Great Idea

Rene,

great idea.  i'm going to try this myself now. 

do you have any pics of the topside with the switchstand target ?

thanks

Tim

Topside with target

The targets will fit into the tube (somehow!)

It might be easier to use the bullfrog to throw the switch points and then use the points throw bar to turn the target. That would put the target mechanism all up top where it's easier to build and maintain....DaveB

Mechanism on top

Working switch stand and Blue Point machines

I am thinking of doing something similar for my stands, however I have picked up a bunch of Blue Point switch machines instead of the bull frogs.  I would think a similar setup would work with the Blue Points.   I'll be pilfering this idea (with credit of course) from you.

Marc Simpson

Blue Points

Bell cranks have lots of uses

You can do the same thing with bell cranks and tortoise type switch machines too.  This is running more than one set of points with one mechanism.

Bell cranks and Tortoises

Thanks for the video, AzBaja.  It's always interesting to see how others tackle problems.

Rene'

Those Remote Turnouts

As you might recall, the first two turnouts on entering Pembroke are actually on the windowsill. I think when I made this design decision, I figured I would use ground throws for these two turnouts. However, since then, I changed my mind and decided they should be remote from the front of the fascia like all the other turnouts. My thinking is that if they are thrown by ground-throws like the turnouts in the staging yard, then they will become conceptually part of the staging yard.

The question then is, how can I transfer the motion from the Bullfrog some six or eight inches (15-20 cm) into the windowsill to drive both the points and the switch stand target? After installing the first two Bullfrogs on the south section with Andrew a couple of weeks ago, I hemmed and hawed over this question for some time, but I think I finally have a good solution.

The first step was to enlarge the holes where the mechanisms have to pass through the edge of the layout proper. The originals made back in October will not be big enough to allow the full motion required for the target. When I made the originals, this was actually a lot of work, but when I went to enlarge them this week, I came up with the idea of using the hole saw and simply continuing into the deeper plywood beyond the stringer. That worked great, and the photo below shows the resulting holes as well as the slots for the mechanisms.

The roadbed is only 1/2 an inch (12 mm) here, and the slots themselves are less than 1/8 of an inch (< 3 mm). So the mechanism that transfers motion has to be pretty thin. To keep everything stable I decided to build the mechanism on a piece of .025" brass, and plop it into place, rather than trying to build it in situ.

For the switch points themselves, it is relatively simple: a Z-shaped piece of .032" brass slides between some K&S H-beam and C-channel to carry the motion to a boss that engages with the bottom of the switch rod assembly. The photo below shows this.

For the target, I needed to transfer the sliding motion into a vertical rotating motion, and so, I soldered a piece of the channel to the end of the slide, and drilled a hole in it. This hole engages with a wire that is soldered into the end of the tube that rotates for the target. The following two photos show the action.

Note that the slot for this mechanism was cut beside the target and switch rod, and so, I had to extend the mechanism to reach. I am using over-size tubes to carry the target motion around beneath the layout so I can easily replace the targets from above the layout; they tend to get bent easily.

The first one took me longer than expected, and I actually haven't finally fitted it into place yet, although I have certainly tested it, and it should work. One more to go, then the Bullfrogs for these two, and then it will be time to get the North section off the ceiling.

Still struggling with remote throws

This week I managed to get the two Bullfrogs for the remote switches installed.

After an evening's head-scratching, I actually managed to get the switches themselves to move relatively sweetly. The secret was to add sufficient screws to the near end of the sliders to keep them from lifting or twisting at all. So far so good.

Then I turned my attention to the switch stand levers. Unfortunately, this is when things stopped going so well. The design calls for the switch stand lever to move an inch (more in one case of miscalculation), and this motion is supposed to come from the bottom of the Bullfrog, where the choke cable moves through that distance.

Unfortunately, there doesn't appear to be any way that I can make the arm stable enough to push the switch stand slider reliably. Adding more brass -- quite a lot more, in fact -- made it work well in one way, but not the other. In the end, I had a mangled mess, which still didn't work.

It's remarkably difficult to photograph because of the surrounding benchwork. However, in these photos, the slider closest to the block of wood drives the switch rod, while the further one drives the switch stand. The first thing I noticed was that the lever flexes substantially, and so, I added a wire to the side to hold it steady. Then I noticed it still wants to lift, and so, I added the long extension, which I would hold against the bottom of the benchwork with a strap or something. While testing that, I found that the arm still really wants to flex. By this time, I was out of ideas, and went to bed.

