of the original FT 120 Gemini Twins and I have checked the OS website but was not able to find any serial numbers. If you come across your list would you mind posting them?

Thanks,

Tip
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Old 10-24-2008, 07:14 PM
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Default RE: OS gemeni 120 connecting rods

This is from the OS help forum: http://www.rcuniverse.com/forum/m_69...tm.htm#6983785

I had read it there before because I own a FT 120II and was there digging up info on my engine.

Mike
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Old 10-24-2008, 07:20 PM
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Default RE: OS gemeni 120 connecting rods

OK Tip,
After some looking through my messy file I did find the paper work on our OS engines.
Remember, I have't looked at this stuff for years and I didn't have this quite right.
I got this information off a old torn out yellow page of High Flight Quarterly newspaper.
It reads:
Some information for owerners of OS FS102 (old style), FT160 twin engines. The early OS 120 engines that are marked with the letters RP under the engine mount lug are somethimes prone to a case separation at the rear crankshaft bearing. If you have one of these engines, carefully inspect the outside of the crankcase around the rear bearing boss for cracks. Some of the O.S. FT160 twins have a possible defectiver connecting rod set. Check the serial number stamped on a small machines flat at the bottom of the crankcase, just behind the carburetor. If it matches one in the series listed below, again, contact you're dealer.
The serial numbers are: 000105-128.....130-189......191-236.....350-473....493-672....001050-1052
001064.....1074.....1077.....1079.....1088.....108 9.....1091
The engines beginning with serial number 001096 and above are all O.K.
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Old 10-24-2008, 10:02 PM
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Default RE: OS gemeni 120 connecting rods


Quote:
ORIGINAL: donkey doctor

Hello; I (vaugely) remember Brian Winch talking (writing really) about early FT 120's coming out with connecting rods that would break after a few uses. I think it was in RC Report magazine a few months ago. I have come into an old FT 120 that has aluminum die cast rods with OS cast into them, and I'm pretty sure that those are the rods he was mentioning.

This particular engine suffered a crank failure, the web between the two crank throws fractured, but has been welded up and balanced, so now all I have to do is polish the mains (to get a bit of welding spatter off) and re-assemble it, to try it out.

I don't want to finish the job if there's a chance that the rods aren't up to the job. I will post pictures if it'll help.

Any body remember that? Brian are you on?
t
It always helps to post photos...give it a go. Thanks Capt,n
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Old 10-25-2008, 07:21 AM
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Default RE: OS gemeni 120 connecting rods

Mmmmmm a welded twin throw crank.


Good luck
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Old 10-27-2008, 02:51 PM
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Default RE: OS gemeni 120 connecting rods

Ok I give up, I have looked on the bottom of my 160 and yes there is a flat surface behind the carb. but no numbers. Is this engine good bad or what-ever?
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Old 10-28-2008, 11:32 AM
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Default RE: OS gemeni 120 connecting rods

Hello; Well, I have been assembling the FT 120, and encountered a bit of a road block. I crocus clothed the crank throws until I'm satisfied that they'll be okay. It's hard to measure but I tried for 3 thou clearance. I have the bottom end done but I can't find the line nut that holds the intake to the head on one side, also 3 of the 8 O-rings on the push rod tubes are missing. Thje engine was diss-assembled when I got it. Also there are two sleeves that look like dowells, about 1/4 long and `1/4 high that I can't find a place for.

I admire the mechanics in Cuba, those guys can fix anything, no matter how bad. Who says that only the newest technology is best? When I was last there, I met a fellow with a 57 Ford that he was doing a brake reline on. It was just another job to him. The pieces were junk, comp[ared to what we see all the time, but he gives a one year warrantee on his jobs and only charges the american equivalent of $1.25/hour. He is willing to barter too.

Any idea on the sleeves/dowells?
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Old 10-28-2008, 01:25 PM
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Default RE: OS gemeni 120 connecting rods

http://www3.towerhobbies.com/cgi-bin...?&I=LXCT66&P=Z
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Old 10-28-2008, 08:01 PM
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Default RE: OS gemeni 120 connecting rods

Here is the part number for the nut and washer.

http://www3.towerhobbies.com/cgi-bin...?&I=LXCM05&P=V
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Old 10-30-2008, 01:48 PM
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Default RE: OS gemeni 120 connecting rods

Hello; Thanks for the help. Here's a picture of the engine. To this stage it spins pretty freely, no binding or tight spots. It's the end that goes into the head, that I need the line nut for, I have the carb to pipe stuff. I'm thinking that the dowell is a spacer for the rocker shaft, which wasn't installed.
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Old 10-30-2008, 09:55 PM
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Default RE: OS gemeni 120 connecting rods

The dowels go on the plate that bolts to the back of the engine. The nuts for the pipe are the same size for the exhaust and the intake (pretty sure). Try one and see.
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