Information on the safe towing of Caravans, School/University Mini Bus Trailers and HGV Trailers, together with a possible explanation of why the Media and Parliament/HMG is seriously short of reliable relevant Science on these subjects.
Archive for the ‘Uncategorized’ Category
Caravan, Trailer and HGV Accidents
July 7, 2009Bath University Research on Caravans
January 23, 2009Paragraph 31a
Peter W Jones MInstP
I am pleased to note that people are reading the Bath University Research to such an extent that Google have now placed this item almost as high as
The above is my brother’s attempt to run an internet newspaper.
He has only been working on this since he eventually gave up part time work at City University about 12 months ago. He retired from his full time post as Senior Lecturer in Journalism some considerable time ago.
_______________________________________________________________
University of Bath
School of Mechanical EngineeringTHE DYNAMICS OF TOWED
VEHICLES
An experimental study into caravan snaking
Final year project
submitted by Christopher J Killer
for the degree of MEng
of the University of Bath
23 May 2003
Assessor RFN
Supervisor JD
Technician PC
__________________________________________________________
Peter W Jones.
The following are a few items of importance that I have pasted in.
_____________________________________________________________
2.1
. This is manifested in the fact that nearly all snaking accidents involve caravans.
_______________________________________________________________
PWJ
Caravans are the most numerous of the high aspect vehicles in this class
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Extensive studies into articulated lorry dynamics have been done, but due to the hobby nature
of caravanning there has been little money or academic interest in this field until
relatively recently.
2.2.1
Friction yaw dampers were found to increase stability; they reduced the amplitude
of oscillation and hence reduced the settling time. However, it was shown that the
stabiliser could not contain unstable oscillations if the situation would otherwise
become unstable without dampers. This was due to limitations of the moments
generated by the stabilisers.
2.2.5
It was discovered that stability reduced with both speed and stability and towing
coefficients. Thus a fast moving caravan with a large mass distributed around the
perimeter would be highly unstable. It was also confirmed that a heavy tow ball load
was more stable than a light tow ball load, and that it is beneficial for the caravan
mass to be low in comparison to the car
2.2.6. This theory is backed up by the fact that snaking does not occur
when the trailer is light and the car is heavy.
2.2.7.1.Even a powerful yaw damper was found to
increase the snaking speed only a little, so generally it was considered an
unsatisfactory solution to the snaking problem
.2.2.7.2 Part 2: active caravan braking
A virtual braking system was developed in light of the results in Part 1. It consisted
of a control system that applied a brake to the caravan wheels in phase with the roll
oscillations, providing the greatest force when the tyre load was at a maximum.
Very effective stabilisation of the snaking vibrations was demonstrated in a variety
of circumstances, many of them much too challenging for friction dampers to deal
with. The power consumption requirements were easily manageable and the
technology is much closer to a prototype as a result of the work
See also paragraph 36 below
October 28, 2008
PARAGRAPH 32
SNAKING CARAVANS AND TRAILERS (INCLUDING HGV TRAILERS
Peter W Jones MInstP
Retired Head of Science in a Birmingham Comprehensive School ( 20 years)
Currently, “Consultant for Towed Vehicle Accidents” (5 years)
Apart from 19 months national service ( ie conscripton) in the RAF my entire career (almost) has been as a full time teacher. I was a comprehensive school Head of Science for 20 years, but I also spent 7 years as a full time lecturer in a Birmingham Technical College (Further Education Sector).
This blog, and the two linked to it, have therefore turned out to be an untidy set of notes and resource material for teachers/lecturers. After 41 years as a teacher I have difficulty switching to the right mode when writing.
I started advising on oscillating trailer accidents in 2003 (after I had been retired for 10 years) when I became an Affiliate of the Institute of Traffic Accident Investigators. I had no desire to become an “Accident Investigator” but learned a great deal by reading their journals, attending some of their meetings/courses, and particularly by exchanging scientfic information concerning road traffic accidents via a private internet site which was used by many ITAI members.
