Rotary couplers

 

Right away, I realized I would need to figure out rotary couplers or the whole thing wouldn't work.  If I couldn't make couplers, there wasn't any reason to motorize the dumper.  About that time I found a page about a model of the Sommerset rotary dumper built by Doug Nagel.  On the page, he described how he modified Kadee couplers and I followed suit.  I was surprised when the first rotary coupler I made actually worked.

Here is a link to Jeff Shultz' interview with Doug in 2014:  https://www.youtube.com/watch?v=I51hynUQI9E

My process for making rotary couplers starts with a Kadee #5 coupler.  It is disassembled by removing the trip pin.  Next a hole is drilled down the center of the shank and the head of the coupler cut off.  A bug pin, intended for mounting insects for display, is inserted through the head and down the shank and when it emerges from the mounting hole bent perpendicular to the shank and cut off.  The head is now held firmly in place but can rotate.  The knuckle is put back in, the trip pin reinstalled and the knuckle spring seated back on its lugs.  I cut the trip pin down to about 1/4 inch to make removal and re-installation easier.  Unfortunately, writing the process is easier than actually doing it.  When doing several at a time each one averages less than 10 minutes and it is a direct replacement for a KD#5.

Here is the result.  You can see the cut just behind the head and the pin poking through where the coupler mounts.

The cars

When I started this project in 2003 or so, I had some Walthers Bethgons, E&C Bethgons and LBF AeroFlos, and have since added Intermountain and Athearn Bethgons as well as Walthers RD4 hoppers, Bethelehem 4000 CuFt hoppers and Pullman Standard PS3 4000CuFt gondolas.  Retrofitting a Walthers cars with rotary couplers was pretty straight forward but the E&C cars had other issues.  A string of E&C cars was noticeably shorter than an equal number of Walthers cars.  This wouldn't work, all the cars need to be exactly the same length or the indexer wouldn't accurately position them in the dumper.

I lined up two five car strings of Walthers cars on one track and E&C cars on a parallel track and measured the difference at the end car.  The difference was just over 0.60".  Since there were 10 couplers in 5 cars, each coupler needed to move just over .06" toward the end of the car.

The solution was to carefully remove the bolster/coupler assembly on the E&C cars and carve off the locating lugs on the draft gear.  That way it could move toward the end of the car.  A piece of .04x.06 styrene strip (just what I had available) at the end of the ridges representing the car's underframe moved the bolster to the correct position.  A liberal application of MEK welded it in place.  The truck mounting screw needed shortening so it didn't pop off the freshly attached bolster since the screw hole in the bolster and screw hole in the car no longer lined up and redrilling it would have it come through the endsheet.

Here's a completed modification:

Intermountain's version of the E&C/LBF car has the same issue except the fix is much more involved because Intermountain retooled the end detail, bolster and draft gear into one piece.  The end detail needs to be carefully removed from the bolster with a razor blade.  I managed to do it without loosing any blood or epidermal cells or destroying the parts.  Regluing the bolster to the car .06" closer to the ends of the car fixed the Intermountain car.

The Walthers Rotary Dumper

The Walthers Rotary Dumper can be assembled two ways, one for woodchip cars in their pulp and paper series of buildings and the second for the coal industry.  There are marks on various dumper kit parts to trim them down to make it fit coal gondolas.  I assembled it mostly as the directions instructed but varied on the clamp assemblies.  I used another motor to raise and lower the clamps because the cams in the kit don't have enough range to both clear the locomotives and then clamp the coal gondolas.

To make the dumper work, I used parts I had laying around including a motor from an old VCR, switches from a broken car stereo as well as some Evergreen strips and parts.  A few years later I rebuilt the clamp system with Burger King display parts I bought from a homeless guy and acrylic scraps from work.

In the end though the Walthers dumper just didn't work to empty coal cars loaded with walnut shells.  The shells got into the gears and into the clamps and I couldn't figure out a way to make them stay out.  Later I found out a club in Seattle had motorized their dumper only to have it fail after a few trains, it just ground itself up.

