All you need to know about Steerable Axles for Trailers

In this post, we will look at a relatively old concept in automobiles but the one that is yet to see the daylight in Indian heavy transport segment. We will talk about rigid axles vs steerable axles.

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The first question that comes to mind is

What is the need for steerable axles?

Well, when talking about the front axle the answer is quite obvious. But what about the rear axles? Do they need steering as well?

Looking at the image on the right we can see that a vehicle takes a turn about an axis of rotation and for all the tires to roll without sliding sideways it is necessary for them to be exactly perpendicular to the line joining the axis of rotation and the center of the tyre. This is the basic reason why the inner wheel of the front axle turns at a higher angle than the outer wheel.

Now consider a multi-axle vehicle. If the rear axles are not steered, the lines drawn from the rear wheels will not meet the steering axis. This means that wheels on these axles will not only roll but also slide sideways. This has many adverse effects:

1. First and foremost this will lead to excessive tyre wear considering the immense load per wheel and the sideways slippage. An estimate of tyre mileage with and without steering in one of the axles (third axle) in a three axle trailer shows that indeed the wear is significant. This also causes additional wear of the pavement surface.
2. The vehicle swept path, i.e., the area that a vehicle requires while making a turn is substantially increased with rigid axles. This can clearly be seen in illustrative examples.
3. The sliding of wheels adds to the resistance to motion. This increases the engine effort required to pull the same load at the same speed, subsequently raising fuel consumption. Actual studies indicate that with steering systems, fuel savings could be about a liter per 100 km for a distribution haulage vehicle. Hence, this system could pay for itself through saved costs in tyre wear and fuel.
4. The slipping and sliding of wheels will also impose excessive lateral forces on the chassis, potentially limiting its weight-carrying capacity as the maximum load without these unnecessary forces would likely be higher.

What are the various mechanisms for steering axles?

Various mechanisms have been developed for steering axles of articulated trailers. Below are several noteworthy types:

1. Self Steering type:

   This is a popular mechanism used in most applications. While there is no control over the steer angle, the wheels guide themselves through the forces developed during steering. Two types include:

   • Free Castering Type:

     The caster angle allows the wheels to tilt freely when the vehicle makes a turn. However, the limited centering force negatively affects high-speed performance and stability while braking. Additionally, in reverse, the wheels must be locked to avoid damage as wheels can turn 180 degrees.

   • Automotive type:

     This mechanism is similar to the free castering type but incorporates additional features to enhance the centering force, improving stability during high-speed driving and braking.

2. Linked Articulation Type:

   This type utilizes steering linkage to adjust the steer angle based on the fifth wheel articulation angle between the vehicle and the trailer. Though these axles are typically more expensive and complex than automotive types, they achieve a smaller swept path and greater stability.

3. Command Steering:

   These axles are actively steered, similar to the front axle of the hauling vehicle. The two types include:

   • Hydraulically Steered:

     Employs hydraulic single-acting cylinders that synchronize with the relative motion between the hauling unit and trailer, providing better performance.

   • Electronically Steered (active steering):

     Features an electronic sensor that measures relative motion, allowing for precise control of the steer angle. This system is versatile and can be manually controlled, especially useful during reverse maneuvers.

What are the applications that it is suited for?

1. Distribution haulage is one application where steerable axles can prove invaluable. In many regions such as India, narrow roads make maneuverability essential; therefore, steerable axles enable trailers to navigate urban settings easily.

2. Transporting long cargos through hilly terrain is another area where steerable axles shine. Traditional rigid axle trailers encounter challenges in such conditions, making steerable designs a preferable choice, as they reduce the swept path substantially.

3. However, there are some drawbacks to consider. Increased complexity may lead to higher maintenance costs and the need for skilled mechanics, although operating drivers may require less expertise. Furthermore, bringing this technology to market would necessitate updates to regulations, a lengthy process.

4. Steerable axles might also facilitate the addition of more axles without increasing tyre scrub, increasing a vehicle's gross combined weight (GCW) and potentially alleviating overloading issues.
5. Companies like Nimbus Logistics, boasting a wealth of mechanical expertise, remain updated with current advancements, allowing them to provide innovative solutions to clients in need.

Nimbus Logistics is an ODC and Heavy transport specialist with over 40 years of experience in moving Super Heavy and Super ODC cargo. We champion ethical logistics and transparency. These articles are our initiative to bring heightened clarity to the complex Indian Transportation Industry. Please support us by sharing our insights and liking our facebook page to stay informed on future posts.

Selecting the right equipment trailer can actually be quite intricate. Understanding your requirements is essential to the selection process.

When deciding on a trailer for equipment transport, rental companies must consider their target customer base, size, and the types and weights of equipment involved. For instance, a customer base consisting of professional contractors may benefit most from a tilt-bed trailer with a stationary deck, with a gross vehicle weight rating (GVWR) around 16,000 pounds, which helps accommodate equipment weighing 8,000 to 10,000 pounds.

Conversely, customers with lighter-duty towing vehicles might prefer a ramp-style trailer, optimized for smaller loads like skid-steer loaders. It's imperative to grasp what you need from your trailer, as this ensures maximum return on your investment.

Capacity concerns

When selecting a trailer, various factors such as ramp type, flooring, and hitch designs should be considered. Determine what you're intending to transport, keeping in mind full gas tanks and attached accessories can significantly affect the weight.

Size is equally important; ensure your chosen trailer can adequately accommodate your load and maintain proper weight distribution to avoid swaying while towing.

Quality questions

Assess craftsmanship and design factors when comparing trailers. Look for structural integrity, like one-piece frames, and check the axle placement to ensure safe towing.

Quality varies across manufacturers, from axle wall thickness to flooring strength. Make sure the trailer meets the rigorous demands of heavy hauling.

Cost-effective brakes

Trailer braking systems vary based on size. For instance, air brakes are typically utilized for larger trailers, while electric brakes are common for trailers ranging from 3,000- to 26,000-pound GVWR.

Maintenance factors

Consider maintenance features in your purchase decision. This includes aspects like rubber-ride axles that simplify upkeep and sealed wiring systems to protect against damage.

The supplier connection

Select a knowledgeable trailer manufacturer to ensure your trailer meets both your needs and industry standards. Ask questions to gauge their credibility and grasp your requirements fully.

Maximizing the payload

When transporting multiple machines, ascertain deck length and weight distribution to avoid problems with tongue weight. Legal maximum gross weight is also crucial; permits are needed for loads exceeding 80,000 pounds.

Ensure trailers have vehicle identification tags outlining their carrying capacities. Proper knowledge of weights and safe loading practices is key to avoiding overloading.

Don't be misled by trailer ratings

Be aware that ratings can vary widely, and ensure the trailer can safely transport your equipment. Concentrated load areas are particularly critical to understand when transporting various types of machinery.

Types of trailers

Common types of trailers include lowbed trailers, tow-behinds which vary in design, size, and function, encompassing enclosed box trailers, flatbeds, tilt beds, dump trailers, and drop-deck trailers.

It's about making it last

Selecting durable equipment is essential for rental businesses. Assess the structure and design to ascertain product longevity. Inquire amongst industry contacts to identify reliable trailer options and avoid maintenance issues down the line.