Brown movement 220 uses two parallel, non-collinear crank shafts; the wrist of one crank works in the slot of the other and continually changes its distance from the follower shaft.
Two-shaft Crank with Slot Interactive Calculator
Enter a desired ideal fast/slow angular-speed ratio and driver revolution period. The tool solves the corresponding normalized shaft offset and ideal extrema; it does not design the pin, slot, shafts or bearings.
Equation Used
- The two shafts are parallel and separated by e.
- The driver wrist radius is R and e/R<1.
- The wrist slides without clearance or friction in a straight radial follower slot.
- Driver angular speed is constant.
- Force, torque, contact stress, slot length, pin diameter, bearings, backlash, wear, lubrication and suitability are omitted.
Brown Movement 220
Henry T. Brown describes two crank shafts parallel in direction but not in line. The wrist of one crank works in the slot of the other; as its distance from the follower shaft continually changes, the transmitted angular velocity varies.
What This Calculator Represents
The calculator solves only the normalized ideal geometry and speed extrema of that pin-in-radial-slot constraint. Brown's source does not supply dimensions, loads, materials or an application.
Ideal Offset and Speed Extrema
driver speed n1 = 60/T
ideal fast extreme = n1/(1-k)
ideal slow extreme = n1/(1+k)
fast/slow = V
These extrema occur on the shaft-center line in the ideal rigid geometry.
Worked Ideal Example
For entered V=3 and driver period T=4 s, k=0.5 and driver speed is 15 rpm. The ideal follower extrema are 30 rpm fast and 10 rpm slow.
Model Boundary
- Mechanism arrangement: two parallel offset crank shafts and one crank wrist sliding in the other's slot.
- Calculated: normalized offset and ideal angular-speed extrema.
- Not calculated: pin/slot dimensions, force, torque, contact stress, clearance, friction, backlash, slot length, bearings, strength, wear, lubrication, vibration or suitability.
Frequently Asked Questions
Does the follower keep constant speed?
No.
Is e/R a physical dimension?
No; it is a normalized ratio.
Why require e/R below one?
It keeps the ideal follower rotating continuously without the radius reaching zero.
Are pin forces calculated?
No.
Does this predict backlash or wear?
No.
Can it size a machine drive?
No.
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