contains Para’s 10ci to 18b and
www.caravanaccidents2.wordpress.com
contains Para’s 1a to 10c
www.caravanaccidents3.wordpress.com
contains Paras 31 to 50
.
Index and List of Contents
(A)
accident statistics 1a : Accident-failure of over run brakes, 3c: Accident-failure of stabiliser, 3c: Acknowledgements, 5d, 5e, 5f, 6b : Air speed indicators, 6c: 33
Aircraft Stalling Speeds, 7g, 7h, 8a, 8b, 8c:
ALKO new brake system- History ; Para 41
(B)
Blog: aims of, 1d: Bath university on stabilisers, 2e: Bath University on effect of bow wave of HGV, 9b:Boat trailer snaking, 4a: Burst tyres (related to centre of mass and stability), 6a, 11e: Boeing 737, 8g:
{C}
Caravan Club, 6a, 6g, 9b, 10, 6h, 6j:Centre of mass calculation, 18a:Centrifugal force calculation, 12c: Conclusions, 16a:
(E)
Equations of motion and stabilisers, 13a: Evidence from sailing supports safer towing, 4c,5a,5b,5c: Electric Brakes, 15b:
(F)
Flying caravans, 6h: Formula 1 racing cars, 9e:
(G)
Government Caravan Accident Statistics, 1a:
.
(H)
.
HGV Trailers - Summary, 18b;
Handbook for air pilots, 6e, 7a: Head wind and side wind components, 7c, 7d: HGV’s and wind speed needed to over turn them, 7e, 7f: HGV‘s and maximum safe air speed, 9a: HGV‘s effect on caravans, 9c, 9d, 10a, 11a: .
.
(I)
Information on stalling speeds for aircraft, 7g, 8a, 8b: Insurance, 17c: .
(J) Jones, Peter W: career summary 1c, 1d:
.
(K)
.
Kinetic Energy and caravans, 11f:
.
(L)
.
Length of HGV Bow Wave related to length of caravan, 11d:
.
(M)
.
Maximum legal caravan speed, 3b: Maximum safe caravan air speed, 6f, 6g, 6j: Mini bus accident, 1f, 1i:Marine safety measures applied to road, 14b:
.
(N)
.
Newton; GCSE and GCE “A” level work 1b
.
(O)
Over run brakes – the case against, 10cii;
Over run brakes, 1e, 1g, 12a: Over run brakes, alternatives, 2a: over run brakes and shock absorbers, 1h: Overloading of caravans, 17b: overloading of tow car, 17d:over run brakes and shock absorbers, 1h: Overloading of caravans, 17b: overloading of tow car, 17d:
. (P) .
.
Physics of over turned minibus, 1g: Prevention of snaking, 4b, 2d, 2e:Phase of HGV bow waves,11d: Principle of Moments and stabilisers, 13a:Parallelogram of Velocities and vehicle air speed, 14b:
.{R}.
Research at Bath University, 9b,d,e.& f, 10a & b, :References, 10c. Resonance and caravans 11d:
. (S).
Safety; actions taken towards effecting improvements; www.caravanaccidents3.wordpress.com
Snaking Tyre marks – evidence produced by, 10ci;
Snaking tyre marks, 17a:Snaking, 2b, 11g: Snaking caravan accidents, 3a: Snaking prevention and stabilisers, 2d, 13a: Stabilisers and Bath University, 2e:
Stabiliser test on friction based type, 10ciii;
Stabilisers (design faults with most of them), 2g:
Stabiliser test (calculation of centre of mass position), 18a: Selby road/rail disaster, 2c, 15a, 10cii: Somersaulting caravan, 3a, 6b: Standen (Bath University) on wind induced snaking, 10b: School Mini Bus, 10d:Snaking calculations approximated to circular motion, 12b:
. (T).
Tyre marks made on the road in a snaking accident, 5g: TV adverts for cars concerning aerodynamic lift, 7h: Trailers-effect of the load on aerodynamics, 8d: .. (U) .University mini bus, 10d: . .(V). Ventrui effect, 11b, 11c: . .(W) . Wind gusts, 6d: Wind deflectors, 8c, 9d: Wind speed monitoring on road and rail, 9g, 7f: Windy weather, 14a: . (Z). .Zero road friction, 6f. . ..
