Rapido (Coupler) retrofit help

[reinhardtjh]

I know this is an odd request and probably goes against the grain of many, but I'm looking to retrofit an Atlas S2 with rapido couplers.  This is for a good friend who is still in the dark ages with what he likes to call the N Scale "Industry standard" coupler. 

Please, no suggestions of a converter car, this is a yard switcher and need bi-directional use of the coupler and having an extra car on front and back won't do in his yard.

At first I thought it would be easy - just cut the coupler and box off a couple of trucks with the couplers molded on, but all of them that I've found wouldn't work.  The couple box isn't suited to either screwing or gluing on the the frame.  That's assuming that body mounting the rapido would even work. I hope it does, I don't even want to contemplate making some sort of truck mounted version.   

Does anyone know of a rapido coupler available in a solid top box that could be glued on?  Or am I looking at building the coupler box from scratch?  Ideas are welcome.

[Nato]

        Most of the current Bachmann cars and all new locomotives come with"reverse engineering" a pair of Rapido couplers designed to fit in the Bachmann knuckle coupler boxes, if I' am recalling correctly  these do not have T Shank ends, but ends like a Mc Henry coupler which might work in the Atlas coupler boxe's. Nate Goodman (Nato).

[Mark5]

Atlas had a Rapido coupler that fit their locos (when they first switched to Accumates they included rapidos in the box). I would think these would work - assuming that the S-2 has the standard Atlas loco coupler box.

Mark

[nkalanaga]

As far as I know nobody ever made an aftermarket Rapido coupler and box.  If you are comfortable with scratchbuilding in styrene it shouldn't be too hard to make one, although getting the dimensions exactly right could take some experimenting.  The box itself isn't that complicated, so here's how I'd do it, for a first try.

Start with a styrene sheet, 0.02 inch or so thick.

Measure the height of the T portion of the shank, and find the closest strip styrene width to that, making sure it's at least that wide.  It can always be sanded down later if needed.

Cut two pieces for the front, wider than needed to fit the width of the T, while leaving a gap in the center for the shank.  Glue these to the sheet, using a metal ruler to make sure they're straight with each other.

Glue two strips to the sheet, perpendicular to the front, to form the sides.  This isn't required, and can be omitted of width is a critical factor.

Glue a rear piece, parallel to the front, spaced to very slightly compress the spring.  You don't want it tight, but it shouldn't be loose enough to fall out either.

Glue a couple blocks to the rear, on either side of the spring, so keep it centered.  Alternately, one could drill a hole and put a rod in the spring, as both methods were used by manufacturers.  The blocks are probably easier for an experimental setup.

After everything dries, trim the box from the sheet, and add a sheet styrene cover.

I would call the original sheet the top, since that way one can assemble the coupler upside down, and the pin won't be in the way.  It may be necessary to cut a notch in the top, but NOT the bottom, to allow the shank to pivot up far enough to couple properly.  That's a matter for experimentation.  The design seems simple enough, and certainly cheap enough, that the first few tries can be discarded if needed.

I wouldn't want to build enough to do a fleet of cars, but for one loco, it should be practical.

Going the other way, I've been building my own boxes for Accumates, for use on lowered tank cars and as cushion underframe extended couplers.  They're not hard to do either. 

[reinhardtjh]

Thanks for the suggestions!  Fortunately, Nato had the winner.  I hadn't checked the rapidos in my latest Bachmann 2-8-4's but they were the right type - solid shank with a hole and centering whiskers on each side.  I knew the 2-8-0's had a coupler with two prongs on it that wouldn't work and the 70-tonners had one with a hole but no whiskers - they were designed to work with a flat metal spring up against the back.  So with the ones from the 2-8-4's all I had to do was enlarge the hole a tad so it slid freely on the center post and screw the Atlas coupler box back on with the Bachmann rapidos inside and all is well.  Well, almost. I had to clip the uncoupling prong off the bottom to clear the footboards as the shank on the rapidos are just a little short.  Luckily they still couple despite the shortness.