Fascia-mounted manual switch stand lever arms

I’ve described the evolution of the design I’m implementing for manual turnout throw mechanisms in previous posts. I’m still making changes, but the basic idea looks like this:

The idea is to mimic the lever action of a typical manual switch stand: unlock the handle, raise it to a horizontal position, turn it through 90 degrees, then lower it. I settled on off-the-shelf quarter inch gravity t-anchor bolts (actually rather hard to find on any shelves around here, I had to special order them) for the hinge arrangement that can take the kind of lateral force necessary.

Prof Klyzr pointed out early on that I could probably fabricate what I need fairly easily, and now that I’ve been working with the materials for a while I’m inclined to agree with him. But I had to go to some trouble to get the t-anchors so I’m using them!

The handle and shank components are cut from K&S telescoping square brass tubing. One student who was eager to work with metal volunteered to cut the tubing, so I set her up with a small miter box and a razor saw.

It took her a while to find a comfortable working arrangement but she was very patient and eventually got into a nice rhythm. After cutting each one and using a file to dress the ends, she clamped one end in a vise and put a slight bend in it to represent a handle.

Jeff Allen

Switch stand masts

One task that I was wary of giving to a student was the delicate job of drilling tiny vertical holes for the masts in the soft white metal of 11 Details West switch stand castings. I’d only done one myself and knew how tricky it was. I considered buying a good precision drill press (which I know will eventually be worthwhile) but thought I’d see how it went manually before making such a big investment.

Naturally, the student who showed the most interest in the job was one of the least likely candidates. Many students these days have “grapho-motor” challenges, meaning they struggle to get their brains to manage the task of hand writing (by that I mean making letters with pencil or pen, students no longer learn handwriting, or cursive lettering at all. Most text is generated on a keyboard these days.) That’s a scary cultural loss to me, and a bit of a problem for math since the symbolic notation tools on keyboards are still pretty cumbersome.  I insist that my students write down their math problems and show all of their steps, and although it is like torture at first after two years with me most of them can spew out page after page with ease.

This student is particularly resistant to that work, but to my amazement he did a fantastic job drilling the switch stands. He enjoyed using the Optivisor and quickly got the feel for exactly the right pressure to put on the bit, how to back it out regularly, and how to gently hold the part in pair of cross lock tweezers so that it didn’t get distorted.

I commiserated with him over the difficulty of chucking those tiny bits in a pin vise, but he appreciated the amazing tooling that must have been used to cut the flutes.

Jeff Allen

Installing electrical bus wires

If you think a task is straightforward and easy to understand, give it to a couple of middle school students and they will help you appreciate how subtle and prone to error it really is.

Our layout is built in sections so that the whole thing can be dismantled at the end of the school year and stored safely away while a summer day camp takes over the building. In addition to bolts and mending plates in the benchwork, I wanted two electrical bus wires to terminate at the end of each section, with jumpers between sections. I had just enough solderless spade lugs for the jumpers and ring lugs for the bus wires, and I bought some new two circuit barrier terminal blocks to make tidy connections.

I demonstrated how to use a wire stripping and crimping tool and marked the locations for the terminal blocks on the benchwork. I suggested that they drill holes in the wood frame rather than staple the wires to the surface, and that the red wire should be in front and the black in back. Wood screws for the terminal blocks. Any questions? Go to it.

Even though I stripped ¼” of insulation in my demonstration, apparently it seemed more logical to them to strip about an inch. Where along that inch of exposed wire you crimp the lug did not seem relevant. They cut one pair of bus wires an inch too short to make the full 8 foot length of the section, so they started to throw the whole thing away (“there’s plenty on the spool”).

That “red in front, black in back” convention seemed like just a formality, as they felt free to cross the wires as much as they pleased.

The attention they paid to redoing their work really made it clear to me how important it is for us to understand what we’re doing, and how impossible that is if we don’t gain some experience through trial and error. And often it’s the errors that propel our mastery.

Painting figures

Although the layout is several stages ahead of the need for scale figures to populate the scenes, the process of preparing plastic people for the layout develops a valuable set of skills and appeals to those of us interested in incorporating a connection between what’s happening on the layout and the real world.

