Timber Frame Design using Google Sketchup

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Google Sketchup is a 3D drawing program available free from Google.  Its a great tool for modeling timber frame designs in 3D, and you can't beat that price!  You can create simple drawings where timbers are represented as simple rectangular solids. This is often all you need to demonstrate to your clients what their frame will look like.  But Sketchup is capable of doing much more.  You can actually make a highly detailed model that includes all of your joinery design.  You can then create accurate shop drawings for laying out timbers in your shop.

Here's an example of a shop drawing that includes all the joinery. These are not hard to make if you lay the proper groundwork by creating a library of timbers and joinery.

Intrigued?  Read on.

Sketchup has a built-in ruby interpreter which allows you to create custom extensions to the program.  I've created a suite of these extensions specifically for timber framers.  I call them the TF Rubies, and I'm making them available for free (all I ask is that you not sue me if something goes wrong :-)

If you're not already using it, download Sketchup.  If you're not familiar with how it works, there a lot of resources available on the web for that.  There's even a Sketchup for Dummies book.  The Sketchup Community Forums are also a great place to ask questions and learn more.  Once you feel comfortable with the basics of Sketchup, continue on...

Here's the Sketchup model of the whole frame that includes the post from the previous example.  Go ahead and download it, and open it with Sketchup.  Grab one of the posts and move it away from the frame.  Look carefully, and you'll see that all of the tenons are included in the model, and that each tenon is part of a parent timber.  Note that none of the mortises are modeled, however.  The mortises are created automatically by the TF Rubies when you create shop drawings.  The mortise will always look exactly like the tenon, only inside out.  And the mortise location will be determined exactly from the location of the tenon.  So if you rearrange the model, the tenons will move with the timbers, and new mortises are created just by re-creating the shop drawings. 

The key to making all of this work is to create a library of timbers and joints that you use frequently.  I'll share mine with you, but they reflect my own style of frame and joinery design.  You'll want to build your own libraries that reflect your own style, using mine as an example.

Installing the TF Rubies

  Download the zipped folder named tf_ruby_scripts. 

  Extract the files to your sketchup plugins folder. 

        On a PC, that should be something like:

            C:\Program Files\Google\Google SketchUp 6\Plugins. 

        On a Mac:

            [User name]/Library/Application Support/Google SketchUp 6/SketchUp/Plugins

  If Sketchup is running, you'll need to close it and restart it.

You should now see a new menu option, TF Rubies, on the Plugins menu.  There should be several submenu items under TF Rubies, including About, which should tell you which version of the TF Rubies you are running.

Using the TF Rubies

Making Shop Drawings

Load the example model, the Queen Post Cabin.  Make sure that the outliner window is closed (it's a performance hog).  All the joinery is already modeled, so making a shop drawing is easy, just right-clink on one of the timbers, and select TF Make Shop Drawings from the context menu.  This may take a few seconds, but a set of shop drawings for that timber should appear, along with a file save dialog.  Go ahead choose a folder and save the shop drawing file.  I usually keep the main model Sketchup file in the main folder for the project, and the shop drawings in their own subfolder under that.  Note that the default file name for the shop drawing is the name of the timber.  The shop drawing should disappear, and you should be back editing the model.  Go ahead and make a few more, if you like.

Now, open one of the shop drawing files you just made.  Note that there are 4 identical copies of the timber, complete with mortises, all rolled so that a different side is facing forward.  There are full 3d copies of the timber.  Go ahead and orbit around and look at them from all sides.  To get back to the default view, choose Camera | Standard Views | Front from the menu, and also Camera | Zoom Extents.  You'll use those two things so often that you may want to map shortcut keys to them.  I use F2 and F3.

Every shop works differently, so you'll want to add or subtract to this shop drawing to make it work right for you. The default behavior is to create the shop drawing file with X-Ray mode turned on.  If you don't like that, choose Plugins | TF Rubies | Configure, and turn it off.  The same for the little N S E W T B labels that are placed on the edges of the drawings.

Dimensioning the drawings is really easy using Sketchup's built-in dimensioning tool.  It does not have a shortcut key, but since I use it so often, I created one, using F4.  Note that the default dimension font size may be a little large for these detailed drawings.  You can change the font from Window | Model Info, select dimensions, and then set the font.  Note that using this dialog, you can change all the dimensions you've already made as well.  Note the the shop drawings will inherit the dimension font size from the main model, so you may want to change the font size in the main model before creating the shop drawings. 

Take a look at the example shop drawing file I created for Post IA.  I used the text tool (shortcut key N) to indicate mortise depths, and any other notes you want to communicate to the shop floor.  Again, you'll want to include enough information for the way your shop floor works, which will probably be different from mine.  Once they look good, save the file.  I recommend you print them all out all at once at the end, in case you make any changes to the model later.

Generating a timber list

Load the main model again.  From the menus, choose Plugins | TF Rubies | Timber List.  Choose a location for the timber list file.  I usually use the main project folder.  This will take a little while.  There's a progress bar in the lower left that will indicate how long.  Depending on how fast your machine is, this might be time for a cup of coffee.  Note that if you switch away from the Sketchup window at this point to do something else, the progress bar will stop.  The program will still run, though, so just be patient. 

The timber list will be saved as a tab-delimited text file.  You can open it with a text editor or word processor, but it works best in a spread sheet, like Excel. 

The columns should be pretty self-explanatory.  Note that there are 2 length fields.  The length in Feet is rounded up to the next 2' increment, with a minimum extra length of 2'.  You can set the minimum extra length with Plugins | TF Rubies | Configure.  The length in inches is the actual length rounded to the nearest inch.

Note that the list is grouped in two sections.  If you give a timber (the component instance) a name, it is assumed to be unique, and will appear in the first section.  If unnamed, it will be counted with the other identical timbers, and appear in the second section, using the definition name.  (More on instances and definitions later).

You can cut and paste these sections into another spreadsheet, to use for pricing your frame.   I also use this file to create a checklist for the shop floor, to track the job progress, and to make sure we don't miss any pieces.  

Creating your own libraries

The key to making all of this work for you is to develop your own library of joints and timbers.  I'll share mine with you, but they will reflect my own design style.  You'll want to create your own that reflects the way you do things in your own shop.  But downloading mine will give you a head start on developing your own, as you can modify mine to look like yours, or at least they provide an example of how to make these components. 

The process of creating your own joints and timbers is straightforward, but I feel it's best left for a live presentation.  I've presented this material at past TF Guild workshops and seminars, and I plan to do that again in the future.  Meanwhile,  I am available for "private lessons".  We can arrange to do that either here in my Minneapolis shop, or at your site.  Contact me directly for more information.