Measurement Terminology
Terminology for describing caster
WHEEL ONLY: A standard wheel has a center rotating hub (or bearing) and a compliant material on its outer side. It can be used for wheelbarrow, roller or replacement purposes.
CASTER: a wheel mounted to a bracket, with an optional, additional offset steering joint with additional suffixes. There are 3 main bracket types:
1. Top plate type
Top plate type caster is one that have square or rectangle (or maybe a triangle) plate on top. On the plate, there are often 4 round or oval shapes holes to install the caster with the truck's platform by sets of bolts and nuts or just welded.
SWIVEL
The wheel center is usually not vertical with the center of the plate.
Hence create a swivel radius, this will help the caster to rate 360° to change the direction.
RIGID
The two bracket leg is straight with center of the plate and center of the wheel on the vertical axis.
The Rigid type often combines with Swivel one. If you combine a set of 4 Rigid caster, your truck can only move one a straight-line: just forward or backward.
SWIVEL, SIDE BRAKE
Often seen as lock and the hip of the caster.
The side brake lock can only lock the rotation of the wheel only.
SWIVEL, DUAL BRAKE
Dual brake mechanism often has an extended pedal point to outside, just slightly under the plate.
Dual brake lock not only can prevent the wheel to roll but also lock the rotation of the swivel head.
Note:
- Side or Dual brake: We classify the side and dual brake based on its functionality. In fact there is a lock in dual brake mode but only function as a side brake.
- Rigid with brake: such thing exits but very rare.
Equivalent terminology:
- Swivel = active = rotate = multi directional = 360° = free = multi ways
- Rigid = fixed = straight = passive = one way only = single directional
- Brake = lock
2. Threaded stem
This kind will have a threaded stem point upward to be installed in a hole, a socket or a nut that will be inside of the leg of the platform.
STEM
STEM, SIDE BRAKE
STEM, DUAL BRAKE
STEM, RIGID (*)
(*) Note: There is no or very rare the stem, rigid type in Vietnam market.
3. Other stems
Includes: solid stem, scaffold stem, modular stem and splinting stem. Details are as follow:
SOLID STEM
Cylindrical solid stem (round or square) facing upwards. There is a small hole through the pillar to thread the shaft through to fix the pillar to the trolley leg. The wheel is eccentric relative to the upper base plate.
SCAFFOLD STEM
In contrast to solid stems, are hollow cylinders to fit snugly against the foot of the scaffold.
MODULAR STEM
Stem type but in modular form waiting to install long and short threaded stems depending on demand.
SPLINTING STEM
Also known as the chair caster. stem head with splinting stem can be plugged and unplugged directly.
Structural diagram of a Caster
Corresponding to the load level, the caster will have a suitable structure to meet the requirements:
LIGHT DUTY and Medium duty
For light duty, the steel thickness is only 1.1 - 1.8 mm.
For medium duty, the steel thickness is 2.0 - 2.5 mm.
The swivel head is a 2-tier ball bearing on top of each other. If you see the caster you are using has only one ball stage, it means that you are using a super cheap, low quality product.
HEAVY DUTY
Steel thickness 5.5 – 6.5 mm to ensure heavy load from 100 – 400kg.
The bracket legs are soldered dead with a swivel head base. Usually cheap goods will only weld the outside, with the inside unwelded.
2 stages of bearing ball feature is a must for heavy duty. In premium kind, both the swivel race way and bearing balls are are heat-treated steel to increase hardness and wear resistance.
EXTRA HEAVY DUTY
Steel thickness 8 - 15 mm. The swivel head is a combination of bearing ball and directional tapered ball to ensure smooth rotation even under heavy loads.
Although the roller bearing is said to capable of higher load capacity. In Heavy and Extra heavy duty Series, ball bearing is usually used.
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