Introduction of Trailer Brake Drums
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A brake drum is the core component of vehicle braking system. Its function is to generate braking force and hinder vehicle movement or movement trend.
A brake drum is a matching part of internal tension shoe friction brakes. It should not only have the strength and stiffness, but also have as high and stable friction coefficient as possible, as well as appropriate wear resistance, heat resistance, heat dissipation and heat capacity.
Brake drums are widely used on axles of semi-trailers.
As shown in Figure 1 below. The brake drum is connected to the axle hub by tire bolts. When the vehicle is braking, the air brake system pushes the camshaft to rotate to spread out the brake shoes to apply pressure to the brake drums, so that the friction force between the brake pad and the brake drum generates braking torque, and finally stop the vehicle. The reliability of brake drums directly affects the driving safety of a vehicle.
A brake drum is one of the important parts of a trailer axle, It is mainly introduced from the following aspects:
1. Technical standards of brake drums
(1) The technical standard of brake drums shall comply with China national standard GB / T37336-2019.
(2) The technical standard of brake drum casting blanks shall comply with China national standard GB / T9439-2010.
2. Technical parameters of brake drums
As shown in Figure 2 below. Common technical parameters of brake drums are as follows:
(1) A：（Overall Diameter of Drum）
(2) B：（Dust Shield Recess Diameter）
(3) C：（Brake Surface Diameter）
(4) D：（Overall Depth）
(5) E：（Brake Surface Flat）
(6) F：（Depth of Dust Shield Recess）
(7) G：（Squeeler Band Thickness）
(8) H：（Distance from Outside of Backface to Start of Taper）
(9) I：（Inside Finished Diameter）
(10) J：（Bolt Circle Diameter）
(11) K：（Pilot Diameter）
(12) L：（Outside Finished Diameter）
(13) M：（Diameter at Taper）
(14) N：（Backplate Thickness）
(15) O：（Bolt Holes: Number and Size）
3. Classification of brake drums
According to structure types of the brake drums, it can be divided into the following two types:
(1) Common brake drums
1) Single material brake drums
As shown in Figure 3 below. This kind of brake drums has the advantages of simple manufacturing process, stable performances and high cost performance. It is widely used in trucks, tractors, full trailers, agricultural vehicles and semi trailers.
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2) Bi-metal brake drums
As shown in Figure 4 below. As the name suggests, the braking part of the bi-metal brake drum is composed of two different metal layers inside and outside. The inner layer in contact with the friction lining is a cast iron part to ensure a good braking performance. The outer layer is made from high-strength steel to improve the strength and toughness of the brake drum. At present, this brake drum is currently in the trial stage in the market.
(2) Brake hub-drums
As shown in Figure 5 below. A brake hub-drum combines the wheel hub and the brake drum into one. This drum is mostly used on light-duty trailers.
4. Selection of brake drums
How to choose a brake drum in need correctly can be determined from the following aspects:
(1) Determine drums according to the OEM number of the automobile manufacturers, axle manufacturers or brake drum manufacturers.
As shown in Table 1 below, the OEM number of common trailer brake drums of well-known manufacturers.
(2) Determine drums according to brake drum drawings.
(3) Determine drums according to the basic sizes of a brake drum.
As shown in Figure 2 above, at least several parameters such as C, D, E, J, K, and O are required to determine the product.
5. How to measure a brake drum
As shown in Table 2 below. Relevant parameters of brake drums shall be measured as shown in the figure below.
6. Maintenance of brake drums
In order to achieve the longest service life and the best service performance of a brake drum, regular maintenance shall be carried out according to the maintenance manual of the vehicle manufacturer or axle manufacturer.
7. Replacement of brake drums
If one of the following problems occurs, the brake drum needs to be replaced. The brake drum must be replaced in pairs to ensure that both ends of a trailer axle have basically the same braking effect.
(1) The brake drum is cracked;
(2) Hot cracks, grooves or wear on the friction surface of the brake drum exceeds the limit of the brake drum;
(3) The mounting surface of the brake drum is cracked;
(4) The bolt hole of the brake drum is damaged;
(5) The brake drum is out-of-round.
8.?Troubleshooting of brake drums
Troubleshooting table-problems, causes and troubleshooting methods are shown in Table 3 below:
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