Root-diameter / span screen
Screw critical speed
Inputs
User-entered minor/root diameter of the stated rotating screw; nominal diameter is not substituted.
Distance between the stated bearing supports; end conditions and support selection are not inferred.
User-entered factor matched to the stated support condition from a controlled source; no support-factor lookup is performed.
User-entered steady screw speed used only for a literal ratio to the calculated critical speed.
Results
Calculated critical speedncrit
3,022.6
Declared operating / critical-speed ration/ncrit
0.39701
1Declared root-diameter / unsupported-length ratio
0.02
1ncrit = Cs·4.76×10⁶·dr(in)/L(in)²; r = ndeclared/ncrit
A first-pass number, not a code check, certification, or approval. Read the method and its limits below. What this is and is not.
Nearby: Force & acceleration · Kinetic energy · Gravitational potential energy · Flywheel energy change
Method
Formula, when it applies, and when it does not
Calculate a screw critical-speed relation and operating-speed ratio from root diameter, unsupported length, end-fixity factor, and operating speed.
ncrit = Cs·4.76×10⁶·dr(in)/L(in)²; r = ndeclared/ncrit
When
- Straight rotating screw
- Declared root diameter and unsupported length
- User-entered end-fixity factor
- Single critical-speed relation
Don’t
- This applies the cited manufacturer critical-speed relation with user-entered root diameter, unsupported length, and end-fixity factor. It does not select a screw, bearing support, or fixity factor; predict actual shaft whirl/resonance; model straightness, preload, bearing stiffness, buckling, acceleration, drive control, load, fatigue, life, safety factor, suitability, or approval.