Introduction. . The Institute of Traffic Accident Investigators. (www.itai.org)..The following Blog is essentially an updated version of a report I completed for the above in 2005. This was circulated in part, in stages, as I wrote it, toRTAInvestigators-owner@yahoogroups.comTraffic Accident Investigators is a private yahoo group set up for the purpose of circulating scientific information likely to be of use to RTA investigators. It is not run, or owned, by itai.I also sent out complete copies of my report by e mail, to Yahoo Group members who requested same. Mainly these were UK Police RTA Investigators, but I also had requests from a private consultant and a Police Investigator in Australia, and one from a Republic of Ireland Police RTA Investigator. I should imagine that these investigators will have passed my report to colleagues ( as I wished them to do).As well as RTA investigators I observed that on other matters there was a considerable input (on the Yahoo site) from University RTA Researchers. As I received no comments from the latter on my work, I assumed that those reading same had no relevant comments to make.This is particularly significant as I do not rely on accidents for my main evidence. I use some of the Physics and Maths taught in schools and colleges for GCSE and GCE “A” level, and some research carried out at Bath University... 1a . The itai did not publish my report in their Journal. The Secretary told me that he would like to see others publish this work before they did.
.THE SCIENCE OF CARAVAN AND TRAILER ACCIDENTS . . 1c . I should therefore make it clear that I am a retired Physics teacher (but the Institute of Physics still recognise me and I am on their www list as an AMInst P). I held my last professional position (Head of Science at a Comprehensive School in Handsworth, Birmingham,) for 20 years. I was also a Full Time Lecturer at a Birmingham Technical College(FE) for 7 years. .1d . In all I was a full time teacher for 41 years, so have an adequate pension and can devote some time to endeavouring to improve road safety .In addition, Schools and Colleges teaching “A” level and GCSE Physics will be able to make use of the Physics in this blog as relevant background material at the appropriate time. . 1e. The most serious design fault in 95% of trailers in the class 750kg to 3500kg is the brakes. These are “Over run” brakes. They work when the tow car brakes and the trailer catches up with the tow car and so pushes on a lever which applies the trailer brakes. This works very well as long as the trailer and tow car are in a straight line. When this is not the case you are in effect operating with no brakes at all (including your tow car), as the consequences of applying the brakes can be so disastrous. . 1f . A case I have learned of through hearing a witness interviewed on the TV (it was an “overseas accident” involved a mini bus carrying about 10 passengers towing a substantial luggage trailer. The driver swerved to avoid a pedestrian. The mini bus missed the almost suicidal pedestrian, but the trailer jack knifed and struck the pedestrian. The mini bus then overturned causing 5 fatalities. It was most likely that the passengers were not wearing safety belts, but even if they had been, the consequences of this type of accident will be most severe.. 1g. It is typical of what will happen when a trailer with over run brakes swerves sharply. The forward momentum will be so great that the trailer will swing round in a wide arc and the centrifugal force generated by the swing (acting away from the tow car) will prevent the brakes being applied as the trailer cannot possibly catch up with the tow car. As long as the trailer’s weight is substantial, as compared with the tow car, an over turning of the latter is almost certain..
Most of the faults mentioned above can be proved with the use of some fairly elementary Physics (Mainly GCSE level, but some may stretch to GCE “A” level.) I will endeavour to write so that non Physicists will be able to understand my arguments.
1h. . The over run mechanism contains a hydraulic shock absorber to prevent the brakes being applied when not really required, so the trailer must exert a considerable force on the tow car to over come the resistance of the shock absorber before it begins to apply the brakes. When a car and trailer are negotiating even a slight bend, if an emergency arises and the driver applies the tow car brakes, it is almost certain that the force applied by the trailer when it catches up with the car will be enough to push the rear of the car off course and possibly turn it around, but not enough to apply the brakes. ..1i.. The accident I referred to above in (1f) was given extensive media cover: I had seen a good picture of the trailer, and had heard that the South African Police had reported to the media that the trailer had caused the mini bus to over turn.On 2-2-04, at 11pm, I then heard on BBC Radio 4 news that the South African Police had told them that the trailer was fitted with the wrong type of brake. This could only mean that the trailer had over run brakes (as is the case with at least 95% of similar UK Caravans and Trailers) and not the electric or electric/electronic brakes that I know are extensively used in Australia and I suspect could be a legal requirement in South Africa.I therefore wrote to the Association of Chief Police Officers (ACPO) and asked if they could check the truth of the above report. They replied that the type of brake on a trailer was a political decision made by the Government and they would not involve themselves. I then wrote to my MP (Birmingham Hall Green). He telephoned me to run through the technicalities to make certain that he had his facts correct. He said he was due to see the Secretary of State at the DfT the next day, and he would raise this problem with him. As 3 years have now passed since this accident took place all legal proceedings must have been completed and I hope that attention will now be given to the question of having safer brakes in the UK. /. 2a .
