Buckstones:
Assuming a coefficient of friction between tyres and road of 1.0 and highly efficient brakes, the best deceleration (without hitting something) is 1g, which applies the same force rearward as gravity does downward. No, acceleration is measured in metres per second per second. Deceleration is measured the same way, but with a negative value. The force an object (person ) feels is also relative to their mass. This is why racing drivers and fighter pilots feel such high negative g’s during maneuvers. There is of course a limit to the ground force that a human body can withstand.
This suggests a 10 ton object will exert 10 tons of force forward and any restraint has to be strong enough to hold that object up in the air - same effect as the trailer being tilted up to a vertical position.Assuming a deceleration of 10ms^2, spot on.
( Friction between the object and the surface its sitting on helps, and if there is a fixed bolster in front, it may not slide but will tend to tip with the bolster as a pivot if its centre of gravity is above that level.) Friction (and resistance of the fluid the object is in) are all opposing forces, but fairly insignificant when the masses become large as in this case. Lever theory, spot on.
I may have missed something here, if so, please correct me.
On further thought, Juddian commented that hard stops from a low speed tend to give a more severe retardation: this sounds correct, at high speed slamming brakes on can lock wheels, tyres will slide, blue smoke and heated rubber, less friction than from 10 mph when grip is nearer to static than sliding.
Formula One cars can stop at 4 or 5 g at 150 mph because the aerodynamics force the car down as if it was 4 or 5 times its actual weight, but the mass to ■■■■■■ is unaffected.
Dimlaith:
Carryfast, a ratchet strap is designed for a specific use,i.e. to secure a load. A bolt is designed for a specific use also. The two are totally sperate things as I think you well know.
A lump of steel weighing as much if not more than the truck,isn’t the same thing as tying down a couple of 1 tonne,probably less,pallets or stillages etc etc.
So tell us what’s the big difference in securing the body of the truck to its chassis. As opposed to securing a lump of steel weighing more than the truck,to the body ? and would you consider webbing strapping good enough for the former and if not then why is it good enough for the latter ?.
Has anyone thought about emailing Hawkins for his theory, we’re drivers not rocket scientists.
A ratchet and strap are designed to secure a load within its SWL as long as they are serviceable and free from wear and tear, including frays and nicks, and they are anchored correctly to the trailer bed using the sunken D rings or the fixed anchor points under the trailer bed, and not using the edge of the trailer ( as many drivers do because they can’t be arsed ), packing must be used on edges that may cause damage to the strap during transit.
Just because several straps are used does not increase a straps breaking strain, once an object regardless of weight has move slightly through excessive acceleration and breaking, the straps become redundant.
In France and Germany it is illegal to use any strap or ratchet which they deem as unserviceable, to fix a strap to a point on a trailer which is not an anchor point, to use insufficient straps.
Buckstones:
This suggests a 10 ton object will exert 10 tons of force forward and any restraint has to be strong enough to hold that object up in the air - same effect as the trailer being tilted up to a vertical position.
Which just goes to show i remember bugger all from Physics, sorry Mr Braithwaite, for i would have expected a 10 ton weight to have exerted far higher relative weight during a rapid stop.
Back to school
This is all assuming that the acedemics haven’t missed something.Such as the question is it really correct to base the load security factor on the relative speeds between the load and carrying vehicle.Or is it the energy contained in a 10t load moving at whatever speed relative to the outside world.In which case that calculation of a 10 t load dangling on a piece of string would seem a bit silly.
It probably also explains why they use something a bit more than webbing straps to hold the axles,body,and engine to the chassis.IE you apply the brakes you’d better hope that the axles and the body are tied on with something better than just something which can take a 1 g static tensile uni directional loading.
The axles, body engine and every thing else is a totally different thing to a dead weight though. Totally different forces at play, the axles hold the wheels which in turn holds the tyres, which hold the whole lot up with nothing more than air pressure. Your points are irrelevant to load security.
Dimlaith:
The axles, body engine and every thing else is a totally different thing to a dead weight though. Totally different forces at play, the axles hold the wheels which in turn holds the tyres, which hold the whole lot up with nothing more than air pressure. Your points are irrelevant to load security.
The body to chassis securing requirement is a fair comparison in having the same types of lateral,vertical and shear forces acting on it as the load to the body securing.Especially when it’s a single unit load weighing as much if not more than the truck.In which case as I said no one would dream of using ratchet straps to secure the body to the chassis so why is it suddenly ok when attaching a big lump of steel to the body.
