Youtube and me

I’m from a generation who was taught that the ultimate source of knowledge are the books. I managed to evolve on my own and found that internet is a wonderful place where lots of people share lots of interesting stuff. I was pretty happy with that situation : look for a blog post or an instructable, a random tutorial, more or less crappy, follow and tune, troll. I had the manual on how to do it, from newsgroup to phpbb forum. Eh, I even got my own personal blog!

The new generation seems however to have moved out of written knowledge and shit into using video as a solution to any problem. I personnally don’t like too much, I find much easier to skip and follow written instruction than a video whose focus is not always on the interesting part. Anyway, if the moves has moved that way and the cool kids are doing that, I guess I don’t have too many choices : follow and try to be a cool kid (ahem) or start becoming obsolete. I feel too young to be obsolete, so I looked at what is the effort required to create a decent youtube tutorial.

Bear with me: I didn’t want to do a crappy video with my smartphone of me doing something stupid (see : tthat how you plug an sdcard into a raspberry pi while focussing on the cable behind. I wanted to do something nice, not prolfessional but somehow useful.

Conclusion, it’s tough! My personal computer environement is composed of mac (corporate laptop), linux (poor laptop) and windows (gaming rig). It seems obvious that I want cross-platform tools, I got kids and less freetime than the average student, not talking about the random teenager which seems to be the most adept at posting content.

Ok, I tried tonight, spent roughly 3 hours on a simple inkscape tutorial

  • I used Open Broadcaster Software for screencasting and mixing video and sound
  • I used lightworks (free as in free beer, not free speech) for assembling clips together

Lessons learnt:

  • if you want to explain something, better know exactly what you are doing. Especially, first try was a one shot with lots of trials and errors. So shot sequences and mix them later.
  • mounting sequences is hard: it took half the time to just link them together and it seems I managed to export a 30 minutes video while having 10 minutes of content
  • software limitations are bitches: I shoot in 1080p, could only export to 720p, which is a major issue when shooting a screencast.
  • my microphone was saturating, so I reduced gain. And then you can’t hear me (used my heaphones as microphone)
  • had to shoot twice cause I used a bad codec the first time, this pissed me of (we’re in 2015, isn’t the codec mayhem supposed to be fixed?)

Next time:

  • redo the same video, I’m becoming exceedingly efficient at drawing dodecahedrons schematics
  • write a script that you can follow
  • keep empty space before and after each recording, it’s easy to trim
  • read more tutorial on mounting tool, maybe switch to cinelerra?
  • prepare an intro, add titles and copyrights
  • merge some sound as background and control current sound level
  • avoid any kind of copyright infringement

If you want to laugh, here is the result:

Designing gears with inkscape

For a hush hush project, I need to use gears and I plan on designing and laser printing them.


I found this old article which explains a lot on how to make gears with (older) inkscape. It relies on the following technical reference. With new version 0.91, things have been a bit simpler.

Unit can now be express in human readable values (i.e. mm). To make gears compatible, you need to use the same circular pitch – let’s use 5mm.

I want to have a 2x transmission ratio : let’s build a 12 teeth gear and a 24 one. I’ll use a turnion as axis, 8mm central hole is then fine.

Gear Teeth Pitch Diameter
Gear 1 12 teeth*p/pi=12*5/3.1415=19.09
Gear 2 24 teeth*p/pi=24*5/3.1415=38.19
Gear 3 18 teeth*p/pi=18*5/3.1415=28.65

Distance between gears is (Di+Dj)/2

Gear 1 Gear 2 Gear 3
Gear 1 19.09 28.65 23.87
Gear 2 28.65 38.19 33.42
Gear 3 23.87 33.42 28.65



Render the 3 gears using the extension: Gear_plugin

Prepare guides to hold support. Motor gear will be Gear 2, offset 100mm. Keeping some space for security (0.3 mm), secondary gears will be Gear 1, offset 100-28.65-0.3=71 and Gear 3, offset 100+33.42+0.3=133.8. Using an horizontal line and snap on center on bounding box, you should end with something like that.Gear_Create_guide Gear_virtual_assembly

Move the gear parts to a dedicated layer, hide it and start with a fresh one. Use my plugin to create the holding box. You’ll want a holding box whose internals are roughly: 95*46*16 (we’ll be using 3mm thick plywood, 16= 3*5 + 1mm margin)Gear_Cut_box

Duplicate the top and bottom lid, prepare holes (9mm) fot the secondary gearsgear_bottom and front

Control will be done using a sg-90 servo (or a chinese equivalent). Mine require a rectangular hole of 23×12, axis is 6mm from top. Prepare hole and drill it.

Set drawing to 0.1mm red (cutting), 0.1mm blue (engraving, used for center of drill) and coloring to yellow pale, copy everything to a new layer and setup on page:gear_to_cut


I cut the prototypes and have a first round of feedback:

  • It’s working !
  • My drilling indicators are wrongly place (for servo), need to measure better, easy to fix
  • The offset I used to allow cranking (0.3 mm) is too much, as the laser itself as a few 1/10th of mm thickness. 0.1 would have been enough (or even 0)
  • Assembly is non trivial, I need to order additional hands
  • I didn’t fully assemble it so there is no picture (just snapped the pieces together to check)
  • The real version based on this proof of concept worked 🙂