Caravan weights
Comments
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Yes, the scales only measure the force pushing down on them, if only the wheels on the van are on the scales they will measure what they 'feel' is pushing down on them.
If you put a separate scales under each wheel and jockey wheel then they would all give different readings but the sum should be 1500Kg.
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but the engine has to pull an extra 1500Kg.
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The engine also has to shift all the payload in the car (its occupants and their luggage) and the noseweight of the caravan is also part of that payload, but the car will only actually be pulling an extra 1400kg. The other 100kg noseweight is not lost in any way, it's just part of the total weight of the car.
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I'll take it that means yes then,
Take a car with whatever payload, then attach a 1500Kg caravan, the engine has to pull an extra 1500kg. In my book (and a few other physicists) pulling an extra 1550Kg is the same as towing an extra 1500Kg.
You cannot separate a car from it's engine
Still not answered my question though Lutz, if you pick up the van's hitch and tow it yourself, are you pulling towing 1500Kg or 1400Kg?
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The towed load is also defined in the regulations as the axle load of the caravan, not its total weight, so you would only be pulling 1400kg. I thought that I had made that clear.
However, the car itself would be 100kg heavier.
The engine will be called upon to shift the gross train weight and that is the sum of the car's weight (including the noseweight of the caravan) and the axle load of the caravan. As far as the ngine is concerned it's irrelevant whether a load is being pulled or carried.
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Perhaps I did not make it clear enough that the noseweight is included in the car's gross vehicle weight. Therefore you can't add the total weight of the caravan as a pulling weight, because then you would be counting the noseweight twice.
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no you did, it's ok for you towing has a different definition to the rest of the world
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There can only be one definition and that is the one quoted in the regulations, as follows:
‘technically permissible maximum towable mass’ (TM)
means the maximum mass of one or more trailers that
may be towed by a towing vehicle which corresponds to
the total load transmitted to the ground by the wheels of
an axle or a group of axles on any trailer coupled to the
towing vehicle;In the case of a caravan, the load transmitted to the ground by the wheels of the axle obviously doesn't include the noseweight. On the other hand, the noseweight is transmitted to the ground by wheels of the towing vehicle, so it is included in the total weight of the towing vehicle.
I see no disagreement between my interpretation and the text of the regulations.
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there is a huge difference, and I thought I was pedantic!
All you are quoting a definition of the maximum towable mass and how it is measured in law and I'm sure it is a sensible definition in law.
But in the real world of physics and mathematics (and for most caravaners as well), this is not a definition of towing.
The accepted definition of towing in physics is to pull an extra weight by the towing vehicle. A car tows or pulls the full weight of the caravan. If the van was not there it would pull nothing extra. As the van is there it has to pull the full weight horizontally
Towing is coupling two or more objects together so that they may be pulled by a designated power source or sources.
We'll just agree to differ?
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To have two definitions, one legal one and one based on convention, is absurd because it can only lead to confusion.
When powers-that-be carry out roadside on-the-spot vehicle weight checks they will inevitably rely on the legal definition, so why introduce another definition which conflicts with what the law says?
Besides, in one statement you are wrong. You say, quote, "As the van is there it has to pull the full weight horizontally". That is simply not true. The car is pulling the axle load horizontally but it is carrying the noseweight vertically. The noseweight is not being pulled horizontally because it is acting in a different direction. It is being carried, not pulled. The term 'pulling' only applies to forces acting in a horizontal direction.
The statement that you have presumably quoted from another source, "Towing is coupling two or more objects together so that they may be pulled by a designated power source or sources." in no way defines the magnitude of the pulling force.
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what? we're only going to post things on here that are important? When did that start? And I assume you'll be the decider on what is really important?
flags, fairy lights...
OK fair point, but I'll keep you to that, so watch out
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Yes the quote is from a famous physics book, and of course legal definitions only matter when discussing legal, and of course it doesn't define the towing force but it is a definition of towing for real physicists not lawyers. I am only speaking, and always have done, that towing is pulling something by the towing vehicle. You are using legal definitions to measure the max load on the towing vehicle to make statements in physics as to what is towing. Keep the law for lawyers I suppose you thought the law was true when it said that the earth was flat/ sun went round the earth
No matter what the legal definition of the tow load you are towing all the weight of the caravan. I never have mentioned the legal tow load, that's your idea to justify what towing is, I just mentioned the horizontal towing force from the engine.I really think you have let law and rules cloud your once pure use of mechanics? The term 'pulling' only applies to forces acting in a horizontal direction. . Well done towing is pulling the van parallel to the road and as Issac Newton stated and the weight pulling at 90 degrees plays no part what so ever. (apart from making friction)
Think I'll end now, but please go on if you wish, we sadly live in different worlds.
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sorry just seen that, that is scary!
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no you may not, I leave that to you as you're the self confessed leg puller remember?
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