Loads

It took awhile to figure out what to use for coal.  I guess I've been good enough, I've never received any in my stocking at Christmas and there isn't much in north Idaho where I was living at the time.  I had a bag of Woodland scenics "coal" and it worked well but was cost prohibitive in trainload quantities.  My mom kept pet birds at the time and suggested crushed walnut shells, usually used in the bottom of the bird cages.  I ended up finding a 25lb box at Harbor Freight.  They were the finer of the two grades offered and were originally intended for media blasting when sand was too aggressive.

Golden brown coal isn't very convincing so I used black RIT fabric dye to make them look more like coal.  They came out with a sort of purple tint but looked much better so that is what I've used.  I used an old toaster oven to dry them in small batches after the dyeing process.  Next time I will also add some green to take out the purple.

A trainload of dyed walnut shell coal on the move;

Recently, I made the doors work on a Walthers hopper car.  They are held shut with very small magnets.  Surprisingly, the magnets were attracted to the dyed walnut shell coal.  Little pieces of coal stick to the magnets and keep the doors from shutting.  I tried the original brown shells and they are not magnetic so it is from the dyeing process.  I haven't figured that one out yet.

Indexer

The indexer is a machine that properly places the cars into the dumper.  It is easy to see why an indexer is needed.  By the time the end of the train is being dumped the locomotives can be about a mile away.  A mile of coal cars has many feet of slack and it would be very challenging and time consuming to use the locomotives to accurately locate the cars.  It is also easy to see how it wouldn't work well to have a car only partly in the dumper when it rotated.  

It took several hours of looking at photos of positioners to figure out how they work.  There at least two types.  One is cable driven, the carrier with the arm that engages the cars is moved back and forth by a large cable and has a driving motor toward one end.  The other is hydraulic and the carrier has a number of hydraulic motors that engage a rack along one side of the carrier's track.

There is a structure next to the indexer that holds the electric and hydraulic cables and lets them move with the carrier.

For visual interest, I chose the cable driven indexer.  I like the pulleys moving as the carrier pulls the cars along.  I found a 7x7 cable (7 bundles of 7 strands) that was only 1/32" diameter.  The rule of thumb for wire rope and pulleys is the diameter of the pulley should be more than 40 times the diameter of the wire rope.  That determined the size of the pulley should be 1.25" or about 9 feet in HO scale.  I didn't have any drawings but a 9 ft scale disc looked about right next to the cars.  I cheated it down to 8 feet and it looked a little better so built the pulleys to 8 feet diameter.  Here's a drone view with the cable in pink:

The indexer's cable is fixed in place on both ends, goes to a pulley on the carriage, then to a fixed pulley next to the anchor, around the driven pulleys, to the fixed pulley at the other end, back to the carriage and finally to the second anchor.  Pulling on the cable makes the loop of cable at one end shorter and pulls the carriage toward that end.  As it moves, the loop at the other end gets longer as the carriage moves away from it.

I turned the pulleys on a lathe and used styrene for the stiffening ribs on the face.  I had some ball bearing and knew there would be a fair bit of stress on the axle so fit the bearings into the pulleys.

I couldn't find a good photo of the the motor to pull the cable so I modeled it after a railcar mover I found online.  The one I built has the cable wound around two large drums and is driven by a gear motor.  The drums' axles also have ball bearings so tension on the mover cable doesn't bind it up.  I had some thin brass gears and added more reduction.  Due to the amount of gear reduction, the electrical current draw is the same if it is running empty or pulling the train with two locomotives sliding along at the head end.  Of course, after it was done I found a photo and what I built is totally different but works really well.  The wires go to the motor on the other side and drive the smaller gear that shows in the middle.

The model has a pulley and cable anchor mounted on a square of 1/16" thick steel at each end of the indexer installation.  The pulleys are the same as on the carrier and are mounted on ball bearings fitted to a two piece post I turned on the lathe and held together with a screw.  The anchor is 1/8" square brass tube but I fitted the top and back leg around a round tube bent into a 90 degree L.  That way I could push the cable through the horizontal top and out the hole in the bottom and hold it in place with a clamp under the layout.  The anchors are held in place with 0-80 hex head screws.

