Classification of Semi Trailer Suspensions

Semi-trailer suspension is an important part connecting the traveling device and the frame of the semi-trailer. The supporting force, braking force, and driving force of the vehicle are all transmitted through the suspension system. And the suspension can also reduce the impact of harsh roads on the vehicle, play a shock absorption effect, and improve the ride comfort of the vehicle. There are many types of semi-trailer suspensions. The common semi-trailer suspensions include: leaf spring mechanical suspensions, air suspensions, and argo bogie suspensions. Their respective characteristics are introduced as follows:

 

1. Leaf spring mechanical suspension

As shown in Figure 1. The leaf spring mechanical suspension takes the leaf spring as the elastic element and also as the guide device. Its main components are: front hangers, middle hangers, equalizers, rear hangers, leaf springs, fixed torque arms, adjustable torque arms, axle clamping plates, lifting lugs, U-bolts, etc.

 

The main advantages of this suspension are low price, good reliability and convenient maintenance. At present, more than 80% of semi trailers in China use leaf spring mechanical  suspensions.

(Figure 1. Leaf spring type mechanical suspension)

Leaf spring mechanical suspensions can be subdivided into the following categories:

1) American type leaf spring mechanical suspension

 

The American type mechanical suspension is widely used all over the world. Usually for this suspension, the capacity of the single axle is 11 tons, 13 tons, 16 tons and other tons. The suspension can be matched with Φ127mm round beam and 150x150mm square beam axles.

 

According to the position of the axle relative to the leaf spring, it can be divided into overslung suspension and underslung suspension. The suspension of the axle under the leaf spring is called overslung suspension, and the suspension of the axle above the leaf spring is called underslung suspension. As shown in Figure 2 and Figure 3.

(Figure 2. 3-axle American type overslung mechanical suspension )                

 

( Figure 3. 3-axle American type underslung mechanical suspension ) 

 

The commonly used American leaf spring suspension has the following three series:

 

A. 68 series American type leaf spring suspension

 

As shown in Figure 4. Usually for this suspension, the capacity of the single axle is 11 tons, the optional number of the semi-trailer axles is 1 axle, 2 axles and 3 axles, and the optional conventional leaf springs are 75x13-9L and 75x13-10L, the parabolic leaf spring is 75x22-3L. The equalizer’s shaft sleeves and torque’s sleeves of the suspension are both tapered rubber sleeves.

 

( Figure 4. 3-axle American type round beam mechanical suspension )

B. 88 series American leaf spring suspension

 

As shown in Figure 5. Usually for this suspension, the capacity of the single axle is 13 tons, the optional number of the semi-trailer axles is 1 axle, 2 axles and 3 axles, and the optional conventional leaf springs are 90x16-7L and 90x13-10L.

 

( Figure 5. 2-axle American type square beam mechanical suspension)

C. 86 series American type leaf spring suspension

 

Usually for this suspension, the capacity of the single axle is 16 tons, the optional number of the semi-trailer axles is 1 axle, 2 axles and 3 axles, and the optional conventional leaf spring is 90x16-9L. The suspension is designed by thickening the hangers on the basis of the 88 series suspension. The outer diameter of the equalizer pins is Φ70mm, and the outer diameter of the torque pins is Φ36mm. The appearance is the same as in Figure 5.

 

2) German type leaf spring suspension

 

As shown in Figure 6. The German type leaf spring suspension is widely used in Europe and Africa, and can be matched with 150mm x 150mm square beam axles. The weight of product is heavier than the that of the American type suspension. This suspension is not suitable for the lightweight design requirements of Chinese semi-trailers. The wearing parts of the German type  suspension are removable and replaceable while The wearing parts of the American type  suspension are welded, which is relatively simple in maintenance, and it is convenient to replace the wearing parts. The common German type suspension has the following two series:

 

( Figure 6. 3-axle German SAF type mechanical suspension )

A. BPW series German leaf spring suspension

 

As shown in Figure 7. The single axle of the suspension are designed to carry 12 tons, 14 tons, 16 tons. The optional semi-trailer axles are 1 axle, 2 axles, 3 axles and 4 axles. The optional conventional leaf spring specifications are 100x12-12L, 100x12-14L and 100x14-12L, etc.

( Figure 7. 3-axle German BPW type mechanical suspension from )

B. SAF series German leaf spring suspension

  

As shown in Figure 8. Usually for this suspension, the capacity of the single axle is 12 tons, 14 tons, 16 tons, the optional number of the semi-trailer axles is 1 axle, 2 axles, 3 axles and 4 axles, and the optional conventional leaf springs are 100x12-12L, 100x12-14L and 100x14-12L, etc.

 

 

 (Figure 8. 3-axle German SAF type mechanical suspension )

 

3) Casting type leaf spring suspension

Casting type suspension is widely used in Southeast Asian and Australian markets (such as the Philippines, Bangladesh, India, Cambodia and other countries and regions) and some European markets. The suspension can be match with Dia. 127mm round beam axles and 150mm x 150mm square beam axles. The common casting suspension has the following three series:

 

A. YTE series casting leaf spring suspension

 

As shown in Figure 9. Usually for this suspension, the capacity of the single axle is 12 tons,  the optional number of the semi-trailer axles is 1 axle, 2 axles and 3 axles, and the optional conventional leaf spring is 75x13-08L.

