I've had a few queries regarding the rotary couplers used on the unit train seen in the youtube link on my sig and the thread in the Moving Coal thread in the Animations forum here:
https://www.therailwire.net/forum/index.php?topic=50633.0The challenge with any rotary coupler is not so much the obvious getting it to rotate as is getting it to reliably work during normal operation without derailing your train. I cheat. Most of mine are not couplers at all, they are drawbars.
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To make a couplers I start with a random Rapido couplered truck. Twist out and remove the knuckle, the spring, and cut off the post inside the coupler that fixes the spring in place. The white plastic is a piece of 1/8" Plastruct square tube, cut square (key skill) to fit in a coupler pocket and slotted to admit the coupler shank. Coupler knuckles are FVM-51020 Fox Valley long shank Unimate couplers carved to permit rotation.
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I had a low success rate making these, only two didn't cause derails. Most pulled to one side or the other, maybe it was the particular brand of Rapido truck. As an alternative you can make a whole unit train with just rotary drawbars, but putting a long string of connected cars on the rails (see below) is painful. These rotaries connect to a normal Micro Trains truck on the adjoining car. The adjoining car's coupler keeps them oriented properly.
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Drawbars are easier and here is the easiest way to build one. I no longer use the rubber bands seen in the video. I use two Micro Trains short shank roller bearing trucks and a fishing swivel. The fishing swivel is, I believe, a number 4 (not 4/0!) size Rolling Barrel swivel - got an assortment from Amazon. Slide the coupler box cover toward the bolster to remove, put the swivel hoop over the coupler's center boss, and put the cover back on. Repeat on the other end of the swivel. I save the MTL innards, watch out for that spring! I used Oily black paint on the barrels.
I don't back up my unit train in normal operation but I've done it and didn't see any issues.
A word about the Johnstown Coalporters in the unit train. One set is from E&C Shops. These are lightweight but look great and operate well. According to Spookshow the same cars were sold under LBF and Huberts branding.
http://www.spookshow.net/freight/freight.php?bathtub=2&rtr=16&plastic=18&sort1=3&sort2=2&sort3=4&compress=1&Submit=Submit The rest are Deluxe Innovations cars. These are weighted but the interiors are ugly and they allow coal to leak out. Both occasionally show up on eBay but today I see similar gons from Kato that look wonderful, already have MTL trucks, have the rotary end paint, and are aluminum. I can't find prototype photos of black Coalporters.
To connect, say, five cars you need 4 pairs of trucks attached by drawbar with out-of-the-box trucks at either end. If you get a working coupler then that replaces the truck at one end and you can add more drawbarred cars after that. All my cars have the brake wheel on the leading end to avoid interference with the dumper's pusher arm. The process for railing a train is to line them up upside down along the track with the brake wheels the same direction. Connect the coupler pairs to the cars, then starting at one end turn one car upright, the next on its side, rail the first one, turn the next car the rest of the way and the car after it on its side while holding the first one down... anyway, you won't want to remove the train from your layout ever again once you do this.
