Double-dovetail Arca-compatible quick release plate (with FreeCAD sources)

TL;DR: this is a double-dovetail (reversible — usable upside down) Arca-compatible quick release plate, with FreeCAD sources, broadly based on a published description of the Novoflex Q=Plate. I include both a simple model containing the profile embodied in a sketch, and an example plate using it.

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Why do another of these?

I need a design I can freely use in my own projects, and I thought it might be useful for people to have a FreeCAD version that can be tweaked more easily than STL. 

Also because this particular profile has a good chance of being highly compatible.

Compatible? Aren't they all? It's a pretty simple standard, right?

Yeah. No.

As the most exasperated among us know, "Arca-Swiss" isn't a standard at all. It's more like a belief. They never published a standards document to look at. As a result, quite a few supposedly-compatible plates either won't fit, or won't tighten fully, in quite a lot of clamps.

Booo :-(

But there are some broad traditions of the faith, and they are slowly merging into a single church:

• a "North American Standard" – this is an imperial-measurements design, e.g. Really Right Stuff's RRS Dovetail Standard
• a recent metric-based, broad European standard called UniQ/C which counts among its members Cullman, FLM and Novoflex
• all the Chinese plates on eBay and Amazon, which are improved knock-offs of various different existing designs from Europe and the USA

I did a fair bit of research on options for my designs, and found this amazing article on the blog of Speedgraphic, a great UK retailer. 

As well as providing much of the detail above, it includes a diagram of the cross-section of the (single-height, double-dovetail) Novoflex Q=Plate, which they have redesigned in the last decade to achieve broader compatibility with North American hardware.

(Edit: alas the fabulous SpeedGraphic are no more, and nor are the diagrams on the blog)

I have implemented a version of this profile as a FreeCAD sketch, with some rounding of corners inspired by other designs.  

I also include an example plate made from that profile; the photos are of an earlier iteration that has tested well in the various clamps I own.

Testing

I've only tested in Chinese-made clamps from different manufacturers. I would be interested to know if the profile does not fit something you own, and if so by how much.

The profile does not include tolerances for FDM printers. I figure the looseness of the Arca-type design probably accommodate those.

You may wish to adjust the profile to use chamfers instead of fillets on the bottom and/or top. I have found that fillets are fine at such a small radius.

I am not a FreeCAD expert by any means, so I welcome feedback or corrections on anything I could have done better.

Licence

Public domain; use these as you like. 

Bear in mind that this is not my profile design. Though it has been openly published, it is really from Novoflex. I don't know what that might mean for commercial use.