Special Note re Brakes and Towing
By Pierre Joubert
Sunpacer Manufacturing CC
March 2011

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Concern has been expressed by a number of customers over the legality of brakes on horseboxes, asking for an explanation. As this is an important issue over which there is a general degree of uncertainty, this special note has been added to this web site to hopefully raise the degree of understanding by all concerned

The National Road Traffic Act, Regulations, Chapter 6 Sec 151(1)c states that if the GVM of the trailer exceeds the Tare mass of the tow vehicle, a service brake is required on the trailer

The simple fact is that many horsebox rigs are out of line relative to this requirement. The typical Japanese type bakkie which is used to tow many horseboxes has a tare mass around 1400 to 1800 kg. Horseboxes generally have a GVM of over 2000 kg. In all cases of bakkies pulling horseboxes the rigs may therefore be found non compliant

In addition, aforesaid Japanese bakkies have traditionally been rated by their manufacturers as having tow capacities around 1000 to 1500 kg. Exceeding the tow capacity does not appear to be in contravention of any regulation, but it could affect an insurance claim. To check the tow capacity of any vehicle, go to specifications on the Unitrans website (click on Unitrans logo). See also notes (1) and (2) below

And, the tow bars on said bakkies are generally rated to match the capacity of the bakkie, so many rigs are out of line on this point as well, meaning a bakkie alowed to tow a 1500kg trailer has a towbar rated at 1500 kg, but it is likely to be used to tow a 2000+kg trailer

Please refer to the attached pdf brakes-and-towing-issues for a further explanation.

Also see article in SA Horseman Nov 2010 issue by Pierre Joubert (425kb with text in Afrikaans)

Also see article from Engineering News 2013-05-22 "Beware what and how you tow, warns Thule boss"

Also see Notes 7 and 8 on main page

Note (1) Please note that specifications referred herein are for guidance only. For reliance there-on readers should confirm directly with manufacturers.

Note (2) Comment re Japenese bakkies is a generalization, intended to raise awareness. In practice there may be exceptions



Action of electric brake inside the drum
For the technical guru, notice that the oval shaped object at the end of the curved lever is an electro magnet. Notice also that as it moves to the right while expanding the brake shoes, it is increasing its distance from the rotation center of the drum. Not shown is a ring of metal inside the brake drum with a radius just outside the position of the magnet. When the magnet is energized during a brake application, it draws itself outwards towards this ring of metal, increasing said distance from the center of rotation, and at the same time causing the swinging action which expands the shoes against the drum. QED. Your science master will further help you work this out if it is still not clear.


     
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