Gas station without pumps

2021 August 29

Good juxtaposition of titles

Filed under: Uncategorized — gasstationwithoutpumps @ 10:22

There was a good juxtaposition of articles on the Guardian web page today:

‘The smartest person in any room anywhere’ In defence of Elon Musk, by Douglas Coupland‘People wanted to believe’ Reporter who exposed Theranos on Elizabeth Holmes’ trial. As blood testing startup founder’s fraud trial looms, John Carreyrou says hero worship is still a problem in Silicon Valley

So we have a hero-worshipping article right next to a warning that “hero worship is still a problem” and the possible consequences (massive fraud) of hero worship. I wonder whether the pairing was deliberate or accidental.

(The article about Elizabeth Holmes’s trial is worth reading, but the one about Musk is a cringey hagiography—guess which one got top billing by the Guardian.)

2021 August 23

Dragon key holder

Filed under: Uncategorized — gasstationwithoutpumps @ 15:18
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In 3D printed names, I showed a key holder for my home and office keys, which finally failed after 3 years.  My family has been bugging me to replace it anyway—pointing out that it is stupid to have one’s name on a key holder, as it makes it easy for anyone to figure out what doors the keys are for if they get lost.


The key holder cracked at one of the bolt holes. It was still sort of usable (the keys were still constrained by the bolt and the cover plate was not yet coming loose), but it looked bad and would sometimes snag when I was trying to get it out.

I decided to make a new key holder with a dragon motif, based on a sweater from Past Times that has gotten too moth-eaten to wear, but that has a pattern I like.


I took only the dragon part of the pattern, which is 18 pixels by 109 pixels (20 by 111, if you include a 1-pixel white border).

My first job was to transcribe the knitted pattern onto squared paper, then type it into the computer.  I had hoped that OpenSCAD’s “surface” function (which I used successfully for the quantum dot pendant) would let me convert this image easily to a 3D relief, but it did a terrible job, as each black dot became a sharp peak.

I ended up using the Pillow fork of the PIL Python package to manipulate the image and export it in PNG format.

    im_5=im.resize([5*(num_rows+2), 5*(num_cols+2)], Image.NEAREST)

I resized it by a factor of 5, ran it through a “max” filter to spread out the black, then smoothed it.


The PNG file is the negative of original image. Unfortunately, the checkerboard grid does not print well at the size I needed to make the image.


I edited the pixels manually to get a somewhat more printable shape, then did the same sort of spreading and smoothing.

I initially printed just the dragon on a little oval, to see how it would come out, before adding the rest of the key-holder design from the original key holder.  Because OpenSCAD produces huge STL files when the “surface” function is used, I simplified the STL files with


Here are the 3 samples. The top one tried just expanding the pixels to 5×5, the second one did the smoothing, and the third one got rid of the checkerboard patterning.


The first two prints were failures. The top print was done face-down on the glass bad (as I had done the previous key holder), but there was too much spreading on the first layer. The second print failed because the glass plate rotated during the print—I had to add hot glue to it again, to keep it in place.


The final key holder is ok, but it would really look better if I had a smaller nozzle (the 0.4mm nozzle limits the horizontal resolution).


Here is the finished key holder with keys—I expect that it will last another 3 years (though I did use 50% fill this time, to make it a little stronger).

I’ve uploaded the design to

Final 3D-printed “quantum dot”

Filed under: Uncategorized — gasstationwithoutpumps @ 14:44
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In 3D-printed “quantum dot” and 3D-printed “quantum dot” revisited, I wrote about my attempts to 3D-print the image from

I finally got good prints from the resin printer at work (they had to clean the optics on the printer) and a decent print of the “stage jewelry” version on my Monoprice Delta Mini printer. I gave away all the prints (including the failed ones) to the physicists who provided the data, except for the one best print in each size.

The STL files from OpenSCAD are ridiculously large (17.8MB and 19.1MB), but they can be reduced using without much loss of detail to under 1MB.

The OpenSCAD program, scaled data file, and two STL files are available at


Here is the resin print, which is 50mm in diameter. The peaks come out clean and sharp, but my only color choices were black and clear (the only two resins BELS had).


The back of the print has the scaling information, but even with sanding the spots from the supports are annoyingly visible.


The stage jewelry version is twice as big, with a diameter of 100mm (I measured it at 104mm—I think my printer calibration may be a bit off).


Again, the back has the scaling information. Using “concentric” for the bottom layers made for some interesting patterning.


Here are the two quantum-dot pendants side-by-side, to show the relative sizes.

2021 August 22

Secret Walks: Branciforte Creek

Filed under: Uncategorized — gasstationwithoutpumps @ 13:37
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On Saturday August 21, my wife and I took another walk from Secret Walks & Staircases in Santa Cruz, by Debbie Bulger and Richard Stover. This time we did the Branciforte Creek loop (which also includes part of Carbonera Creek).  Including the walk downtown and back, the whole walk was about 6 miles. We spent some time downtown after the walk (at Bookshop Santa Cruz and New Leaf), so we don’t have a good estimate of our walking speed.


The water lilies in the duck pond at San Lorenzo Park were in bloom—something we rarely see.


In the other part of the duck pond, the water lilies were not quite so exuberant, with the leaves resting on the surface and most of the flowers still in bud.


The playground at Central Park is being renovated (though it is apparently way behind schedule). It looks like they will be putting the carousel back after the renovation.


I have no idea what these concrete structures are at the end of May Ave, where the path on the north side of Branciforte Creek path starts. (I rarely take the path on the north side—I take the path on the south side of the creek far more often.)


We saw this tree with scaly needles and fluffy seeds, but we have no idea what it is.


Cattails grow in the concrete ditch that is Branciforte Creek in the city.