Students used a small drill in a pin vise to make holes in the unpainted plastic figures (I bought a bag of 100 assorted figures) so tiny wires could installed to hold figures during painting. Some of the students didn’t completely understand that the wires would remain and be used to secure the figures on the layout, so some of the figures have wires installed in locations other than the bottoms of their feet. Certain locations were amusing to middle school students, and the sounds of mirth at their table alerted me that something was amiss.

The only neutral color of spray primer that was in stock at my local hardware store was a too dark shade of gray, so this first group of figures is going to need some work on skin tones, but one student spent an entire afternoon mixing oil paints to get the colors she wanted for clothing, shoes and other details.

Jeff Allen

Cutting mast assemblies

One of the big shifts in manufacturing processes has been the recognition that the experience of line workers needs to be fed back into the design cycle and formalizing that feedback channel. I highly recommend reading “Set Up Running, The Life of a Pennsylvania Railroad Engineman” by John W. Orr, writing about his father’s career. One of the striking themes was the layer of insulation between the design and management of the railroad and the people operating it day to day, and the missed opportunities that resulted.

I knew my design for the switch lever mechanism was half-baked and evolving, so it wasn’t surprising that the student who took on the task of cutting the pieces of round brass tubing for the mast bearing assembly came up with a significant improvement.

The working model pictured in the first comment post used a single vertical tube for the mast with a ¼” hole laterally through the top for the t-anchor arm and another at 90 degrees to that in the bottom for a 4-40 threaded rod crank arm. A ¾” length of ½” diameter tubing is glued into a ½” hole in the pine 1x2 to provide a bearing. The mast tube is one size smaller and rotates snugly in the bearing, but I had to file a steel washer for the anchor nuts to ride on to reduce the vertical play in the assembly.

For the “production” version I decided to eliminate the washer by cutting three pieces of ½” tubing totaling the same length as the mast piece and let the top and bottom sections ride the captured middle bearing piece. The tube walls are thin, 0.014”, and I didn’t like the way they tended to deform when cutting and drilling so I also decided to add a third concentric tube inside the mast.

A problem arose immediately when we employed a pipe cutting tool to cut the pieces of pipe - the force of the cutter necked down the cut ends slightly, enough that the telescoping fit no longer worked. We tried flaring them with a brass plumb bob, and filing them with a half round file, but couldn’t get a satisfactory fit that maintained the smooth bearing action we needed.

My student discovered that by putting all three tubes together and cutting through them all at once, the pinching action captured the inner tubes and still allowed them to rotate freely inside. Then she could make both cuts in the outer tube just deep enough to create the three rings - with perfect bearing surfaces - a complete assembly with just three cuts and no fussy filing required!

Jeff Allen

Love the discoveries ...

  I would have never guessed that one of the offshoots of technology in the classroom being the loss of things older generations take for granted.  The way things are going, these kids will probably never own a checkbook!  Learning to write as a motor development skill in addition to being able to effectively communicate was something I never considered.

  The discovery of the method to fabricate the brass pivot pieces is brilliant!  More process engineering curriculum  for that one.

  Do your students read your posts and/or do you share what  you post here with them?

Great Skills

Model railroading brings in so many skills I think it makes for a great school project.  Plus you have the added benefit of learning teamwork and the joy of Acheivement. 

Joe

discovering these posts

Good question Toni. My students learned about this blog during the work session last week. I wanted to show them some photos of prototype switch stands so I used Google image search on "manual switchstand" and one of the pictures that popped up was of the lever assembly I've been working on - and they recognized it as the thing right there in the room with them!

I'm not sure they're quite ready for all of the model railroad jargon just yet, but as their interest develops I will certainly be guiding them towards MRH.

Jeff Allen

soldering shanks to t-anchors

The activity the kids were most interested to try was soldering. My experience with soldering is pretty limited - a fair amount of electrical soldering of the layout wiring variety and soldering lead canes on stained glass windows, but I hadn’t soldered brass and copper parts before.

What I was able to learn about silver soldering was pretty daunting - very high temperatures. But I duly went out and bought silver solder, the appropriate flux, and a high-temperature torch (along with a heat shield and a few other safety items).

