Monthly Archives: July 2015

Misc week 15-30

Not much happened for me on-line last week, cause I spent an awful amount of time travelling:

  • ZRH -> ZRH airport: tram + train
  • ZRH – airport -> Milan airport: flying Swiss
  • Milan airport -> Shanghai airport: flying Air China, need to get my luggage and checking in again forced me to spend 6 hours in the public zone tof the airport :-/
  • Shanghai airport -> Sydney airport: flying Air China
  • Sydney airport -> Sydney office/hotel: Über black

5 days in Australia and time to head back

  • Sydney office -> Sydney airport: ÜberX
  • Sydney airport -> Beijing airport: Air China
  • Beijing airport -> Milan airport: Air China
  • Milan airport -> Milan train station: Taxi
  • Milan train station -> Dijon train station: night train
  • Dijon train station -> Dole: local train
  • Dole -> Arbois: car (non driver)
  • Arbois -> Zürich: car (driver)

My comments on this small adventures are multiple:

  • I had to get my luggage and check in again in Shanghai, meaning spending 8 hours on a bank in the check in zone (cause I could not check in too early) and passing customs twice. Gross.
  • Air china is really great: cheap enough to fly business, great blankets and pillows, great chinese food. Not so great western food and flight entertainment is mostly Chinese
  • I’ve used most transportation means except buses 🙂
  • Milan train station is far from Milan airport : 1h taxi ride, worth 120EUR, ouch
  • Über in Australia is strange, couldn’t pick an UberX to go from the airport and ended up with quite a big fee. I might have been too jetlagged to read the app correctly though.
  • Night train from Milan to Paris is awful: I couldn’t fit into the bed, was supposed to have booked 1st class, ended up into a 6 beds container, no sheets, quite dirty, very noisy despite noise cancelling headphones and customs officers barging at 2:00am
  • I bless the battery life of my mac book air who left me with something to watch for most of the trips
  • Showers in Beijing were broken in business lounge, but I could use the one from first class
  • It’s an awful trip for 5 days on site
  • Everything went smooth, as planned
  • I had to come back to France for my dad’s birthdays, meaning I spent most of my week-end working. No jet lag! (or it didn’t kick yet)
  • “winter” in Australia is overrated : it felt like late spring at home, very nice compared to the local heat
  • I had forgotten to apply for a visa: good thing ESTA could be done the previous week

 

Designing gears with inkscape

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

Theory

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

 

Inkscape

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

Test

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 🙂

Misc Week 15-28

This week, quickly:

  • I looked for a parametric 2D design tool : I currently use inkscape for preparing design to laser cut, but switching from one thickness to another requires mostly a full redesign. I want to be able to draw with parameters and change easily thickness without having to do a full redesign. I found an interesting serie of articles named the failed promise of parametric cad
    • OpenCad, which is 3d, text-based (hence fully parametric): works not too bad in 3d, can be awfully slow to render pieces.
    • FreeCad: Mostly 3d, everything is parametric, but I’ve hard a had time pinning references (which is critical for parametric). Reworking a model can lead to broken pieces, better to have frequent backups (and soft is not too stable, tested on 3 different platforms). Never really tried the 2D mode.
    • Inkscape: no parameters, once it’s done, it’s done.
    • SolveSpace seems to be a solution, I failed at using it…
    • Lots of references here, I didn’t try them all but it seems that a quick scan of the references yields no magic result
    • Any proposition welcome, I’ve almost started my own…
  • Discovered a new tool for annotating online videos. I haven’t tried it but ClipMine seems pretty great, it’s in my todo list
  • I like Visual Studio as an IDE and it has now a Community version, free for hobbyists (it’s not a news in itself, it’s only for me). I must say that I like the trend of companies offering their tools for free for hobbyists. In the same context, Altium has a free version for hobbyist (with some restrictions, like storing everything publicly on the cloud, which is fine for home electronics). Note that Eagle for hobbyists is AFAIK much more limited. If you’re more into making things, Autodesk offers Fusion-360 for free to hobbyists (and start ups). Yoohoo, most of the tools I need are actually legal. Wish they were open-source rather than free to use, but it’s really great (and currently, there  is no OSS competition on these subjects).
  • I know have more than 5k rep on stack overflow, mostly just answering one question from time to time when I got bored
  • I’ve played with arduino, ESP8266 and Internet of things, more details (full post) to come soon.
  • Some howto on living hinges: it’s a topic I want to try but I didn’t find enough time yet. As usual with living hinge, it got me pretty excited and I got quite a few ideasin my mind.

R.I.P Billy

R.I.P Billy, for thou shallt be reborn and never forgotten.

I had an old Billy shelf which was starting to collapse and had the wrong color (moved from one room to another…). It was time to swap for a brand new one (yeah, trip to ikea!!!). The old one got repurposed in my cellar to store my tools.

For those interested:

  • I used 5 horizontal layers of the Billy, 3 vertical to make the back, 2 horizontal, held by EKBY STÖDIS
  • The top of the shelf is reinforced with a vertical part of GORM that was lying around that I cut to size and screw
  • A set of nails was used to hold the tools
  • The shelf itself is hanging using hose clamps (holes are 8mm, inside both the vertical billy and the grolm)
IMG_20150712_113204
top of the shelf and hose clamp (front)
IMG_20150712_113215
back (from the public area surrounding my cellar)
IMG_20150712_120802
finished result

PC cooling

I had a Corsair H60 cooling kit which used to be quite silent. It died: pump did not pump any more and it led to overheating.

I changed the kit to the superior Corsair H80, which is a crank higher. Ever since, the noise has been really loud. The H80 is using a pump and a closed circuit, with the intercooler being fanned by 2 12cm (push-pull). The trick is that the H80 pump is connected to USB and control the fan directly (not the mainboard). I had never given it much thoughts, but it seems that despite being connected to USB, there is no user interface and no way to change a response profile (speed vs temperature). This is dumb as my PC is clocked at standard speed and I end up with a CPU at 37°C while gaming.

Yesterday, I removed the connexion of the fans to the pump and plugged them directly with the mainboard (3yrs old good quality Asus). A few minutes of tuning and CPU burning later, my PC is quiet again. I plugged the following way:

  • pump : plugged to main CPU FAN
  • push to intercooler : OPT CPU FAN
  • pull from intercooler : ALT CASE FAN
  • Pull on toop of case : CASE FAN

I added an additional tuning of the graphic card using afterburner.

I played Borderlands for 2 hours as a benchmark. Conclusion : the CPU now rests at 45°C and the case becomes quiet in 5 minutes after gaming stops. The graphic card is much hotter 70°C but seems to be fine.

I’m happy (and my wife who complained about the noise even more). As a side note, the temperature in the room where the computer is raised to 35°C after gaming : not the best season….