Pianos & Steel. CAD Block Giveaway!

I just realized I never posted those grand piano cad blocks I promised months ago.  You can snag them here (version 2k).  Egg. face. mine.

While I’m at it – this is a link to some commonly used steel profile blocks.  Some of them are dynamic, so you’ll need a newer (2006? I’m too lazy to look it up right now) version of autocad to utilize them.  Inside you’ll find:

  • Common (small) rectangular tubing (d-d-d-d-dynamic!)
  • Angle Iron (dynamic)
  • 1 5/8″ Unistrut
  • 280 Track
  • Iron Pipe (dynamic)
  • 2×4 metal stud

Scratch! v0.8 Released.

Scratch! has been updated to version 0.8.

Download Scratch! v.8

This version adds a couple of features and bug-fixes:

  • The AutoCAD text window no longer pops up when running the EST command.  Thank goodness, that was annoying.
  • A new confirmation (with a cool view of all items on the temporary layer) has been added to the EST command.  This allows you to see what you are deleting before you do.  If you want to empty the temporary layer without the confirmation, you can use the EST` command.
  • If the temporary layer is off or frozen when invoked, it is automatically thawed and turned on.

For those of you who don’t know what I’m talking about, Scratch! is an Autolisp utility for AutoCAD that provides a quick & simple way to utilize a temporary scratchpad layer. Scratch allows you to quickly switch in & out of the scratchpad layer, and empty it away whenever you want.  You can read more about it at the original article, Scratch! (an AutoCAD Scratchpad Utility)

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Scratch! (An AutoCAD Scratchpad Utility)

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)


UPDATE: Scratch v0.8 is now available.

Download Scratch v0.7 now!


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.


  • 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.

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Flattening Cones

Update:  I just updated this frustum calculator with javascript versions that will run from the browser.  One will calculate the flattened frustum from the radii, the other uses the circumferences of the frustum shape.

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.

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

Update: There is a great description of how to flatten a frustum in AutoCAD over at Woodweb.

CADalyzer (AutoCAD Command Counter)

I’ve been working on a Ruby utility to analyze AutoCAD log files. The goal is to count how many times each command is invoked. The basic functionality is all in place, I’ve plans to add more in-depth analysis and perhaps even turn it into a web based tool. For now, you’ll have to download it and run it in the command line. If you want to run this, you’ll need the Ruby programming language runtime installed on your computer. Here is a link to the Ruby download. My CADalyzer utility can be downloaded here.

Download the .zip file, and unpack it. To run the utility, you will need to tell it where your AutoCAD log files are stored. (You can find that location in AutoCAD, via the Preferences.) Open the Cadalyzer.rb file and enter the path to your log directory next to the word path, like so:

Excerpt from top of Cadalyzer.rb file:

path = “insert full path to log file directory here”

The utility will combine & analyze the data from every log file in the directory specified.

Happy analyzing.

Roll Bender Forces Chart

How much force does it take to bend 3”x16ga box tube to a 5’ radius in one pass? What’s the largest steel shape you can jam in a typical scene shop-built manual roll bender without cracking a roller? A week ago I didn’t know the answer to either one of these questions, now I’ve got a pretty good idea.

We’re talking about making a roll bender at work, and are waffling over whether to build a manual or motorized bender. I realized that we didn’t really have a handle on the forces involved in bending various steels to various radii; these numbers are instrumental when making this decision. (Not to mention during the design process.) Earlier this week I sat down and created an excel file to shed some light on the situation. Figured I might as well share it with my peoples.

Snag the files here: XLS or PDF

The majority of the worksheet calculates for:

  1. The force required to bend a variety of steel shapes to various radii in one pass (à la motorized bender).
  2. Adjustments for three different roller/die distances: 12”, 16” & 20” apart.

The manual pass sections are intended to show how much force would be needed when making the first pass in a manual roll bender. It calculates:

  1. The force required to reach the yield point of each steel shape.
  2. The resultant deflection and radius achieved in the first pass.
  3. The above calculations adjusted for three roller/die distances (12”, 16” & 20”).

Big effin disclaimer!
Lets be honest folks, I’m not an engineer. Confidentially (just between you and me) I am confident that the calculations are fairly accurate. But under no circumstances will I claim that they are 100% accurate. The reason is this: the last thing I need is a lawsuit because someone too lazy to verify the math took it in the eye from a flying bit of steel. Don’t you dare cut corners.

This worksheet is only intended to give a general idea of the numbers involved when bending steel. It cannot be counted on to give precise data concerning specing and designing of a specific machine. There are no allowances for the inherent springy-ness of mild steel, dodgy steel quality and varying manufacturing tolerances.

Bending steel is indeed a fudgy art. But now you’ve got some numbers.

Around the World in 80 Days – Sound Design

Recently designed a radio play for the Long Wharf Theatre Radio Auction. Unfortunately air time became limited, so we could only broadcast one six minute scene. Good new everybody! The play is available for download here. Downloads as zipped MP3s.80Days.zip

The Long Wharf Radio Theatre Presents: Around the World in 80 Days. Adapted from the Orson Wells’ Mercury Theatre Radio play (based on Jules Verne’s book by the same title.)