Archive for February, 2008

Para 40 The IVRA conversion for O/R Brakes

February 28, 2008


Peter W Jones AMInstP

I would like to draw attention to the efforts of Charles Irving of Preston Lancs who has for  over 30 years endeavoured to improve caravan stability, but in the past has  mainly been  side lined by the Caravan Industry.

The IVRA system depicted in this brochure was tested and approved by the Caravan Club’s experts whose account was published on page 80 of the July 2000 Caravan Club Magaazine. It can just be seen that Charles Irving is named at the end of the brochure and the IVRA system had been developed from Charles Irving’s original design.

In spite of this approval the Managing Director of a  Caravan Group told a large meeting of Caravan Club members (Thistle Hotel, East Midlands Air Port) in February 2004 that he had never been so frightened in his life as when he was given one of these systems to test on the motor way.

However, he failed to tell the meeting whether the person who fitted the system had been trained for this new type of work and whether he himself had been advised by an expert of the different nature of the response compared with over run brakes. The CC, CCC, and the NCC control the quality of the work in a large number of the Caravan Workshops in the UK and training in electrical/electronic braking systems will only be given when the former give approval.

Further on is a Short History of the New ALKO braking system; this short item is an introducton.


Para 40 IVRA Conversion Kit

February 28, 2008


February 28, 2008


Para 41


A Short History of the New ALKO Brakes


Peter W Jones AMInstP


The above type of system was “invented” by Charles Irving of Preston, Lancs, about 30 years ago.

Charles Irving was first brought to my attention in 2003 by several members of the Institute of Traffic Accident Investigators (ITAI) communicating via a private e mail system.
I had circulated an out line proposal for an electric/electronic device to make over run brakes safer. I was immediately told that Charles Irving had already demonstrated his similar device at an ITAI conference some years previously. ITAI members had been very impressed. I spoke at length by telephone to Charles Irving in 2003; in April 2007, after I had published my results on the web, we had a further telephone conversation and decided to meet at Keele Services on the M6 to discuss this and other matters in more detail.
Charles Irving’s electronic device was later developed and marketed by and it was under this label that the Caravan Club’s experts tested same and published their approval in the CC magazine some considerable time ago. IVRA have now been taken over by Reich Benelux.Charles Irving told me that he had also “invented” another system for making caravans and small trailers safer, and this system had been tried out very successfully for 12 months by a journalist working for Practical Caravan Magazine. (Charles Irving later sent me all the technical details by post). This ingenious device was pneumatic, the air pressure needed to operate the system being produced by an electric pump, and being electric the system could apply the brakes as soon as the tow car driver operated the brake pedal. (Over run brakes only work when and if the trailer catches up with the tow car. When a trailer is snaking this will never happen as the trailer is travelling further then the tow car. Drivers are advised not to brake whilst snaking is taking place, because the trailer would then very rapidly catch up and if it was not in line with the tow car when the trailer eventually “pushed” on the brake lever the whole out fit could be spun round out of control.)

I understand that ALKO are only fitting their device to new caravans. Charles Irving had been fitting his invention to existing caravans for some years.
If “electric brakes” is put into the Google search engine it will take only a few minutes to establish that ALKO Australia has caravan electric brakes available for caravans of comparable size to those in the UK. When some years ago a Caravan Club member wrote to the CC magazine to inform us about the extensive use of electric brakes “down under,” the editor informed the members that the Australian brakes were only suitable for larger vans and were very expensive.
If the results from Google are examined a little further it will be seen that currently in the USA caravan electric brakes are being sold that would cost less than the over run system plus the ALKO friction based stabiliser ( at current rates of exchange).
Clearly part of the solution to caravan and trailer instability is electric brakes for new caravans, not an electric/electronic adaptation of the 1929 over run brake. ALKO’s latest device must be fitted to existing caravans and trailers.

