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Comment by dougk16 | Hacker News Reader

Sort of related tool I made a year or two ago: http://dougkoellmer.com/front_rack

I used this tool to make a PVC front rack for my bike: http://dougkoellmer.com/front_rack/attached_side.jpg

I tried to do all the calculations by hand, but eventually realized I needed to make a little custom CAD program like this to help me. I tried more general-purpose CAD programs but couldn't figure out how to set up the constraints I needed.

Anyway I think there's a lot of usefulness in purpose-built online tools like this for generating templates and plans. Such programs are pretty easy to whip up too using the Canvas API and a basic geometric primitives library.

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Do you know about OpenSCAD and OpenJSCAD?

https://www.openscad.org/

https://openjscad.org/

They are both basically "CAD/CAM for programmers" - and allow for parametric models to be designed. In fact, there are more than a few models like that on Thingiverse, so if you needed to resize something to fit your needs, you can (plus tons of gear and other similar custom power-transmission systems).

Of course, that's all for design and modeling - it wouldn't help for other problems, where some form of calculation and checking of a "model" (in the sense of a simulation or idea - not necessarily a complete physical object rendering) is needed.

You see a ton of these kinds of tools in the electronics and hobbyist realms; quick calculators to tell you how much resistance to use for various LED configurations, or 555 timer customizers for common circuits - things like that. I know of one out there which gives you torque/power curves for a variety of different RC hobby electric motors. There are of course several for physics simulation and testing, too...

> it wouldn't help for other problems

I once had a problem with OpenSCAD when I needed to sort - within model - objects of different kinds. The example sorting algorithm (a quicksort) is shown in the documentation, but it was working only with a particular kind of objects.

Long story short, OpenSCAD turned out to be powerful enough to have a Lisp written in it. Lisp manipulated strings and allowed factoring out the sorting algorithm and applying it with different comparison algorithms, supplied as parameters. Given Lisp, I think it's possible that a lot of things can be done in an OpenSCAD script.

Wow nice links, thank you! No I didn't run across those. I was attempting it mainly with AutoCAD and its SDK since that's what I knew best. Will definitely be using OpenSCAD now for...something!

How did you decide to fasten with zipties and overhangs instead of holes through both pipes and bolts?

I didn't even really consider holes since my goal was to prove an idea I had of using "lincoln log joints" with "impact-tightened constrictor knot lashing". I'm put quotes around those terms since I made them up.

Check out https://www.youtube.com/watch?v=Mn0m104NVAY for how I tied and tightened all the knots.

If I did use holes though, assuming I kept the lincoln log joints as well, then I reckon that would weaken the joints too much, e.g. crack the pipe on hard impacts. Also all the weight of all the bolts would add up quick. Hmm I suppose I could use plastic bolts of some kind, but then they'd have to be thicker, thus making the holes bigger, thus weakening structure further. Just thinking out loud. There could be a way, but yea I was proving the lashing concept first and foremost.

Thanks for the question. :)

You're giving me some ideas for what to do with a bunch of bamboo I have overgrowing my area. "Standard" methods for dealing with wood cylinders aren't very strong or convenient so I'm seeing from your work how traditional asian construction arrived at lashings. Bamboo is so strong and light, it's a shame not to use more around the house.

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