mcdanlj

mcdanlj, 2 minutes ago

@smellsofbikes Wow. I just went and looked — 2721 kg load on hook! That's almost exactly 3 short tons...

A third the purchase price must be for four long perfectly clear pieces of spruce good enough to trust for those rotors. 🤪

mcdanlj, 5 hours ago

@chrishuck @smellsofbikes Approximating the cuts with a straight dovetail cutter and accepting curved lines on the side, or making a set of custom dovetail cutters?

If you have a CNC lathe handy, I think you have a better chance than me of making all the custom dovetail cutters. I think with Realthunder's fork, the ability to use imported geometry as defining geometry in a sketch could make the cutters easier to define.

The fact that any set of eight cutters would be specific to a single size of box (ignoring height) makes this feel like a lot of work to me.

mcdanlj, 4 hours ago

@kbob @smellsofbikes @chrishuck I used a sketch to look at what the cutters would have to look like. For my example 4mm high dovetails 15mm max width, 30° angle, and a 60mm outside box with rotation point 4mm inset in both X and Y in from the corner, it looks like if one used straight cutters instead of curved cutters, the max deviation from the defined curve would be about .016 mm, which in reality would be half of that if you split the difference top to bottom. In imperial, that's about 3 tenths (ten thousandths of an inch) which is beyond the skills of most home gamers like me.

Also, good luck finding a set of 10.736°, 17.541°, 30.399°, and 30.965° dovetail cutters off the shelf! 🤣

Realistically, I do wonder how close the most extreme angle would have to be to deceive the eye on casual inspection. Especially after some creative deburring work. It doesn't have to be straight, it only has to look straight.

Extreme close-up view of dimension showing max deviation of chord from conic section

mcdanlj, 3 hours ago

@chrishuck @smellsofbikes I just pushed a fix to my model. I had somehow gotten a sketch attachment not parameterized. Now the box resizes when the parameters are changed.

My model with 200mm square plan

mcdanlj, 2 hours ago

@kbob @smellsofbikes @chrishuck Never having taken analytic geometry, I am not equipped to find the chord mathematically, even though I can model it concretely.

I haven't figured out how to model it in a robust parametric way. An analytical solution would let me use expressions to determine cutter angles for each surface parametrically, so if anyone wants to contribute those expressions I'm all (virtual) ears. Besides an analytical solution, it's possible that the TNP mitigations could make a model sufficiently robust in practice to allow configuration.

For recording iterative solutions, I could reasonably set up multiple configuration tables, including one just for the combinations of parameters that impact dovetail edge shape, and keep that separate from other configuration.

mcdanlj, 15 minutes ago

@kbob @smellsofbikes @chrishuck I was being silly.

I was thinking that I needed to find the conic section, then project it into a plane, then take the chord.

I was making it hard.

It's just triangles.