The channelized creek is really quite ugly when there is almost no water in it.


The transition from the natural creek to the concrete channel is really quite startling.


If I remember right, these stairs down to the creek are across Carbonera Creek from the path we were on.


The day was damp (unusual for summer in Santa Cruz) and there were raindrops captured by cobwebs on juniper bushes.


This cute house is on Kennan Street.


This old concrete building is in an enclosure with a lot of power poles—I suspect is it an old power substation, from back when they built them like buildings.


Another tree we couldn’t identify. It is probably some sort of sycamore (genus Platanus), but the ones we know have single seed heads, not garlands of them.


This amusing (and inaccurate) cartoon is part of the plaque in San Lorenzo Park commemorating where bullfights and bear baiting used to take place.


The cloudy grey sky made a good backdrop for the shiny scales of the dragon on the Chinatown gate.


The Nickelodeon has been closed for over a year, but they will have to move these planters before they can reopen.


This weird succulent is growing in our neighborhood—I rather like the snake-like appearance.

2021 August 15

Secret Walks: Woodrow-Swanton-Derby Park

Filed under: Uncategorized — gasstationwithoutpumps @ 11:15
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On Saturday August 14, my wife and I took another walk from Secret Walks & Staircases in Santa Cruz, by Debbie Bulger and Richard Stover. Because our last walk was hilly, we decided to do a flat one in the neighborhood this week.  The total walk was about 6.8 miles, with 1.7 miles to walk to the start at Woodrow and West Cliff and a somewhat longer route home.

We took King to Miramar, where we crossed Mission to the Safeway shopping center, then Rankin to Bethany Curve, and Bethany Curve to West Cliff. We crossed at West Cliff at Woodrow, and walked west along the West Cliff path.  The path has been eroded in a number of places and is really too narrow now for both pedestrians and bicyclists.  I think that it is time to close a lane of West Cliff Drive and move the bike path onto the closed lane.

We turned up Swanton and right on Modesto Avenue, as the book suggests, but we discovered that there is a parallel secret route, which I’m really surprised is not included in the book: Modesto Alley, parallel to Swanton.  We walked back down Modesto Alley, then a block back on West Cliff to go up Chico Avenue back to Modesto Avenue, where we rejoined the original route that went through Sergeant Derby Park.

We made another modification to the route when we got to Swift and Ingalls, walking through the courtyard and past West End Tap to the rail trail, rather than the route up Swift suggested in the book.  We continued the route in the book back to West Cliff, but did not feel like repeating any section of West Cliff, so we went east of De La Costa, north on Almar, east on Plateau, north on Woodrow, and counterclockwise on Walk Circle.  We stopped at Santa Cruz Market for an It’s It sandwich each, then took California to Palm to Mason to Bay to King to Van Ness to get home.

Here are some pictures from the walk:


This is the pedestrian cut-through connecting the two parts of Bethany Curve. It is one of the wider “secret” connections, but is surprisingly hard to see from even half a block away.


I showed this frame in a post for an earlier walk, but I thought it might be useful to give little more context.


The “naked ladies” (Amaryllis belladonna) are surprisingly hardy and can be found at this time of year all over Santa Cruz. These are near the ocean end of Bethany Curve. We like the bare stalks, but don’t care as much for the pinkness of the flowers. There are other naked-stalk lilies with bolder colors (various Lycoris species), but I’ve not seen them in Santa Cruz.


The walk along West Cliff Drive has several impressive views of waves breaking on the rocks.


Views of beaches, cliffs, and trees are also plentiful.


These conifers (I think a pine and two cypress) are particularly fine.


My wife and I are both partial to the growth patterns of cypress trees.


The waves sometimes get quite high, as evidenced by this strand of kelp dangling from the edge of the cliff, obviously washed up by a high wave and tangled in the ice plant at the top of the cliff.


We’ve known about the existence of the wavemotor for a long time, but never looked for it before. It is easily seen from the point just east of Chico Ave.


The waves were not cooperating while I was photographing, but I did get one shot of the jets of water coming up through the wavemotor. When the waves are bigger, it is probably more impressive.


This map (basemap from Google Maps) shows the location of Modesto Alley and the approximate location of the wavemotor, which is just visible in the satellite view on Google Maps.


Here is the entrance to Modesto Alley from Modesto Ave. The road only extends to the Modesto Alley sewage-lift station.


Past the sewage-lift station is a pleasant walkway that the neighbors have planted as a garden.


I’ve never used this entrance to Sergeant Derby Park before—it used to be easy to cross the Natural Bridges School property (now rented out to Gateway School), but all the Santa Cruz City School properties have now been fenced in to keep the public out, making schools much more prison-like.


The skatebowl in Derby Park is not as modern a skatepark as the others in the city, but it was one of the first public skate parks in the country and is still popular.


Graffiti in the skate bowl is accepted as part of the skateboard culture, but I’m not sure what the building owners think of the graffiti facing the park.


On all our walks, we stop at little free libraries, which Santa Cruz has by the dozens. I was going to check, to see how many were mapped (only a small fraction, I suspect), but the website was not responding.


The obelisk at the “Court of Mysteries” has been nicely restored, but chopping the site up into two lots does somewhat damage the integrity of the art.


The gate and the main building have been restored also, but the big house added on the lot does intrude a bit—unfortunately, building the house was probably the only way to provide the funds for restoring the site and making sure that it was properly cared for.


The second obelisk is really quite close to the new house.


My wife likes this cactus garden, though she thinks that the few non-succulent plants around the edges should be removed and a full desert look maintained.


This fountain decorated with large abalone shells has clearly been here for a while—large abalone shells are now extremely difficult to obtain.

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