How does a towing A frame work?

I am trying to find out how the type of A frame works listed at:
http://www.aframes.co.uk/aframes.html

I have already done some research and came across a site that stated:

?most people have trouble understanding how the car doesn't wander all
over the road, it's pretty hard to explain, so my usual answer is "it
just does, ok",
But I will try to explain for you, it's down to the camber/castor
settings, (as well as the A-frame), your car wants to go straight on
all the time, when you turn a corner, if you let go of the steering
wheel, it returns to the straight ahead position, and if the road is
sloping to the left a bit, (road camber), the car wants to steer to
the left,
Now the A-frame has it's 2 attachment points connected to the car, and
the single point is connected to the van's tow bar, when you turn the
van, the A-frame pivot's on the tow bar hitch point, and the car has
to follow because the A-frame pulls it round the corner, and because
of the sheering's camber/castor settings the wheels will turn to
follow the frame, it still wants to go straight on, but it can't until
you straighten the van up, now even that explanation has complicated
me,
Another way to try to explain it, is to think of a supermarket
trolley, when you apply more pressure to one side of the handle, the
trolley will steer, it steers the opposite way you push because you
are doing it the opposite way to the A-frame, (pull a trolley behind
you next time your at the supermarket, to get an idea of how it
works).
There is one thing that you can't do when your car is on it's A-frame,
and that is reverse, because the car's wheels have the camber/castor
settings dialed in for forwards travel (because you spend most of your
time driving the car forwards), if you try to reverse the van with the
car on the A-frame, the car's wheels will spin over to full lock
either left or right?


While the above information is a start, it does not explain the
process simply and comprehensively enough.  I would like a more
detailed explanation from somebody technically minded.  It would be
helpful if you could maybe include some drawings in your answer.  When
it comes to engineering I am a complete idiot and want real basic
language.  Please explain the principle as extensively as you can
presuming that I know nothing!

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Request for Question Clarification by answerfinder-ga on 11 Jan 2006 05:10 PST

Dear adamhelenandy-ga,

I suspect that my knowledge of engineering is even less than yours, so
I am unable to help you with any explanation as to how it works.

However, I can direct you to a 16 page document prepared by the
inventors of this apparatus in which they describe in great detail how
the apparatus operates and provide three pages of very detailed
drawings.

Would this answer your question?

answerfinder-ga

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Clarification of Question by adamhelenandy-ga on 11 Jan 2006 08:06 PST

The link would partially answer my questions; however I suspect that
it may be a bit too technical for my level of knowledge.  If somebody
was able to provide the link and go some way to decoding the
information into simple layman?s terms that would truly answer my
question.

Thanks Adam

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Request for Question Clarification by answerfinder-ga on 11 Jan 2006 08:32 PST

Well we seem to come to a bit of an impass as I can only provide half
the answer. May I suggest something? You can alter the price of this
question to let's say $10 and I?ll post the link to the document. You
can then read the document (and print it off if necessary) and if you
need further assistance you could post a further question and refer to
the document?s URL and perhaps another researcher may be able to
assist.

answerfinder-ga

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Clarification of Question by adamhelenandy-ga on 11 Jan 2006 16:44 PST

ok I have changed the question price to $10.  Please can you post the link.

Thanks Adam

Dear adamhelenandy-ga,

Thank you for your clarification. I do not think you will be
disappointed with the document for it is very detailed, also
socraticinstlouis-ga?s helpful comment should assist you.

The document I referred to is the Patent filing by Intertrade
Engineering. This is the direct link to the page. If this does not
work for some reason, I have placed below instructions as to how to
access it by searching the Patent database. It is a pdf format but if
you need to save it to your computer you have to save each page as a
separate file.

http://gb.espacenet.com/search97cgi/s97_cgi.exe?action=View&VdkVgwKey=GB2398052A&DocOffset=1&DocsFound=2&QueryZip=%28towing+AND+a+AND+frame%29+%3CIN%3E+ti&Collection=dips&SearchUrl=http%3A%2F%2Fgb%2Eespacenet%2Ecom%2Fsearch97cgi%2Fs97%5Fcgi%2Eexe%3Faction%3DFilterSearch%26QueryZip%3D%2528towing%2BAND%2Ba%2BAND%2Bframe%2529%2B%253CIN%253E%2Bti%26Filter%3Dgb%252Fen%252Fespacefilt%252Ehts%26ResultTem
plate%3Dgb%252Fen%252Fresults%252Ehts%26Collection%3Ddips%26ResultStart%3D1%26ResultCount%3D10&ViewTemplate=gb/en/textdraw.hts&ViewErrorTemplate=gb/en/incerror.hts&DocsFound1=2&BeginHighlight=%3Cspan%3E&EndHighlight=%3C/span%3E&HLNavigate=



Alternative access:
Go to 
http://gb.espacenet.com/search97cgi/s97_cgi.exe?Action=FormGen&Template=gb/en/quick.hts

Select patent database drop down box> GB-esp@cenet
Click> Person or organisations
Search terms> Intertrade

It should appear first on the list titled: A-frame towing apparatus 

Click the tab> Original document

I hope this answers your question. If it does not, or you cannot
access the document, then please ask for clarification of this
research before rating the answer. I shall respond to the
clarification request as soon as I receive it.
Thank you
answerfinder


Search strategy
Knew of the resource

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Request for Answer Clarification by adamhelenandy-ga on 22 Jan 2006 05:49 PST

sorry it has taken me a while to respond, but I have been away for a
while.  The link that you have provide looks good, however when I
click the link I can never save the whole pdf document, only ever 1
page?  I have tried lots of different ways but no matter what I do I
can never get the whole document.  Due to the problems I have been
experiencing it would be helpful if you could email me the whole pdf. 
If you do this I will be able to provide good feedback for you

Thanks

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Clarification of Answer by answerfinder-ga on 23 Jan 2006 01:19 PST

Dear adamhelenandy-ga,
As I indicated in my answer, you have you have to save each page as a
separate file. Click on page one and save it, when saving it delete
their file name and insert your own as a 'page one', then go to page
two and then save it as 'page two', and so on. At the end you will
have 16 individual files each representing a page of the document. I'm
not familiar with pdfs so I do not know how they can be combined in
one, I suspect only the author can do that.
Hope this helps.
answerfinder-ga

Intertrade's Solomatic takes advantage of an aspect of a car's
front-wheel steering mechanism that is universal among the world's
production cars, called "caster". By maintaining a fixed relationship
between the towed car's chassis and the pivot point of the towing
frame (i.e. the ball-hitch on the towing vehicle), the A-frame assures
that slight changes in the otherwise straight-line motion of the
towing vehicle produce an immediate change in the orientation of the
towed vehicle. Because of the caster built into the front suspension
of the towed vehicle, the steering mechanism in these cars will
respond to this change in the car's orientation in such a way as to
maintain alignment between the motion of the car's front end, and the
steering direction. This works for both vehicles with and those
without power steering, because another universal aspect of car
manufacturers' front-wheel steering mechanisms is that their
power-assist steering is to some degree "reversible", meaning that
while it is easy for the driver to move the steering with the
assistance of the system, it is also possible for the steered wheels
to move the driver's steering wheel. This is intentional, and is
engineered to give the driver an indication of how much force the
power-assist system is applying to the steering mechanism.

I believe that A-frame towing works with any vehicle that has what is
known as Ackerman steering (probably invented by a Mr Ackerman) and
that all three elements of self-centering steering "toe-in" etc
contribute.

 It works on roads, but probably would't qork in sand, mud etc.  And
it's a bugger to reverse with.