Concept: High-Tension "Closed Force Loop" X-Axis (Tested for 5 years)
I designed a simple modification 5 years ago that allows you to tension your X-belt until it tunes to a high E on a piano, without bending the Z-rods or destroying your stepper motor. It's so simple I'm amazed it's not on printers. Therefore I share this.
Telescopic X-Ends: The right X-end uses dual horizontal pins sliding into the bearing holder. Belt tension pulls the blocks together internally, completely isolating the vertical Z-rods from frame-bowing forces.
Counter-Bearing Motor Mount: The motor shaft on the left is supported by an external bearing, preventing radial forces from bending the motor shaft or ruining the internal motor bearings.
Floating Z-Nuts: The X-axis rests freely on top of the Z-nuts using gravity, combined with a printed anti-backlash spacer that locks rotation but allows horizontal movement.
I don't have the STL files anymore, but it's so mechanically simple that anyone can model this for their own setup. It has been running flawlessly for 5 years and is perfect for high-speed printing / Input Shaping on older i3 frames.
[img] 
[/img]
[img] 
[/img]
[img] 
[/img]