Could caster flutter be putting you, your business, or your employees at risk? Casters are essential components within materials handling or office equipment. If they fail, the consequences could be dire for the person using the equipment and everything around them.

Here, Caster Central’s experts break down the basic anatomy of caster wheels. They also discuss why caster flutter occurs so that you know how to prevent the problem.

What are Casters?

A caster rig includes two main components: the small wheel that attaches to the equipment and the framing around it. Unlike regular wheels, casters increase the mobility of the "vehicles" to which they attach. However, as with anything that moves, these rigs wear out over time.

The basic anatomy of a caster includes the wheel, mounting component, and fork. 

• The mounting component is either a stem or plate, depending on the model.
• The fork attaches to either side of the wheel itself. Manufacturers secure the fork by attaching bolts to either side and threading an axle through the middle of the wheel. 
• Some casters may include brakes or locks as well. 

One of the problems that develop as the caster experiences wear and tear is caster flutter. The term describes the action of a rig that moves rapidly from side to side (or spins perpendicularly) as you push or pull the vehicle. The motion can cause a shopping cart, heavy-duty trolley, chair, and other equipment to fishtail or, worse, to tip over.

What Are the Different Types of Casters?

There are three main distinctions between different caster rigs:

Rigid vs. Swivel

When investing in new casters, you can choose between a model that tracks in a straight line or one that has 360-degree motion capabilities. 

• Rigid casters only move back and forth. They are common for applications like the back wheels of a shopping cart.
• Swivel casters are more useful, as you can move them in any direction without changing the orientation of the object. 

It is possible to combine swivel casters with rigid casters in certain vehicles to save money or to offer more control in directing the piece of equipment.

Stem vs. Top Plate

Top-plate casters attach to a vehicle using a simple plate with four bolts. These caster rigs are mostly used for heavy-duty applications. On the other hand, stem casters use a smooth or screw-like "stem" to attach to the vehicle. 

Kingpin vs. Kingpinless

Swivel casters normally require a kingpin to facilitate 360-degree movement. This pin aligns with the races that hold the ball bearings. However, kingpins frequently break, so kingpinless casters are a good alternative.

Kingpinless casters use an inner and outer raceway with ball bearings mounted between the two. These models are less likely to malfunction. 

Everything You Need to Know About Caster Flutter

Here’s more about how to detect a flutter problem in the caster,  minimize the impact, and prevent it from happening again.

How to Detect Caster Flutter

The most obvious way to detect a caster flutter is by noticing your vehicle wobbling from side to side while moving. Casters might shimmy when you interlock different vehicles, such as carts. As you increase your velocity, any carts with caster problems will fishtail or not track in a straight line.

You may also hear the flutter before you see it, as shimmying casters make a noticeable rattling or flapping noise. To find the problematic caster, it is easiest to watch someone else use the vehicle. Check which caster vibrates as the person pushes or pulls the vehicle along.

What causes these flutters in casters? Common rig issues include the following:

• Uneven loading: When you unevenly distribute a load on your vehicle, one caster may need to support more weight than the others. All caster rigs have a certain weight capacity, so uneven loading can break casters as it exceeds this limit.
• Environmental deterioration: Where do you primarily use your equipment? Environmental conditions can affect the functionality of your casters. For example, uneven surfaces can loosen components, while dirt and debris clog your caster rigs.
• Weight overload: If you overload your vehicle (and exceed the weight capacity of your casters), these components will eventually give way.

All of the above problems can lead to caster "shimmies." However, you may also need to look at the following mechanical caster problems that can lead to fluttering: 

• Loose swivel component: A loose swiveling component, such as the kingpin, will make the caster begin to flutter. It creates resonance, which leads to uncontrollable flutters as the vehicle moves. 
• High speeds: Any caster will reach its natural frequency (which leads to shimmying) at high speeds. Misaligned or imbalanced casters moving at greater velocities will highlight the problem due to increasing friction.
• Bad mounting: Wear and tear isn’t the only problem; incorrectly mounted, angled, or bent casters also cause a flutter.

Though a caster’s fluttering may seem like a simple inconvenience, it can drastically shorten the lifespan of your rig. One caster with shimmies puts extra stress on the rest, and it won’t be long before all of the vehicle’s caster rigs start to malfunction. 

Two Proven Ways to Minimize Caster Flutter Movement

Since loose or misaligned swivel components are the principal cause of a flutter, this is a good place to begin. For example, a common issue includes a worn-out or angled fork. 

• Worn forks happen with prolonged use, shortening the distance between the wheel and the swiveling component. It sometimes results in the swiveling component catching the wheel to cause a flutter. You will notice the flutter increase as the vehicle moves faster.
• Angled forks also cause caster issues. Whether the fork has a slight or significant angle, it changes the distance between the center of the swivel component and the center of the wheel. The caster becomes vulnerable to forces that will push it sideways, correcting itself as the wheel hits the opposite axle (causing the side-to-side motion). 

How can you minimize this movement? Replace the fork or the entire rig. If you notice that a certain bolt or other component is loose, you could also tighten it to see if that eliminates the flutter.

Expert Tips For Caster Flutter Prevention

Sometimes, you must replace an entire caster rig to address the flutter. However, you can also do the following to prevent caster issues:

• Regular cleaning gets rid of dirt and debris in the caster mechanism
• Lubrication minimizes the amount of friction between the wheel and the rig frame for a smoother rolling motion
• Immediate removal of large pieces of debris prevents casters from bending as they begin to shimmy

You can also spray your casters with water or manually remove debris to prevent caster flutter and mitigate damage to your rig.

Caster Replacements: Where to Find High-Quality Casters

Do you need to replace a shimmying caster rig? Trust Caster Central for quality service and products as the top caster rig supplier in the United States. We provide our customers with premium caster brands, such as Pemco, Jarvis, and Colson.

We also provide caster hardware solutions so that you can perform DIY repairs of your casters at your home or office. Why not ask our experienced Caster Central staff for advice about the latest caster rig models or the number of casters you need? After 150 years in business, we can guarantee the most reliable solutions for all your mobility needs.

Call Caster Central at 1 (800) 445-4082 today for caster flutter solutions and anything else you need to know.