My indexer carriage isn't prototypical but fit the parts I had and does the job it needs to do.  The main part is a linear bearing I found at a surplus store called Surplus Gizmos.  I machined a piece of 3/8 thick piece of aluminum to fit over the carriage on the bearing.  It also holds the mover arm and pulleys.

I machined the mover arm from a piece of aluminum.  A drawing showing the relationships between all the parts was very helpful in determining the dimensions.  I made a plan view and an elevation from the end.  The elevation showed the plywood layout top, track with roadbed and the car as well as the indexer and linear bearing on a base.

The arm is moved by a small gear motor from ebay and mounted in a box on top of the carriage.  I made a split ring from a piece of brass tubing to fit on the motor shaft.  The two parts of the ring are connected to a third ring with diodes.  That way the electricity to the motor can be sent via a wiper, made from phosphor bronze wire, through the rings and the diodes limit the travel.

In the background is the rack to hold the wires as the carriage moves.  It doesn't work yet, I think its little trolleys (not shown) need actual wheels or some other way to move along the beam.

If I try to build a more prototypical carriage I will build a track like Mad Doc and Nickel Queen did on their indexer.  It can be seen in this thread: https://model-railroad-hobbyist.com/node/31428?page=1

Can't wait to see this in motion

C'mon Paul, don't keep us in suspense.

New Rotary Dumper

I have been collecting online coal handling machinery photos since I started this project about 2003.  I couldn't find any dumpers that looked like the Walthers model.  Not that it looked bad, it just didn't look like any photos I could find.  It also looked too big.  I scaled several photos, using the track gauge as a known dimension, and consistently calculated the single car dumper to be 30ft diameter which also matched what I was able to measure on the dumpers I found on Google maps.  Walthers dumper measures 38 ft diameter. 

This is a comparison of the end rings for the dumper I built with a Walthers end ring.

I started a Autodesk Inventor digital model of a dumper and played with the dimensions a little and decided I would build one 32ft diameter.  I carefully mocked up the opening matching the digital drawing to make sure the locomotives could fit through.  A hi-cube box car will fit through the Walthers dumper but the tolerances are tighter with one in scale. 

I actually started building the dumper by making the trunnions that support the barrel.  They are based on a patent drawing I found online and the parts were cut with a water jet.  They each have two ball bearings that sit in a frame held by a steel base made of parts brazed together.  I added some plastic detail to simulate the structural details.  Here is a photo illustrating the progression from flat sheet to finished part.

I figured out how to draw gears in Inventor and supposedly a water jet can compensate for the wedge shape kerf of the water steam to actually cut working gears.  It turns out it mostly does, leaving only the slightest angle on the 1/4" aluminum end rings and Delrin drive gears.  Turning the bevel on drive gears the opposite direction works just fine.

I left a triangle of material in the opening of each end so I could hold them in the lathe to machine the faces while leaving the rim a full 1/4" thick.  I machined off part of the gear with the ends held in a rotary table on the mill.  After the machining was done on the ends I cut out the extra material and filed the opening smooth.  It turned out I got a better finish on the outer edge using the rotary table so here is a photo of the end ring on the mill.

To complete the barrel frame, I cut three 3/8" round steel bars the same length and drilled and taped 4-40 holes in the ends.  When attached to the end rings, most of the barrel structure was finished.  The platen is styrene and built to fit.  The only critical dimension was the height.  The barrel  needs to rotate about the coupler so the rotary couplers stay connected.  I used dimensions from my digital drawing to work out the height, taking into account the code 83 rail on top.

I was trying to make the dumper barrel as heavy as possible so the force required to turn it wouldn't make it skip teeth on the drive gear.  To that end I made the spill wall from two pieces of 1/8th by 1/2 inch steel and the surface the cars rest on from 1/32nd sheet.  The extra weight also helped balance the two bars and clamps on the opposite side.  The truss work was laser cut from styrene and built up with .030 x .156" Evergreen strip.

Rotary dumper clamps

The clamps that hold the car are an integral part of the rotary dumper because, well, gravity.  There are several styles of clamps to hold the cars in place while the dumper is inverted but they are of two types, mechanical and hydraulic.  The hydraulic uses hydraulic rams to move the clamps and apply pressure and mechanical use springs and gravity.  

