Scenic-Shop

I like to take detailed pictures of the scene designer’s model for each set we build.  Inevitably the director and stage managers want the model in rehearsal, and it becomes difficult to share.  Things get really hairy when the scenic charge wants a piece of the action.

Obviously, the stiller the camera, the clearer the picture.  I set out to find a secondhand something I could use as a monopod.  Let this be a lesson: ask a prop person for a monopod, and you’ll get a showerhead.  Thanks Billy!  Its the best free showerhead I’ve ever received, I’m glad I didn’t waste money on a monopod.  After making a quick & dirty adapter to fit the camera, this baby can perform more wacky positioning and tilting maneuvers than the “actors” on those scrambled channels. (You know the ones I’m talkin’ about.)  For those curious folks, the adaptor is a 1/4″ flat head bolt epoxied into a pipe-to-hose adaptor.  Since the items were in stock, it was mighty cheap.

This one’s for the mech heads and purveyors of fine machinery.

Cornell University’s Reuleaux Collection is a collection of 220 machines.  The machines include various crank mechanisms, couplings, linkages, compound gearing… the list goes on.  The website itself is a catalogue of the 19th century machines – some with accompanying videos and technical documentation.  In my opinion, the machines themselves are functional, beautifully crafted works of art; they deserve some attention.

There are also three books that I highly recommend all mech heads have on a shelf somewhere.  Or in the powder room (your choice, no judgement here).

507 Mechanical Movements: Mechanisms and Devices by  Henry T. Brown

• This slim paperback from 1868 is as simple as it gets: 507 drawings of various mechanisms, and text that describes their operations and uses.

Machine Devices and Components Illustrated Sourcebook by Robert Parmley

• This bad boy is a compendium of 1,500 different mechanisms.  It’s broken down into assemblies, power transmission, and mechanical components.  A great way to kick start the brain when you need some inspiration.

Mechanisms and Mechanical Devices Sourcebook by Neil Sclater and Nicholas Chironis.

• This 500 page beast is a good companion to the Machine Devices and Components… title listed above.  I like to think of it as the sequel.

Of course there is Mechanical Design for the Stage by Alan Hendrickson, but I know you already own that one, right?

Note that the book links go to Amazon pages, I’m not saying you should buy from Amazon, in fact I recommend saving a few bucks and getting used copies.

Scratch provides a quick & simple way to utilize a temporary scratchpad layer in AutoCAD. Scratch allows you to quickly switch in & out of the scratchpad layer, and throw it away whenever you want, leaving the rest of your AutoCAD drawing untouched.

I’ve been using it for

• transferring geometry
• building complex shapes (I use the boundary command later to create objects)
• throwaway dimensions (when estimating & sketching ideas)

Download

UPDATE: Scratch v0.8 is now available.

Download Scratch v0.7 now!

Use

Scratch is super simple, there are only two commands (+1 bonus command).

1. cst – will toggle you between the magenta scratchpad layer and the original layer.
2. est – deletes the scratchpad layer and everything in it.
3. 1` – changes your current layer to your prior layer.

Crosshair Colors

Loading the second file scratchColor.lsp enables the crosshair color switcher.  Whenever you make the scratchpad layer current, the crosshair color will change to magenta.  This provides a constant, unobtrusive reminder when the scratchpad layer is current.

Notes

• Scratch runs on AutoCAD v2000 – 2010 (v2006 and earlier require the Express Tools.)
• Scratch stores your original crosshair colors; if you have them customized, it will not clobber your original settings.
• You can change the name, lineweight, color, and linetype of the scratchpad layer in the top of the scratch.lsp file.

What is RubyShapes?

RubyShapes is a Ruby library that defines Shape objects analogous to geometric cross-sections. These Shape objects “have” the same geometric properties that their real world counterparts do. The long term goal is to use RubyShape objects as building blocks for a larger structural and mechanical calculation software library.

Geometric cross sections?

These are cross sections of 3D objects (square rods, circular rods, rectangular tubing, etc.) Each shapes’ cross section has properties that are that are used in structural and mechanical calculations.

Current version?

The current version of RubyShapes is v0.2.9.1. It has been tested on Ruby 1.8 & later.

License

RubyShapes is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at your option) any later version. RubyShapes is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. For license specifics, see

Where is the source code?

The source can be found at the github RubyShapes repository.

Properties for each shape class

x = x dimension (in.) (equiv. to outer diameter for round shapes)
y = y dimension (in.) (equiv. to outer diameter for round shapes)
a = square area (in^2)
ix = second moment of area for xx (in^4)
iy = second moment of area for yy (in^4)
sx = section modulus for xx (in^3)
sy = section modulus for yy (in^3)
rx = radius of gyration for xx (in)
ry = radius of gyration for yy (in)
w = weight of shape per linear foot (lbs/ft) – right now assumes all shapes are steel

RubyShapes Structure:

RubyShapes.rb – the main file, contains the definitions & calculations for each shape class. There is a testing area at the bottom of the file.
Most of the shared code for RubyShapes is divided into several modules, each module lives as a file in the /lib/ folder:
DiagUtils Module – Diagnostic messages.
OutputUtils Module – Defines the methods that return values from the shape values.
ShapeUtils Module – Defines property calculations that are common to multiple.