Caravanners and trailer towers will have to drive more slowly to remain safer until this business is resolved and in this respect it should be remembered that the legal speed limit was 50 mph when I started towing boats in 1976 ( my boat towing light board still has a “50” sticker on same). It can be seen from my other reports on the web that this matter is far more complicated than originally realised; it is air speed which should really be considered.





Para 40 (cont) IVRA Brakes

February 28, 2008


Para 42 USA Electric Brakes

February 27, 2008


Peter W Jones.

These three pages are typical examples of items found on the internet after putting “Electric Brakes” into the Google search engine.

The internet has not been available for 30 years but these brakes have been in use for trailers and caravans (down to about 1000kg weight) in Australia, South Africa, and the USA over this period and should have been used in the UK/EU instead of the over run brake.


February 27, 2008

February 27, 2008

February 27, 2008

February 27, 2008



 Paragraph 43




  Stabiliser Test




……………………………….Centre of Mass


 …………………      A = axle of caravan/trailer


w hitch = tow hitch







Peter W Jones  AMInstP

I was begining to think that spam had permanently sunk, but they came on line again about 2200, 26-02-08.

Today they are off line again so I am adding a further two essential items, the first one being on friction based stabilisers


18a A Caravan/Trailer Stabiliser Test.To carry out this test fix a suitable length of tubular steel or wood to the stabiliser when it is fixed to the tow car, but not the caravan/trailer. Support the end away from the car on wheels as its weight will be considerable (I used furniture castors).Grasp the length of steel or wood at the position which is the same distance from the tow car as the centre of mass of the caravan. Move the wood/steel with one hand and judge whether the amount of force exerted on the hand is likely to have any retarding effect on a caravan snaking at 50mph.Following the caravan clubs rules ( and those of Dr Darling of Bath University, according to his web site), all heavy objects should be loaded as close to the axle/axles as possible commensurate with keeping to the tow car manufacturer’s figure for the maximum allowed weight on the tow hitch. This will result in the centre of mass being a short distance in front of the axle/axles.The position of the centre of mass can therefore be estimated with some degree of precision.For those with experience of calculations I add the following:-Calculation of the distance of the centre of mass of a caravan/ trailer from the tow hitch.

F= maximum allowed weight on tow hitch ( see tow cars’ handbook for drivers)
d= distance of tow hitch from axle ( or the mid point between the axles)
x= distance of centre of mass from axle (or mid point between axles)

W= weight of caravan/trailer

Using the Principle of Moments, for equilibrium :-

Fd = Wx

x = Fd/W

ie x = F multiplied by d divided by W

It is then necessary to construct a lever of length = d- x

For my small 4m body length caravan this came out to be 3.33 m

To make quite certain that it is feasible to carry out this test, I performed it myself.

The lever (made of wood) is in two pieces, to make it easily transportable in my Land Rover.

It can be clamped to a stabiliser by means of bolts and nuts which only pass through

the wood.

To test a stabiliser fixed permanently to the caravan draw bar, simply remove same,

(usually only held by two bolts), and fix some tubular steel in place of the draw bar.

In the case of my caravan, the tubular steel would have to be 3.33m long.

Whether using wood or steel, the weight is considerable and the end away from

the stabiliser needs supporting on wheels (I used furniture castors).

Fix the stabiliser to the car in the normal way. In my case I then found that I could

easily move the stabiliser from side to side by gripping the long lever between

finger and thumb. Even this test over estimates the effectiveness of the stabiliser

as there is also the friction between the ground and the castor wheels.

However, it can be seen that my stabiliser, that I have fixed to my caravan and boat

trailers every time I was on the road with them for the last 30 years, is completely

ineffective. If it were not for my special interest in this matter, I would have confined the item of scrap metal to the recycling bin.

Before carrying out the test I checked that the force of friction that my stabiliser

could exert was the same as when I purchased it, and as stated in the Haynes

Caravan manual.

I await with interest reports of tests on other stabilisers.

