An oblique disc fixed to a rotating shaft drives a guided rod through a roller. Moving the roller farther from the centre increases the stroke. Explore the arrangement in Hiscox item 1085 and calculate ideal stroke, peak rod speed and revolution period.
Ideal Oblique-Disc Rod Travel
Enter declared roller radius from the disc centre, disc tilt and shaft speed. The worksheet reports the ideal plane-intersection stroke, peak speed and period only; it does not size a swashplate, follower, bearing, pump or compressor.
Equation Used
- The disc is an ideal rigid plane fixed at the declared tilt to a straight rotating shaft.
- The roller contact lies at declared radius R and the rod is constrained to move only along the shaft axis.
- Continuous contact is assumed and the motion is sinusoidal at constant shaft speed.
- Disc thickness, roller radius, preload, friction, slip, Hertz contact, lubrication, wear, bearings, runout, deflection, loads, torque, strength, pump displacement, pressure and safety are excluded.
The ideal rotating-plane model makes stroke proportional to roller distance from the centre. Tilt changes the stroke, while shaft speed changes the calculated velocity and revolution period.
A tilted disc drives a guided rod through a roller
Hiscox item 1085 fixes a disc obliquely on the end of a rotating shaft. A roller follows the disc face while its rod is constrained to rectilinear motion.
Moving the roller farther from the disc centre increases travel. The side projection illustrates the rod and roller following the disc; the calculation assumes continuous contact.
A historical rotary-to-rectilinear mechanism
The mechanism illustrates conversion from rotary to reciprocating motion with adjustable travel. This ideal motion calculation does not determine the loads or contact design needed for a particular machine.
Ideal rotating-plane displacement
The result is kinematic only and assumes continuous roller contact with a perfectly flat disc.
Declared geometry example
For R=50 mm, θ=15° and n=20 rpm, ideal half-stroke is 13.40 mm, full stroke is 26.79 mm, peak rod speed is 28.05 mm/s, and one shaft revolution takes 3.000 s.
Motion calculations and contact design
The stroke relation describes an ideal rotating plane and continuously guided contact. A working follower also needs adequate contact force, suitable roller and disc geometry, and support for the applied loads. Those requirements, and any pump or compressor performance, are outside this motion calculation.
Oblique disc-motion questions
Does changing roller radius change stroke?
Yes, linearly in this ideal plane model.
Does the calculator size a pump or compressor?
No.
Is animation speed the entered rpm?
No. The display is slowed for inspection; the numeric velocity and period use the entered rpm.
Oblique disc-motion reference
- Hiscox, Mechanical Movements, page 269, item 1085: primary public-domain figure and caption documenting the angled disc, guided rod and roller, and variable radius.
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