Peter Jones MInstP
Consultant for Towed Vehicle Accidents
(Voluntary Status to be Applied for)
Alko Electric Brakes
I noticed on 28-01-11 that the brief summary on Google concerning Alko that appears when one enters “Caravan and HGV Trailer Snaking Accidents” in to Google contained a reference to Turbulence, snaking and HGV’s .
I had not read anything technical on the web originating from the caravan/trailer industry since my clash with them via TouringandTenting.com which I wrote about some time ago in www.caravanaccidents.wordpress.com
From the short reference above it is clear that the caravan/trailer industry think that turbulence from HGV’s may cause high sided trailers to snake. This is quite impossible. When any fixed wing aircraft takes off it is because the streamlined air flow over the wings produces “aerodynamic lift.” Whenever, on very rare occasions, an aircraft encounters an area of turbulence it immediately looses all aerodynamic lift and drops like a stone until calmer air is encountered.
It follows therefore that if HGV’s and similar large vehicles produced turbulence we would have far fewer caravan snaking accidents caused by HGV’s. There is still of course what cruiser and dingy sailors call the “Ventrui Effect.” This happens when an HGV passes very close to a caravan when overtaking, and the effect is even stronger when the caravan overtakes the HGV when they are very close together. There could even be a disastrous snake in this instance even though the caravan was moving below the critical air speed which I have explained previously. This is because ( in my opinion) the force exerted on the caravan is so much greater than when the “bow wave” of the HGV influences the caravan.
Standen of Bath University, showed in his 1999 Phd thesis “Towed Vehicle Aerodynamics,” that suitably sized caravan aerofoils (similar to those on the front and back of F1 racing cars) could reduce snaking by creating extra down force on caravans and high aspect trailers. Standen verified this important item of Physics by extensive experiments with models in the university wind tunnel.
If any Scientific Academics do wish to take an interest the exact parts of Standen’s results that I am using will be found in “quotes” in my unpublished report (apart from blogs) sent to the Institute of Traffic Accident Investigators (www.itai.org) in 2005.
See “Archives for April 2007” in www.caravanaccidents2.wordpress.com
Edit 14-02-11
I have now copied parts of my 20six.co.uk blog in to
www.itai2005reportpart2.wordpress.com
Caravan/trailer brakes:- 5f,6b,6e&f,7b,8a,9d,10c[1,10 & 14]
Selby Rail/Road disaster:- (Did the over run brake contribute to this disaster?)
see www.caravanaccidents3.wordpress.com Scroll to Para 31i and for stabilisers scroll to para 36 for Bath University results and to para 43 for the Peter Jones stabiliser test which is suitable to carry out in schools.
I think I showed ( using Standen’s results) that the “air disturbance” produced by a HGV was a bow wave and not turbulence. ( Assuming air acts in a similar way to water the bow wave effect is confirmed every time a boat is observed moving through calm water).
Similarly the Ventrui/suction effect is confirmed if one notes that a boat never moves close to and parallel with a harbour wall. The crew man/woman holding the rope in the bow always jumps on to the wall as the boat gets close when approaching at an angle of about 30 degrees. (It will cost sailors a great deal of money if they overlook this when taking a 2 million pound sterling GRP boat alongside a harbour wall built for ancient sailing ships.)
It is possible that if turbulence could be created using many simple and small wind deflectors on the top of HGV trailers, the aerodynamic lift would be eliminated and jack knifing would be much reduced.
See also www.aerodynamicsoftrailers.wordpress.com
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COPIED FROM ALKO’S ON LINE ADVERTISING BLOG ON 28-01-2011
AL-KO has created an automatic system which detects signs of Caravan Instability, to take preventative action at the earliest stage, before disaster takes place. It was also vitally important that the existing caravan braking systems was used to quickly control the problem.
Thus taking the Car and Caravan combination down below the “critical speed, and prevent a disaster situation”
AL-KO ATC is the emergency braking system for caravans and works in a similar way to ESP systems for cars. The sophisticated, but simple electronic system monitors the lateral movement of a caravan during travel. When difficult driving conditions are experienced, such as evasive manoeuvring, high side winds and turbulence encountered while overtaking HGV’s, AL-KO ATC takes control to regain stability and prevent dangerous snaking accidents.
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PWJ
The caravan clubs/industry (to the best of my knowledge) have never tried to explain what the “critical speed” for a caravan is, or how it varies. In fact, I have not before noticed that they now agree there is such a thing as a “critical speed.”
( see my explanation near the start of
www.caravanaccidents4.wordpress.com
and entitled “Paragraph 103; Caravan Club Technical Advice.”)
Concerning the rest of the material I have quoted above I suggest that readers look at my blog
www.caravanaccidents4.wordpress.com
and scroll down to “Caravan and Camping Club 2008 Tow Car Awards Tests.”
In addition if one scrolls further down this blog some rather poor copies of the CCC 2008 Tow Car Awards Tests can be seen, plus a link to www.caravanaccidents4.wordpress.com