See also  




Para 44 HGV Trailers

February 25, 2008



Peter W Jones MInstP

For hgv accident statistics

scroll down to end of section




Air liner statistics (cont)

Fairchild Aviation C123B

Weight, 27 tonnes. Stalling air speed, 96mph

Based on the above I would therefore estimate that a 27 tonne HGV trailer (if such a trailer is legal and exists) with approximately central axles would become liable to snaking when the air speed reached 96mph. The driver would be aware of the air speed if he/she had an appropriate indicator.

At 55mph road speed one only needs a head wind component of 41 mph (gale force is about 44 mph) to reach the estimated critical speed.

Tiger Moth Biplane.

As one of my main recreational activties over the last 32 years has been estuary and coastal sailing, I have never had the usual experience of flying off to wamer climates for my holidays.

I have only taken to the air twice, and that was as a passenger in a Tiger Moth Biplane in 1951. During the Summer holidays HMG “called me up” again to do an additional two weeks National Service in the RAF. During my 18 months national service I was an “Audiometrician,” so it was deemed appropriate that I did some flying.

In 2003 when I started enquiring about the reasons for caravans snaking I recalled that the Tiger Moth take off speed was about 60 mph and that it must have weighed about the same as my small caravan.

You will see from my blogs that my memory had not failed as similar sized modern light aircraft have comparable statistics.


As I have noticed that monitoring for wind speed at critical points on our major roads is only done with pre ww2 wind socks, I will start by trying to establish why it is vital that this facility be improved. Every sailing cruiser only slightly larger than my Jaguar 21 (with 2 crew weight = 1000kg ) seems to be equipped with an anemometer giving a digital read out of wind speed in front of the person steering.

We need these devices on our major roads wired to traffic control centres so that Police can give out on the indicator boards actual wind speeds so that drivers can act on their own initiative as appropriate for their own vehicles and trailers, instead of just being told (for instance) that there is a speed restriction of 40 mph due to strong winds.

My small 4m body length caravan weighing 1000kg is susceptible to snaking when its air speed exceeds 50 mph and the side wind component exceeds 30 mph. I need to know therefore if the side wind component at a particularly exposed section of road exceeds 30 mph. I have already explained in other parts of my blogs how I arrived at these values, partly using my experience gained on open waters with sailing cruisers.

I started looking into trailer safety in 2003 when one of my daughters narrowly escaped death or serious injury when her (brand new) snaking caravan somersaulted over the roof of her car (when she stopped) due in my opinion to the failure of the over run brake actuating mechanism of the caravan. I reactivated my associate membership of the Institute of Physics (AMInstP) for the sole purpose of conducting the enquiry. As I have explained elsewhere in these blogs I soon discovered that the Caravan industry and the caravan clubs have a very flawed policy on caravan safety, but when I also realised that there was a lack of such obvious provision as anemometers to monitor wind speeds on major roads I concluded that a situation of this type could only have arisen if the most Senior Executives who control the Road Haulage Industry were involved. The Industry is supported by extensive lobbying at Westminster and if the Senior Executives really wished wind speeds to be measured accurately at vulnerable positions on our major roads, it would have been done a long time ago.

Similarly with caravans; the two MP’s who are paid to lobby by the Caravan Club could have made an impact if the club had not had, in my opinion, such a flawed safety policy.