Most of what’s been said seems correct to me. Some things don’t seem quite right. Here’s my takes on it. I’ll use some words that would give my old physics teachers apoplexy but I trust it’ll be acceptable to you all.
Given a flat level road and a flat level vehicle load bed and no suspension. No collisions
The maximum force is going to be about 1g under braking. A load placed on a bed with no bolsters and not against a headboard can be restrained by straps or whatever around the front and by friction between the load and the bed.
By using rubber or similar mats the coefficient of friction can be increased, similarly we put steel on timber bearers between layers as this has more friction/grip than steel-on-steel.
If we had a ten ton block of steel sat on the middle of our flat trailer there may be a coefficient of friction (greek letter mu ų) about 0.5? So to stop it we need a (normal reaction) force of 20 tons forcing it onto the bed. Putting straps or chains over it and tightening those straps will force it down. It’s not just the breaking strain of those straps that’s important, but how tight they are.
Remembering the lump ‘weighs’ 10 tons we need our straps to bear down with 10 tons so the lump presses 20 tons onto the bed.
This would give enough friction to stop the lump in an emergency stop.
In the real world that isn’t the best option. Bolsters, strong headboards etc are better alternatives, as are straps etc sround the front of our lump.
As we all know from carrying sloppily loaded steel timber etc any gaps between different items will soon close up and straps will need re tightening.
And to address Carryfast’s point, we only need to consider the motion (or hopefully lack of it) of the load relative to the vehicle bed. Given we’re all travelling at 30 kilometres every second relative to the sun we’d need a lot more than a few straps to secure anything.
Another note the static coefficient of friction is greater than the dynamic c of f so it’s easier to stop something from moving than restrain it
Once it has started off. Notice how it’s hard to get something sliding, but its easier once it starts? That’s why.
Put a nicely angled semi trailer under your load and that’s a bonus.
Personally- I wouldn’t be happy with that.
Worse case scenario, kid runs out in front of you, you stand on the brakes, that lot is off toward the unit.
In an ideal world, its going nowhere but in the event of a sudden stop, I wouldn’t trust those straps!
If those coils are 10 ton each, how much force do they have at 40 MPH? A lot more than 10 ton.
Dimlaith:
The axles, body engine and every thing else is a totally different thing to a dead weight though. Totally different forces at play, the axles hold the wheels which in turn holds the tyres, which hold the whole lot up with nothing more than air pressure. Your points are irrelevant to load security.
The body to chassis securing requirement is a fair comparison in having the same types of lateral,vertical and shear forces acting on it as the load to the body securing.Especially when it’s a single unit load weighing as much if not more than the truck.In which case as I said no one would dream of using ratchet straps to secure the body to the chassis so why is it suddenly ok when attaching a big lump of steel to the body.
The body has ben engineered to carry a load, the restraints have been designed to secure a load to the body. The body has to bear its own weight as well as the load. The thread is basically about securing a top hat coil, you seem to be going of on a tangent and it is not relevant. I just don’t see your point at all sorry.
Why is it not acceptable to lash down a piece of plant on a flat like a 10-ton excavator with rachet straps yet it is with a 10 or 20 ton steel coil??
The reason is that there’s a chance that the straps will snap.
So whats the bloody difference with a steel coil load??
You couldn’t make this ■■■■■ up!!
Franglais:
Most of what’s been said seems correct to me. Some things don’t seem quite right. Here’s my takes on it. I’ll use some words that would give my old physics teachers apoplexy but I trust it’ll be acceptable to you all.
Given a flat level road and a flat level vehicle load bed and no suspension. No collisions
The maximum force is going to be about 1g under braking. A load placed on a bed with no bolsters and not against a headboard can be restrained by straps or whatever around the front and by friction between the load and the bed.
By using rubber or similar mats the coefficient of friction can be increased, similarly we put steel on timber bearers between layers as this has more friction/grip than steel-on-steel.
If we had a ten ton block of steel sat on the middle of our flat trailer there may be a coefficient of friction (greek letter mu ų) about 0.5? So to stop it we need a (normal reaction) force of 20 tons forcing it onto the bed. Putting straps or chains over it and tightening those straps will force it down. It’s not just the breaking strain of those straps that’s important, but how tight they are.
Remembering the lump ‘weighs’ 10 tons we need our straps to bear down with 10 tons so the lump presses 20 tons onto the bed.
This would give enough friction to stop the lump in an emergency stop.
