The historical Repsold rotary pump uses two cylinders with larger and smaller sector surfaces inside adjoining housings. Hiscox describes their surfaces as matching to close the space between the shafts. Explore opposite rotation in the simplified illustration below, and compare its speed and drawing radii. The illustration does not reproduce that sealing contact or calculate fluid delivery.
Repsold Rotary Pump Interactive Calculator
Set the display speed and two drawing radii. The shafts turn at equal speed in opposite directions. The drawing does not form sealed pumping chambers.
Equation Used
- The two sector cylinders rotate at equal speed in opposite directions.
- Each simplified shape has one large-radius half and one small-radius half.
- Entered radii control the drawing; they are not dimensions from a historical pump.
- Fluid performance, clearances, contact, strength and sealing are excluded.
The companion view shows the same simplified shapes and current settings. Use Pause or the cycle slider to inspect a position.
The historical sector-cylinder principle
In Hiscox figure 531, each cylinder has larger and smaller sector surfaces. As the cylinders rotate, those surfaces match across the space between the shafts. The adjoining housings surround the pair.
The interactive drawing uses simplified large- and small-radius halves to illustrate opposite rotation. Its profiles and fixed shaft spacing leave gaps; they do not demonstrate the matching contact or sealed fluid chambers of the historical design.
What this model demonstrates
Change display speed to alter the rotation period. Change either radius to compare the radius ratio and radial difference. The fixed shaft-speed ratio remains minus one.
It is not a pump selection or performance tool. It does not calculate swept volume, delivered flow, pressure, leakage, efficiency, torque, power, contact, stress, cavitation, wear or suitability for a fluid.
Rotation and radius relationships
The two shafts have an ideal angular-speed ratio of minus one: omegaright/omegaleft = -1. At display speed n, the animation period is 60/n seconds.
The large-to-small radius ratio and radial difference are reported only as drawing summaries. They are not displacement, clearance, leakage or efficiency equations.
Worked display example
At 20 rpm display speed, one illustrative revolution lasts 3 seconds. The entered large and small drawing radii are 60 mm and 25 mm, giving a drawing-radius ratio of 2.4 and radial difference of 35 mm.
What the drawing leaves out
A pump needs chamber boundaries and ports that control where fluid enters and leaves. This illustration has no defined ports or fluid path, and its separated rotor shapes do not establish sealing contact.
The radius ratio is R/r and the radial difference is R minus r. Neither quantity is swept volume or running clearance. Housing geometry and shaft spacing stay fixed while the radius inputs change.
Flow, pressure and efficiency require a complete pump geometry and operating conditions. Use the historical references to study the original arrangement; use pump-specific data to assess fluid service.
Repsold pump questions
What is distinctive about the historical Repsold pump?
Hiscox describes two rotating cylinders with larger and smaller sector surfaces. Their matching surfaces alternately close the space between their axes, within adjoining cylindrical housings.
Does the animation show sealed pumping chambers?
No. It shows two simplified sector shapes turning in opposite directions. Their spacing and profiles do not create the matching closure described for the historical pump, and fluid movement is not simulated.
What does the speed ratio of minus one mean?
The two illustrated shafts turn at the same speed in opposite directions. Changing the speed input changes both together; it does not change this fixed ratio.
Does the radius difference represent a clearance?
No. It is simply R minus r for the two entered drawing radii. It is not the gap between a rotor and housing or between the two rotors.
Can the outputs predict flow or efficiency?
No. The tool reports rotation period, speed ratio and two radius comparisons. Displacement and performance require complete chamber profiles, axial width, porting, sealing and operating conditions.
Historical references
- Hiscox, Mechanical Movements, Powers, Devices, and Appliances, figure 531 — Repsold pump described as two differential sector cylinders in contiguous shells with greater and smaller surfaces alternately closing the inter-center area.
- Hiscox, alternate digitization — diagram and matching description of the historical Repsold rotary pump.
- Kikai no moto, class 27, Repsold pump — historical diagram index and opposite equal-speed directions.
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