The only slight ray of light at the end of a very dark tunnel emerged in May 2007 when I purchased a commercial trailer (for recreational purposes) from and discovered in their handbook for trailer towers the very clear advice that “Blustery cross winds” can cause snaking. In an e mail to myself from the caravan club Technical Manager ( 2003) sent on the instructions of the Executive Secretary after I had spoken about related matters at a large CC meeting, I was told that snaking only takes place if the caravan is incorrectly loaded (for instance).In the latest 2007/8 CC members’ Handbook on page 622 the club now qualifies this position slightly by saying that a cross wind may affect the situation when one is being overtaken by a coach or large lorry. On page 625 we are told, “If in doubt about the advisability of towing in stormy or windy conditions, let common sense prevail. Telephone a motoring organisation or Weathercall to check.”As I have previously pointed out for the weather forecast to be of any use one has to know the critical speeds for a particular trailer.All vehicles are subject to be being blown off course, or even off the road, in certain conditions.If the weather forecast is for a wind of 60 mph one cannot rely on there not being a Hurricane force gust in a particularly exposed position.My 2000kg Land Rover Discovery is particularly prone to drifting in gale force cross winds (about 44mph), but when I am not towing the matter is usually easily rectified by steering modifications, followed by a drastic reduction in speed.As there are notices on the back of a large number of HGV’s inviting the public to phone a particular number to report any drivers seen to be driving badly, I can only assume that the industry thinks bad driving is the main cause of snaking/jack knifing and further wonder if drivers are being given similar advice to that given by the Caravan Club.I have previously pointed out that vehicle manufacturers ( as with air craft manufacturers) should be required to establish critical wind speeds with some degree of accuracy for each type of vehicle sold.I have observed that road users are increasingly prepared to pay for extra safety devices such as electronic brakes and air bags, and feel certain that when they understand why knowledge of air speeds and side wind components is important for safety reasons, they will be prepared to payextra for vehicles that are sold with the relevant information in the owner’s handbook.As I have never driven an HGV or sailed a boat larger than my daughter’s 29ft Westerly (about 4000kg), my estimates for HGV critical air speeds and side wind components would not be very accurate. I am therefore pointing out how to make estimates so that those with relevant towing experience can do this for themselves.

I can be quite accurate concerning the fact that in the USA (for instance) when a Hurricane force wind is expected those able to do so move out of the immediate coastal area until the danger has passed. The remainder of the population go into buildings constructed so that they can withstand Hurricane force winds.
According to the Beaufort Wind Scale for Mariners a Hurricane is Force 12 ( about 78 mph) and above. If you are driving at an indicated 55 mph it will only take a head wind of 23 mph to bring the air speed that the vehicle/trailer is subjected to up to the bottom end of the dreaded Hurricane strength. The aerodynamics of trailers in particular needs to be taken very seriously.
In 1999 Bath University published “Towed Vehicle Aerodynamics” by Standen; the wind tunnel tests had proved that aerofoils to create down force as speed increases improved the stability of a caravan with a (approximately) central axle.
Aerodynamically a HGV trailer with approximately central axles/axle is the same as a caravan.
Only a minority of HGV’s tow trailers with central axles, but there will also be the evidence of tyre marks on the road from all accidents which will be similar to those which have been “leaked” to me concerning caravan accidents; I am sure they will show similar results to those I have outlined for caravans.
The above Bath university results clearly stated that some trailer snaking is caused by the wind and explained how this happens.
As I feel that I have established that the maximum safe air speed for my small caravan is about 50 mph, and this is the stalling speed for a typical light aircraft of the same weight, I feel that I am justified in saying that the maximum safe air speed for a central axle HGV trailer is VERY ROUGHLY the same as the stalling speed of an aircraft of the same weight. In the absence at the moment of accurate figures from people with access to instrumentation that can measure the amount of lift created by the air around the vehicles, I suggest that HGV drivers cultivate the acquaintance of an airline pilot and try and obtain some confidential advice concerning stalling speeds to compare with their own experiences of the air speeds and side wind speeds when snaking/jack knifing has taken place. Starting about 30 years ago I always managed to avoid wind induced snaking by obtaining information from Radio 4 shipping forecasts and estimating the likely speeds inland. More recently I have been able to get a very good wind speed forecast from the BBC weather forecast on the web.
As I started towing when I purchased my first sailing cruiser I was always very aware of the power of the wind and those who doubt this should talk to people who sail some of the types of boat I list below. These sailors will be only too pleased to help as the relevant information concerning sailing cruisers is not confidential. I want the sailing community to tell people the area of sail they use to sail their boats in gale force winds (about 44mph) in sheltered waters where the sea is calm. If HGV drivers then compare the relevant sail area with the area of the side of their trailer of the same weight as a sailing cruiser, they will then understand why something needs to be done to improve road safety by using electronic braking systems and aerofoils to create down force on all trailers as well as paying greater attention to weather forecasts.
Aerofoils for HGV trailers would have to be quite large, and as this matter was not allowed for when bridges were built engineers will have a difficult problem to solve when designing the aerofoils for large trailers. For those who can afford the million euro VW sports car this problem has been solved by a computer controlled aerofoil over the rear wheels ( but I would not suggest that the latter is a good tow car!) Formula 1 racing cars, after years of development, now have two fixed aerofoils, one between the front wheels and one over the rear wheels. Rally cars are beginning to use fixed aerofoils and when the latter are above the level of the car roof they must be very effective.
A few Statistics:-
Nicholson 55 (Weight 17.3 metric tonnes; area of main sail = 48.3 square metres ); Nicholson 42 (wt 10.16 tonnes)
Bowman 57 ( wt 19.05 tonnes); Ocean 71 (29.06 tonnes);
Source:- Boating World Guide to Sailing Cruisers; 1976
Boeing 737; weight 45.36 tonnes; take off speed 150 mph.
Source of information:- My estimate of stalling speed = 120 mph.



