Category Archives: Entertainment

Babylon The Master Builder’s Puzzle Cube

BabylonSet

We have been printing out little puzzles to test dimensional accuracy on the 3D printer in the lab, and it reminded me of a cube puzzle I had as a kid, which is now rather difficult to find information on. I’m putting this on the ‘net largely because coming up with search terms to unify all the relevant information was nearly impossible – I had to go root around at my parent’s house to find my set to connect all the dots. It was the source of many ragequits as a child, and it would be a shame to deprive future generations of the same …stimulation.
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Learning to LDP

I’ve wanted to learn to LDP (Long Distance Pump) since before I started skating. Every summer, I spend some time trying to learn to pump, and make minor adjustments to my setups to make it more practical, and for my efforts I could impart energy, but my setups have always been sufficiently sub-optimal that I only managed sustain speed with a pump a handful of times, and never accelerated.

LDParts_md

This summer I decided do it right. I bought the classic inexpensive LDP truck set (A Bennett Vector and a Tracker RTS, I picked the 5.0 and 129mm variants respectively), modded them for LDP, and installed them on my suitably sized deck with suitable bushings and wheels.

Distance skating attracts the best sort of crazies – It’s something of an equipment sport, so they tend to obsessively purchase and modify gear. It’s remarkably physically demanding, so there is a lot of the classic solo endurance sport mentality. It also has carryover from the “raah hardcore” skate world. Fortunately, the internet has brought together the appropriate crazies at sites like Pavedwave and skatefurther, where the discipline has been developed from its roots in the 70s.

Designed-for-LDP decks (Subsonic Pulse, LBL Walkabout, RoeRacing Mermaid, etc.) are boutique items and tend to cost in excess of $150 for the bare deck, so I wanted to ease in financially in smaller steps since I’m not sure how capable I’ll be. Most sources say 26″ to 31″ is suitable for an LDP wheelbase, and my Pakala III is around 25.6, so it is manageable if a little tight-pumping.

The mods for the trucks are pretty interesting, I implemented a number of the suggestions from this excellent thread on the pavedwave forums.

On the Bennett, I made myself a nice Polyoxymethylene(aka Delrin/Acetal) insert for the pivot. I think the technical name for this thing would be a bushing, but since that term is already in use for trucks, people have taken to calling these “hobo sphericals” or “fixed spehericals,” as the more elaborate alternative is to install a spherical bushing. I saw that Griffin sells fixed spehricals for Bennett trucks that look to be machined out of some flavor of Polyoxymethylene, looked at the sheet of 1/8″ Aceteal I had for another project, and decided to DIY. For those looking closely at the numbers, the insert is a little thinner than ideal (0.125″ sheet, gap depth measures around 0.16″) but it seems sufficient.

I hacked a small chunk off the sheet, held it under the truck pivot, and scribed the diameter into the sheet with a pin. I then did the typical chords-and-90°-angles center of a circle stunt, sanity checked it against a washer, and drilled the center to 25/64″ in a couple steps (starter drill, some intermediate size grabbed at random, 3/8″ because I wasn’t sure how sloppy I was being, then 25/64″) — Kingpins are 3/8, and it should slide freely, so a V letter drill would probably be technically correct, but I’ve never contrived an excuse to own a letter drill set, and was free-handing it with pliers and a handheld drill anyway, so 25/64. I then followed my scribe line with a coarse sanding drum chucked into a rotary tool, and fitted/finished it with a finer sanding drum. I’ve checked on it a couple times as I fiddle with the configuration, and it seems to be holding up and doing its job.

If I ever get my Shapeoko into shape for this sort of thing I should be able to punch out some nice precision parts for this on it.

On the RTS, I clipped the wings a bit with a file, as apparently the wings will chew up the pivot cup if you don’t. I then polished out the file marks and the whole pivot pin on both trucks with some tripoli compound and a felt wheel chucked up in a rotary tool.

Inital_LDP_Setup_md

At the moment I have the Bennett wedged to +10°, with Green and Yellow tall Reflex barrels, and the RTS at -7° with some blue Khiro barrels I had around, both stacked on top of 3/4″ of risers to keep it from biting – gives a ~5″ ride height, which is not ideal.