The above problems are much less likely to occur when the trailer brakes are electrically, hydraulically or pneumatically controlled. In the UK all hgv trailers have hydraulic or pneumatic brakes. In Australia most caravans have electric and/or electronically controlled brakes. We have very few of these safer braking systems in the UK because (as far as I know) the matter has never been explained adequately to caravan and trailer users. European brake manufacturers ( with one exception) have not woken up to the fact that one needs to brake a trailer independently of the tow vehicle to stand any chance of controlling a snake. This is one of the most important reasons for my blog.
I have been towing (on a recreational basis) sailing cruisers and caravans since 1976. They have all, in certain circumstances, been liable to snake. Expressing this in more Scientific terms, caravans and trailers are given to oscillating in a direction at right angles to the direction of travel, and these oscillations very often lead to a serious accident.
.. It will surprise some people, but the most expensive RTA in UK History was caused by a Land Rover towing a car on a transporter. The combination managed to get on to the main railway line (by running down an embankment of the motor way). An express train was derailed when it hit the Land Rover. The express then collided with a goods train travelling in the opposite direction causing several fatalities and serious injuries. This took place at Selby in Yorkshire. This however was not a snaking related accident. The jury convicted the driver of “going to sleep whilst driving.” I quote this case because it is typical of what might happen as a consequence of a trailer snaking accident..
.2d.
.2e
. I have pasted in the following from my 2005 report for the itai:-
Section 9. Stabilisers (addendum)Bath University Research (see section on references) Fratilla states on page 159,“Stabilisers on their own are insufficient to guarantee satisfactory operation ( of the caravan).”This extract from a 1994 Phd thesis represents the result of a careful assessment.All the work was done using a computer model set up by a previous researcher. This result was obtained 11 years ago. I have never seen it quoted in the caravan media. In one magazine ( January 2005) a two page article was devoted to reviewing a number of stabilisers ranging in price up to £450. The Bath University research was praised in the article, but no mention was made of the above result.
.2f
. I came to a similar conclusion by carrying out some approximate calculations using some “A” level Physics, but it is not worth including these calculations here as I more recently had a better idea of how to do the same thing more effectively using only a little GCSE Physics. I have now proved, quite conclusively, that my own highly regarded stabiliser, is completely ineffective at controlling or stopping snaking. I have included a Science addendum with my “road traffic accidents” blog. One item describes my stabiliser test. Any one else could repeat the procedure with their own stabiliser. .
2g .I am also fairly certain that similar results to mine will be obtained for all stabilisers as in early 2006 the Caravan Club Technical Section of their www site (members only) gave the figures for the amount of frictional force that could be exerted by most of the stabilisers on the market. When new, they were all almost exactly the same. My stabiliser can be adjusted, but in some there is no means of adjusting for wear other than by replacing the friction pads.
3a
Snaking Accidents
In the Summer of 2002 my second daughter and her husband escaped a horrendous caravan snaking accident with only post traumatic stress. As they declined to go to hospital in the ambulance that attended, the traffic police did not call for police traffic accident investigators, so there was no official enquiry. However the detailed and precise account of the accident that I have received has convinced me that they were travelling at less than 60mph; an HGV caused the caravan to snake; the caravan and stabiliser were brand new and on only their second trip. (3b) They had travelled about 60 miles after hitching up their van; my daughter brought the out fit to a controlled stop (facing in the right direction) on the grass verge of the A 34, but the snaking caravan continued straight on over the top of the tow car, executing a complete somersault to land on its wheels in front of the tow car . (3c)The caravan was of the “raising roof” type. I concluded that the brand new over run brakes and the new stabiliser were of no use whatsoever in this situation. (3e) The brakes and stabilisers used today are of a very robust construction, and although caravan bodies are usually reduced to a pile of wooden pieces in such accidents I would have thought that in future a post accident inspection of the brakes and stabiliser would be well worthwhile as if they were shown to be in a mechanically sound condition the case against these items would be finally proven.