 From Hansard





































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Help Topics Members EDMs Search Home

Early Day Motion



EDM 565



Iddon, Brian

That this House is concerned that the most recent road accident statistics show that in 2007 the number of fatal accidents involving heavy goods vehicles (HGVs) increased despite a drop in the overall number of accidents; notes that although HGVs make up just 5.7 per cent. of road traffic, they are involved in 15 per cent. of all fatal road accidents; recalls that a report commissioned by the Department for Transport concluded that fitting retro-reflective markings to the sides and back of HGVs increases conspicuity and reduces fatalities and that there is a cost-benefit to making this measure mandatory on all newly registered HGVs; understands the financial pressures currently facing the haulage industry, but notes that this measure would cost approximately 0.001 per cent. of the price of a new vehicle; is dismayed that despite an undertaking to introduce such a measure for all newly registered HGVs by 10 October 2009, under the draft statutory instrument published by the Department for Transport, only around five per cent. of newly registered vehicles will be required to have conspicuity markings; and calls on the Government to ensure that all newly registered vehicles and their trailers are fitted with conspicuity markings from that date, and to use the annual HGV test to enforce this measure.

( 70)




  Iddon, Brian


  Goodwill, Robert


  Leech, John


  Drew, David


  Waterson, Nigel


  Carmichael, Alistair


  Russell, Bob


  Spink, Bob


  Harris, Evan


  Illsley, Eric


  McCafferty, Chris


  McDonnell, John


  Miller, Andrew


  Murphy, Denis


  Naysmith, Doug


  O’Hara, Edward


  Cryer, Ann


  Dowd, Jim


  George, Andrew


  Anderson, Janet


  Betts, Clive


  Bottomley, Peter


  Stunell, Andrew


  Taylor, David


  Turner, Desmond


  Prentice, Gordon


  Simpson, Alan


  Hoyle, Lindsay


  Humble, Joan


  Jackson, Glenda


  Jones, Lynne


  Loughton, Tim


  Osborne, Sandra


  Burgon, Colin


  Cohen, Harry


  Corbyn, Jeremy


  Dismore, Andrew


  Durkan, Mark


  Stringer, Graham


  Wareing, Robert N


  Winterton, Nicholas


  Hunter, Mark


  McCrea, Dr William


  Olner, Bill


  Brooke, Annette


  Campbell, Ronnie


  Caton, Martin


  Dean, Janet


  Dobbin, Jim


  Foster, Don


  Willis, Phil


  Williams, Stephen


  Harvey, Nick


  Hughes, Simon


  Gerrard, Neil


  Hemming, John


  Rowen, Paul


  Mason, John


  McCartney, Ian


  Etherington, Bill


  Flynn, Paul


  Vis, Rudi


  Williams, Betty


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  Williams, Roger


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  Pope, Greg


  McDonnell, Alasdair


  Foster, Michael Jabez


  Thornberry, Emily




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PWJ; above is from:-

The wording of the above is the same as Hansard, but my laptop software has changed the layout.








