[CamperBob2]

Great info, makes sense. (Mostly... I'm not sure I see how the tighter clearances with AngleLock are somehow immune to the tolerance concerns that exist with the legacy hardware.)

If it's backward-compatible as you note, that's definitely a win.

[johnwalkr]

The video/timestamp in my last comment is probably easier to understand than my explanation. Using z as the long axis of a beam, let's set up a coordinate system. There are 6 possible degrees of freedom: rotation about x, y or z or moving in x, y, or z.

     y  
     | 
     |___ x
     /
    /
   /
  z

Anglelock doesn't have tighter clearances per se. The anglelock is designed so that there is lots of clearance for assembly but when the screw is tightened, the part is not only clamped to the surface of the beam but also wedged into the slot. The only constraint that is not a hard shoulder is in the z movement direction. But it's wedged in the slot and not only held by the friction on the xz surface. So both movement and rotation are very well constrained in x, y and z.

Normal t-slot beams are designed so that when the screw is tightened, the part is clamped to the surface of the beam only. So movement is very well constrained in y only, and rotation is very well constrained about x and z only. The remaining constraints are all limited by friction on the xz surface.

Does this matter for most structures? Probably not. But if you need something very stiff and precise/self-aligning, anglelock would be a nice solution compared both t-slot beams or weldments.

You can add more screws but from experience to make stiff structures from t-slot beams, you have to connect beams together in multiple planes. i.e.: it takes a combination of machining threaded and thru holes in mating beams, corner brackets and/or cross-members plus plates. And you have to be quite deliberate in where/how to connect things together because you also need space to everything else like doors, motors, sensors to the structure. Plus all this stuff is not automatically perfectly aligned due to the clearances involved.

In my last comment I was trying to explain how just reducing clearances won't work. You always need some clearance to assemble and account for tolerances of parts, so even if you add a feature to constrain movement, when you apply load in some/most directions, it's only reacted by friction at first. So it won't turn into a parallelogram, but it also won't add stiffness in the same way. It also won't have the wedge everything together in the same way.

I think anglelock beams/legacy parts are compatible, but not legacy beams/anglelock parts. But this still means all your existing doors, mounts etc work with anglelock beams. In a new design you would still probably still use standard parts except for the structure, and in a pinch you could always add legacy beams to your anglelock structure.