we need new topics so here's one "couplers"

Kadees.  I have converted about 65% of my rolling stock already.  Scale size, super easy to couple, well worth the effort to convert.

O does not have the variety HO has.....but I bought a good size box of OOP Walthers die cast solid non-operating couplers. I use them in scratchbuilding and re-fit of AHM and/or Roco plastic O cars. These solid couplers NEVER uncouple! 

Nice scale size operating couplers like a HO Kadee or other would be good....but don't think there is enough interest converting as we do not have a universal box like HO has adapted.

Kadee, Protocraft, San Juan, Precision Scale...etc.

Another option for unit trains or cars that you don't plan to uncouple...a drawbar made from Evergreen Scale Models or Plastruct strip styrene.  The February 1976 Model Railroader Magazine has photos and how to model them in N, HO and O scale.

Three Rail Scale Forum.

This Thread has a lot of information on O-scale  KD couplers and installation. (4 pages to date).

Copy of a post from that thread, that shows some of what is available in O-scale.  You should be able to link to the Kadee site for additional information.
Helpful diagrams from the Kadee site. A lot of information on this page. 
Added 745 and 746 diagrams. 4/3/13

Kadee 805

Kadee 806 short

Kadee 847 Underset shank. Coupler center and mounting height are the same.
Kadee 742 Overset shank Increases mounting height.

Kadee 745  Plastic #817 draft gear.

Kadee 746   Longer coupler shank noted.

Hard to believe that you are not aware of Kadee couplers!

I like zip ties!!!!!!!!!

stupid MTH couplers are

notorious for coming apart

when im not looking and the loco

speeds around the track and BAM!!!!!!!

The guys in the caboose don't like those

sudden jolts!!!

As I have close to "O" talent and mechanical skills, just how easy is it to change couplers? Most of my rolling stock is Lionel. Right now I am using zip ties. How do you determine the correct Kadee Coupler (745-745)

Just read the link Mike CT referenced.  Forget my question.

 Lionel cars are too difficult for the beginner to convert.  

Brent

I haven't had any of my MTH Rugged Rail or Atlas Industrial couplers come open, just Lionel ones.  And I've twist tied those as they reveal themselves.

There have been a number of previous posts where operators say they just glue Lionel style couplers shut.

I've seen a lot of stuff on the Kadees for O scale. My interest is in how you get them to uncouple? I have Atlas track with those buzz uncouplers for the thumbtacks. The ones that I haven't burned up work ok but they are a pain in general. With the Kadees is it the undertrack magnet like it is with HO?

Try a "Search" and read some of the other posts on this subject.

A lot of hobbyists just like the look of those giant couplers - same for the flanges and the center rail.  I personally understand that - I prefer the now non- standard .172 scale wheel for appearance, even though it is way too fat compared to scale wheels.

I run Kadees without problems.  The only scale couplers that give me no problems are the Lionel 700- series.  The rest get glued shut, and that includes the beautiful Clouser/Protocraft couplers.  Most of my rolling stock gets dummy scale couplers.

For those of you who have converted to "Body Mounted" Kadee couplers, tell everyone how small a radius of a curve they can be used on and how they work through those notorious esse curves.

Thats the only reason I don't even think about Kadee couplers.  I have 0-36 curves and therefore I cannot use them!  Even my outside line is 42 I think.

A little grinding away at the left & right side of the coupler journal opening will give you more flexibility with minimum radius.

I thought that Bob Delbridge already covered that on another thread, i.e. 042, with 40 foot cars,maybe? I have nothing under 072 and even body mounted Kadees work OK on my Golden Gate Depot 21" heavyweight passenger cars.

I have not had Lionel couplers come open on me, K-Line couplers on some lower price freight cars come open. Williams SD-45's and sometimes the F-7's will open their couplers when you don't want them to, so I added black nylon ties to keep them closed.

I am not going to change over Kadee couplers in O gauge. It would be too expensive for my collection.

Lee Fritz

36" radius (O-72) for everything I've run so far. This is everything from 34-foot PS2 covered hoppers to 89-foot trailer flats. No "S" curves, though (even with truck-mounted couplers, you shouldn't do it either.) The catch is that you can't put a 40-footer next to an 89-foot flat or 86-foot excess-height box car because of the distance between the pulling face and the truck bolster on the longer car will fight the shorter car.

In the video below, the hidden curve in the tunnel is 36" radius (O-72). This was the initial test run. The lead car has Atlas scale couplers on one end and a three-rail coupler on the rear as a transition flat for the others. The locomotives have Kadee 805's. Unfortunately, I didn't do a video with the other scale-wheeled/scale-coupler 89-foot flats I have, but they ran through the 36" radius curve in the tunnel just fine.