ADDENDUM NOV 2008
3 years after writing the above I noticed today that I failed to mention that the caravan had a burst tyre and the traffic police who attended said that this had caused the accident.
(See also Para 601 of this blog)
This error arose because the above is a much condensed version of the original document.
(4a)
A Boat and Trailer Snaking Accident (almost), and two near approaches to disaster with caravans.
I had an unpleasant experience in 1976, the first time I towed anything on the road. I was overtaken by an HGV whilst moving at the then legal maximum speed of 50 mph whilst towing the sailing cruiser shown in photo “A” with a Vauxhall Victor 101 (1600cc). My son, then aged 14, as I learned many years later, was thrown right across the back seat of the car and clearly thought that we were about to crash. In the front seat of the tow car I just experienced the shock as the bow wave hit the boat.
(4b)
PREVENTION OF SNAKING I have not had an accident over the 40 year period that I have been towing sailing cruisers and/or caravans. This is because my first venture in 1976 was with an 18ft sailing cruiser. I learned very quickly that my sailing cruiser which, (with the trailer, was about the same weight as my tow car at that time) was impossible to handle on the sea under even the smallest scrap of sail at wind speeds over about 30mph. If all HGV drivers and caravan towers had experienced the force of the wind when trying to handle a sailing cruiser, our roads would be a great deal safer. The side area of my current small caravan is approximately the same as the area of the fore sail on my current sailing cruiser (a Jaguar 21)
.
(5b)
At wind speeds over about 20mph I only use a fore sail. My boat (with 3 crew) weighs approx 1000kg (the same as my small caravan) and with a 20mph wind from the side the boat moves forward at approaching 5mph. It follows therefore that my caravan, with two small tyres, is going to drift sideways (with a 20mph side wind) sooner than my Land Rover, which has, by comparison, 4 huge tyres and weighs 2000kg. This is what sets off wind induced snaking.
(5c)
In spite of my great respect for the force of the wind I have still had three very near accidents due to the effect of the bow waves of HGV’s. I do not tow when the wind speed is over gale force (about 44mph) and keep off motor ways when wind speed is over 30mph. I am sure that caravan accidents would be much more frequent were it not for the fact that most caravanners have come to a similar conclusion on the basis of their towing experience.
ACKNOWLEDGEMENTS
(5d)
It was my reading of the Bath University Phd thesis by Standen that has been the greatest help in understanding the behaviour of “Towed Vehicles.
(5e)
However, it was the dedicated members of the internet group RTA_Investigators-owner@yahoogroups.com that have provided the support and stimulated the motivation which has made me quite determined, over a considerable period of time, to complete this enquiry. ( even over a long period whilst the NHS successfully treated me for cancer). The two most notable examples of this assistance came from a New York Police Traffic Accident Investigator and a UK Private Accident Consultant(Early 2003)
.
.(5f)
.On reading my circulated account of the first accident described above (plus my “proof” based on Newtonian Physics of the non functioning of over run Brakes during snaking) the New York man wrote to say that in the USA over run brakes were no longer allowed on commercial trailers due to the centrifugal force generated during snaking preventing the application of the brakes. There are of course other design faults with over run brakes
.
(5g)
.
The UK consultant (a retired UK Police investigator) sent me a description of the tyre marks made on the road by a typical snaking caravan. He indicated that no one had been able to explain this phenomena. I eventually managed to explain that burst tyres could be the result of snaking accidents and not their cause. Details of this account are in www.20six.co.uk/roadtrafficaccidents paragraph 17a
.
(6a)
.
I read in a January 2007 issue of the Caravan Club Magazine that officials of the Club have now accepted that burst tyres may not cause snaking and the snaking may actually be the cause of the burst tyres
.