I was also an Associate Member of the Society of Expert Witnesses for a further 12 months and derived great benefit from their extensive written legal advice for “expert witnesses,” and their “mentoring support.”
I am not allowing a direct connection with myself via the web as I was originally (in 2007) almost put out of action by “comments” to my blog on 20six.co.uk which were mainly pornographic. I am currently relying on private contacts and exploring other means of advertising at low cost as I am working on a charitable basis in support of road safety. My blog details have been circulated by a group of interested solicitors and I am always available to give advice by telephone, particularly as most questions can be answered by reference to items I have written and published on the net. If the solicitors have a problem with passing on technical information I am prepared also to discuss the matter by telephone with the Accident Investigators.
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Addendum Oct 2009
Technorati/WordPress, as you will see on the internet, have from the beginning of October 2009, started to give more prominence to my blogs. They are keen to promote blogs of a Scientific/Technological nature.
A feature of the new system is that comments are allowed, but these will be carefully screened to eliminate spam.
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VOCATIONAL COURSES FOR TRAFFIC ACCIDENT INVESTIGATORS, ROAD SAFETY OFFICIALS, AND HGV drivers.
Leaving out my “political” offerings most of the items I have written about should be considered for inclusion in the above courses.
SCHOOL LEVEL WORK
GCSE Physics; The effect of the centre of Mass of a vehicle on its stability is one item I have taught at this level.
I expect that there is at least one of the many courses for GCSE which contain some Physics for which my lever test for friction based caravan/trailer stabilisers would be a good “practical application.”
I have used Newton’s First Law of Motion to explain why it is very foolish of us to allow unbraked trailers (up to 0.75 tonnes) to be used on our motor ways.
Vectors using scale diagrams
GCE “A” level Maths (Theoretical Mechanics/Applied Maths) and GCE “A” level Physics
I have made use of Vectors in writing about the effect of the wind on high aspect vehicles and although I later had the better idea above I originally used some equations of motion to show very approximately that friction based stabilisers could not make any significant contribution to bringing a snaking trailer under control.
October 23, 2008
Peter W Jones MInstP
See also
www.improvingroadsafety.wordpress.com the most rcent blog
plus
www.caravanaccidents2.wordpress.com
www.caravanaccidents.wordpress.com
www.20six.co.uk/roadtrafficaccidents
Advice for Physics and Maths teachers (GCSE and GCE “A” level)
www.schoolminibusaccidents.wordpress.com and
www.schoolminibustrailers.wordpress.com
Index
31 Highways Agency Fit to Tow Video
31a Bath University Caravan Research
32 Summary of ideas behind Blogs by Peter W Jones
33 Air Speed Indicators
34 Lobbying Parliament
35 Letter to Dr Tony Wright MP
36 Bath University on Stabilisers (cont)
37 Stabilisers; further details
38 Letter to Mrs Dunwoody MP
39 Caravan Stabilisers explained for
non caravanners
40 IVRA Conversion Kit for Over run Brakes
41 History of New ALKO electronic conversion kit
42 USA Electric Brakes
43 Stabiliser test by Peter W Jones
44 HGV Trailers ( includes accident statistics)
45 Wind induced Road Accident
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Paragraph 31
THE HIGHWAYS AGENCY FIT TO TOW VIDEO (see their web site)
Peter W Jones MInstP
The Highways Agency “Fit to Tow” video, presented by Carol Smillie, has been available for viewing on the inter net for some time.
I welcome the fact that the HA have now modified the DfT presentation of Caravan and Trailer accident statistics. (see my 2006 paper published by the HoC Select Committee on Transport by putting “Caravan and HGV trailer accidents” in to the search engine of www.parliament.uk )
It is well known that the Caravan Club/Caravan Industry policy is that incorrect “load distribution” is the main cause of towing accidents. I do not think it appropriate that this video, with a contribution from ACPO, should promote this viewpoint. Bath University Research has proved that friction based stabilisers do not improve safety and hgv’s can destabilise caravans. The HA in other published items is also now warning caravanners of the effects of strong cross winds and these factors will cause problems even when your caravan is correctly loaded and you are towing with a suitable tow car.
