ADDENDUM ON TOWING EXPERIENCE; MARCH 2009
Although I have never towed an hgv trailer I must remind readers that essentially the aerodynamics of the trailers I do tow are virtually identical with those of a central (approx) axle/axles HGV trailer.
Caravan/trailer brakes in the UK have not been improved since 1930 as modifications currently on the market in the EU/UK have yet to be critically assessed.
I have no practical experience of electronic braking systems, but am a strong supporter of them in principle. My current Land Rover Discovery is 15 years old (I have owned same for 13 years) and is maintained by a Birmingham/Solihull firm specialising in renovating vintage Land Rovers.
Had Land Rover actually produced their new “green” version of the Discovery I would have purchased one. However the current Discovery weighs 2.7 tonnes compared with my models’ 2 tonnes and consequently needs a much larger engine. It is possible that with electronic braking on my tow car I may agree that the critical safe air speed when towing my Swift 400 caravan is slightly over 50 mph, but it should be noted that when (as reported in the Caravan Club Magazine) Bath University tested a tow car with electronic brakes they did not exceed 50mph when towing a caravan similar to my Swift 400.
Currently I own and am fully insured for towing the above ( see photograph)trailer; the Swift 400; and a recently purchased 23ft twin axle caravan. My boat trailer at 27 years old is not currently road worthy but I am having it modified this year. The wheels springs and axle will be removed and replaced with 4 wheels with no brakes or springs. It can then be winched on to a hired car transporter when necessary.
Peter W Jones MInstP
The above photograph depicts my latest purchase (May 2007). Apologies for the software bug producing two images.
I had resolved to purchase nothing further in this field until I could buy something with electric brakes, but I needed the above to continue enjoying my retirement during the Summer months.
Using the internet I went to an enormous amount of trouble to find a trailer with electric brakes, but none are available in the UK.
The Daxara 198F was sold to myself by indespension.co.uk and the chassis was made by ALKO. As with all caravans and most trailers the ALKO suspension depends on a solid piece of rubber/plastic which is compressed and the system should not need a hydraulic damper. My first new car (an 850cc Morris Mini Minor) acquired in 1960, had this type of system and, by the standards of that era, was quite satisfactory.
However, the Daxara trailer has a problem with undue “bounce” whether it is lightly or heavily loaded. It was sold with hydraulic dampers, but these do not eliminate all the vertical oscillations that are set off by quite minor road faults.
I am however quite satisfied; I have no intention of exceeding 50mph air speed as I have previously explained. Athough this type of trailer would be safer with electric brakes, an aerofoil to produce down force would have to be quite high if towing was with a car, but with a van or 4×4 I doubt whether it would be feasible.
When I wished to tow there was hardly any wind, and at 50mph I experienced no trouble when overtaken by large vehicles.
I noticed that Jeremy Clarkson ( BBC 2) was showing off a very expensive sports car this week with a computer controlled aerofoil, but the rally car on the same programme seemed to have a boot mounted aerofoil which I thought was too low to be effective. The air flow over the car roof would possibly create some turbulance and reduce the effect of the aerofoil. The sports car aerofoil was also low, but due to the exceptionally good aerodynamic shape of the car, I thought it could produce effective downforce on the wheels. The million euro VW sports car ( the Bugatti Veyron) has a similar computer controlled areofoil, but this seems to be higher. I cannot see any justification for introducing aeofoils for most cars on UK roads. However, as they get lighter to reduce the carbon foot print, a variable pitch aerofoil may well be necessary.
I have experienced sideways drift in a gale force cross wind at 70 mph when driving my Rover SDI 3500 V8. This was lower than most saloon cars, very heavy, and was carrying three adults plus luggage. I did not expect this to happen, but I cured the problem by slowing down and I think this is the best solution.
I “sensed” the drifting so had a second chance to correct my error and slow down. When towing it is not possible to feel oscillations of a trailer until they are quite considerable. We need electronic sensors to detect snaking and apply the trailer brakes, but electric trailer brakes would be a good start as it is safe to apply your foot to the tow car brake pedal when snaking begins, but highly dangerous to do the same thing with over run brakes. In the case of trailers aerofoils are needed to improve braking when snaking takes place. Aerofoils would also reduce the possibility of snaking by increasing friction between tyres and the road.
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Addendum December 2008
I have now had the above trailer for two seasons and have covered about 2000 miles with this new item in tow with my Discovery.
I have still not experienced any snaking when being overtaken by HGV’s, but I shall not be increasing my air speed of 50 mph. (NB. As there are no suitable anemometers available at present I only know my air speed accurately when there is no wind and road speed = air speed).
I have also not had to brake sharply in an emergency situation so have found the over run brake satisfactory. I have been wearing a seat belt since 1967 and have never had to rely on same, but I strongly support use of seat belts and improved brakes for caravans and trailers.
School/University Mini buses are lighter than Land Rovers and are more likely to be destabilised during heavy braking (with over run trailer brakes) if trailer and tow car are not in a straight line. Just another reason to stick to 50 mph until better brakes can be obtained. In an emergency braking situation your trailer may start off in line with the tow car but as soon as a slight skid starts this will no longer apply and the over run brakes may cease to operate. Electric, Pneumatic or Hydraulic Trailer Brakes operate as soon as the tow car driver pushes the brake pedal down and stay applied until the brake pedal pressure is eased.
See also www.caravanaccidents3.wordpress.com
