Metal vs. Plastic Gearboxes for Kadees

I agree with the above reply, however I use the plastic gearboxes on locomotives/ tenders to insulate from the middle rail. I have had a few little mishaps where a low trip pin or a slightly raised middle rail contacted for a short, the plastic box has eliminated any worry. 

To prevent shorts, it as been a safe practice to use metal boxes on plastic cars and plastic boxes on metal cars. The coupler themselves for durability use metal, for ease of operation use plastic.   I have pulled an amazing amount of cars with all plastic Kadees.

It took 2-railers decades to get Kadee to put metal couplers and plastic boxes together.  The boxes never fail, they completely insulate, and are no more obvious than wheelset insulation.  If 3-railers buy them it reinforces Kadee's choice to offer them that way.  Please do.  You have no idea how important this is for 2-rail.

bob2 posted:

It took 2-railers decades to get Kadee to put metal couplers and plastic boxes together.  The boxes never fail, they completely insulate, and are no more obvious than wheelset insulation.  If 3-railers buy them it reinforces Kadee's choice to offer them that way.  Please do.  You have no idea how important this is for 2-rail.

Completely agree. 

However, on the issue of durability, I've never had any of the plastic couplers or boxes fail in any way.

I use metal where possible, as mentioned above.  I do like the plastic gearboxes in places where I need to cutoff the rear portion of the gearbox for clearance, such as with a lot of MTH locomotives unless you want to cutoff the loop on the truck block instead?   Just easier for me to use clippers on plastic gearbox vs dremel with cutoff wheel on metal gearbox.  As noted, I've never had a failure of a plastic gearbox or plastic Kadee coupler, so it's really your personal choice.   

I can fully appreciate why the 2-Rail modelers (both in HO and O) like/need the plastic gear box. However, in my experience when using just the center and rear mounting holes in the plastic gear box, they tend to warp when rightening the mounting screws good & tight. Thus, I use ONLY the metal Kadee gear boxes.

Never had a issue with hundreds of cars unless they hit the floor but then it's Ebay time.

Train6666 posted:

Never had a issue with hundreds of cars unless they hit the floor but then it's Ebay time.

OK, never had an issue with WHAT? The plastic gear box warping when tightening mounting screws?

Hot Water posted:

Train6666 posted:

Never had a issue with hundreds of cars unless they hit the floor but then it's Ebay time.

OK, never had an issue with WHAT? The plastic gear box warping when tightening mounting screws?

All the above in G Little bit in O maybe 40 cars 2 rail.

I am surprised  you can tighten the screws through the boxes so tight to warp them without stripping out the threads in the carbody!

prrjim posted:

I am surprised  you can tighten the screws through the boxes so tight to warp them without stripping out the threads in the carbody!

By ever so slightly reaming the center hole in the metal Kadee gear box, a 2-56 machine screw will fit through that hole. Drilling the proper hole in the under frame, and then taping to 2-56, one can tighten that screw pretty darn tight, which warps the plastic cover & gear box assembly.

My experience shows that if you over tighten the plastic gear boxes the coupler freezes inside due to pressure. Metal boxes are very nice. I use both. Plastic on my locos, both on my freight cars. However, I am pretty much sold on Kadee's new 740 series couplers.  These are as good as it can get for sure. 

I only use metal boxes. Tried plastic, didnt like them. Too much flex preventing the coupler from swinging side to side freely. I get the 2R rail shorting issue, but for 3R...metal all the way, no doubt about it. 

I had one short out on the third rail when it derailed. I prefer the plastic 800 series couplers only because they work better. The new 740 series look great ! and the metal ones are strong !!  I just find the plastic boxes with plastic couplers couple and uncouple a lot easier, with the magnets and the pick. However 95% of my couplers are the new 740 series all metal.

Clem  

I like the metal, because I’m constantly having to modify them to fit the location, especially on diesels. But on my motive power I trim the pin anyway, so I can see why plastic would be important for 3rd rail isolation. 

-Mario

I prefer metal, but use plastic boxes on brass cars. The plastic box insulates the car from the metal couplers. The mounting screw provides the strength that prevents misalignment of the coupler under load. Over-tightening the box will inhibit coupler movement, though, so be judicious in tightening things down. Kadee 806 and 743's only come with plastic boxes.