38. The changes in deaths over the whole period, compared to the 1994-98 average, are shown in Table 1. This shows that 632 fewer people (18%) died on the roads in 2007. Table 1: Change in deaths by road user group, 1994-98 average to 2007

Road user group  

1994-98 Average  


Change (%)  

Pedestrians 1008 646 -362 (-36%)
Cyclists 186 136 -50 (-27%)
Motorcyclists 467 588 +121 (+26%)
Car users 1762 1432 -330 (-19%)
Bus & Coach 20 12 -8 (-40%)
LGV & HGV 118 110 -8 (-7%)
All users  



-632 (-18%)  


Source: Department for Transport, Road Casualties Great Britain 2007: Annual Report, September 2008.


The lowest rate of reduction in the accident deaths is for LGV’s and HGV’s.

The above table, I assume, does not include other fatalities resulting from the 118 hgv/lgv user deaths.












Mr Lilley 

To ask the Secretary of State for the Environment, Transport and the Regions if he will list the number of road accidents involving a heavy goods vehicle for each month since January 1994. [78481]

Road Accidents (HGVs)

Dr. Reid:
The number of road accidents involving a Heavy Goods Vehicle which resulted in personal injury is shown in the following table:


Road accidents per month involving at least one Heavy Goods

Vehicle (1): 1994-97 Number of accidents










Year of accident






































































































































































































(1) Accidents may involve more than one Heavy Goods Vehicle

 I show these statistics to draw attention to the serious disruption caused to our road transport system by hgv’s, the vast majority of which tow trailers.

It can be seen that there are on average 247  hgv accidents per week ( for the years 1994 to 1997, inclusive)   and each one of these will involve enormous disruption due to the size of the vehicles involved. There  is a very considerable cost to the UK economy of having many thousands ( in a great many cases when the accident is on a motor way) of people stuck in a traffic jam for some time until the police have finished their investigations and the accident scene has been cleared up. This is not being taken in to account when viability of road versus rail traffic as well as very large hgv’s versus large hgv’s is being considered.

This is of course in addition to the great loss of life and serious injuries sustained.


The Department for Transport only keeps records of accidents which involve fatalities or serious injuries.

Trailer accidents in particular would be greatly reduced if we knew the side wind speeds at which snaking/jack knifing was set off in particular vehicles; the maximum safe air speed for individual trailers; and had anemometers on tow vehicles plus more road/rail side anemometers linked to remote electronic warning signs.

The air craft industry already does something similar.


I have been unable to find anything more relevant to current conditions, but discovered that the late Mrs Dunwoody asked a similar question to the above  in 1995. These statistics covered the period 1990 to 1994 (inclusive) and gave an average of 262 HGV accidents per week  involving injury.






BBC internet news



#Last Updated: Tuesday, 11 January, 2005, 23:30 GMT            

E-mail this to a friend Printable version  


Lorry driver dies in bridge fall    


A man has been killed after an articulated lorry was blown off a bridge amid high winds in Londonderry


The Roads Service said it had been monitoring wind speeds on the bridge at the time of the incident.

A spokesman said: “If the average wind speed is over 50 mph, Roads Service consults the PSNI about the closure of the bridge.

“Roads Service was monitoring the wind speeds prior to the accident and they had not reached a level that would normally cause it to consult with the PSNI




The above is typical of the type of accident which should be reported by police accident investigators to the DfT so that a body of knowledge can be built up as for air and rail accidents. Every time there are high winds there are always similar accidents. There is no point in the DfT adopting targets for accident reduction on our roads without there being in place a procedure to take precautions against exactly the same thing happening again.

In addition this accident also reveals that this particular bridge was only being monitored in the interest of HGV’s not being over turned. No consideration was being given to the lower wind speed which could have caused HGV jack knifing, or the still lower wind speeds which would cause high sided recreational trailers/caravans to snake and then over turn.