Playing that torch for a couple of seconds on the small tubular brass turned it glowing hot, and for a few seconds more disintegrated it! And I had a very hard time getting the flux and heat combination right to get the solder to flow into the joints evenly. Yikes, even if the kids didn’t burn the place down it wasn’t going to be easy to learn.

Just for fun, I took out the soldering pencil I use for electrical work and tried it. Much better! I don’t suppose I’m doing it properly, but the joints seemed strong enough and looked fine with a little clean up. This was something the kids could handle.

Of course, their first efforts came out about as well as my first tries with the torch. But they are alert learners, and soon got the hang of it.

Some of the students in this crew have taken my elective featuring shaping and polishing Alabaster stone, so they have acquired some patience and appreciation for using abrasives to refine form. They totally “got” the difference between the properties of stone and the properties of metal, with a commensurate rise in enjoyment of both.

Jeff Allen

Keys to silver soldering ...

From what i remember in my jewelry class in high school. 

Clean all mating surfaces thoroughly, scuff lightly with Scotch Brite pad

Position pieces and secure (clamp, weight) in position

Apply liquid flux along seam of joint.  Let capillary action 'wick' it between parts

Cut a TINY piece if solder (head of straight pin size), place it against the seam (long joints will need a piece of solder every couple of inches)

Apply heat away from solder and work towards the solder on each side.  Heat gradually and evenly.  When the parts reach the proper temperature, the solder will melt and be sucked into the joint like magic!

You may find this torch easier to manage

Safer, too.

When I'm soldering with a torch, I like to manage the solder with a brass tube:

pqe

torch tips

The guy at the hardware store told me that I needed special high-heat gas in order to silver solder. I'm guessing that you're finding the small torch with "normal" fuel to work fine? 

Great idea to have a feed tube for the solder! 

My real question is, how fragile are my "low temp" solder joints? They seem fine, but will they break down over time? They aren't static like jewelry, the parts that I'm soldering will take real (though minor) stresses with regular operation of the levers. 

Jeff Allen

I think it is fantastic the

I think it is fantastic the work you are doing with the kids to teach them additional processes and to stimulate their problem solving skills. The process is very rewarding. Years ago while I was operating my own accident reconstruction business I got involved with teaching some classes with kids at local schools. I receieved great feed back from the schools staff who were amazed how I caused such a rise in interest in the subjects of mathematics and science.

In the classes I gave the kids information needed and formulas to solve some basic problems in accident reconstruction and time distance analysis. It started out with "Oh I hate story problems" which was followed by I solve story problems for a living, "you do?" By the end of class kids that started out with tremendous disinterest were working feverishly to complete the next portion of the problem. They expressed real surprise that all that math could actually be used to solve real world problems.

I believe you must feel a real sense of accomplishment from your additions to the curriculum and the responses you are getting from the children. Even better you have done something that much of the present education system seems to pass on, the awakening of the mind of your students and developing the thought process.

Story problems

Thanks Rob, I'm glad to hear you share my enjoyment of teaching! It is very rewarding indeed. 

The "I hate story problems" mindset is astonishing to me, but it is almost universal. I would say that my career goal is to become effective at dissolving whatever the factors are that create it in the first place. When I taught high school math and kids came in with that feeling I thought I could head it off by teaching middle school - but many students have already been turned off much earlier. 

I'm still working my way into the elementary curriculum to find where this problem sets in. In the meantime I feel like I'm having some success turning kids around in time to get some pleasure out of high school math to come!

Jeff Allen

Crank arms

Another area where the design of the throw mechanism is evolving is in the linkage. I spent some time poring over the online catalogs of various RC airplane and robotics suppliers and other possible sources and was mostly boggled by the options. I needed an arrangement that was easy to mount to my brass mast tube, disassemblable, and tolerant of minor misalignments. My first attempt used a ball clevis because it accommodated a wide range of motion on multiple axes:

The problems was that the ball moved freely on the threaded rod and had to be retained by nuts, which interfered with the control rod at extreme ends of the crank travel. And the slipping of the ball on the crank rod during travel was funky. The ball clevis was a good solution at the Bullfrog end of the control rod, but not here.

A better solution was to use whats called a control horn on the threaded rod with a nylon clevis connector. That solved the range of motion problem and eliminates the play in the linkage, but requires a bit more precision in aligning the plane of crank travel with the level of the Bullfrog connection.

