How to Make "A" Frames better

Discussion in 'Tech/Mech General' started by Enodreven, Sep 19, 2007.

Thread Status:
Not open for further replies.
  1. Enodreven

    Enodreven Deleted User

    Hi, Everyone

    What I really find quite strange that when most questions are asked on any of the motorhome internet forums everyone tries to provide helpful suggestion s on ways to overcome the problems EXCEPT WHEN "A" FRAMES ARE MENTIONED everyone comes out with the same old stuff regarding the legalities, and even to the extent of some people finding enjoyment in trying to ridicule people who use them WHY ???

    What would be interesting and a lot more helpful is to put all of the expertises that exist on this site into finding a method for making them legal. as from all of the information I have read it does seem from a motorhomers point of view if these could be made legal then they would become a much more used resource as they certainly are more user friendly than a trailer and so far no one appears to be saying they are dangerous it appears the only problem if you chose and "A" frame with an overrun device operating a cable braking system is one of reversing it and I certainly know quite a number of people who tow so called legal vechlices that cannot reverses them ?? .

    So come on lets examine what would need to be done to make them legal and then lets put all of our minds together to overcome the problems please don't let us get bogged down on the legalities.

    If you actaully look at one with a overrun cable braking system and hand brake etc. and assume that they can achive the minimum braking affect that is required ? without the servo operational what would need to be done to make this legal and far more important HOW WOULD YOU DO IT


    If I haven't explained myself correctly please don't start nit picking I am sure you can all understand what I am trying to say


    So come on stop quoting the legal system put your heads together and find a method of making them legal.

    Brian
     
  2. GeorgeTelford

    GeorgeTelford Deleted User

    Hi Brian

    I see your idea, but in the case of legal trailers they can be reversed under control, in the case of A frames Roadsurface castor and camber decide where the vehicle is going not the skill of the driver. So unless the law changes to allow reversing in any random direction without control, I dont see that it is possible.

    We cannot just assume that the braking effort on any given vehicle would be high enough, that would be dangerous.

    If you want them to be legal then you need to get the law changed to allow trailers that cannot be reversed under control and that have suspect untested braking systems
     
  3. fordy

    fordy Deleted User

    Very helpful George :Doh:

    hi Brian if the wheels are locked with the steering lock it is then controllable as a 4 wheel trailer, and the braking can be tested on each car to see if it needs any extra help like adding extra cable to the hand brake cable of the car to give more power to the braking, but most will be towing a small car which will have more than enough power from the overrun to be legal without the servo ..

    FORDY:Smile:
     
  4. Geo

    Geo Trader - Funster

    Joined:
    Jul 29, 2007
    Messages:
    9,508
    Likes Received:
    5,561
    Location:
    Mansfield,Notts
    They call them caravans George:Rofl1:
    geo
     
  5. moandick

    moandick Read Only Funster

    Joined:
    Jul 28, 2007
    Messages:
    1,318
    Likes Received:
    112
    Location:
    Landrake, Cornwall
    Reverse steering?

    Fordy

    I have a £2K trailer sitting on the park rotting for at least eleven months of the year and so I am really interested in seeing someone achieve a legal 'A' Frame.

    Following your thoughts through, I simply cannot for the life of me see how the car could be steered backwards or forwards as a four-wheel trailer - if the steering wheels are locked?

    If you are talking about an 'A' frame that fits directly onto the front axle ( for want of a better description) then I can agree with you to a certain extent but even so the steering shouldn't be locked, surely?

    If you are talking about an 'A' frame that simply locks onto a bar that sits in front of the radiator - that could have no effect whatsoever on the steering, locked or otherwise.

    Dick
     
    • Like Like x 1
  6. Enodreven

    Enodreven Deleted User

    Hi, Fordy & Dick

    Thanks for taking the time and trouble to look at this positively, I don't know enough about towing to really comment on reversing but from what you have said i really can't see why if the steering was locked with the wheels aligned why it wouldn't respond the same as any other 4 wheeled trailer or caravan. I also can't see why as you say that the brakes can't be tested in the same manner as trailers.

    The problem that seems to keep being raised is the method for allowing the car/trailer to be reversed and from what i have read on other forums people keep saying that the mechanism for releasing the brakes when you want to reverse has to be automatic is this true or is it legal to make adjustments before you reverse e.g. by removing a pin and then locking the steering ??

    Dick
    "Quote
    If you are talking about an 'A' frame that simply locks onto a bar that sits in front of the radiator - that could have no effect whatsoever on the steering, locked or otherwise.Quote"

    Dick, I don't quiet understand your reasoning can you explain a little more as my thoughts were that when that "A" frame is attached to the bar it effectively makes the whole vehicle ridge e.g. the cars chassis becomes part of the "A" frame and visa/versa and if the front wheels of the car were locked in alignment with the rear wheels what would be the difference between that and your trailer ?

    Please Everyone try to be positive in your replies don't keep trying to move the thread into the legality area

    Brian

     
    Last edited by a moderator: Sep 19, 2007
  7. fordy

    fordy Deleted User

    Hi Brian that's exactly what i mean all wheels aligned it becomes the same as a trailer hence it can be reversed,and not allowed to turn on its own as i said before i have tried my car with the steering lock on and it backs up fine and tows fine but i do tend to tow with the lock off. the auto reveres is part of the aframe hitch or car coupler as it should be called now same as a caravan:BigGrin:
    We are talking about the same thing here i hope a fitted Aframe not a cheep recovery type strap on effort that are not safe for long term towing but the ones that have a frame fitted to the tow car permanently and you fit the tow hitch as and when you need to tow??

    FORDY:Smile:
     
  8. kands

    kands Read Only Funster

    Joined:
    Jul 20, 2007
    Messages:
    1,286
    Likes Received:
    13
    Hi Brian
    I like your approach to this problem mate...
    I have read somewhere that an American company markets an A Frame system that provides a vacuum pump that is operated when the toad is connected to the towing vehicle, this then provides the same braking efficiency as when the car driver puts their foot on the brake pedal. It also mentioned that the braking effort was proportional not just on/off. I will try to find this company and if I manage I will put up a link.
    I think the overrun braking could be overcome in much the same way as on a caravan, and that is by having a heavy duty damper on the head, which is sufficiently powerful to at least slow down the compression of the braking system, but not too powerful as to prevent it from operating when the towing vehicle applies its brakes.
    Regarding steering, I think the problem is that with the front wheels locked in the straight ahead position (if this was possible, as most steering locks are not in the straight ahead but at some other, non defined angle...) the front wheels would drag when steering around corners etc. With a conventional trailer the wheels are amidships and as such the body of the trailer swings about the central axis, when there are wheels on each corner this is not possible, so the front wheels would inevitably scrub. When you see a four wheeled trailer the wheels are usually in the center as said except when they are mounted on a bogey and this allows the whole front axle to pivot around its mid point and thereby allows the trailer to steer.
    The pivoting bogey does provide an element of steering control and allows the towing vehicle driver to determine the direction that the towed vehicle will travel in.
    I hope this helps :Smile:

    Keith
     
  9. fordy

    fordy Deleted User

    Hi dick well if the steering wheels are fix IE not steering then the only pivot point is from the hitch point same as a trailer i take it your wheels on the trailer don't steer? this was what made backing up a car on an aframe non controllable if that makes sense.

    FORDY:Smile:
     
  10. Enodreven

    Enodreven Deleted User

    Hi, Fordy

    I think we are talking about the same thing but i must first admit I have never towed anything so i really don't know the methods, but from the "A" frames I have looked at the only ones which seem to cover most of the objections I have read are the ones that have plates bolted onto the chassis of the vehicle and these have a tie bar across the front of the radiator to which you mount a "A" frame and it is held on to the lugs by some removal pins, they then have a brake cable that is routed through the car and connected to the brake pedal this from what i understand is actuated by a ALKO overrun device that forms the towing hitch they then have the wiring to connect the lights etc

    Is that the same sort of thing as you are talking about

    On the part of the automatic reversing someone gave me this link

    http://www.ukcampsite.co.uk/articles/view.asp?id=18


    the link states that EEC 71/320/EEC covers auto reverse braking systems and couplings. I did a Google on this reference number and found this site

    http://ec.europa.eu/enterprise/automotive/directives/vehicles/dir71_320_cee.html

    I started to read through the documents and I don't seem to be able to find any specific mention within the main document or the supplemental changes of the need to have automatic brakes that will allow the vehicle to reverse ?

    Obviously there needs to be a method to reverse the vehicle but its the automatic part that is the real concern, as in the orginal documents a drivers mate was acceptable for control purposes ? that's not to say we all want to have "motorhome mates" LoL but it does start to question some of the information that has been raised as to the method of releasing the brakes before affecting a reverse maneuver.

    I will continue to search the documents but if anyone knows where within the EEC legislation this can be found I would be grateful

    Brian
     
  11. fordy

    fordy Deleted User

    Hi yes that's the same as I'm talking about. and all good aframes have auto reverse couplers as far as i can see from looking at them and breakaway and hand brake
    and overrun. so its just the backing up under control:Smile:

    FORDY:Smile:
     
  12. GeorgeTelford

    GeorgeTelford Deleted User

    Hi

    right with proper trailer brakes they are a known quantity and have been tested, with random cars there is no tesing done without servo assistance, trailers also have a built in facility to not apply the brakes when reversing.

    At present the steering wheels on the car are free to turn at will, which works without problem when being dragged forwards, however on reversing they will turn one way or the other seemingly at will (its the Road camber, caster angles and roadsurface that cause this random behaviour)

    Brian to give you an idea of the problem, try to reverse your car without holding the steering wheel and try to guess which way it will swing. The other problem is that if an over-run is fitted it will apply the brakes because car brakes are not fitted with auto reverse backplates.

    Keith

    A simple electric vacuum pump would do the same thing as used on electric vehicle conversions http://www.evconvert.com/article/electric-vacuum-pump
     
  13. GeorgeTelford

    GeorgeTelford Deleted User

    Hi Fordy

    The auto reverse part is in the backplate on the hub thats all sorted in a trailer hub, but not in car Hubs and is there even such a thing fior a disc brake?

    [​IMG]

    The silver part drops the pressure off the shoe if it is applied to the shoe in reverse, beautifully simple pce of engineering but alas not fitted to cars

    Before anyone races out to reverse engineer their car, think about what it would do? yes thats right you would have no braking at all when reversing.......... unless of course you dont mind changing all the hubs over when on site (assuming you can find a car with 4 drum brakes)
     
  14. kands

    kands Read Only Funster

    Joined:
    Jul 20, 2007
    Messages:
    1,286
    Likes Received:
    13
    Hi George
    I have obviously misunderstood this auto reverse concept. I did not realise that trailers had different brake back plates to achieve the reversing maneuver. I understood that the overrun device was a damper fitted between the coupling head and the brake actuation linkage so as to allow the brakes to actuate under towing vehicle braking, but hold off the application of the trailer brakes during the (gentler forces) reversing maneuver. I am certain that my caravan worked in this way?
    I have seen, many times, a caravan being reversed up a slight gradient only to find that half way up (or thereabouts) the trailer brakes became engaged and reversing maneuvers stopped, this being due to the weight of the trailer being applied to the coupling and overcoming the overrun damper, thereby applying the brakes, in the same way that braking of the towing vehicle forces the weight of the towed vehicle to be subjected to the towing head and compression of the overrun device engages the trailer brakes.
    I would be interested to find out more on this topic :Smile:

    Keith
     
  15. moandick

    moandick Read Only Funster

    Joined:
    Jul 28, 2007
    Messages:
    1,318
    Likes Received:
    112
    Location:
    Landrake, Cornwall
    Trailer wheels and steering

    Hi Fordy

    I'm still not on the same wavelength as you, at present.