The hydraulic connections to the rotating dumper as well as the challenge of mini hydraulic cylinders and pumps complicate modeling hydraulic clamps.  For simplicity and visual interest, I chose mechanical clamps. They make the dumper self contained with no connections to the base.  They use gravity to lower the clamps and a spring actuated brake mechanism to lock them in place.

In the images, I kept seeing pulleys and cable or chain.  It took a long time to figure out how it worked because pictures of rotary dumpers are taken from only a few angles and some parts are hidden behind other parts.  Eventually, I found a video online and, with another online series of photos, I figured it out.  

Here are most of the parts that make up one of the clamps:

Here is a photo of the end of my dumper with the end ring removed so the assembled parts are visible:

The clamp that moves to hold the cars in place is tinted green.  The brake and brake arm are red.  The cable connecting everything is shown in pink.  In the photo the clamp is in its lowest position as it would be to hold a car in place.  As it returns upright, a post adjacent to the dumper catches the red brake arm and raises it, releasing the brake.  As the dumper continues to upright itself, the green clamp arm lands on another post raising it up and letting the car be moved.  

Here is a close up of the brake arm.  This is version 2.3.  It is the third attempt at the second design.  It is another example of after it was built I know how I should have done it.  The arm that lifts the car clamps should be a little longer and offset to one side instead of centered.  That would allow the brake arm to be offset to the other side.  As built, the challenge was to get the brake arm to clear the car clamp lifting post and still let the spring rest on the brake arm.  It the photo above, it still has version 2.1 and the spring doesn't sit well.

The cable is fixed at both ends.  As the clamp raises, the loop of cable around the first pulley on the left gets shorter while the part through the clamp on the right gets longer.  As it moves it turns the pulley at the brake.  As the dumper moves to start dumping the brake engages and doesn't allow the clamp to move.  Before the brake engages, the dumper tips enough to settle the car against the spill wall before it is clamped in place, just like the prototype.  If it clamped down on the car when it was still upright, a prototype car would be damaged as the 110 tons of coal would need to be supported by only the car side as it rotates. 

The Dumper Base

The base for the rotary dumper is a box that sits in the ground.  In real life, it has a grate in the bottom and under that a conveyor to move the dumped coal to a stockpile.  Some dumpers have a hammer mill just above the grate to break up frozen or larger chunks that don't go through the grate.  The hammer mill is a rotating bar with small pivoting hammers and moves on a track back and forth the length of the dumper pit.

The base also has supports for the trunnions and posts for the clamps.  The height of the trunnions and position of the posts are really the only critical dimensions.  The trunnions need to hold the track on the dumper the same height as the approach tracks and the posts need to be the right height to release the clamp brake and lift the clamp at the correct time. Here is a  photo that shows the ramp that releases the brake as well as the post that lifts the clamp and one of the drive gears.  The cars dump to the right in this photo.

My dumper is motorized with a gear motor from a 'Billy Bass' singing fish.  There was a contest at work to see what could be made with such a thing and afterward I found a couple extra motors in the trash.  It works well because it has a square output shaft that sleeved into square K&S tubing.  The square tubing has a piece of 1/8 steel rod pressed into it.  The steel rod has the water jet cut drive gears on it and turns in styrene brackets sleeved with K&S tubing.  

The whole rotary dumper facility is mounted on a module 12 inches wide and 42 inches long.  I made a bracket underneath to hold a plastic storage tub to collect dumped coal.  It is large enough to hold at least 30 car loads.

Controls

For now I have four DPDT switches for various functions, the barrel, indexer trolley, indexer arm and the brake that is under development.  Each function has limit switches to stop the motion at the appropriate spot.  Some care is needed since there isn't appropriate electrical interlocking yet.  For example, if the indexer is moving cars, I could still rotate the barrel which wouldn't end well.

Scenery

It is an industrial site so it is kept fairly clean and organized and well lit.  Someday the model might have that as well.  Currently it has some brown paint representing dirt/gravel areas and gray representing concrete.  I haven't decided if the dumper will be enclosed in a building like the Sommerset model but most dumpers seem to be in some sort of structure.  There should also be some dust abatement.  Real dumpers use a fine water mist or vacuum extraction or a combination.  The vacuum facilities are more interesting to look at and the water could be messy on a module so I'll probably go with a vacuum dust collector.