(6b)
.
The UK consultant also sent me an excellent photograph of an accident where a caravan had lifted that far into the air when the tow car braked suddenly, that the following car had run under the elevated caravan before it dropped on to the following car. However, it seemed this accident was the result of faulty brakes. I cannot of course publish this photograph as it would identify the consultant and the motorist. This caravan was very similar to my current small touring van. I have included a photograph of this van in my blog. My daughter‘s caravan was smaller than the one involved in this accident, and also had a roof section which dropped down to reduce wind resistance on the road.
.
(6c)
.
AIR SPEED INDICATORS To tow safely I think that all tow vehicles should be fitted with an air speed indicator..
(6d).
The speed of the wind varies enormously; the forecasted speeds are only “averages;” even on the open sea this can be observed, and on land the matter is complicated by valleys, bridges, and when you come to the end of a tree screen and suddenly feel the full force of the wind..
(6e).
Air pilots have to learn very early that if their plane leaves the ground at 60mph in still air, with a head wind of 30mph it will leave the ground at 30 mph ( although the air speed indicator would still show 60mph at take off). All aircraft have to carry a handbook available to pilots, showing the lowest air speed at which an aircraft can fly (called the stalling speed), and the take off speed (when an air craft reaches this air speed the pilot must never abort the take off).
.(6f)
.Our road vehicles would come a step nearer aircraft safety levels if each vehicle handbook stated clearly the “air speed” at which the aerodynamic lift was sufficient to reduce the tyre friction to almost zero and leave the vehicle open to being pushed sideways. With the aid of road observations over a long period of time I think that this critical speed for my small caravan (weight 1000kg, 4m body length, single axle) is 50mph air speed. I came to the conclusion in about August 2003..
(6h,j)
. At a private Caravan Club Meeting held at the Thistle Hotel, East Midlands Airport, at the end of February 2004, the Vice Chairman of the CC (responsible for technical matters) told members present the speed at which a caravan under test had been virtually “flying.” Also present on the platform was the MD of a very large Group of Caravan Manufacturers. I was that surprised by this admission, that when allowed to speak I repeated what had just been said to emphasise the significance of the revelation. I expected the remark to be retracted, but it was not. No further elucidation was given on the matter of critical speed for caravans; it has also never been explained in the Technical Information Section of the Club Handbook.
.(7a)
Also in the air pilots handbooks is the maximum allowed side wind component ( in mph, or knots) for landing. Clearly the obvious thing to do is land your aircraft straight into the wind. Light aircraft may be able to do this as they can land on firm grass, but larger aircraft must land on solid runways which do not always run in the right direction. This even applies to Jumbo Jets.
.(7b)
.If the side wind component is above the prescribed figure the pilot has to divert to another air port where they have a runway available to meet the requirements. A side wind will blow an aircraft sideways, but as it touches the ground it will continue to go in the direction it was pointing in flight. This could place such an extra strain on the undercarriage that the latter could collapse. I will explain the matter of wind components in more detail in the Science addendum.
.(7c).
When there is a head wind of 30 mph blowing at 45 degrees to the direction of travel there will be a direct head wind component of approx 20mph and a side wind component of the same speed. If you are towing the type of caravan mentioned above the critical speed will be reached at 30mph (20+30=50mph air speed).
(7d)
I think the side wind component of 20mph would then set the caravan snaking as I have explained above, but we really need this critical side wind component to be accurately quoted in the handbooks, as it is for air craft
(7e)
Quite apart from the matter of aerodynamic lift, information should be given concerning the side wind speed required to overturn any high aspect vehicle.
.. (7f).
. Every time a caravan or high aspect hgv takes to the road in strong winds the driver does not know whether the forecasted wind is likely to overturn the vehicle. Even the weather forecasters remind us about certain winds being likely to produce structural damage to buildings, but there must be a policy of pretending that high aspect vehicles cannot possibly be at risk, as I rarely hear the roads mentioned at such times.
NB 3-2-08 I have recently noticed an increase in the number of warnings given on weather forecasts when it is possible that the strength of the wind could over turn high aspect vehicles.
