Has anyone had any success making funtional rotary couplers for coal cars? I tried a few things but couldn't come up with anything reliable. The best I could do was more of a drawbar, but they pulled off center and I got derailments.
I would think a dummy coupler welded to a plastic rod that would be flared out inside the coupler box to hold it in place also with a spring in place to hold the coupler from dipping in the box. Big thing I see would be the side to side action of the coupler being absent possibly on body mounts. Might work on truck mounts though. Then again if one could get a thin enough rod, yet with enough strength, one could have the side to side action of the regular coupler.
I think its possible. Here's my thoughts, FWIW. 1) Your basic prototype to tinker on would be the Caboose Industries short-shank 'unimate' coupler, one solid piece with a T-type shank. You can make a lot of mistakes without a lot of money in tinkering. 2) Don't get fancy. Try a truck mount box, roller-bearing truck, probably not MT. Look at some of the old-school stuff to tinker on. 3) I'd try something stupid-simple, try a wire brad through a piece brass sheet right into the dummy coupler knuckle. I'd think you'd have to be metal-to-metal rotating surfaces to hold up to the rotation and shock loads. 4) Remember only the coupler on the painted end rotates. So only one coupler is nearly 'fixed', maybe only one coupler needs to be truck mounted? The other could be body mounted? I don't know, just trying to think out of the box here.
Has anyone tried welding a coupler? I assume styrene cement won't work on the coupler plastic (delrin?). It's that part where you have to flare the end inside the coupler box that I couldn't do. The flare needs to be perfectly symetrical or it pulls to the side. Goes thru the dumper just fine but does not go down the track so well. Best I did was found a Plastruct square stock that happens to snap fit into a Rapido coupler box if you cut a short length (about a cube). Cutting it perfectly square turns out to be a big issue. The stock has a round hole thru it. I inserted a steel pin into one, added a black bead from the craft store as a coulpler-sized spacer, and then added the other cube. I bent the pin 90 degrees to secure it (the flare) and cut off the rest. There is a lot of wiggle because the pin is much smaller than the hole, but basically you have two cubes permanently connected. Then snapped the now-joined cubes into the trucks and then the trucks went on the cars. Any more than four cars eventually derailed. Worked great in the dumper, just not on the track. The problem was the bent pin pulls to the side. There has to be a better flare that can go right angled to the pin. Thought about threaded rod and nuts but couldn't find any small enough.
Another brief flare up in the old gray cells. Craft beads come in different sizes so maybe a short link of wire and a craft bead at either end. As long as the bead fits in the coupler box you should have perfect 360 rotation and the side to side play needed on the track. They are fairly cheap at some place like Micheals and maybe even at Walmart. As long as you can put up with the visual of a round rod between cars should work.
This would be a project for Shapeways but what about a T-shank coupler that the top of the T is round rather that rectangular. Perhaps if the circle was the right size it would be a drop-in for Rapido with a nub for the centering spring. To ease rotation the shaft between the knuckle and retainer would be round. This design would work for the one piece coupler socket. The two piece mounts would have to have a slot for the circle to poke through. To make it operational the knuckle would be like a McHenry. For semi operation couplers the design would be similar to a two piece Kato 11-702. They would not be molded in FUD but their black vinyl material.
Wow, the thread came back! Here is my best attempt: I found styrene square stock that press fits into Rapido coupler pockets if you cut it short enough. The stock has a round hole. I cut them into square cubes to fit the coupler pockets. Getting cuts square is a challenge. My drawbar is a metal pin. I use small black beads as spacers (representing the couplers). I thread onto the pin in turn a coupler cube, two beads, and another coupler cube. Here is the catch: I bend the pin 90 degrees (hah!) to retain it the the second cube. Then I cut off the end of the pin. Snap the cubes into two truck-mounted couplers, and now I have two trucks connected to eachother and swiveling. Then i lay a few coal gons on their backs, snap in the trucks, and voila! Except... things derail just pulling a short train forward. The pin is quite loose in the holes. I think what is happening is the bend used to retain it in the second cube. Depending on the orientation it is probably pulling up, down, or sideways at all times. Will follow up with pics.
I think you're overthinking a little bit. All you need to do is to take any shanked n scale coupler and cut the munting hole end of it off. File the shank roughly round enough, drill a hole in a small styrene block the same diameter as your new shank, shoveit all the way through, then superglue a Washer onto your shank on the other side to keep it from pulling back through. And at that, you may want to gowith something a little stronger,like Gorilla glue. Just don't glue the whole assembly to the styrene block like I'd be doing. You might need to make a swingarm as well, by securing the styrene box to a rod (might want to make that out of brass or something stiffer) that mounts a little farther back on the car. If you can position it right, and you may need to support the swing arm someplace, a swingarm around the truck bolster would not be a bad place to start. And if that sounds like a lot of work, it really isn't. You only need a rotary coupler on one end of each car. Sergent Engineering makes rotaries in Ho and while decent, they too are radius hogs on curves. Some people have had luck mounting them without tightening the screws all the way, so that they'll turn and pivot some.