With regard to the towing of trailers with no brakes the HA is assuming that the tow car brakes will be adequate to stop a 0.75 tonne trailer. However, this will not be the case if sharp braking is used at normal motor way speeds. When the tow car brakes sharply, If the trailer is directly in line with the tow car the trailer will rise and smash into the back of the car or pass right over the top if the HA suggested safety chain is unable to prevent this taking place. When the trailer and tow car are not in line the trailer will jack knife, and if the latter is much greater in weight than 50% of the tow car weight ( the legal limit ?) there is a high probability of the tow car being destabilised.
All this follows directly from Newton’s First Law of Motion.
The Institute of Traffic Accident Investigators reported in 2002 in their Journal that they had tested braking a tow car with an unbraked trailer at 40 mph and found that the trailer jack knifed every time.
Also see para 3a of my blog www.caravanaccidents2.wordpress.com for an account of a related accident when the “over run” brakes failed to function.
March 29, 2008
See also
www.caravanaccidents2.wordpress.com
Paragraph 33
Air Speed Indicators
.
Peter W Jones MInstP
.
.In drawing attention to the need for the above I am suggesting a change that has not, as far as I know, been proposed elsewhere.The Caravan Industry and the Caravan Clubs have regrettably resisted the use of safer technology for some years and have left the EU/UK very much in a technological backwater, whilst the air craft industry (Air Bus) are now amongst the world leaders.As Standen’s 1999 Bath University Phd thesis (Towed Vehicle Aerodynamics) still only resides in the British Library on microfiche, few people are aware of the fact that he proved in wind tunnel tests (with scale models) that an HGV could destabilise a car/caravan combination and aerofoils improved the stability of a caravan.In 2003 when I was using the Road Traffic Accident Investigators private Yahoo e mail system and circulated the above and other details of the Bath University research I discovered that the aerodynamic research mentioned above was quite unique far beyond the EU, and the fact that it must also at least apply to some HGV trailers ( the need for aerofoils) was also not known.
However, it may well be that research has been done that has not been published.
Even with aerofoils and electronic brakes there will still be an upper speed limit for all vehicles, particularly trailers, which must be decided on the basis of the Laws of Physics and then enshrined in Government regulations as is already done in a similar manner for the air craft industry.
I do not think it will ever be necessary to take as many precautions for solo vehicles as if you cannot sense yourself the effect of the wind on the vehicle you are driving, you should not be in charge on the road. When towing a trailer there is another vehicle to be considered with very different characteristics, and an electronic system is needed to give information about the forces on the trailer as well as an air speed indicator.
Designing a suitable air speed indicator for use by road and rail vehicles will be comparatively easy once the need for same has been accepted. All that is required is a “weather vane” (to sense direction) and rotating parts ( to sense speed) .
The direction that the “weather vane” would point is determined by the wind produced by the forward motion of the vehicle and the wind ( if any) resulting from natural weather fluctuations. The software would then convert this into a “Head wind” component (in mph) and a “side wind” component. The two speeds would be displayed for the driver to read.
The maximum safe air speed ( road speed plus head wind component) must be established for each vehicle, but this as with aircraft will vary depending on the load being carried.
Similarly the side wind component will vary, but for the driver (as with the pilot) this only has to be looked up once in a set of tables for each journey. There would have to be anemometers in exposed places at the side of major roads to send out details of side wind speeds by radio ( information is currently transmitted by the RAC that determines “congestion points” by measuring traffic speed at many points on all major roads in the UK).
For minor roads drivers would still have to depend on the wind speed forecasts given by the met office, as we shall still have to do for some time in all cases.