.(7g). (7h)
.I have seen two TV adverts when car manufacturers have claimed, in general terms, that the shape of their new model is such that it stands a much better chance of sticking on the ground than models made by their rivals. The public should not accept such vague statements. We need technical details commensurate with the computer age in which we live.
.(8a) (8b) (8c).
. HGV’s need similar wind deflectors to caravans, particularly the trailers of huge articulated lorries. Some people will need reminding that an articulated lorry is two vehicles. A hefty tractor towing a very long trailer.
. (8d)
.Flat bed trailers are a greater problem, as anything loaded on changes the critical airspeed, particularly if it has a high wind resistance.
.(8g)
.According to www.Aerospaceweb.org a Boeing 737 has a take off speed of 150mph when it weighs 45.36 tonnes. I would estimate the stalling speed at about 120mph.
This would mean that an HGV with trailer weighing the same would most probably become unstable due to aerodynamic lift at 60 mph when there was a head wind of 60mph. I make this very rough prediction as no information has been released by the Road Haulage Industry or academia and I feel certain that these critical values could easily be measured.
.(9a).
However, all HGV’s of this size are two vehicles:- tractor and trailer, and first you would need to consider the trailer, as it will have a different critical air speed to that of the towing vehicle.
.(9b)
. BATH UNIVERSITY RESEARCH.
. The Standen Phd thesis of 1999 had involved very extensive wind tunnel research. Standen used scale models of tow car, caravan and an HGV. He managed to measure the actual force generated by the bow wave of the hgv.
Results from Bath University (Standen)
The Standen thesis, page 65, states, “Therefore during the overtaking action the rear end of the caravan is drawn in towards the HGV as it is approached, then when the front of the HGV is just forward of the rear of the caravan the two vehicles are pushed apart.”This variation in pressure is characteristic of a “wave motion” and readers will recognise in any case that the action of the HGV is similar to my previous account. The fact that the researcher did not comment on this fact is simply due to him looking for another item at the time and concentrating on the accuracy of his measurements, which was the principle reason for his research. He made these observations using scale models of tow car/caravan and the overtaking HGV in the Bath University wind tunnel.I would conclude that this result proves that HGV’s produce waves, as I understand the above quotation from Standen to apply to a number of his experimental wind tunnel results, and probably all of them. In “Conclusions” on page 67 Standen also states, ” The action of an HGV lorry overtaking a car-caravan combination was shown to have a strong aerodynamic influence on the caravan body. The magnitude of the aerodynamic forces and moments acting on the caravan are likely to be strong enough to affect the lateral stability of the system.”My ideas have been developed on the basis of observations “on the road” so it is gratifying to know that wind tunnel measurements confirm that HGV’s can destabilise caravans.
.(9c)
. In support of my view of this matter I suggest a repeat of what I unintentionally first observed on a “B” road near Meridan. In a “Torrential rain storm” I pulled off the road into a layby and got into the caravan without winding down the corner steadies and found that even when I was standing over the axle the van shook quite violently every time a car or light van passed at about 50mph. I further later observed (when sitting in the stationary Land rover) that similar traffic had no effect on the Land Rover, although it was hitched to the caravan.
(9d)
. Standen also did many tests to try and find a practical wind deflector that would cause the caravan to be subjected to a “Down Force” by the wind and so counteract the aerodynamic lift. He did not succeed in finding a practical solution, but he did make a significant discovery. He found that using wind deflectors to create down force at the side of the van at the front, the stability of the van was much improved. It therefore only needs someone to develop a practical down force creator for caravans, and the latter will begin to close the large gap in technology between themselves and Formula 1 racing cars.
.(9e) ..
The formula 1 cars have one deflector at the front near the ground and one above the level of the drivers’ head at the rear. The Million Euro Bugatti Veyran sports car (made by VW) has a computer controlled variable pitch deflector at the rear. The reason why six years after Standen’s results were published nothing has been done is that Caravan Club Officials have not kept the membership informed of this development.
.(9f)
. This matter also applies to hgv’s with trailers,paticularly those with approximately central axles. Fast Trains are suitably shaped at the front to produce some down force, but by how much is not well known..
