Using Sketchup to Mockup

If want to know the mechanics of how to use Google Sketchup there are plenty of tutorials on YouTube. That’s how I learned to use the program. This isn’t a how-to. This tutorial focuses on using Sketchup to mock up projects prior to modeling.

The Project

I am building a small dam for my layout only 24 feet wide and 10 feet, 5 inches high at the spillway top. I worked it up in Sketchup and have completed the main dam structure. I still need to add the sub-structure for the intake. When that is done I can then prime the model and do some final sanding, filling and texturing.

The Source

The plans I followed were in a book published in 1920 titled Power development of small streams.

The Plan

The original dam measured 8 feet to the spillway top. I had planned to scale the model to 12 ft to the top of the spillway but managed to scale 12 feet to the top of the apron wall instead. That’s how I ended up with that 10 feet, 5 inches in height.

The height of the water or the head is important since that is the purpose of the dam in the first place, to raise the intake point so that we can convert that to Horsepower. So we can figure that to create one horsepower, we will need to move 33,000 pounds of water or, 1 foot of water in one minute. To do that, we are raising the water up and converting the weight of the water to energy. Water weighs 62.5 lbs per cu.ft., so the higher the water the more ‘work’ we can get out of it.

I may write another article to show how you can calculate how much horsepower you can extract from even a small stream but for now, just know that I was irritated. That simple difference of 1.5 feet meant a loss of around 10 hp!

I was looking at where I wanted the dam and it occurred to me that a stream flows from high to low. The water had to be higher upstream so I decided to raise the entire dam up on a ledge. My thought was the dam was built on an old waterfall which meant I now had 16.5 feet of head.

Now comes the reason for using Sketchup in the first place. As I am designing my structure, I can easily make changes to my dimensions and see the changes in real-time before I spend the time building up the actual model.

Dam Intake

At the top of the dam we can see Gordon standing on a platform. That’s part of the intake system for the dam and the focus of this tutorial. From the book we have this excellent description of the intake.

In the left background at A is the dam. In the foreground at B is the forebay. C is the trash rack and D the gate hoist to control the flow of water into the penstock E. When this gate is closed the penstock E is emptied by opening the gates of the wheel, in which case it is frequently an advantage to have the little air inlet valve F in the penstock to let air into the penstock automatically, thus relieving the penstock of outside air pressure, as the draining of the penstock naturally creates a vacuum within the penstock. Such a vacuum would be a heavy strain on any type of construction, but in this case the simple little air inlet valve relieves the pressure immediately. This picture shows an ideal arrangement for the home or small town power plant. It has every practical convenience and refinement that the huge water power plants have.

Let’s get into Sketchup and make an Intake. I’ll divide this into steps although there aren’t any really. This is just to keep track where we are in this tutorial.

Take a look

Let spin the dam around so we are looking from the right rear toward the left front. That’s where I want the intake since it will be feeding a turbine below this point at the pump house. Here we can see the spillway top, the rock ledge that the dam is sitting on and below that we can see Caddo Creek.

Add Water

Here I have filled the dam up to the top of the spillway. At this point the water will spill over and flow down the face of the dam. This is simply to orient you to what follows.

Insert Penstock

The purpose of the dam is to deliver water from a higher point (the head) to the turbine below the dam. The higher the head is, the more power that can be created by the water pressure. To do this we use a pipe called a Penstock. I pushed it through the dam at the top leaving a bit of concrete above it for strength and slanting down to just above the edge of the rock ledge. There will be a support of some sort at that point.

The penstock is simply a tube 1/2 inches in diameter which is equal to two feet in O scale. I grouped this in Sketchup so I can move it up, down, left, right and rotate along it's long axis until it was where I wanted it without it interfering with the rest of the model.

Sluice Gate Closed

The flow of water into the Penstock is controlled by a sluice gate. This is simply a metal gate that slides up and down within a couple of guides to shut off the flow of water when all the way down or allow water to flow when it is raised. The flow can be adjusted by how much the gate is raised. In this photo I have drawn a rectangle representing the gate at the fully closed position. The bottom is below the level of the Penstock intake and the top of the gate is above that intake. It extends a bit to either side. Note, I’m not concerned with engineering the sluice gate. I simply want to identify the boundaries of the other various bits and pieces.

Sluice Gate Open

Since I created a sluice gate earlier that will shut off the flow of water, I now take that same gate which was created in Sketchup and raise it until the bottom edge clears the top of the Penstock intake.

Both Closed and Open!

Because everything we are doing is virtual, I can now display the sluice gate both fully closed and fully open (I copied the first one and moved that copy vertically). With these positions established I can now add the gate guides. Remember, this is only to give me the limits that I need to take into account.

Left Side Guide

I made a guide for the left hand side. The sluice gate I made 1 inch thick. The guide is just large enough and seems like it is just right. Since this won’t actually be modeled it doesn’t really matter, good enough is OK. Again, we are just arraigning pieces so that the other pieces that we will actually see are in their correct places.

If you look close at that gate guide you will see that it doesn’t go all the way to the bottom of the sluice gate when that gate is fully closed. It actually will only go ¼ of an inch below the level of the epoxy that will represent the water.

Set Water Depth

I removed the water so you can see this better. I drew a line showing the lowest depth of “water”. At this point I will put in a shelf which will take the epoxy “water”. Using Sketchup I simply dropped a line ¼ of an inch from the top of the spillway and cut off everything below that on the guide.

Creating the Gate Walls

I removed the lower gate leaving the one fully open. The gate guide was just floating in the air so I added a wall. It is the height of the gate guide. When creating the wall thickness, I just made sure they looked right with the rest of the design. I'll shorten the length of the side walls later after I have everything else constructed.

For the Right side, I simply copied the left wall and gate guide and mirrored them on the other side of the sluice gate.

Valve Stem

The gate is raised and lowered by this valve stem. I made the length approximately what I needed as I could change that later once I had a little person to gauge the height.

The valve stem is fixed to the gate. The handwheel is fixed between a bracket allowing the valve stem to move vertically, raising and lowering the gate.

Something to Stand On

My little person needs a platform to sand on, so I laid some 2 x 6 boards across the area around the gate valve mechanism. I know it’s not that big but I’m not worried about that. I will extend and add on to the platform size as needed. Again, we are using Sketchup just to get the various bits in the right position.

The Valve Stem

With the handwheel in position, the position of the valve stem just above the handwheel shows that the sluice valve is in the fully closed position. The hand wheel is locked in the vertical position by some sort of brace. When it turns, the threaded rod raises and lowers carrying the gate with it.

The height of the sluice valve rod in the photo above indicates that the sluice valve is fully open. This will not be working on my finished model, however, I can create the brace based on the position of the hand wheel and the amount of stem above the hand wheel is equal to the distance the gate moves between fully closed and fully open. Since I will be modeling the gate as fully open I need that measurement.

Trash Rack

Now I added the trash rack. In the original print it looked like a series of bars. The rack is used to keep debris from clogging up the pipe and damaging the turbine. Because of their position on the dam located on the module, I doubt if anyone will see it. The main reason for this is to set the length of those side-walls.

Now I pushed the walls in until I thought they looked OK.

Mockup?

So there you have it. I made use of Sketchup as a tool much like you would cut out cardboard to mock up something except, it’s a lot easier to do it this way.