Even if there are no fatalities or serious injuries every time an HGV trailer over turns or otherwise gets out of control we have a major problem as it takes some hours to get a crane to the site which is capable of lifting up the wreckage. A caravan is easily pushed out of the way by a Police Land Rover.
When considering the costs of my proposals the lost productive hours of the many thousands of people caught up in resulting traffic jams should be taken into account.
Currently I do not think the DfT have any records concerning HGV or caravan accidents resulting from the effects of the wind, as this in the past has not been properly recognised as a serious problem.
.
Addendum 5-11-08.
It seems that I was seeking information concerning currently available anemometers for road and rail vehicles in the wrong place. I should have used Google !
There are suitable appliances on the market that will only need a comparatively minor modification ( to the software only in some cases) to meet the requirements of locomotives and road trailers.
It is most probable that suitable hardware already exists and the only remaining task is to programme same so that the “air speed” and “side wind component” can be displayed.
I have also recently realised that I have failed to draw attention to another aspect of this matter. Formula 1 racing cars and HGV’s with trailers frequently travel at about 100mph air speed, but only the former have the benefit of aerofoils to help keep them in good contact with the road and more able to resist any side forces from the wind. Racing cars are viewed by thousands of spectators and officials are prompt in their control of the situation when extreme weather conditions apply. On the motorways little can currently be done by traffic police in the same situation as critical air speeds and side wind components need to be known for each type of vehicle, as is the case for air craft.
However as I feel certain that the anemometers/air speed indicators that I have outlined above could be produced at a reasonable price and even if they were only half as popular as GPS navigation ( and I feel certain they would cost much less), a considerable contribution could be made towards reducing accidents because drivers would use their own judgement. Governments would then eventually legislate to ensure that ( as with the air craft industry) the critical speeds for each type of vehicle were stated in the manufacturers’ manuals for drivers.
ADDENDUM 22-11-08
I have now written to several manufacturers of anemometers and had one positive reply.
www.biral.com of Portishead, Bristol, UK sell a suitable anemometer which only needs extra software to be written to convert to my above mentioned specifications.
edit 30-09-09
I received a quote from biral.com of around 1500 pounds sterling (UK) for the above during the Summer.
This type of cost will be considered reasonable when more people become aware of the reduction in accidents that would result. However, Governments would have to legislate before the HGV industry would install these devices.
For recreational trailer towers like myself the cost would be unacceptable at present and I shall continue pestering our Met Office to make more widely available their internet wind speed forecasts. I can always use the internet beore I leave home, but this Summer found myself having to restrict my speed considerably on one journey because I failed to get to an internet cafe before setting out. In another instance I made a detour to avoid the M5 bridge over the river Avon when it may not have been necessary. However, I have lived to start my 34th year of receational towing if the cancer clinic eventually discharge me tomorrow after 5 years of “monitoring.”
Lobbying Parliament
March 24, 2008
Para 34
Lobbying Parliament
Peter W Jones MInstP
..
I have several times attended at Westminster for the purpose of “Lobbying,” but I was always accompanied by many other affiliated members of the TUC.I have recently come to realise that lobbying by persons who are employed by the “Corporate Sector” is far more effective and I am endeavouring to draw attention to one particular item where the Corporate Sector have made a Scientific Error on the same scale as King Canute. He was reputed to have sat on his throne on a beach with the object of preventing the incoming tide covering the beach. Corporate Sector Lobbyists have clearly managed to convince parliament that however strongly the wind blows, it cannot possibly be of danger to road traffic (even high aspect HGV’s and Caravans.)Accordingly I wrote to Dr Tony Wright MP on this subject and I have printed his reply below...
(see www.20six.co.uk/roadtrafficaccidents Section 18b, for details concerning the effect of the wind on road vehicles)
********************************************************
Para 35 Letter from Dr Tony Wright MP
Dear Mr Jones,
Thanks for your letter.
The subject matter of your letter is of course not within the remit of the Public Administration Select Committee, but it does offer an interesting insight into the role of lobbying. I shall bring it to the attention of the Committee.
Yours sincerely,
Tony Wright
Dr Tony Wright MP (Cannock Chase)
www.tonywright.org
—–Original Message—–
From: peterw****************************
Sent: 07 March 2008 19:18
To: Public Admin Committee
Subject: Committee on lobbying
Peter W Jones MInstP
Consultant for Towed Vehicle Accidents
HGV Trailers, Caravans and Small Trailers Charitable Status to be Applied for
www.caravanaccidents.wordpress.com
Tony Wright MP
Chair of the Committee on Lobbying
Dear Sir,
Although I have been in receipt of e mails from the HoC on all committees I had over looked the relevance of your work to mine until John Humpreys enlightened me at about 0745 today on Radio 4 News.
I wrote to the Hon Mrs Dunwoody MP in late 2005 concerning the lobbying by the Caravan club ( via two MP’s whose names were at that time listed in “members’ interests” as being paid to lobby by the Caravan club).
The Caravan Club sponsored a considerable amount of research that was carried out by the Department of Mechanical Engineering at Bath University; some of this gave rise to two Phd theses and an Mphil thesis. On the basis of this research Caravan Club officials assured myself and about 120 other CC members present at a meeting at the Thistle Hotel, East Midlands Airport in March 2003 that matters I had reported on concerning caravan instability were quite irrelevant as they had had everything researched at Bath university.
Their long held policies on caravan safety had been proved to be correct.
When I eventually managed to obtain and read these theses I found that the CC were seriously misleading the membership (and possibly the HoC) and since March of 2007 I have had blogs on the web setting out in detail my reasons for this allegation.
Mrs Dunwoody wrote that she would be pleased to consider any report that I wished to make that was within the existing terms of reference of the House of Commons Select Committee on Transport. Accordingly you will find in Hansard for February 2006 a report I wrote concerning Caravan Accident Statistics and the lack of adequate monitoring for wind speed by the Highways Agency (NB It was revealed this last weekend that Network Rail also fail to monitor for wind speed).
I gathered from John Humphreys’ news item that the committee enquiring into lobbying were so alarmed by the fact that firms of lobbyists were specialising in misleading Parliament, (and that some MP’s were
involved,) that they would wish to sweep this item back under the carpet.
Accordingly I am directing this letter via your committee’s press secretary, to emphasise the fact that I shall also be attempting to publish this material.
However, do not be unduly alarmed as the BBC have three times spurned items I have sent them, two having been rejected by BBC Watchdog.
Yours faithfully,
Peter W Jones
__________________________________________________
Para 36 Stabilisers; Bath University
March 22, 2008
Para 36
Peter W Jones MInstP
The above graph and the photograph below have been copied from the Bath University Report (see further below).
The electronically produced graph above shows the effect of an ALKO stabiliser on a snaking caravan (blue graph). The red part of the graph shows the oscillations without the stabiliser in place. This graph should have appeared in the space in the account below.
The photograph below shows the ALKO stabiliser tested by Bath University.
Stabilisers; Bath University
March 22, 2008
March 21, 2008
Peter W Jones MInstP
.
Copied from the internet
University of Bath
School of Mechanical Engineering
THE DYNAMICS OF TOWEDVEHICLES
An experimental study into caravan snakingFinal year project
submitted by Christopher J Killer
for the degree of MEng
of the University of Bath
23 May 2003
Assessor RFN
Supervisor JD
Technician PC
*******************************************************************11 Conclusion
********************************************************************************************The performance of the Alko 2004 tow ball friction damper has been shown to be
very effective at smoothing down snaking oscillations and reducing settling time. But this does not necessarily mean that it makes the coupled combination any safer, i.e. increase the snaking speed. Theory states that this type of damping has little effect on the snaking speed, and tests have shown no evidence to suggest otherwise.