(9g)
.There is also a need to monitor rail wind speeds at critical points, particularly the many Victorian bridges still in use. It also amazes me that the only evidence I see on Motor Ways of wind monitoring is wind socks, which I first saw in use on air fields pre ww2. All vulnerable points need monitoring with automatic devices feeding their results to the police motor way control centres. When the police close roads because of “strong winds” it must be pure guesswork on their part. They need better support to eliminate unnecessary closures. Motorists need to have more information so that they can make decisions based on a first rate scientific knowledge.
. (10a)
.Standen also found in his wind tunnel experiments evidence that when scaled to motorway distances lead him to believe that one could move away from an hgv on seeing it approaching to reduce its effect. I read in the Caravan Cub magazine that he had never towed a caravan. If he had I think he would have reviewed this result. This is the only one of his results that has been reported by the caravan club. It is still in the latest edition of the CC handbook ( page 622 under “Snaking”. (2005)
. (10b)
.Standen also explained the effect of the wind. He argued that high aspect trailers act like a wind vane when subjected to a wind ( eg) at 45degrees to the direction of travel. He wrote that the trailer would swing into line with the wind, but the swing would continue until, due to the wind’s reduced effect the trailer would then swing back, so setting up a snake.
.(10c) .
References:-
.. Bath University Department of Mechanical Engineering, Phd Theses.
(1) Fratilla. 1994 “Lateral Stability of Passenger Car/Caravan Combinations.” Page 159 Results of Tests on Stabilisers.
(2)Standen. 1999. “Towed Vehicle Aerodynamics” Page 65 Results that I think show that HGV’s produce waves (as opposed to turbulence).Page 67 Conclusions for wind tunnel tests on the effect of an HGV bow wave on a Caravan. Complete chapter on investigations into creating “down force” on a caravan with wind deflectors.The above can be obtained on microfiche from the British Library by a local UK public library.
(2a) Vibration Isolation Characteristics of Caravan Trailer Suspension Systems and Factors Leading to Moisture Ingress; a M Phil Dissertation by JMA McDonald, University of Bath, 1999. (All the above were sponsored by the Caravan Club)
(3) “The Air Pilots’ Manual” by Trevor Than. Page 292. Take off Performance Tables for a Gulf Stream AA-5A Cheeta. The book is in the Aeronautical section of the Birmingham Central Reference Library. Also volumes one and four of a later edition by the same author.
(4) The Highway Code. “New Expanded Edition.” (Driving Standards Agency) See Science addendum.
(5) Most of the school level Physics and Maths is derived from Sir Isaac Newton, Laws of Mechanics, 1686.
(6) Test Report from Caravan Club Magazine on an electronic/ electric caravan brake system.
(7) Negative reference; Bath University have not investigated over run brakes.
(8) The Haynes Caravan Manual by John Wickersham. (adjusting caravan stabilisers.)
(9) The Haynes Manual for the Land Rover Discovery (Tdi).
(10) “Impact” the Journal of the ITAI (Institute of Traffic Accident Investigators) (2002). (see www.itai.org.uk) (Report by the investigator who attended the scene of the Selby Road/Rail Disaster)
(11) A University academic wrote an article for itai “Impact” which was published in the Winter 2000 edition. I have been unable to confirm this but I understand that some of his conclusions for caravans were as follows:- “Drivers should be aware that under steady conditions at speeds above 50 mph, a small change due to a sudden wind gust or a steering manoeuvre may lead to uncontrolled behaviour,” and also “exceeding the legal speed limits with a caravan is potentially much more serious than similar behaviour with a car. This is particularly true if the towed load and its distribution exceed the values discussed in this article.” (Similar values are also given in the Caravan Club Handbook).
(12) The Handbook of the Caravan Club. (Technical Information Section) See www.caravanclub.co.uk (2005)Page 637 Stabilisers Page 622 How to avoid the effect of the bow wave of an HGV.
(13) Camping and Caravanning Club Magazine Page 11January 2005. A two page article about the leading Stabilisers on the market (up to 450 pounds stirling each). The article praised the Bath University Research but did not quote Fratilla’s 1994 resulton stabilisers.
(14) Stabilisers; 11 page document available to Caravan Club members only by internet download. (see 9b above and www.caravanclub.co.uk)..See also:-. www.caravanaccidents.wordpress.com and
for paragraphs 10ci to 18b see www.20six.co.uk/roadtrafficaccidents
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