In the real world that isn’t the best option. Bolsters, strong headboards etc are better alternatives, as are straps etc sround the front of our lump.
As we all know from carrying sloppily loaded steel timber etc any gaps between different items will soon close up and straps will need re tightening.
And to address Carryfast’s point, we only need to consider the motion (or hopefully lack of it) of the load relative to the vehicle bed. Given we’re all travelling at 30 kilometres every second relative to the sun we’d need a lot more than a few straps to secure anything.
Another note the static coefficient of friction is greater than the dynamic c of f so it’s easier to stop something from moving than restrain it
Once it has started off. Notice how it’s hard to get something sliding, but its easier once it starts? That’s why.
Put a nicely angled semi trailer under your load and that’s a bonus.
The issue in contention is the question of the kinetic energy contained in a big lump of metal based on its speed relative to planet Earth,not the vehicle that’s carrying it,being a large factor.In which case co efficient of friction v the load bed won’t cut it.Nor possibly will the resistance,to all the possible potential resulting forces,of ratchet straps.Which,as I said,is why we don’t generally secure the load bed to the chassis,or for that matter loaded containers,with ratchet straps.
It’s clear in this case that the load security of coils has a massive question mark over it in the case of anything other than ideally being carried in a well or at least the shotgun/axial configuration and secured by chains in all cases.
Gembo:
Why is it not acceptable to lash down a piece of plant on a flat like a 10-ton excavator with rachet straps yet it is with a 10 or 20 ton steel coil??
The reason is that there’s a chance that the straps will snap.
So whats the bloody difference with a steel coil load??
You couldn’t make this [zb] up!!
I have no idea, TATA wants it done this way, with anti slip matting after losing a coil or two. They probably spent a fair bit of money on this. I would rather put my trust in the way they want the coil strapped than in the advice of some on here. I would also feel more comfortable carrying a coil strapped that way than 24 pallets of cans of beer with nothing other than a few internals stopping the forward motion in an emergency. Can’t see what ■■■■ is being made up.
Gembo:
If those coils are 10 ton each, how much force do they have at 40 MPH? A lot more than 10 ton.
^ This is the question in contention.The scientists seem to think that it’s all about the relative speed between the load and truck.According to them so long as that relative speed is kept to zero then all they need to do is apply an opposite 1g pull,or even less with a bit more friction against the load bed,to cancel out all of the kinetic energy contained within the 40 mph load which sounds like bollox to me.That’s even without factoring in any potential shear loadings against the straps by the load. IE their whole case is that a 10t + lump of metal travelling at 40 mph contains no kinetic energy at all,so long as it’s supposedly stopped from moving relative to the load bed,by supposedly applying an opposing pull equal to its static gravitational weight. Which seems to defy all the laws of kinetics to me.
This was NOT a Tata load… so therefore there’s no actual load security specs in place at point of loading…
Secondly, Kay Transport does have a comprehensive training programme, so the drivers aren’t sent out in complete ignorance… However, training only works if the driver uses it… I’m not saying this guy didn’t do as he’d been trained on this occasion but…you can lead a horse to water etc etc etc…
Buckstones:
Assuming a coefficient of friction between tyres and road of 1.0 and highly efficient brakes, the best deceleration (without hitting something) is 1g, which applies the same force rearward as gravity does downward. No, acceleration is measured in metres per second per second. Deceleration is measured the same way, but with a negative value. The force an object (person ) feels is also relative to their mass. This is why racing drivers and fighter pilots feel such high negative g’s during maneuvers. There is of course a limit to the ground force that a human body can withstand.
This suggests a 10 ton object will exert 10 tons of force forward and any restraint has to be strong enough to hold that object up in the air - same effect as the trailer being tilted up to a vertical position.Assuming a deceleration of 10ms^2, spot on.
( Friction between the object and the surface its sitting on helps, and if there is a fixed bolster in front, it may not slide but will tend to tip with the bolster as a pivot if its centre of gravity is above that level.) Friction (and resistance of the fluid the object is in) are all opposing forces, but fairly insignificant when the masses become large as in this case. Lever theory, spot on.
I may have missed something here, if so, please correct me.
On further thought, Juddian commented that hard stops from a low speed tend to give a more severe retardation: this sounds correct, at high speed slamming brakes on can lock wheels, tyres will slide, blue smoke and heated rubber, less friction than from 10 mph when grip is nearer to static than sliding.
Without doing the math, my gut instinct is that that is correct. A slower deceleration caused by skidding (or any other reason, like considerate driving!!) will reduce the forces acting on the load.