I built up speed by pumping the first time I stepped on this thing (and then wheelbit, got some road rash on my elbow, installed some more risers, and accelerated again without the painful sudden deceleration). I’m still clumsy and slow pumping, and I’m sure the setup can be improved, but it feels wild, and the dedicated trucks make a world of difference.

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Adventures in 3D Printing

The MakerGear M2 3D printer the KAOS lab ordered arrived last week. I am thoroughly impressed with the machine and how little fussing has been required to get decent prints out of it.

I’ve been pushing annotated pictures of our adventures with the M2 to a G+ album, because the auto-upload from my phone is too good to give up, even if the G+ album manager sucks. Take a look to get a taste of our massive new distraction.

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Shapeoko: Part 5

SH6-1
This was originally posted as Shapeoko: Part 6, because I apparently can’t count.

A while ago I ordered a 300W ER-11 DC spindle kit from China to install in my Shapeoko. I finally got to the post office yesterday (stupid recipient-must-be-present shipping) to pick it up, am impressed with the whole process. Most of this post is about the spindle, there is some more belt tensioner tinkering down at the bottom.

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Favorite Talks of 29C3

I’ve been watching the talks out of 29c3 as they become available online for the last couple days, and these are my favorites with comments. I’ve never come up with an excuse to actually go, but always find that it is the conference with the most things I am excited about every year, and end up watching more recorded sessions than I could have attended had I been present. The ones I picked below were both topics I found interesting and good presentations – there were a couple I hoped would be good but had talks that made me just give up and read the paper that I won’t mention here.

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Shapeoko: Part 4

I got some more time to work on my Shapeoko over the last few days, and now have mostly correct 3-axis motion. As before, details under the fold.

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SC12: A Review in Schwag

All the Schwag I brought back from SC12, as packed.

I’ve made a habit of these posts after SC every year, and took the pictures, so away we go.
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Shapeoko: Part 2

This continues from where I left off in my previous post Shapeoko: Part 1.

I alternated my Sunday afternoon/evening between tackling my grading backlog and building pieces of the Shapeoko. This pattern works well for tapping since they are both exceptionally tedious tasks, but in different ways. Gallery with captions below the fold:
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Shapeoko: Part 1

My Shapeoko kit arrived from Inventables while I was away at SC.

I’ve been trying to build myself a small CNC milling machine since 2009, and contemplating it for longer than that. It became clear that my original design, however educational, was a dead end sometime last year. I’d been idly watching the Shapeoko project for some time as it had similar aspirations to my design, and a couple months ago I was in a particularly mechanical mood when I saw that a batch had reached enough buyers to be produced, so I bought in for a mechanical kit to mount my existing electronics on.

The Shapeoko community is really excellent, and the kit was designed to be flexible, so I’m starting off with some suggested modifications – I’m using NEMA23 motors instead of the usual NEMA17 on the X and Y axis, because I already had some nice Lin Engineering 130 oz-in NEMA23 motors and the frame can fit them. I’m configuring for dual Y motors, which give more even force across the Y axis, and routing my belts on the outside of the frame, since I needed to buy different hardware for the NEMA23 motors anyway and this particular modification is widely recommended.

There is a gallery to document my first round of assembly below the fold (captions don’t display properly in the RSS feed).
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As a fun aside to the previous post, there is a story my parents like to tell from my childhood, which generalizes the kind of permissive learning objects learning computers are an instance of. When I was very little, I had a log into which I drove vast numbers of random fasteners – nails and bolts and screws and things of that sort. The log was just a piece of scrap wood, and the fasteners were leftovers and foundlings and other unimportant bits given to me, but it was undoubtedly good for my hand-eye coordination in general and tool use in particular. It also probably contributed to my now fairly developed mechanical intuition. At some point the ridiculous fastener-studded log came to be referred to as “the porcupine,” and for some years it was mined for fasteners whenever something odd was needed, until it began to rust and crumble and was thrown away.

To learn anything well, you need to do the thing repeatedly, you need to experience the variation in the thing, and you need to be free to experiment without worrying about how messing up this thing will affect other things. There is nothing better than a pile of scrap material to learn from.

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