Barrys News

3D bottom swing-arm for custom recumbent trike

February 13, 2025 — BarryK

I posted about exploring various 3D CAD apps, script-based then came back to SolveSpace:

SolveSpace extrude limitation — February 13, 2025
Scripted 3D CAD applications for Linux — February 12, 2025

...designed the top swing-arm for my custom trike.

If you look at my custom trike project, the swing-arms, also known as A-arms or wishbones, are welded steel and ball-joints:

"Solar-powered recumbent trike"
https://bkhome.org/nomad/solar-powered-recumbent-trike.html

I'm planning to put stiffer springs on the front suspension, and reduce the wheels from 20 inch to 16 inch.

But also there is this germ of an idea to create plans so anyone can build a similar trike, from scratch. Plan for it to be mostly aluminium, including the swing-arms.

Working toward that, want to model the entire trike in 3D.

Haven't taken my trike on any journeys yet, just ridden around locally. Have learnt a lot about the handling, which is why want the stiffer springs -- they are on order. Going around corners, I can see that stability would be improved if the trike can lean into the corner, so would like to implement that on the next build. Either that, or make it a quad.

Can't go off touring on the trike anyway, as having an eye operation soon, followed sometime after by a train journey.

This evening designed the bottom swing-arm in SolveSpace:

...notice something a bit odd; there are two brackets to which the shock absorber will bolt, a choice of two positions, but you cannot see right through one of the holes. SolveSpace is having some kind of logic problem there. It doesn't surprise me, the complicated mathematics that SolveSpace has to analyze.

The bottom-arm SolveSpace file is here.

Posting this in the "light" category, as it could be the start of an entirely new traveling-light custom-trike project.

Tags: light

SolveSpace extrude limitation

February 13, 2025 — BarryK

I posted about examining script-based 3D CAD apps, then returing to SolveSpace:

Scripted 3D CAD applications for Linux — February 12, 2025

previously, I have only done wire-constructions, both 2D and 3D; now learning how to do extrusions, so as to get a proper-looking 3D object. I designed the upper-swing-arm of my trike, using knowledge from the SolveSpace getting-started tutorial here:

https://solvespace.com/bracket.pl

It was OK, designed the swing arm and exported a PNG image:

Nice, but there is a problem. Notice the ends of the swing-arm; sharp corners. I was unable to get rounded corners. The extrude feature does not support it. The holes were created by punching-through circles, and I thought that the same technique could be used on the corners. But no-go. I tried triangles and arcs, but it seems that the punch-through only works for circles.

I came across some discussion; the developers are aware of this limitiation, and there is a hint that SolveSpace v4 might tackle it.

It's not a deal-breaker. For anyone interested, the SolveSpace file is here.

Tags: linux

Scripted 3D CAD applications for Linux

February 12, 2025 — BarryK

EasyOS has SolveSpace builtin, that I have been using for years. It is very powerful, and relatively easy to use; however, recently I have been wondering about the script-based CAD apps.

Reason is, the precision of defining a 3D design in code, appeals, as opposed to sketching on a GUI work surface. Basically, you write code in an editor, click on a "Render" button and another window shows the generated 3D image.

Started off looking at OpenSCAD, then some others, such as PyMADCAD and ZenCAD. But then started to wonder about limitations. In a forum, someone who was using OpenSCAD, asked, how to measure the distance between two arbitrary points on the rendered 3D image? He commented that he often needs to be able to do that, and I thought, me too. But you can't; that is going "backwards". The 3D image is just a render, and seems that none of the script-based 3D CAD apps support measuring distance between arbitrary points?

This page has links to lots of script-based CAD apps:

https://www.reddit.com/r/openscad/comments/135dllm/better_openscad/

That is not a complete list. For example PyMADCAD:

https://github.com/jimy-byerley/pymadcad

There are so many to investigate, it just goes on and on. But for me, wanting to be able to experiment with adjusting linkages directly on the 3D image in the custom trike project, SolveSpace does it beautifully. So, I've been working through some SolveSpace tutorials, learning more how to use it.

SolveSpace homepage:

https://solvespace.com/index.pl

...there are tutorials, here are more:

https://www.farwire.net/SolveSpace-LearningGuide.htm

https://www.youtube.com/watch?v=dHnVAw7fCPg

https://www.youtube.com/watch?v=IlY1YFid8HA

...there are heaps more on YouTube.

So despite the title, I am back on SolveSpace. It was an entertaining diversion for awhile, and I might even look at a couple more.

Tags: linux

Limit Chromium disk cache size

February 09, 2025 — BarryK

Wow, a file 919MB:

https://forum.puppylinux.com/viewtopic.php?t=13807

I'm running Chromium right now, and /home/chromium/.config folder is 381MB. No single huge file like TerryH has experienced; even so, a 381MB folder is too big. I have done what TerryH suggests, put in a limit of 100MB, see github:

https://github.com/bkauler/woofq/commit/36ab8ba5d75b641026a8d367ea447ccce703f93b

To fix right now, you can add this option "--disk-cache-size=100000000" in chromium.desktop, as TerryH has done, or insert it into /usr/bin/chromium, line 5.

Tags: easy

Rollback if broken after version update

February 08, 2025 — BarryK

It happens. We have feedback of various things going wrong, for example Xorg won't start and just dumps you to the commandline.

If you have tried to fix it, but no-go, you can rollback to the previous version. The initrd has a boot menu:

Number 5, "Rollback to previous version" will do it; however, there is a catch. It will rollback to the last snapshot of the previous version. If you didn't take a snapshot just before updating, then you might lose something important. If you didn't take any snapshots, there will only be one, that EasyOS takes automatically at the time of the previous update.

Forum member Federico updated from 6.5.4 to 6.6.1, but Xorg was broken. I explained about this "Rollback to previous version" trick:

https://forum.puppylinux.com/viewtopic.php?p=142163#p142163

Explained:

EasyOS automatically takes a snapshot at the update. In Federico's case, this will be /mnt/wkg/releases/easy-6.6.1/rw-6.6.1.sfs

The thing is, this snapshot is the status just before the update, so the trick I explained in that post was to copy rw-6.6.1.sfs to /mnt/wkg/releases/easy-6.5.4/rw-<today date in format YYYMMDDHHMM>.sfs

But, no need to even copy it, just a hard link (not a symlink). So why can't EasyOS do that automatically? Yes, now done:

https://github.com/bkauler/woofq/commit/4502aeb78fe5d3b2ef945b95a8c6f264474a88e9

So EasyOS has now automatically created a snapshot in version 6.5.4, then updated to 6.6.1. This makes it real easy when you choose "Rollback to previous version" in the initrd menu; you will be back to exactly just before you updated. This is good.

EDIT 2025-02-09:
Improvement, see github:

https://github.com/bkauler/woofq/commit/80a8dd4e2eab0ae2c2f9f21cdb3cfab2676c5b61

Tags: easy

EasyOS Daedalus-series version 6.6.2 released

February 08, 2025 — BarryK

Easy Daedalus has now reached feature-parity with Easy Scarthgap version 6.6.2. They are, however, built with different packages; Scarthgap with packages compiled in OpenEmbedded/Yocto and Daedalus with Devuan Daedalus (Debian Bookworm) .deb packages. There are advantages and disadvantages of each, but newcomers to EasyOS are recommended to choose Scarthgap.

Scarthgap 6.6.2 was released yesterday: