Caravan Stability 2

[Hutch]

I believe in layman's terms, You have developed a mechanical, (non Electronic) system to apply the brakes independently when a sway happens to the caravan/trailer, but why pitch. ?
Very interesting, I think I would like to know more about the system.
:evil:
Hutch.

 

[Dustydog]

I believe in layman's terms, You have developed a mechanical, (non Electronic) system to apply the brakes independently when a sway happens to the caravan/trailer, but why pitch. ?
Very interesting, I think I would like to know more about the system.
:evil:
Hutch.

That’s interesting. I didn’t get the independent brake bit. Having tested my ATC visually, all that happens is both brakes apply in unison causing drag to dampen out the snake.
Is John MW’s an independent mechanical brake system?
Does it have anything to do with the brakes?
This is better than Gafferbill’s Christmas quiz!

 

[Hutch]

I believe in layman's terms, You have developed a mechanical, (non Electronic) system to apply the brakes independently when a sway happens to the caravan/trailer, but why pitch. ?
Very interesting, I think I would like to know more about the system.
:evil:
Hutch.

That’s interesting. I didn’t get the independent brake bit. Having tested my ATC visually, all that happens is both brakes apply in unison causing drag to dampen out the snake.
Is John MW’s an independent mechanical brake system?
Does it have anything to do with the brakes?

I think JMW, project is wonderfull , but he has dis missed the fact that the, other trailer
teams have researched a system using a 5 phase electronic discriminator , combined with the Hydraulic towball clamp. . Maybe your a touch to late.
But good luck..

This is better than Gafferbill’s Christmas quiz!

 

[ProfJohnL]

I believe in layman's terms, You have developed a mechanical, (non Electronic) system to apply the brakes independently when a sway happens to the caravan/trailer, but why pitch. ?
Very interesting, I think I would like to know more about the system.
:evil:
Hutch.

Hello Hutch,
Given the dynamic effects of towing produces highly complex loads on the tow ball, it means that at different instants the effective imposed force vector on the tow ball can be in almost any direction, it follows that at times the down force load will be greater than the static value, and at other times it will be less. This would definitely be the case if the caravan pitches.

When the caravan pitches nose up, it will unload the towball and at the same time reduce load on the tow vehicles rear wheels, which means it will less able to resist any side ways (Yaw) forces from moving the tow vehicle off line.

If the forces are big enough and synchronised, this could lead to the tow vehicle loosing control of the outfit.

 

[JohnMW]

Hi johnL
Thanks for answering that one so eloquently - pitch is a difficult one to solve especially how to integrate it with the other control vectors. The problem is that one cannot make it ridgid so a solution must be capable of allowing it flex or something will break eventually, yet prevent oscillations developing. Close attention to the tow vehicle helps a lot by stiffening the suspension but remember that simply putting inserts between the coil spring only shortens the spring compression distance it may not stiffen it - unless of course you fill the whole spring with rubber.
This action only affects the tow vehicle since the trailer can still rotate around the ball - up and down. To reduce this effect always fit shock absorbers to the van to reduce bounce - Alko don't always fit then as standard but they do provide an excellent easy retrofit to all their chassis.
To give an analogy of where mechanical solutions can be better - the success of automotive road holding in modern cars that we all take for granted is the evolution of multilink suspensions where the geometry is accurately controlling the variables just by simple linkages together with precision damping.
In my early days in transport There was a problem that was labeled "The slow roll over phenomenon" artics were going over a lot and speed was not the cause - I was very concerned since I had a fleet of them. The police and the authorities did know why it was occurring. I found the cause and the solution. I called it "Geometric anti rollover" and I applied for a patent with temporary success. The IRTE and Cambridge University started work on the problem and were forced to abandon the results partly because it was to expensive to solve and they could not make the fifth wheel turn in two axis at the same time.
They developed a hydraulic system to tilt the trailer into the turn - it was too slow to react, too heavy and to complex to implement. What I found was the if the trailer was higher at the front than the rear the geometry caused the front of the trailer to tilt severely towards the outside of the turn therefore the load simple fell over at low speeds when turning. My solution was to ensure that the trailer was lower at the front than the rear and the trailer miraculously leaned in to the turn when cornering so I designed a fifth wheel plate that was angled just six degrees to lower the plate. I took it to shows and demonstrated it to all. By this time trucks were being fitted with air suspensions and rather than mess with plates they simply lowered the outfit to ensure it was level or lower at the front but I did find the cause and the solution was easy for me.

 

[JohnMW]

Hi Dusty
Let me make clear - the regulations now make it such that all modifications to vehicle systems must be type approved - Accessories do not apply here. It is prohibited to drill or weld any part of the chassis, it must not interfere with the approved systems such as brakes. any addition must be overridden by the approved system. Quite a challenge eh - be assured all these points have been covered. This can be retro fitted to any trailer with standard overrun brakes by any competent individual - it does require an element of setting up but with the ability to read this post they will be fine. Thereafter it is just a simple push in and clip one item - job done. I carry two electric mountain bikes on the back of my van - and can bop along at any legal speed without any worry other than watching out for the nutters one gets in any road situation - just towing a van presents extra care.

 

[Dustydog]

That’s very interesting John MW. I wrote this just before you last post. Crossed.
My old caravanning mentors always said tow with the caravan level or in a slight nose down attitude but never nose up. Your own experiences with artics prove the same point.
Years ago I used the Scott stabiliser. A friction damper which also used a cart spring to stiffen up the outfit , but no damping for the pitch change. Towing without it was noticeable particularly when being overtaken by large vehicles.
The main point that I think gets lost is that a properly loaded, nose load correctly adjusted caravan is still the most important factor in stability. All the safety add ons eg hitch dampers , ATC etc will help but not make a poorly adjusted outfit safe.

 

[JohnMW]

Hi EH5,
Ok - I love a challenge but where are the results of the 5 phase electronic discriminator , combined with the Hydraulic tow ball clamp. I agree that if the clamping could be controlled rather than static then it would provide a solution. Definition of good luck - when Preparation meets opportunity.
I purchased an Arduino chip for about £10 and produced the lateral sensing device and other electronic parts to emulate the apparatus used in the ATC/iDC and using an old windscreen wiper motor I got it to work my caravan brakes on the differential principle in the same way. The problems with the electronic version were the difficulty applying a proportional effort to the brakes and releasing at the precise moment compared to the mechanical option. I know I can overcome these discrepancies but the one I had trouble with was getting the proportional effort at or near the centre of equilibrium which is the key to this success.
If I persevere I know I could overcome this too but at what costs. I am working on an interface on the car to connect the Canbus system to the caravan with the intention of passing data to a module that may make the differential sensing more intuitive.

John

 

[JohnMW]

Hi Dusty
That's correct for the ones you mentioned but not mine - you can be very naughty with all those points and my system will cope very well and just tell you gently if you been a bad boy.

 

[JohnMW]

Otherclive,
I agree the term is not appropriate - I was referring to overseas students and the only point was that the work done on that model illustrated was not the work of the Dr had it been done by him I'm confident more could have been achieved. Often students with no practical experience can miss the clues to a successful conclusion simply because they cannot be expected to derive the impact of missed values. I have given an example of this where insufficient knowledge of a problem led to much wasted time and money even by very intelligent seniors on another problem I was involved with.

Regards and thanks
John

 

[ProfJohnL]

Hello Dusty,

On a virtually a daily basis I have passed a major island on the A5 in the Midlands for over 40 years, The island has a slightly unusual egg shape having a much tighter radius of turn on the west bound side compared to a much bigger radius on the east bound side. Two or three times a year west bound lorries have literally tipped over onto the verge at the side of the island, Not where you might at first suspect on the sharp bend, but on the 50M straight section just after the bend. I have never witnessed it occurring but have often come across the widespread congestion it causes in the area.

It is only whilst considering this thread that the significance of the usual landing place for these lorries has become interesting. One would normally expect the greatest toppling force to occur at the tightest point of the bend, but in fact it seems to be when the bend is actually straitening out. and now I believe several factors are involved. Approaching the island drivers will naturally be slow down, to not only negotiate the left hand feed in bend, but also to look for traffic on the island and planning their entry to the island. Consequently their speed will already be much reduced or even stopped. The nature of the island and the traffic flows encourages drives to accelerate hard when joining the traffic flow, at the same time having to wind into the tight right hand curve of the island. Especially at rush hour, the traffic flow leaving the island west bound can rapidly build up and back onto the island meaning the driver just entering and having accelerated is then almost immediately faced with braking hard.

The artic is still slightly cranked and the momentum of the trailer acts tangentially to push the tractor unit laterally towards the outer kerb. if the tractor unit skids the tyres will slide to outer edge of the island and be stopped by the kerb side, providing the fulcrum for the whole vehicle to start to tip over. The forward momentum means they whole unit can leave the curved section and be on the straight section before it actually lands on its side. I have seen solid and Articulated vehicles mostly high sided vehicles, but we have also had tankers, and lots of shed loads from flat beds. Ironically in all of the last 40 odd years I have never seen or heard of a caravan coming to grief at this spot.

I have related these incidents to emphasise there are some significant differences between the tow coupling of lorries and car with caravans.

The fifth wheel system used on lorries has a limited degree of freedom to alter from the near horizontal plane it will normally adopt when coupled. This should allow enough articulation to accommodate all the normal road angles and undulations The system does offer some resilience to these motions so as JMW suggests pre-setting a few degrees of offset can be used to impart some angel bias to the trailer during turns.By comparison the normal caravan coupling has considerable freedom of articulation and the tow vehicle and trailer can experience consider opposite roll, pitch and turn motions before any real mechanical opposition is experienced. The friction based ball stabilisers do try to offer some resistance to relative horizontal rotation motion on the ball, the amount of resistive force they can apply is very small compared to the torque that a trailer will apply when turning a corner.

These differences mean that whilst biasing and offering a slight nose down attitude an articulated HGV may pay dividends, but the same mechanical restrictions do not apply to at a ball hitch.

In particular the EU prescribed tow hitch height limits of 350 to 420mm in conjunction with the caravan manufactures specification for the height of the trailers hitch when the trailer is LEVEL (to 395 to 465mm) does encompass as situation when the height of the loaded tow ball is at its maximum of 420,, and a caravan with a "level" to coupling at 395mm the coupled outfit will have a 25mm nose elevation or slightly nose up.

This is permitted and will not have the same consequence as on the HGV fifth wheel system. It is the case that most caravans will probably towed nose down, and there is nothing wrong with that but I challenge the traditional advice that towing nose down is better than nose up within the EU's prescribed limits.

 

[camel]

I love this thread going on about some top secret device to stop caravans going over tits, but if we have such brilliant engineers in this country in venting the wheel again why is it when any good product comes on the market it ends up being made abroad just like what Dyson does today, down my local I did mention this to a couple of my engineering mates and they just went off to play pool when I got on the subject of caravans, I don't think JohnMW this will stop the world spinning,

 

[ProfJohnL]

Hi EH5,
... Definition of good luck - when Preparation meets opportunity...

That presumes some preparatory action has been planned, so the element provided by "luck" should have been reduced

Try
"Unplanned success" = Good luck
"Unplanned failure" = Bad luck

EDIT - Oh and I've just thought of another one

Unplanned = caravan quality :woohoo:

 

[JohnMW]

Johnl
That was never meant to associate caravans with artics - it was to point out that Universities etc do miss out finding a solution because they sometimes do not understand the problem they are trying to solve. Fifth wheels are totally different to the tow ball on a caravan. I agree totally it makes no difference up or down with a caravan - on an artic the fifth wheel holds/supports the plate fore and aft and across the bed so it is limited in the axis rotation
This is why they could not just jack up one side to tilt the trailer because it would also lift the Tractor Unit with a very dangerous consequence. On that subject many still run with the trailer tilting back from the unit especially the foreign ones - they don't learn.
Regards
John

 

[Parksy]

Johnl
That was never meant to associate caravans with artics - it was to point out that Universities etc do miss out finding a solution because they sometimes do not understand the problem they are trying to solve. Fifth wheels are totally different to the tow ball on a caravan. Please tell us a little about yourself and your expertise in the automotive sector.

Moderator Note:
No forum member is obliged to provide any personal details whatsoever unless they wish to do so.

 

[ProfJohnL]

Thank you Parksy,

Hello John,
For reasons that I will not make public I value my privacy. I have informed the moderators of those reasons and they are generally content to let things continue. Suffice to say I am retired, I was a caravanner until about a year a ago, I have qualifications and experience in Electronics, Electrical, LPG and general mechanical engineering, I have worked for companies who have had connections with caravan OEM supplies, I latterly worked in Reliability testing of design concepts and final product for consistency. And as a Quality Management Consultant to a variety of well known appliance manufactures and including some involved with Aerospace.

From time to time where a subject requires a more in depth analysis or specific private advice may be required, Parksy and Damian have acted as a go between for forum users. I am pleased to be able to say that using this private behind the forum system we have helped a number of users to get a better outcome to some difficult situations.

In all of this, I try to focus on facts, using logic to evaluate cause and effects, which often illustrates how outdated many caravanning traditions and accepted norms are. all I offer is advice and opinions it is up to the recipient to verify it before acting on it.

 

[JohnMW]

Hi JohnL
Thanks for that - Now I am better informed about how I should address you - I simply just try not be too technical but i have difficulty balancing this between the those that just want low level info and the extreme - I have now learnt to be politically correct with my words otherwise great offence can be the result. I am one that can take criticism by the bucket full as long as it is not for speaking out when things are obviously wrong. You know if those in ALKo or BPW come up with right solution at fair price why should I bother. BPW are leaders in commercial chassis suspension systems I am very surprised they have not responded. I am also puzzled why Dexter did answer my correspondence with interest and directed be to a named high level person in ALKo Germany who will not respond. I guess they would like a differential solution for overrun brakes in Europe but maybe they won't listen to an Englishman - too proud maybe.
Ah well - Happy new year.

 

[ProfJohnL]

"Hi JohnL
Thanks for that - Now I am better informed about how I should address you"

Hmmm My forum name is ProfJohnL - and there is justification for it, I was awarded the salutation having done some work at education establishments both in the Midlands and the West Country.

PJL

 

[JohnMW]

Hello JohnL
Now that I know you a little better I have be honest with you. When I said I agreed with your hypothesis on the nose up or down with caravans I should have added that only if there is a control system in place. The observations made by all the caravan /chassis builders is spot on even if they could not explain why - nose down is the only attitude that should be aimed for. You actually made the correct statement that pitch reduction is very important to control, however, you did miss the point when you correctly explained why. If the nose is kept lower then if pitch is presented it could prevent the nose elevating above the centre line and thus producing a negative nose load.
There are so many small things like this that are missed when finding a solution. I will go on to explain why it is ok to carry cycles on the rear of a caravan under specific conditions -

Moderator Note: No you will not ! Enough Is Enough ! By all means return and tell all how stupid we are not to listen when you have your wonderful invention adopted by the major manufacturers and have been lauded by them for not thinking about it long ago !

John

 

[Gafferbill]

I grew up on a farm so can easily recognise bull effluent when I see it. :huh:

I will leave it to the Prof to engage as he undoubtedly will

PS. Sorry Parksy if this post breaks the rules.

 

[DrZhivago]

An entertaining thread at a time of year when, as Parksy said, there is less general activity on the forum. It is intriguing to try to guess what JohnMW has devised (whether it is any good or not) as he is obviously not going to reveal it.

I think that JohnMW would improve his case if he were a bit lighter on technobabble, self-congratulation and disparagement of others' abilities to understand the issues.

The secret to the success is that it uses no electronics and can apply an equal and opposite force at the centre of equilibrium and is proactive in that it stops a snake before it starts - it does not interfere with. the normal overrun brakes and will never shut off on rough roads, costs about £200 and will retrofit any caravan or trailer. This system can be connected in under 10 seconds

You refer to "differential stability" but never actually use the term "differential braking" (altough ProfJL does). I can envisage an inertial lateral hydraulic damper perhaps at the rear of the caravan, but such a device would be "fitted" not "connected", and it would certainly take more than 10 seconds to fit. Perhaps JohnMW has in mind to fit and remove it every trip, which could be done in 10 seconds with a quick release, but why? No-one would do that in practice - they would fit and forget.

If differential braking is involved the "10 seconds" is even more puzzling. My brakes involve a rod from the over-run/handbrake to an equalising beam under the centre of the van, which splits the pull into two Bowden cables to the two wheels. Any differential braking is going to need to break into this system, most likely at the equalising beam point. It would be at least an hours work by a professional fitter, then the user could forget about it. We can rule out any idea of braking via the tyre treads (motor mover style). I can however envisage a mechanical inertial mechanism to apply such differential braking.

As for the "secret to the success" being no electronics, I am afraid that cuts no ice these days. Any vehicle maker, including of caravans, is going to think of electronics as the much prefered option for any kind of control system.

I ...have offered it to the majors who have not responded to my correspondence.

It is rude of them not to make any response at all. At least they should acknowledge letters. As with almost all corporations these days the only way to contact them is to wait on a call centre phone line, only to be answered by someone with a set of pre-printed answers or to be told to go and look at their website.

 

[ProfJohnL]

Oh dear!

Thank you Gaffer
I think I'm beaten on this one.

I don't think were are going to get any meaningful details about JMW's concept.

We will never know if he really has a towing miracle or not.

 

[Lutz]

Hello JohnL
If the nose is kept lower then if pitch is presented it could prevent the nose elevating above the centre line and thus producing a negative nose load.

I don't know where the idea came from that a nose-down attitude prevents a negative noseload. Perhaps you might like to explain that.
I was always led to believe that exposed frontal area of the caravan being well above the roof line of the towing vehicle and therefore also above the centreline of the caravan's axle, will always create a negative noseload at speed, regardless of whether the nose is up or down in the first place.

 

[ProfJohnL]

Welcome home Lutz

 

[JRS1]

Hi John MW
Having gone through much of the same thing with major companies Etc. I think I might be able to help you. Cheers jrs