I see them often on m-ways, just creeping mm under the gantries. Then speculating, what are they used for? Why are they used? If loaded to the top, they must be very heavy and unstable. If not loaded to the top, they have excessive wind resistance for the load.
For bulky but lightweight items? Quilts, bubble wrap?
With the increasing capital cost of vehicles and the running costs in terms of fuel, insurance, and road tax, it must surely be cheaper to make products nearer their consumer market than transport products long distances ???
It would seem not - when it comes to long distances via sea. That is an incredibly cheap way to move goods. But regardless of where anything is made, it will still need local transport to its final destination.
I think I saw something that suggested the cost / item say when shipping clothes by sea from China to the UK was only a few pence.
And people to get to where they have to make it and the materials to be brought to where it's made if the workers don't go to the material etc.
Cheers, T i m
Empty beer cans going for filling.
It must be. Plenty of electronic components on Ebay to prove that. Like
100 2N2222 transistors for £0.99 with free postage from China.
I IIRC there is some sort of reciprocal approach with Chinese mail which is weighted heavily in their favor.
Examples seen: dpd and royal mail; packqages. Must be heavy to fill to the top.
And some of this stuff comes by air.
Have you seen how much dead space there is in there in mail packages?
Filled with air bags, bubble wrap or screwed up thick paper.
Back of the envelope calculations make that 150 m^3 giving 15 tons for 100 Kg/m^3 conservative. If half of that is above middle level, the lorry would not be easy around the bends or high winds.
Right - it usually takes about 3 weeks to arrive.
Agreed, as long as that put the CoG higher than 'usual' etc. ;-)
Why would the GoG of a load impact the sensitivity to 'high winds' (within reason)?
Cheers, T i m
A good question since the force of the wind is just the area of the high side. However, if height of COG is raised, then it becomes more difficult to react or compensate to sideway forces; the lorry becomes less stable, and the wind can easier push it over.
Goes through customs. But I've had some come faster than that, and I've definitely had some with air freight markings on the packaging.
I think it may depend on the type of wind the lorry is experiencing. eg, If it's a continuous crosswind then it wouldn't matter where the CoG was as long as it stayed within the wheelbase.
If it was gusty then a high CoG might be better from a 'resisting the gusts' POV as it would offer a greater resistance to the turning moment (assuming it didn't become dynamically unstable whilst being driven etc).
Cheers, T i m
I was helping a neighbour a while back with a question which might help. See Qn 6 on page 8 in
Coincidence eh. ;-)
However, I'm not sure that it covers the particular dynamics we are talking about here?
eg, If we are talking of a constant side load then a lower CoG would probably be safer as it would keep the CoG within the wheelbase longer, should the vehicle start to tip (although it would probably be too late by then ITRW).
My thought was that if it was gusty, then a higher CoG might act a bit like a damper because it would increase the torque required to make the lorry tilt in the first place (as a function of the speed / interval of the gusts etc).
Cheers, T i m
I approve of scepticism; and don't care anywhere near enough to ask for a sworn statement to be sent from Ghana :)
Other things being equal a higher CoG makes a lorry less stable because it cannot tilt as far before the CoG passes the pivot. That's where I thought the diagram in the exam paper might help.
Of course other things are not equal with a lorry in a cross wind - eg because the area presented to the crosswind increases as the lorry tilts.
[Oops. Apologies for premature wotsit. I blame the call to booze. Was meant to continue with]
So far I think we are at one.
Where I think we differ is the effect of the CoG on the torque. The weight of the lorry acts downwards through the CoG. That gives the same torque (weight x 1/2 the track width) no matter how high the CoG. Looking again at the diagram in the exam paper, the force acts down through G; and there was no need to show how high the CoG was when asking what force was required to tilt the lorry.
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