This partial calculator evaluates selected Coulomb-friction limits for two identical roll contacts and the kinematics of a selected roll diameter and speed. It does not predict stalk extraction, crop damage, soil release, throughput or field performance.
Stalk Puller - Selected Two-Contact Ledger
Explore selected two-contact Coulomb-friction limits and roll-speed kinematics without predicting stalk extraction.
Equation Used
- N is an entered normal-force assumption for each of two identical contacts.
- mu is an entered Coulomb-friction coefficient assumption.
- The two-contact value is an arithmetic sum of limiting magnitudes, not achieved extraction force.
- The speed ratio uses 540 rpm only as a numerical reference and does not establish a drivetrain.
- Crop, soil, slip, losses, structure, power and safety are excluded.
The secondary figure shows an abstract symmetric roll pair and reference line; it is not a validated machine drawing.
Selected two-contact ledger
Each idealized contact has selected limiting friction mu N. With two identical contacts, their arithmetic sum is 2 mu N. Roll peripheral speed is pi D n/60. These are input relationships, not a validated stalk-puller model.
What the calculator determines
Use it to inspect a selected two-contact friction-capacity assumption, roll surface speed and speed relative to a 540 rpm reference. Do not use it to select equipment or predict extraction force.
Selected relationships
Per-contact limiting friction=mu N; two-contact arithmetic sum=2 mu N; surface speed=pi D n/60; selected/reference speed ratio=n/540.
Selected-input example
At mu=0.50, N=800 N per contact, n=600 rpm and D=200 mm, the per-contact limit is 400 N, the two-contact sum is 800 N, roll surface speed is about 6.28 m/s and the selected/reference speed ratio is 1.111.
Not an extraction-force model
The entered coefficient and normal force are assumptions. Stalk compliance, crushing, contact area, contamination, moisture, slip, roll texture, preload mechanics, root geometry, soil resistance, machine motion, power, structure and safety are excluded.
Questions
Is the two-contact sum an available pulling force?
No. It is only the sum of two selected limiting-friction magnitudes under an idealized Coulomb model.
Does the 540 rpm comparison imply a PTO connection?
No. It is only the selected roll speed divided by a numerical reference.
Does the video validate the model?
No. The embedded source video is titled as a stalk chopper, not a two-roll stalk-puller test.
Authoritative references
- U.S. Department of Energy Fundamentals Handbook: Application of Newton's Laws — gives the limiting static-friction relation F=mu N and distinguishes it from kinetic friction.
- USPTO Class 460 definitions — describes crop-handling apparatus using rollers or cylinders to grasp and pull plant material, without supplying this calculator's performance constants.
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