Ball Screw Non Drive End Floating Bearing Design Variants and Help

[Halbmond]

I have a work station setup for a tribute to university lab.
The previous ball screw was 40 mm diameter and 2078 mm travel with 5 mm pitch.for a vertical application.

For the motor drive end, there is standard FK30 fixed bearing. (with angular contact bearing pairs 16x30x62 mm and lock nuts and spacer collars)
For the loose end there is FF30 floating bearing arrangement. (with one piece of deep groove ball bearing and a snap ring 16x30x62 mm)

Due to excess vibration and resonance at ball screw I plan to shorten the ball screw from 2078 down to 1552 mm to increase tolerance to the critical speed. I also changed the frame design for motor drive end to shorten screw.
In addition I want to modify the floating end bearing arrangement by increasing the supported journal length with 1 additional bearing set and increasing the misalignment tolerance to the floating end.
Because even if I reduce the length by 50 cm the screw is still very long and I am sure there will be misalignments.
Using deep groov ball bearings misalignment tolerance is low, for the double row deep groob ball bearing it is not permitted.

For the FF30 bearing the exising deep groobe ball bearing grade is P5.
I want to replace it wilth a self aligning ball bearing and/or spherical roller bearing with a P5 grade tolerance.

The width of the FF30 bearing housing is 27 mm while the deep groove ball bearing has 16 mm width.
For the same inner/outer diameter equivalent self aligning and spherical roller bearing the width is 20 mm. Therefore 7 mm distance will be left instead of 11 mm for the floating of the shaft.

For the loose end there are only radial loads to be carried. I wonder what is your gentlemen idea about using 2 bearing sets. or only 1 bearing set?

I dont know if there is any shielded and sealed spherical roller bearings off the shelf but I am sure self alignng ball bearings with seals and shields are easy to procure.

Revised drawings







Previous Drawings







I will upload videos showing the resonance of the ball screw.
According to the calculations for a fixed - free bearing arrangement the critical speed for a 40x2078 mm ball screw with a 37 mm root diameter : 1036 rpm.
For the same bearing arrangement the with a shortened screw 40x1552 mm critical speed : 1857 rpm

Link for the ball screw critical speed calculation sheet according to end fixity :
http://www.nookindustries.com/Engine...cCriticalSpeed