Still to do

The dumper and indexer both work and I can empty those trains I filled years ago.  I'm currently in the process of painting the dumper which involves a fair bit of disassembly, not exactly a one step forward, two steps back thing but close.  The end rings will get a layer of detail to match the stiffening ribs on a prototype Heyl Patterson dumper.  There is some fine tuning to make it work more smoothly and then general site detailing which will be the control shack, more safety railing, lighting.  I'll post updates as they occur.

Control Room mockup

Here is the currently winning design mockup for the control room for the rotary dumper/ indexer.  It is shown rendered in cereal box. Probably Oatmeal Squares.  Obviously, the stairs have not been installed yet but will most likely go down to the right and land behind the yellow indexer pulley.  There has been some consideration of the exit and stairs being moved to the back of the building farther away from the tracks.

The crossover bridge allowing personnel to access the other side of the tracks while a train is being dumped is undecided. It makes sense for it to continue from the platform in front of the door but would block the operator's view of the indexer.  Theoretically, a person could go under the tracks through the upper level of the dump pit access to get to the other side.

Short update

I've added a little more paint and terra forming to the site and have been trying to figure out how to make two bar safety railing so the little guys don't fall into the pit.  Awhile ago I made another video that shows all the parts working:

Yesterday, the air in western Oregon was so bad we were sent home from work so I decided to get the arm on the indexer working better.  It is driven with a small N20 size gear motor (I don't remember what reduction) and I didn't glue things because occasionally the arm doesn't land in the gap between the coupler head and draft gear and would bind.  With things just pressed together, it could move but would also occasionally fall apart.

The solution was to mount the lever on the motor to a piece of tubing.  The tube has a slit cut in it.  A spring mounted through the slit into the hub allows the lever to move but keeps it from falling off.  The other end of the spring holds the lever in the correct position but allows it to pivot if something jams.  Here it is installed:

In the following photo, the individual pieces are visible.  From the left, there is the lever mounted on a piece of tubing with a slit in it.  Next is the spring fit in the slot.  The spring shown is the version before the one in the previous photo.  To the right of that is the pickup ring part of the limit switch.  The pick up wiper is visible in the above photo.  The orange and white thing is one of two steering diodes.  They are oriented opposite directions and connect the 'up' and 'down' traces to the pickup ring. The increase in diameter holds the two traces for the up and down wipers.  When the wiper gets to the end of the rotation, it ends up on the trace for the other direction and the motor stops.  The square part on the right has a set screw to mount it to the motor shaft.

Here is a photo with the gear motor in place but with out the above part attached.  The wipers can be seen near the output shaft.  The two closest wipers ride on the up and down rings and the one slightly outside the cover is connected to the motor.

This is a very small and hard to explain piece but is important to making the indexer work and I'm happy to finally have it done and working well.  

2 bar safety rail....

Plastruct makes it... or you can use the same method I use for making Chain Link Fencing and simply don't add the fence.

N scale Chain Link Fence tutorial

Amazing work. Years ago

Amazing work. Years ago when the original Walthers dumper was off the market Walthers was considering making their new version operable. They soon discovered that it needed to be completely designed and that it would be what they determined to be too expensive as an operating accessory. That's a shame. -------  Ken 

It's always a real mechanical

It's always a real mechanical challenge to build working machine in scale like this one.

Ingeniousity is really a necessity when starting such project.

I have begun to build a high lift rotary dumper in N scale; work is now stopped on the machinery since I emigrate to Canada and didn't have many time to work on  any layout projects since I live here.

Such projects are really interesting and the acces to CAD and CNC machine are a very big help to build such things

Keep going, I wait for update,

https://forum.mrhmag.com/post/a-rotary-coal-dumper-in-n-scale-from-an-old-kit-of-45-years-old-12207571

https://forum.mrhmag.com/post/a-big-project-a-working-high-lift-rotary-coal-dumper-in-nscale-12199359 ( Unfortunately, many pictures are off since Photobucket play me a sad joke….)