I was delighted to learn that the opportunity to use a hacksaw was an exciting prospect for a student, and he worked his way from frustration to efficient and satisfying productivity over the course of cutting 12 lengths of 4-40 threaded steel rod.

Jeff Allen

The switch to ME turnouts

I’ve been planning to use some old Walthers/Shinohara turnouts despite some uncertainty about whether to retool them to make them “DCC Friendly.” I used them on the Inglenook and with a few additional gaps and feeders they generally work fine, but I left the electrically connected points alone and we do occasionally get shorts when the back of a wheel kisses an open point. Slight finger pressure usually takes care of it, but the odds of annoying problems will go up with lots more turnouts on the big layout.

I’m very interested in well-modeled track, so when it came to buying flex track (I didn’t have enough of the old Walthers/Shinohara code 83 sticks lying around) I decided to try the Micro Engineering track, and I’m impressed, it looks great.

Just for fun, I ordered a couple of ME turnouts just to see whether the trouble of fixing all of the old turnouts outweighed the cost of new DCC friendly ones.

I replaced the old turnout on my switch stand mockup with the new ME one and discovered that the ME turnouts have a very sweet snap action spring on the points.

Which makes my Bullfrogs a bit of overkill. And, since my entire switch stand crank lever geometry is based on the 1” throw of the Bullfrogs, any change I make there will ripple through the whole contraption. Fun.

For now I’ve decided to install ME turnouts but stay the course with the Bullfrogs. They are reasonably economical and deliver (plenty of) motion to the point rod, and they include the switch for powering the frog. And not least, they’re fun and instructive to for students to build.

Jeff Allen

Track Video

Jeff,

I saw your comment on the How Railroad Tracks Really Work (video) post, so I thought I would add another video reference to your training tools. If you have not already seen them take a look at How The Frog Point Works on the Fast Tracks videos page. The Demystifying The NMRA Standards Part 1, Part 2, Part 3, Part 4 provide additional information on model train wheel and wheel operation.

More mechanics and math. Love it!

Heat and temperature

The little torch produces as  high a temperature as your big one-- the difference is the amount of heat energy available. It's the same principle as big vs. little soldering irons. The parts melted because they couldn't dissipate heat as fast as the torch was supplying it. Soldering is a race to get the joint to the melting temperature before the associated parts are damaged-- the big torch probably melted the solder in the first few seconds.

On the other hand, the little torch would never be able to solder a water pipe. The pipe would dissipate heat so well you wouldn't even notice it was warm.

This might be a good subject for a unit for your students.

pqe

how fragile are my "low temp" solder joints?

Depends-

If it's a cold joint (meaning the metal did not get hot enough to alloy with the solder) it will let go immediately. You can tell by a discoloration in the brass. It should have changed color on both sides of the joint. If the solder only melted around the edges of the joint, it may let go after a while. Look carefully for any motion of the joint. If the solder is flexing it will work harden and break in a matter of days. Otherwise, it's probably OK.

pqe

heat flow

Great feedback, thanks, as ever I have lots to learn!

The principles that I've used enough to understand intuitively (soldering tiny feeders to the web of code 83 nickel silver rail on plastic ties) haven't been quite enough to fully untangle a new set of problems with larger, mechanical parts. These comments are a huge help in steering me in the right direction. 

Thinking back over the details of the design for this manual switch stand control, I remember that I went to some trouble to avoid putting any significant stress on soldered joints. Given the current state of my skills, that was a wise move!

Thanks also to Ken for reminding me of the Fast Tracks videos - I'd forgotten about them even though I've been placing orders there recently. I watched them again and they are terrific, both because the content is highly relevant and because they remind me of how valuable moving 3D animations can be when explaining certain concepts. I need to devote some time to creating some for my math classes (it's up my alley, I worked for Autodesk for 7 years!), but my skills have gotten rusty and there are so many other things to do (like build a model railroad). I love having a job where almost everything on my "to do" list is interesting!

Jeff Allen

Another Video Link

I commented about this video on the other post, but I though you might want an exaggerated animation. May save you some time developing your own. There was also a very good video of a live demonstration of the effects of exaggerated conical wheels, I think on a BBC science show, but I have not been able to find the link. If I find it I will add it to the list.