Pics as promised... Assembled rotary coupler from the top. The one on the left has the bent end of the pin.: As mounted on cars. Note: here I am pulling the cars away from eachother. Clearly the trucks are pulled sideways, the fatal flaw of this design. The head of the pin is on the right this time. And finally in actual use. Needs flat black paint here... but no need to worry about the looks if it isn't reliable.
Here's the attempts that did not work. With t-shanks the rapido boxes have a detent that the tees go into. Cutting down the T-shank made them fall out of rapido mounts. Seems if you cut enough off to get rotation, it no longers stays in the box. Assembling something with glue is a lot harder than it sounds. Too tiny, you get glue in places you shouldn't. And nothing that I glued to the shank stayed there very long. Maybe I'll give it another stab. Best would be find a way to put detent on the pin that keeps the pin square to the coupler. I wonder if I can drill a centered and squared pin-size hole on the back of a t-shank and run the pin thru a cube...
My biggest question is why? Rotary dumpers are located inside buildings, so when the cars are dumped, you wouldn't see it, unless you make a roofless or sideless building. And I see these adding more headache to normal operations than it would be worth for a few minutes of dumping action...just me. All my "rotary" dumped cars use standard couplers, as I'm not going to try to model the dumping actions.
Ok, I have a lame idea. Get a truck with a rapido coupler. Remove coupler and spring. Cut a small flat piece of plastic in a rectangular shape that would fit in the draft gear box of the truck. Drill a hole just big enough for a microtrain screw to go through. Take a Unimate and cut the pin off the back and drill and tap the back so the microtrain screw will fit in. Put it together and install in draft gear box. Ok, I havent tried it myself. I'm heading to the trainroom for a try.....
Here it is. It works. Not the greatest idea Ive ever seen but here goes. I cut a little square of plastic. drill hole in middle for a microtrains screw to go through. Remove rapido coupler and spring and cut of shank that spring fits on so the back of the box is flat. Cut off sides of box so square piece of plastic can be glued in box. Cut off shank on Unimate coupler. Cut a short length of square bar of plastic and drill hole and tap for microtrain screw. Cut microtrain screw in half. Run screw through plastic square with hole into square shaft with tapped hole until just before snug. This will alow square to pivot. Glue into back of draft gear. Glue Unimate knuckle to square shaft. I used a liberal amount of ACC to do this. Here are pix.
we have a WINNAH! And not only that, but the coupler's normal plY should still give you quite a bit of swing for turning.
The same reason somebody decided to jump out of a perfectly good airplane with nylon sheets in a backpack. Because we can.
Dude, you're talking to a guy who builds Sergent Couplers in HO. Those being a two piece couler with a magnetic ball bearing you have to get inside without gluing eother the ball bearing or the knuckle it locks shut to the coupler housing, the jig, or your finger. I know your pain, believe me.
Another failure at a reliable drawbar, this one involving two pins, very tiny brass tubing, a crimping tool, and the usual frustration of tiny parts and big fat fingers. The good news is success with a rotary coupler! Based on oldrk's idea of a backer board, but I don't trust a drop of ACC to hold a train together in tension. I got something that puts the tension on the coupler tee, not an ACC joint. I used a long shank unimate coupler and a section of 1/8 plastruct ABS square tube - the gray stuff with the round hole. The hole is perfectly centered and square and fits the coupler pocket, and that is too good to pass up. I cut a slot in the side of the cube thru which I could insert the coupler into the hole. I whittled away parts of the coupler so it would spin in the hole. The tee is not a tee anymore, but it is big enough that it can't pull thru the hole. There is a mismatch on the height of the coupler but it pulled 12 trailing cars no problem. I ordered some more unimate couplers, including short shanks for the fixed ends. I can send pics of the next one if anyone is interested. I only have to make about 24 more of them.
Ike, regarding the "why a rotary coupler" question, I have a rotary dumper that needs them. It does model the dumping action. The cars get loaded by a working flood loader too. This is for the modern bit - there is also an old school mine and dumper with a kickback that requires uncoupling each car to dump it. That dumper is how I got sucked into this coal business - the kickback is like a roller coaster and I couldn't pass up putting one on my layout.
