Henry T. Brown's movement 252 uses two rollers, A and B, constrained to horizontal slot C. Moving yoke D up and down makes its two mirror-image oblique slotted arms drive the rollers equal distances in opposite directions. Enter yoke stroke and slot angle to calculate the travel of each roller and the change in their separation.
Equally-traversing Rollers via Slotted Bar Interactive Calculator
Explore Brown movement 252 and calculate the equal roller travel produced by a vertical yoke stroke and straight oblique slots.
Equation Used
- One rigid V-yoke translates vertically.
- Roller centres remain in fixed horizontal slot C.
- Oblique arms are straight and mirror-symmetric.
- No friction, contact stress, strength, jamming or manufacturing-rating model.
The two rollers follow straight, mirror-image slots. The clearance result is a geometric bound on mismatch; it does not include wear, deflection or manufacturing errors.
Brown movement 252
Rollers A and B are constrained to move horizontally in fixed slot C. Each roller also runs in one of the two oblique slotted arms of yoke D. Because the arms are mirror images, vertical motion of D produces equal horizontal motion of the rollers in opposite directions.
The diagram keeps Brown's A, B, C and D labels and enlarges the follower rollers and slots for readability.
Equal and opposite motion
This arrangement couples the motion of two rollers through a single moving yoke. Its symmetry sets equal travel in opposite directions; the drawing does not give manufacturing fits or load capacity.
Straight-slot geometry
For vertical yoke stroke y and slot angle alpha measured from horizontal, each roller's peak-to-peak travel is x=y/tan(alpha). The roller separation changes by 2x. The displacement ratio is x/y=1/tan(alpha).
If c is total normal pin-to-slot clearance, a conservative two-pin horizontal mismatch bound is 2c/sin(alpha). It is only a geometric bound.
80 mm yoke-stroke example
At a 45 degree slot angle, an 80 mm yoke stroke moves each roller 80 mm peak to peak and changes their separation by 160 mm. With 0.2 mm total clearance per slot, the two-pin horizontal mismatch bound is about 0.57 mm.
Scope and limitations
Equal motion follows from mirror symmetry and straight slots. This model does not calculate contact stress, friction, pin strength, wear, jamming, actuator force or a production accuracy rating.
Frequently asked questions
How many rollers does this mechanism use?
Two rollers, labeled A and B, share the fixed horizontal guide and follow the two oblique slots.
Do the rollers move in the same direction?
No. They move equal distances in opposite directions as yoke D moves vertically.
Is the clearance result a tolerance specification?
No. It is a geometric mismatch bound calculated from the entered normal pin-to-slot clearance. It does not include wear, bending or other manufacturing errors.
Primary reference
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