    My trailer is a twin axle, with both axles in the middle of the trailer, so when I go around corners, the front wheel rotates while the second wheel tends to 'skid' around a little bit quicker having a further distance to travel.

    My car obviously has two axles , one at front and one at back but the distance between the axles makes it impossible to turn corners if the wheels are locked in line. One set of wheels must be able to turn corners in order to make the car go around a corner - just like a shopping trolley etc., etc., etc.
    Surely you must have, at one time, tried to push a shopping trolley where the wheels are locked and the darned thing simply will not go where you want it to.

    If you are going to turn the car into a four wheel trailer with all wheels locked into a straight line - then yes, you can push it forward or backward quite happily - but the camber of the road etc., etc will try to push it all over the place.

    In order to counteract that movement you must be able to steer the trailer - which you cannot do if the wheels are locked in a straight line. (Or am I getting this thing entirely wrong?)

    Dick
     
    Last edited: Sep 19, 2007
  16. Enodreven

    Enodreven Deleted User

    Hi,

    As said above we will probably need to get the brakes tested without the servo unless the people on here like yourself can devise an acceptable method or making the servo operable when its being towed, so lets start devising before we give up ??

    As said above there have been some suggestions that applying the steering lock and using this to lock the front wheels aligned with the rear may allow a reasonable reversing maneuver to be carried out (I have never reversed anything) but it does appear to look like a possibility albeit it may cause tyre wear ?

    The over run brakes are only a problem if the legislation dictates that these must allow reversing to take place without the driver being allowed to leave his/her seat and not ask anyone to do it for them, e.g. walk to the rear of the vehicle and remove install a pin? to release the brakes for the reverse maneuver ? Having said that if they can't leave their seat or ask anyone else can they use electronic assistance ??

    loads of questions and we are getting some very helpful input, lets solve this its surly not impossible? I have faith in you lot ?


    Brian




     
  17. moandick

    moandick Read Only Funster

    Joined:
    Jul 28, 2007
    Messages:
    1,318
    Likes Received:
    112
    Location:
    Landrake, Cornwall
    Reverse steering

    As far as I can see, the only way you can reverse a four wheel trailer (car+A Frame) is if the A Frame is locked rigid to the steering mechanism - be that an axle or whatever. That way the car has to go in the direction that you point the A Frame.

    For an example I point you to the many 'drive and drag' lorries operated on the Continent. Not the 'mid-trailer' axle or the Artic type trailers but proper full-blooded trailers with a wheel in each corner.

    As any decent driver, whether HGV or farm-tractor driver will tell you, these trailers can be reversed quite happily BUT it takes lots and lots and lots of practise!

    From my caravan park management experience, many average caravan drivers can't reverse a simple caravan (hence the growth in the caravan motor-mover devices) let alone a four wheel trailer.

    Dick
     
  18. kands

    kands Read Only Funster

    Joined:
    Jul 20, 2007
    Messages:
    1,286
    Likes Received:
    13
    Hi Brian
    I have answered some of your points in my post above matey :Laughing::Laughing:

    Keith
     
  19. justme AKA Grath

    justme AKA Grath BANNED

    Joined:
    Aug 16, 2007
    Messages:
    479
    Likes Received:
    2
    How about something where by the 2 front wheels of the towed car ride on an articulated boggie and this way it could be reversed under control!:thumb:
     
  20. kands

    kands Read Only Funster

    Joined:
    Jul 20, 2007
    Messages:
    1,286
    Likes Received:
    13
    Hi Justme
    Are you suggesting that the front wheels are lifted off the ground, like a suspended tow? If so this will transfer a huge proportion of the towed vehicles weight onto the tow ball/hitch and probably more than the 50 kgs that is recommended. It would also have adverse handling characteristics for both vehicles as well as preventing proper braking by the towed vehicle :Smile:
    Just a thought

    Keith
     
Loading...
Thread Status:
Not open for further replies.

Share This Page