What is Footstep Bearing?
Footstep bearing is used to support shafts that are placed vertically and transmit axial thrust. The function of footstep bearing is to support the lower end of a vertical shaft. It consists of a cast-iron block in which a bush is there. Bush consists of a collar that fits at the top & shaft rotates inside the bush. The bottom portion of the shaft rests on the bearing disc & locking pin prevents its rotation. It is partially placed inside the block and partially in the pad but away from the center. Generally, the shape of the collar is hollow because it acts as an oil sump which is for lubrication of bearing.
As we know, footstep bearing is subjected to heavy thrust load along the axis, and it also operates without any clearance or gap between its mating part. So, the supply of lubrication oil is necessary for footstep bearing. Unlike the pedestal bearing, the footstep bearing can place along with the bottom of the shaft.
Construction of footstep bearing
Footstep bearing consists of the following parts
- The body
- Locking Pin
1) The Body
The body of the footstep bearing is nothing but the base of the bearing. The base material is mainly grey cast iron, spheroidal cast iron. This base is attached to a rigid structure using a bolt.
The body of the bearing is cylindrically extruded from inside, and there is one small hole to fit the pin in it.
The disc of the footstep bearing is circular and flat from the bottom, and the top surface of the disc is concave. This disc is placed at the bottom of the cylinder & both holes of the disc and base get perfectly aligned. The material of the disc of bearing is sifter material, primarily gunmetal.
The disc is to support the main face of the shaft. Due to the continually rotating of the shaft, there is a chance of wear and tear of the disc. So, there is a need to replace the disc when it wears.
3) Locking Pin
The function of the locking pin is to secure the disc from beating up and prevent the disc from rotating. The material of the locking pin is Fe410W. Half a portion of the locking pin is set within the body while half inside the disc.
The bush is a hollow cylindrical element in which the shaft rotates. It is inserted into the cylindrical part of the body. The main function of the bush is to protect the body of bearing from wear and tear, which happens due to consecutive rotation of shaft within the body.
The material of the bush is gunmetal and other soft materials. The bush having some external part located at its side is called snug. Thus, snug fits at the cut-out section of the body and prevents the shaft from rotating inside the body.
How to Assemble Footstep Bearing
- The first step of assembly of footstep bearing is to set up the base. The base of the bearing is attached to the strong foundation with the help of a bolt.
- After the clamping of the base, the lock pin needs to insert into the hole at the cylindrical body.
- Make the disc hole align with the pin & insert the disc into the locking pin.
- Now, the bush is placed and fitted in a cylindrical body in such a way that snug fits in a place.
- Our footstep bearing assembly is ready. Now we must place our shaft inside this assembly.
- Repeating the same processes in the reverse direction to dismantle the footstep bearing.
Limitation/Disadvantages of Footstep Bearing
- Footstep bearing is placed only at the bottom of the shaft.
- We can’t lubricate efficiently.
- It is suitable for the slow-speed shaft, which carries the minimum load.
- Wear and tear is the main and common problem in the bushing and disc parts. So it is compulsory to replace this part wherever necessary.