List of Classes

Bar(x/y dimension) – Square bar shapes
Plate(x dimension, y dimension) – Rectangular bar shapes
Square_tube(x/y dimension, gauge/thickness) – Mild Steel As-Welded Mechanical Tubing
Rec_tube(x dimension, y dimension, gauge/thickness) – Mild Steel As-Welded Mechanical Tubing
Round_tube(outside diameter, thickness)
Rod(outside diameter) – Round rod shapes

Output Methods

These methods are used to retrieve the calculated properties from the shape objects.
.props
Returns a human-readable list of the shape object’s properties (as floats, rounded to 4 places). Optional: include a (”variable”) parameter to the method to return that specific parameter’s value.
.bigprops
Returns a human-readable list of the shape object’s properties (as BigDecimals). Optional: include a (”variable”) parameter to the method to return that specific parameter’s value.
.hash
Returns the hash of Object properties (as floats, rounded to 4 places).
.bighash
Returns the hash of Object properties (as BigDecimals).
.columns_header
Prints a pretty, human-readable header for the columns method. Spacing is not currently ideal.
.columns
Returns the Object properties in a column format (as floats, rounded to 4 places).

ShapeUtilites Methods

These methods are invoked by the shape classes during object initialization. They are not very useful to the end user.
Float::to_d
.corner_radius
Calculates corner radius for calculations. This method is not implemented yet.
.gauge_converter
Converts from steel gauge thicknesses to decimal thickness.
.calc_weight
Calculates weight values – currently assumes all shapes are mild steel.
.build_hash
Builds a hash of the shape object’s properties. Result is stored in the shape object’s hash variable.

Diagnostics Methods

These methods mostly only run when DIAGNOSTICS = on.
.diag_section(”message”)
Outputs a diagnostic section(header) line to the screen.
— message —
.diag_line(arg)
Outputs a diagnostic line to the screen
.diag_class
Outputs which class is currently initializing. Prints the following:
==== Now initiating a Rec_tube class ====
.test_output
Prints Output Module Methods all at once for the receiver object. Good for batch testing the Output Module methods
.var_classes
Prints the classes for a predefined list of instance variables in the receiver object. DIAGNOSTIC flag independent.
.var_values
Prints the values for a predefined list of instance variable in the receiver object. DIAGNOSTIC flag independent.
.diag_all
Not implemented yet. It will be a comprehensive diagnostic inspection for any object. DIAGNOSTIC flag independent.

For those of you who are interested in new materials, check out Transmaterial. I can’t describe it better than this quote from the site:

…Transmaterial online is intended to be a clear, concise, accessible, and carefully edited resource that provides information about the latest and most intriguing materials commercially available.

A little more…

As the speed of technological progress continues to accelerate, innovation threatens to outpace architects’ and designers’ working knowledge of materials thereby limiting their applicability. In order to stay at the cutting edge of design, a knowledge of the uses, properties, and sources of new materials is essential. A companion to the Transmaterial books written by Blaine Brownell and published by Princeton Architectural Press…

While most of us in theatre probably couldn’t afford any of these new materials, they do provide inspiration for solving some of our… err… unique challenges. Added bonus — some of them are just super cool.
All in all, this here is some top notch geek porn.

“Have you ever wanted to lay out the frustum of a cone on a flat surface?”
“A what?”
“A frustum, the part of a cone that is left when you lop off the top.”
“Oh, yeah. If I had a nickel… sadly, I’m still poor.”

It can be a little intimidating if you’re not familiar with the concept of how to go about it. Our draper came to me wondering how she could accurately lay out a dress based on an actor’s measurements. (Apparently the traditional layout method wastes fabric.) So I came up with this simple excel sheet that does the calculations based on the following measurements: waist (small circumference), hem (large circumference) & inseam (height of the frustum.) It gives back the details needed to lay the cone frustum out on a flat surface. The diagram below gives the general gist of what’s what. There is a larger version of the image in the excel document.

Frustum.xls
From fabric to sheet goods, I hope this calculator finds some use.

This is an update to the Cadalyzer script that I posted a few months ago. It will count the number of commands you have used in AutoCAD; it does this by examining your AutoCAD log files. (You can enable log files in AutoCAD’s options dialogue box.)

Cadalyzer 0.6b download
New features are listed below

• Counting mechanism has be rebuilt, the script now computes 25 times faster than the previous version!
• shows the total number of commands used (Apparently I’ve invoked approx. 38,000 commands since this previous October. Ouch.)
• several command line options have been implemented:

• • unused – shows all the commands you didn’t use; this is helpful when you want to learn more commands
• • compile – compiles all of the logs in the directory and saves them to a single file
• • results – saves the results to a file
• • percent – formats the each command as a percentage of the total commands used

You will need Ruby installed (tested on 1.8.6 and up.) You can find the Ruby download here. If you don’t use Ruby but would like to learn to program, I highly recommend it. Ruby is an excellent language for beginners and advanced alike.

The only other thing you will need is to tell the script where to find your log file directory. Open the Cadalyzer.rb file and look for the line path = '/Path/to/log/files/” Replace the/Path/to/log/files/ with your path and run the script.

Happy analyzing!

If you’ve downloaded the Dykes Moulding CAD files from their website you may have noticed that the profiles are not to scale. From what I could see, the scale factor seems to be the same for all the files, approximately 0.056568174 (find the humor in that.)

Found out a couple of pitfalls when building flats with mirrored acrylic skins. Our usual acrylic adhesive is a two part methacrylate based adhesive. It works incredibly well when bonding acrylic to just about any substrate (steel, wood, other plastics…) Some formulations cure to a relatively clear finish, which is quite the selling point. Unfortunately, we found that methacrylates will distort the mirror coating on mirrored plexi. Whoops. You can see the distortion in the picture below. It’s probably better to stick to liquid nails next time. As a side note, 3/16” mirror acrylic does not look great with toggles on 2’ centers; I recommend a thinner acrylic sheet contact cemented over a plywood skin to realize a flatter surface.