Thin Drop plates on IRS and Drop Axles are continuing to Cause Problems.
Drop plates with a thickness of 25mm are breaking during shock loading events. Couplemate™ and Alko use 32mm drop plates, which effectively results in less damage to IRS and drop axle builds.
Shock loading events occur unexpectedly, such as when the trailer jumps a roundabout curb or when the caravan is forced off the road, climbing a gutter.
The trailer shown in the above image, which suffered a broken drop plate, was a 2000kg tandem trailer. The problem is magnified substantially on a 4.5t vehicle.
Forensic Investigation
There may be a more sinister, unseen reason for this drop plate breakage.
Did you notice the bearing buddy that replaced the dust cap? We suspected the owner inadvertently overfilled the bearing buddy.
As a result of overfilling the bearing buddy, grease was expelled out of the back grease seal and into the mechanical backing plate cavity.
This, in turn, caused the brake shoes to become contaminated, which then caused brake failure.
So was the brake failure the cause of the accident, or was it the broken drop plate?
In our opinion, excess grease from the bearing buddy escapes through the rear seal once the hub is at speed and pressurised. The heat caused an increase in the grease viscosity, thereby causing contamination of the brake shoes.
As a result of contamination, the brake shoes became ineffective.
At this point, we can only theorise that a sway event occurred: that a brake event failed to rectify sway before the wheel hit the gutter, thereby causing shock loading on to the drop plate and breaking it.
Bearing Buddy
Bearing buddies are designed for unbraked disc brakes and hydraulic-braked trailer axles. Should bearing buddies be overfilled on this type of axle, the excess grease is expelled to the ground of the highway. Brake pads are generally not subject to contamination on this type of axle assembly.
In our opinion, bearing buddies can cause grease contamination of brake shoes when overfilled.
Couplemate has concluded that bearing buddies are unsafe for use in conjunction with drum brakes; they should be immediately replaced with conventional or grommetted grease caps.
50mm Square x 4″ Drop Axle
How Can Drop Plate breakages be minimised
The hollow electric drop axle assembly in the right-hand image has a 32mm-thick drop plate.
Couplemate uses 32mm plates; as a result of finding too many examples of 25mm plate breakages.
Furthermore, sturdy drop plates cannot prevent grease from escaping into brake cavities, but they can prevent equipment breakages.
The drop plates below are 32mm wide and suitable for 45mm Square and 50mm Square Axles.
- 45mm Square Beam x 45mm Round Stub x 3-inch Drop
- 45mm Square Beam x 45mm Round Stub x 4-inch Drop
- 50mm Square Beam x 45mm Round Stub x 4-inch Drop
- 50mm Square Beam x 56mm Round Stub x 4-inch Drop
© Stephen Wotherspoon, 14th April 2020
0 Comments