Highball Sim

With the steam pistons in place in both cylinders, it’s time to button them up, making the saddle/cylinder assembly complete.

Above: both cylinders are closed off with front and rear caps. Note also the driver springs and equalizer system are now in place.

Below shows the right piston (blue) inside the cylinder. The rear cylinder cap is also shown with gland packing detail. The 2 blocks welded on the cap will be used to attach the crosshead guides.

Extra: this view shows the spring and equalizer assembly. Fairly straightforward.

Time to turn attention to a different component: the steam piston, or, the thing that makes the train go choo-choo.

A relatively straightforward part to model. Since there are, I think, literally no material available on the make-up of the DLRR #1 piston, I had to rely on more traditional sources.

I assume that DLRR uses a built-up piston, the most common type for the period.

The steam piston is made with several parts: the main body called “spider”, the cover plate or “follower”, and the packing.

The spider is simply a casting with 5 points to mount the cover plate. DLRR may have simplified the design to 4 points, but not knowing this for sure, I just go with the traditional design.

The packing consists of a “T” ring and 2 packing rings fitted on the spider. They are supposed to be cast slightly larger than the piston itself. This way, the packing will fit tight against the inside bore of the cylinder. The following cross section shows how the pieces fit together.

Note the notches around the circumference of the packing rings. This allow the rings to expand with heat. The gaps between parts serve the same purposed.

And here’s the piston as a whole, with transparent cover plate so that the spider can be seen.

The truck is mounted into the “groove” molded on the bottom of the half saddles. As far as I know, there’s no “rigid” connection between the truck and the engine. The only thing keeping the engine on the truck is its weight.

This might be clearer. One of the half saddle is hidden, showing how the other saddle “engage” the truck.

The swing casting is finished. With it placed in the assembly, one can see just how exactly the swing casting system works:

[youtube http://www.youtube.com/watch?v=clPFcE4FYKc&w=560&h=315]

Here’s a general overview. The swing casting is connect by 4 links, forming something similar to a “swing set” found on kid’s playgrounds. The casting is highlighted in blue.

The cosmetic components (pins, bolts, etc.) have not been added to the model yet, but the mechanical definitions are there, which make the above animation possible.

Thanks to the discussion at Burnsland, I was able to refine the pilot truck a bit more:

The equalizer bars were made to be thinner to allow the bottom of the leaf spring to show. Transverse bar and longitudinal bar remodeled, etc.

Interesting that the pilot only has three longitudinal bars. The side with two bars faces the front… I think.

There is now a discussion on Burnsland about the pilot truck, with rare pictures of the truck detached from the engine.

Some observations I took from the thread:

• Disney used almost no bolted connections on the frame itself! Everything appears to be (heavily) welded. In one way it makes some sense given the scale of the truck, but I wonder how easy it is to perform maintenance. For example, if one of the braces crack?
• The transverse bar has a different profile–more trapezoidal than rectangular. That’s easy to fix, but it also appears to be “doubled”–having an inside and outside pair.
• I can finally see the center swing casting–but unfortunately the photos aren’t clear enough to show how it’s assembled. However, I think I have enough to make a good guess.
• I will revise the equalizer bars to be thinner.
• A good point was brought up that I give a bit of thought to previously. In actual pictures of the engine you will see the bottom of the leaf spring, and in the side profile of the truck I made, you do not. I believe this is attributed to the actual weight of the engine flattening the spring. The spring I model is a static solid body, so it cannot compress.

I’ve never drafted suspension system before and I’ll have to think about which state to show: compressed or uncompressed. The purpose of the drawing should govern first, but there’s a question of faithfulness representation of the engine “as seen” by the user.

As there is so little material out there on the Holliday’s pilot truck, what I’ve made is pretty much a guess of what it would look like based on contemporary sources and a few known major dimensions.

The major shapes and look, I think, are at least correct: the flat equalizing bars, the leaf springs, the axle boxes, the squared pedestals. These parts were drawn from the original Holliday drawing. The truck’s profile shows these components:

Back from vacation now. The lifting shaft (blue) is finished and is now connected to the links via the lifting links.

Now, time for something a bit different. Here’s start of the truck assembly, with the equalizing bars connected to the axle boxes.

In working and viewing the model in solidworks, which shows an isometric view of the model, one can forget the size and depth of the model being built. Today I did a little photo-real rendering test, which gives the image accurate perspective and lighting.

The mid-tone gray coloring is commonly used in rendering tests.

Here’s detailing of the valve gear and link.

Several things to note that are artifacts of rendering: the faceting on circular solids making them appear rough, and the corners that are “too sharp”. In reality, there is no such thing as a perfect corner so these “computer perfect” generated images tend to give that “fake” look. Once the modeling is completely done, I would have to go in and chamfer these corners to allow the “light” to reflect in a more realistic way.