_

barr_ceo Thanks for the suggestions.  I thought about the Plastruct but am stuck on the square cross section and short height.  The chain link fence jig is a good idea but the thought of precisely fitting the in-between horizontal pieces so it all lays on the same plane gives me pause.

Ken, I did build one of the Walthers kits and have another unassembled one.  I got it to move but never really got it to work well.  There was so much friction and couldn't figure out a way to keep 'coal' out of the gears. 

Marc, I'm looking forward to seeing you high lift dumper working, your metal working is impressive and even more so in N scale.

I appreciate the challenges with gravity that doesn't scale.  I want the indexer to have a festoon cable next to it but a cable heavy enough to hang is too stiff.  Then there is the challenge of the little carriages.  Even things like the walnut shell coal interacting with static electricity can make for interesting observations, things like coal jumping out of the cars.

Maybe I'll switch to 1/8 scale live steam and hang out with ChiloquinRuss.  But then there are wildfires, a little too much reality.

Paul

Adding weight to have gravity and inertia

Inertia is a big challenge for scale.

And we need inertia and gravity to achieve prototypical movement in scale.

My answer is weight to create this effect, as much as I could put, the more, the best achievement I can obtain.

I even go over half kilo, to achieve such effect in N scale; don't be afraid to have very heavy moving parts, this is in any case better.

When I studied the how to do for my High lift, it become evident inertia and weight was needed to make it run better.

The answer was to make parts in heaviest way and put weight everywhere were possible.

Some of the brass tube I use for the clamp, very tiny,1x1mm were filled with lead, liquid lead to make them heavier, because naturally they didn't have enough weight to slide inside the guide and positioning a spring was not possible.

Many parts of the lift are filled with tungsten, in fact the lift itself in my N scale model  weight this way around 850 grams, this allow very slow motion and a constantly tension of the scaled cable which make the motion of the lift well better.

The counterweight of the clamp for the cars  works like the real thing; it was important they all weight the same, the brass box which simulate the counterweight were loaded also with tungsten with extremely care to be sure to have the exact same weight and a good balance of the pushing action on the cars.

Before I stop work on the model because of my move to Canada, I was in the way to invent a brake system for the cars which go out of the lift when empty, because they were rocket cars even in an 0.5% grade, again small counterweight work as mover of small rails which pinch a little the wheels of the cars; very difficult to manage because of N scale, of course.

Inertia and gravity are often forget elements in moving models, but they are needed to achieve natural movements

This is probably the reason some plastic model didn't work properly.

barr_ceo Thanks for the

Look at their N scale railings then...

For no more than you need, it's not that difficult. Use the technique of drawing your pattern then stretching double stick tape over it, applying the bits onto the tape and then soldering them, I've done a number of short sections and gates that way.

Prototypical?

I wonder if this ever happened in real life?  Just a photo, the rest is up to your imagination, to protect the innocent, of course.

Not cabooses...

But every once in a while a locomotive tries to go for a spin...

There's a reason why rotatory couplers all need to be facing the same direction.

Bridgetown RPM 2021 with it sceniced? No promises on my end with the Snow Dozer. 

Bridgetown

I've seen the photos of the Canadian National locomotive in the dumper at Prince Rupert.  I was curious so looked up the photos again and it seems there have been at least 3 incidents, CN 8022 at Prince Rupert, CN 8017 and CP 9624 at Roberts Bank.  I guess real couplers don't twist apart like KD#5s.

The Power Plant Men blog has a story about a caboose getting tipped, https://powerplantmen.wordpress.com/tag/caboose/

Getting the dumper detailed was the goal was for the meet that was supposed to be tomorrow but cancelled.  It has been a challenge to figure out what details are around such a facility.  There aren't many dumpers that are out in the open but putting the model in a building sort of defeats the purpose of building it.  There is one in Longview,WA, for chips and it can be seen from the highway about 700 yards away so the details aren't easy to see.  Photos online are all taken from just a few angles and usually pretty close in because they are in a building.  So I'm just making it up as I go.

Early forecasts for this winter suggest lots of snow in the PNW, a Snow Dozer might be handy to have around.

Personally I am thinking the

Personally I am thinking the crew is going to be a bit upset...

just saying

-Doug M