Solved: Remote Turnout Control

Okay, I think I've got this problem with throwing both the switch and the switch stand for the turnouts on the window sill licked! The trick was to think about the parts that have to move the same distance and to design something that would hold them rigidly together.

Then I remembered Pembroke's Victorian or at least Edwardian roots, and realized that there is no problem that can't be solved with enough wood, iron and rivets (or in my case Robertson-head screws). The contraption is shown below.

As you can see, I looked around the garage for something that wouldn't flex too much and found a block of wood. I used this to replace the choke cable, which hadn't been installed yet anyway, and this driving block pushes both the Bullfrog and the switch stand slider. The block of wood has a rod that connects with the Bullfrog, and a steel hook that connects with the switch stand slider. This is better than trying to transfer the motion from the choke cable through the Bullfrog to the switch stand slider.

The free end of the block of wood has a hinge, which will connect via some threaded rod with the turnout control, once that's built.

One more to go, then I can put the south section away until it is installed.

Refined Bullfrogs

It might not have been apparent, but that first Bullfrog posting showed pictures of a proof of concept installation. Now that I am installing them on the actual layout, here is an update on some of the refinements I've made.

The two shown above are the switches for the two spurs off the siding on the south section. The top (nearer) one is the second, and slightly improved version. Here are the improvements made:

• The switch stand is thrown by an accurately drilled plate, rather than relying on bending the end of the push rod in a pig tail. The pig tail proved to be too difficult to adjust, and when it was made out of threaded rod, it didn't allow the end of the switch stand lever to glide through the hole easily. I'm calling this plate the "push rod extension" and it is tapped to engage the threaded rod on one end, and drilled to allow the switch stand lever to rotate at the other end.
• The switch stand lever is supported by a heavier tube, which also serves as a bearing. This keeps it from flexing as much and thereby finding other ways to accommodate the movement of the push rod, rather than rotating. Notice in the bottom installation, I didn't do this, and had to add a collar to the switch stand lever to force the rotation; you can see it is trying to bend.
• I've beefed up the Bullfrog itself with a chunk of 3/4" plywood. This gives me a positive place to anchor the end of the choke cable, and also takes the strain off the Bullfrog itself.

I found the switch stand rotation is surprisingly sensitive to the length of the extension to the push rod. The best thing to do was to center the Bullfrog, and mark the extension plate at the hole in the Bullfrog and at the switch stand lever. Even then, there is a lot of adjusting to be done by screwing the extension up and down the threaded rod; I was glad to be working with the module upright, rather than trying to do it Michelangelo-style.

More Switchstand refinements

Andrew and I got together the other day and finished up the switch stands for the north section. This resulted in yet more refinements to the design, as well as some creative problem-solving.

The first refinement was Andrew's suggestion to not tap the hole in the throw rod extension, but rather to use two nuts, visible on the image below of the south switch of the freight shed runaround. I had been tapping the hole so that the adjacent nut would lock the extension and keep it from rotating. However, allowing the extension to slide along the threaded rod makes the adjustment virtually trivial in comparisons to the contortions I had to go through before.

This installation also demonstrated that some of these switch stands want to bob up and down. If the Bullfrog is not exactly vertical, the switch stand target will bob more up than down, and so, it's important to assemble and install the Bullfrogs accurately.

The next switch along is right at the rear edge of the layout. Now, the layout is not going to be exactly up against the wall, and so, we have a little space where the lever for the switch stand can swing. We cut a big hole in the stringer to allow this swing. For some reason, this target really wants to bob up and down. It returns to the same height at both ends of the travel, but it moves about 1.5 mm. Andrew fashioned a collar to ride at the top of the stand. It now accommodates the radial motion of the bottom of the Bullfrog by flexing the switch stand lever. No more bobbing.

The last two switches on the line, for the north end of the freight shed runaround and the yard stub track, were too close together to allow for the version 1 mechanism. So, this time, rather than pulling directly on the Bullfrog, the push rod pulls on the extension arm, which in turn connects to the Bullfrog. To do this, I bent over the end of the extension and passed a 2-56 screw through a hole in it. This screw engages with the push rod. Andrew thinks this is a better design anyway, and he may be right.

We still have one more Bullfrog to install, but that will not be until the turnout at the north end of the siding has been built, after installation. The last one will be installed upside down over a table - a very awkward spot. So, I'm delighted we've come so far with this design. While the first one took an evening, these last five were all completed in one evening, and we were getting faster.