Hi, Howard,
I was curious about your dilemma so I pried one of my Broadway cars apart to see what your solution could be. I run on slightly broader curves and the Broadway cars don't give me any problems.
You have to carefully release the tabs — I used a very small, flat blade screw driver — that lock in the "carrier" to the car floor, which retains the plastic swing bracket. The coupler that fits into this swing bracket is either a genuine Kadee #5 or a very close "clone"
IMG_9492_fix by Edmund, on Flickr
As far as I know the only replacement for a #5 Kadee with a longer shank is the Kadee #26 or #36 (same coupler, different draft gear) which is actually a plastic coupler but much stronger than the McHenry type plastic couplers.
https://kadee.com/htmbord/page26.htm
Kadee also has a "Scale Whisker" long shank coupler but I can't be too sure of the fit. You would have to cut off the whiskers, of course. Scale head couplers are less forgiving of track irregularities, too.
Good Luck, Ed
Haven't had the Bluebird cars, but understand they are very similar to the Zephyr cars. You're lucky if they do work on 22" as most consider them and simolar cars as eeding a 24" min R. A longer shanked coupler could make 22" more reliable.
18" R, though? I think you're going to find that it will take much more than longer shank couplers to solve that. There's the swing of the trucks and lots of potentially interfering underbody details to deal with. Also, side skirting could need to be cut away. Full length cars in 18" curves will also look pretty ugly, even if you hack away enough stuff underneath to make it work.
Mike Lehman
Urbana, IL
Howard, go to the Kadee site and ask Sam the Kadee Answer Man to help you out. Send him an email via the contacts button on the site. The Kadee site says you will get a response within 24 hours. 2 to 3 hours is more like it. Kadee and Sam are wonderful.
Bear "It's all about having fun."
Could you just glue a thin sheet of plastic over the diaphragms so that they just slide against each other without catching while going through curves?
Dave
Just be glad you don't have to press "2" for English.
http://www.youtube.com/watch?v=zQ_ALEdDUB8
http://www.youtube.com/watch?v=6hqFS1GZL4s
http://s73.photobucket.com/user/steemtrayn/media/MovingcoalontheDCM.mp4.html?sort=3&o=27