Handle bearings in the commonly deployed India Mark II hand pump have been found to frequently fail, often in less than one year.
Here is why they fail so soon:
- Ball bearings are designed to run smoothly with full rotations at high speeds with low static loads
- All the bearing stress is concentrated at the contact points of a few balls; small area = large stress
- India MKII pump handles only rotate about 30 degrees in an oscillating motion so only a small number of balls engage the load
- Because rotation speed is relatively low and rotation is incomplete the hydrodynamic lubrication is ineffective leading to wear and degredation.
- It’s not just the down time of a broken pump. Neglected long enough, bearing failures can cascade into other frame errors, sometimes causing hundreds of dollars of damage.
Select Bearings are better because:
- Sintered iron bushings are a mature technology optimized for low rotation speeds, heavy static loads and self lubrication.
- Select Bearing’s simple sleeve bearing design spreads the loading over a large area, so large area = lower stress
- Oil impregnation ensures permanent lubrication for the life of the bearing
- The Select Bearing design is compatible with existing MKII design without any modification to the pump!
