Safe towing at over 100% a reality

[Lutz]

There was a press release in my mail yesterday that Knott, the brake manufacturers, have developed an electro-hydraulic system for caravans that would easily allow safe towing at over 100% weight ratio, subject to the car manufacturer permitting a high enough tow limit.

In effect, it is a stabiliser with pads like the AlKo/Winterhoff but the pressure applied by the pads to the towball is variable and automatically adjusted to be proportional with speed. In addition, it also has a device that senses sideways movement of the caravan and applies its brakes as soon as any sway is detected (similar to the LEAS stabiliser). There is no longer any mechanical connection between the coupling and the overrun brake. As a result, it has the added advantage of being able to release the caravan brakes completely when reversing unless, of course, the brakes of the car are applied. It also allows self adjusting brakes which are otherwise technically not possible with current auto-reverse systems.

Apparently the system is already fully developed for series production and some caravan manufacturers are considering it as a possible factory-fitted option to be available in the near future.

At the same time, AlKo are about to offer their version of the LEAS electronic stabiliser but I gather there are some problems with possible infringement of patent rights which could delay start of sales.

It looks as though caravan chassis design is slowly being drawn out of the horse-drawn cart era.

 

[Steve L]

It's about time the manufacturers came out of the ark.

For many years we have relied on the old catch up braking of trailers, while our commercial friends have "suzie" couplings and air powered brakes. They even reverse designed the trailer brake system so that spring power held the brakes on to brake an uncoupled trailer automatically. A kind of fail safe system.

Often wondered why cars could not have a compressor fitted and the trailers be of the air brake variety. It would be fairly straight forward to regulate pressure.

Being one who tows to the max, I'd recomend that the towing law is changed so that those who tow beyond the kerb weight of the car are trained to advanced standards, as heavey towing is not for the complacent types. You have to have your nerve about you and concentrate 100%, anticipate others on the road and be aware of how your outfit behaves when things go wrong.

My brother in law thought he was good at towing until one day while using my Diahatsu fourtrak and 3500Kg Ifor Williams goods trailer, he had to stop quickly on the M5 after lighting a *** on the move. He hit the brakes and tried to steer to the hard shoulder to avoid the car in lane 1, but ended up jack knifeing and going up the embankment. He was so lucky not to of involved any other vehicle or seriously injured himself.

The Diahatsu had severe damage to the back quater and the trailer had an "a" frame drawbar that was a foot off center. Due to my insistance on using 5 ton ratchet straps to hold the load down, that stayed intact.

That was just five seconds to spark up a ***, what about using the phone or playing with the sat nav, or eating a sarnie. All the bad thing we all do on the move. See what I mean about complaicency.

Driver training should be next on the up date list.

 

[RogerL]

UK law would have to be changed to permit this sort of coupling.

An over-run braking system is mandatory on any trailer with a MTPLM exceeding 750kg.

I thought this mandatory over-run coupling was required throughout the EC as well but I'm not well versed on that.

 

[Lutz]

It works just like a regular overrun coupling, Roger, the only difference being that the brakes are actuated electronically rather than through a mechanical connection. As such, it fulfils all existing regulations.

 

[RogerL]

Electric or electronic trailer brakes (on their own) aren't permitted in the UK either. Trailer over-run brakes must be mechanical ie, cable, rod, hydraulic or vacuum/spring.

I doubt very much that UK law, and EU law if necessary, would be altered for trailers BEFORE it's altered for conventional vehicles.

There may well be a case to alter vehicle construction regulations to allow electronic brakes but this should be led by vehicle manufacturers, not trailer makers.

 

[Lutz]

Following your statement I took a second closer look at the description of the Knott coupling and can confirm that the overrun feature is purely hydraulic, so the brakes would work even if there is an electric power failure. The electronics only control the pressure in the system just like ABS in a car and they also control the anti-snake feature.

 

[RogerL]

If the over-run coupling is hydraulic then it should meet existing legislation.

It sounds as though the braking side is similar, perhaps identical, to the electronic stability systems being fitted to an increasing number of cars. It would seem sensible to incorporate ABS at the same time.

An advance in caravan chassis design is long overdue. They currently use car design from the 1930's - rod and cable drum brakes with un-boxed channel section chassis members.