********************************************************************************************
11.1 Practical advice for caravan owners & designers
Nothing fundamentally new was discovered in this study, but theoretical factorssuggested in the past have been substantiated by road-tested evidence. The
theoretical advice that is now known to be significant in increasing stability includes
the following points.
For owners:
• Make sure car is suitable for the size of caravan
• Load heaviest items in the car if possible
• Locate other heavy items in the centre of the caravan, just forward of its axle
• Make sure tow ball load is adequately high
• Avoid sharp steer inputs at high speed
• Never exceed 60mph
for designers:
• Put the heaviest parts of the caravan, e.g. kitchen, in the centre
• Consider the distance h between the C.G. and the axle, and its significance in
terms of stability
• Calculate the new stability coefficient (incorporating h) for each design
and although not tested in this study, other recommendations from mathematicalanalysis include:
• Make distance from tow hook to axle as long as possible
• Move back the C.G. so as not to induce excessive tow ball load
• Maintain a high tyre pressure to keep lateral stiffness high
March 21, 2008
Bath University Report (cont)
.
(extracts)
.
9.5 The effect of using the stabiliser………….., small amplitude oscillations are attenuated considerably more than large ones. Theory also predicted that the frequency of oscillation would decrease when the damper was present, the graph does show this to a very small degree, though frequency was essentially unaffected.
.
………………………….), therefore if the initial one is too large for the friction damper to have any significant effect, thensubsequent oscillations will not decrease in amplitude and the system will become Unstable
Figure 23: Effect of stabiliser shown in blue.
THE ABOVE GRAPH HAS NOT APPEARED. IT CAN BE SEEN ON THE BATH UNIVERSITY WEB SITE AND IS NOW ALSO SHOWN AT THE START OF THIS BLOG.
..
Peter W Jones MInstP
.
I have selected the above items from Mr Killers’ work, but as this is displayed on the web it is very easy for interested parties to view the whole document. Mr Killer has made it clear in another section of his report that excessive load on the tow ball can lead to steering deficiencies in the tow car; this is not quite clear from the conclusions.In my view Mr Killer should not, on the basis of his results, suggest never exceeding 60mph. All his results were in the range 30 to 50 mph so it is only justifiable to say that the ALKO stabiliser does not necessarily make the car/caravan combination safer within the speed range 30 to 50 mph.
Standen (Towed Vehicle Aerodynamics 1999) showed in his wind tunnel tests that aerofoils increased caravan stability; my extensive experience towing on the road leads me to believe that aerodynamic lift is a factor over about 50 mph (air speed) and any future studies should investigate this matter in particular. I only have one vote in the caravan club, but I hope that other members will ensure that the research at Bath University continues and that the results appear on the internet without editing.
I do not agree that sharp steering inputs ( when towing) should only be avoided at high speed. Such in puts are potentially dangerous from about 40mph. However, sharp steering inputs only have a minor effect on caravan/trailer snaking compared with the effect of side winds or the effects of Large High Aspect Vehicles (Standen 1999). When concluding that the ALKO Stabiliser did not necessarily improve safety Mr Killer did not consider the last two factors. The condemnation should have been much stronger.
My conclusion is that on the basis of Fratilla 1994, Killer 2003 and my further analysis of the ALKO stabiliser below, any friction based stabiliser failing the simple test I have outlined also below should only be sold in the UK with a clear “large type” summary of the Fratilla and Killer conclusions.
This action would encourage the caravan/trailer industries to seriously consider using the electric brakes which have been in use elsewhere for over thirty years and are cheaper than over run brakes plus stabiliser. Pneumatic and hydraulic brakes are also feasible; an example of the former was successfully tested for over 12 months by a journalist from Practical Caravan Magazine. Furthermore enterprising companies would develop aerofoils following the public attention given to friction based stabilisers, and HGV trailer manufacturers would also have to consider aerofoils as well as electronic brakes to improve safety.
