Firstly does your small towed car need a braking system when towed behind a 3 1/2 tonne + motor-home NO, unbraked trailers of the up he 750kg can be towed behind most medium sized cars weighing less than half the weight of the motor-home. However you are REQUIRED to have an operational braking system as the D.F.T (Dept. For Transport) ruling is, that a car being towed on an 'A' frame is effectively a trailer, and if a trailer has brakes, they must work. Its that simple!
We have major concerns with existing systems
The method of attachment (to the towed car). This is often simply by towing on the existing crash beam using the existing towing eye, cutting another hole through the bumper, and fixing another 'eye' to the other side. This is a thoroughly unsafe practice as, firstly the crash beam is not designed to take this sort of loading's, (for example on the original 'smart' cars the crash beam is only attached by three 8mm bolts per side!) Attaching the second 'eye' facility requires welding in new attachments into a beam which often high strength or 'Boron' steel, safe welding to which, requires specialist knowledge of the type of steel and the correct welding wire, gas, etc none of which is likely to be available to the fitters of this equipment.
The flimsiness of the 'A' frame itself. Whilst they may be adequate for straight line towing, the sideways forces exerted when going round tight corners should not be underestimated. Our own frame is only a little heavier at around 12kg, but is vastly stronger.
The operating principle of all the existing systems is to say the least bizarre. All work by using an 'accelorometer' to detect deceleration, and once detected, to apply the brakes. In practice this means the car has to be slowing down before the brakes apply themselves, putting cyclic loading's onto the 'a'-frame and attachments. The majority of systems currently offered are of American origin and include 'toy' sized compressor units, which if they fail have to be purchased from importers, who seem strangely reluctant to quote prices for replacement parts!