Two rotating wipers lift a lug on a guided stamp rod. When each wiper clears the lug, the stamp falls under its own weight. The animation distinguishes powered lifting from the unpowered drop.
Cam-Wiper Stamper Interactive Calculator
Set drop height, moving mass and shaft speed. Explore ideal drop energy, fall time and the speed limit for this illustrative two-wiper lift profile.
Equation Used
- No guide friction, aerodynamic drag, bounce or losses; constant shaft speed.
- Each of two identical wipers gives 90 degrees of cycloidal lift and then releases the lug.
- Illustrative base radius is twice lift; frame and stamp proportions are schematic.
- Gravity-contact speed limit uses nonnegative vertical cam reaction; it is not a rated machine speed.
- For an excessive requested speed, animation uses 95 percent of the contact limit before a 20-fold display slowdown. Numerical results retain entered speed.
Two opposed wipers each raise the stamp through a 90-degree cycloidal lift, then release it to fall under gravity. Drop height sets the ideal fall time and impact speed; mass also sets drop energy. If the requested speed would cause early separation, playback demonstrates a slower feasible cycle while the results use the entered speed.
Wipers lift; gravity makes the drop
Brown’s movement 85 shows a continuously rotating shaft carrying two cams or wipers. They lift a projection on a vertically guided rod. After release the rod falls under its own weight. The stamp head at its lower end delivers the blow.
The drawing here uses the same arrangement, with two opposed wipers and a lug that ends at the release edge. A fixed frame supports the shaft and two rod guides. The contour is an illustrative cycloidal lift, not a reconstruction of manufacturing dimensions.
Historical stamping motion
Brown lists ore stampers, pulverizers and hammers as applications. This mechanism is distinct from a positive-return cam press: the rotating shaft raises the mass, while gravity supplies the downward motion after release.
Drop energy and timing
For a drop h from rest under gravity g, fall time is √(2h/g), final speed is √(2gh), and available gravitational energy is mgh. Use meters and kilograms for SI results. None of these gives impact force without a model of stopping distance or deformation.
The illustrative lift is cycloidal over β = π/2 radians. Its peak acceleration magnitude is 2πhω²/β². Ideal peak vertical cam force is m(g + a_peak). For maintained contact during deceleration, a_peak must not exceed g; this sets a speed limit.
Two wipers give one lift every half-turn. A quarter-turn remains after each lift, or 15/N seconds at N rpm. Return time margin is this interval minus the free-fall time. The displayed speed limit is the smaller of the gravity-contact and return-time limits. It is an ideal kinematic check, not a machine rating.
A 25 mm gravity drop
A 5 kg stamp falling 25 mm has approximately 1.23 J of potential energy, reaches 0.70 m/s and falls for 71.4 ms. At 60 rpm the two-wiper shaft supplies 120 lifts per minute, with 250 ms available for each return.
Doubling mass doubles drop energy and ideal lifting force. It does not change free-fall time or speed in this frictionless model. Increasing shaft speed shortens the return window and increases lift acceleration with the square of speed.
Where the model stops
The model assumes a rigid guide, no drag and a stamp that settles on the anvil before the next lift. Bounce, deformation, material processing, bearing loads and guide friction are not solved.
If the selected shaft speed exceeds the contact limit, the stamp could leave the lift profile before the intended release. The page flags that condition and demonstrates a slower valid cycle rather than depicting impossible contact. The force result remains an ideal demand for the requested lift law, not a prediction of the separated motion.
Questions about the stamper
Why is there no return spring?
In Brown’s illustrated mechanism the rod drops by its own weight. A spring-return follower would be a different mechanism.
Why are there two blows per revolution?
The shaft carries two opposed wipers. Each lifts and releases the same stamp once.
Does a heavier stamp fall faster?
Not in this ideal gravity-only calculation. More mass increases energy and lifting force, while drop time and final speed depend on height.
Why can playback use a lower speed?
When the requested speed cannot maintain the assumed lifting contact, the animation shows a slower valid demonstration. The warning states the adjustment, and numerical results still use the requested speed.
Primary mechanism reference
Henry T. Brown, Five Hundred and Seven Mechanical Movements, movement 85, pages 24–25, Cornell University Library scan. The drawing identifies the rod and lifting projection; the text specifies two wipers and gravity return.
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