 

 

 (Figure 9. 2-axle YTE casting type mechanical suspension)

 

B. European series casting leaf spring suspension

 

As shown in Figure 10. Usually for this suspension, the capacity of the single axle is 13 tons,  the optional number of the semi-trailer axles is 1 axle, 2 axles and 3 axles, and the optional conventional leaf spring is 75x13x10L. 

 

(Figure 10. 2-axle ROR casting type mechanical suspension )

 

C. Reyco series casting leaf spring suspension

 

As shown in Figure 11. Usually for this suspension, the capacity of the single axle is 12 tons,  the optional number of the semi-trailer axles is 1 axle, 2 axles and 3 axles, and the optional conventional leaf spring is 90x14-11L. 

 

( Figure 11. 2-axle REYCO casting type mechanical suspension )

4) Bogie suspension(Single point suspension)

As shown in Figure 12. Bogie/boogie suspension is to change the common leaf spring front and rear hangers into a single bracket platform. The leaf springs, axle assembly and braking system are integrated into one unit. The installation of the suspension and the frame can be completed through the bolt connection, making it more convenient to assemble and adjust the vehicle. The suspension has strong adaptability and can meet the requirements of harsh road conditions. The front and rear axles can achieve large swings, the tires can effectively land on the ground during driving, and the load distribution is more uniform. The suspension is mainly used in heavy-duty semi-trailers and trucks, and is used more in areas with poor road conditions.

 

( Figure 12. 2-axle high mounting plate type bogie suspension )

 

The load capacity of single point suspension is 24 tons, 28 tons, 32 tons and 36 tons respectively. The equipped axles can be German drum axles or German spoke axles.

There are several common type bogie/boogie suspensions as following:

 

A. High platform bogie suspension 

As shown in Figure 13. High platform bogie suspension is the most widely used bogie suspension, which is mainly used on heavy-duty two axle semi-trailers.

(Figure 13. 2-axle high mounting spoke type bogie suspension )

B. Double bracket bogie suspension

As shown in Figure 14. The double-bracket bogie suspension uses two small brackets to replace the high platform installation panel. The balance shaft connects with the bracket at four points, and the stress of the balance shaft is well improved. The balance shaft with smaller diameter can be adopted, and the overall weight of the bogie suspension can be reduced.

( Figure 14. 2-axle double bracket type bogie suspension )

C. Low platform bogie suspension

 

As shown in Figure 15. The suspension adopts two mounting brackets instead of the high platform single point suspension mounting platform, which can effectively reduce the body height of the semi-trailer. The vehicle has a lower center of gravity and better stability

 

( Figure 15. 2-axle low mounting plate type bogie suspension )

 

5) Other type leaf spring suspension

Leaf spring suspensions in different regions of the world have their own characteristics. According to their market characteristics, there are many other leaf spring suspensions.

For example, the South African leaf spring suspension widely used in southern Africa which can be matched with Φ127mm round beam axles are available in overslung and underslung installation, and the optional conventional leaf spring is 75x13-8L, as shown in Figure 16 and Figure 17.

( Figure 16. 3-axle South African overslung type mechanical suspension)

( Figure 17. 3-axle South African underslung type mechanical suspension )

2. Air suspension

 

As shown in Figure 18. Air suspension uses air springs/air bags as elastic elements, air as elastic medium, and the compressed air is filled into a sealed bag to realize its elastic purpose by using the compressibility of gas.

(Figure 18. 3-axle air linker type air suspension from)

 

The air suspension has variable stiffness, ideal elastic characteristics, good damping effect and high vehicle comfort. The height of the frame can be adjusted within a certain range. The disadvantage is that the cost is high and overload is prohibited. Air suspension can be divided into lifting type and non lifting type. There are several types of air suspensions as follows:

 

1) Air linker type air suspension

 

As shown in Figure 19. Usually for this suspension, the capacity of the single axle is 9 tons, 11 tons and 13 tons. It can be matched with a Φ127mm round beam, Φ146mm round beam or a 150x150mm square beam of a semi trailer axle.

 

( Figure 19. Air linker type air suspension )

 

2)Beam type air suspension

  

As shown in Figure 20. Usually for this suspension, the capacity of the single axle is 9 tons, 11 tons and 13 tons. It can be matched with a Φ127mm, Φ146mm round beam or a 150mm x 150mm square beam of a semi trailer axle.

  

 

( Figure 20.  Beam type air suspension)

3) Large airbag lifting device

 

As shown in Figure 21. The device is suitable for leaf spring axle lifting when the vehicle with a mechanical suspension is unloaded, which can reduce tire wear, fuel consumption and bearing wear and prolong the service life of vehicle suspension. The lifting device has the advantages of simple installation and low maintenance cost.

( Figure 21. Large airbag lifting device)

3. Argo bogie suspension

 

As shown in Figure 22. This suspension has a variety of combinations such as two-line four-bridge, three-line six-bridge, etc.

The loading capacity is designed on demand, even up to hundreds of tons. It is mainly suitable for special transportation vehicles for road transportation of low-speed and overweight goods.

( Figure 22. one-seat with two-axle argo bogie suspension )

 

From: WONDEE AUTOPARTS