Formula One cars can stop at 4 or 5 g at 150 mph because the aerodynamics force the car down as if it was 4 or 5 times its actual weight, but the mass to ■■■■■■ is unaffected.
I did read up on the theory that the downforce created by F1 cars can reach several tonne, that should be enough for the vehicle to be driven (once a sufficient speed has been reached) upside down. On a side note, for a science project I did an accident report into Ayrton Senna’s death. The conclusion I reached was that his vehicle bottomed out. Ideally, the closer to the ground you get, the greater down force you can create. However, touching the ground makes that down force instantly disappear. Once that happens, you may as well be driving on ice. IIRC, he would have actually survived if he hadn’t been struck on the head by debris.
Assuming this coil weighs 10t and considering the distance it’s travelled along the trailer bed, the driver must have slammed on pretty hard for it to move that distance, but even so it can’t have travelled more than 2 metres from the headboard, as 10t against the headboard would make the unit and trailer over weight on the pin even with a 6x2
Gembo:
If those coils are 10 ton each, how much force do they have at 40 MPH? A lot more than 10 ton.
^ This is the question in contention.The scientists seem to think that it’s all about the relative speed between the load and truck.According to them so long as that relative speed is kept to zero then all they need to do is apply an opposite 1g pull,or even less with a bit more friction against the load bed,to cancel out all of the kinetic energy contained within the 40 mph load which sounds like bollox to me.That’s even without factoring in any potential shear loadings against the straps by the load. IE their whole case is that a 10t + lump of metal travelling at 40 mph contains no kinetic energy at all,so long as it’s supposedly stopped from moving relative to the load bed,by supposedly applying an opposing pull equal to its static gravitational weight. Which seems to defy all the laws of kinetics to me.
The laws of kinetics simply say Energy = Mass x (Velocity squared) divided by 2, Momentum (not Corbyn’s mates)
= Mass x Velocity.
These apply to the entire vehicle and its load, the issue of restraining the load (as for passengers with seatbelts) is purely what force is necessary to keep the load in place under a deceleration of the whole vehicle.
I never said the load had no kinetic energy, I used Newton’s Law of Force = Mass x Acceleration, from which one g of deceleration or acceleration will cause a mass to exert a force equal to its weight.
That is why you weigh what you do, and astronauts weigh nothing.
This is certainly one of the most interesting,informative and relevant threads on here for a long time. I joined this site 15 years ago (under a different user name) as a newbie and this was the sort of stuff the helped me learn the ropes. Without the likes of Wiretwister and Zzarbean I wouldn’t have learnt how to tie a dolly knot. I learnt by asking those who have done the job far longer than I have been breathing, I still learn by asking and can hopefully help those that ask me.
Gembo:
If those coils are 10 ton each, how much force do they have at 40 MPH? A lot more than 10 ton.
^ This is the question in contention.The scientists seem to think that it’s all about the relative speed between the load and truck.According to them so long as that relative speed is kept to zero then all they need to do is apply an opposite 1g pull,or even less with a bit more friction against the load bed,to cancel out all of the kinetic energy contained within the 40 mph load which sounds like bollox to me.That’s even without factoring in any potential shear loadings against the straps by the load. IE their whole case is that a 10t + lump of metal travelling at 40 mph contains no kinetic energy at all,so long as it’s supposedly stopped from moving relative to the load bed,by supposedly applying an opposing pull equal to its static gravitational weight. Which seems to defy all the laws of kinetics to me.
The laws of kinetics simply say Energy = Mass x (Velocity squared) divided by 2, Momentum (not Corbyn’s mates)
= Mass x Velocity.
These apply to the entire vehicle and its load, the issue of restraining the load (as for passengers with seatbelts) is purely what force is necessary to keep the load in place under a deceleration of the whole vehicle.
I never said the load had no kinetic energy, I used Newton’s Law of Force = Mass x Acceleration, from which one g of deceleration or acceleration will cause a mass to exert a force equal to its weight.
That is why you weigh what you do, and astronauts weigh nothing.
Great so we put a 10t + steel coil in the cargo hold of the space station with no straps on it at all then we reduce orbital velocity for a lower orbit and the thing will just stay there and not punch its way through the side because it weighs nothing ?.
Or we fire an 88 mm anti tank shell at the armour of a Sherman it will just stop and fall to the floor and do no damage when it hits the side because at that point it’s lost its velocity and is travelling at the same speed as the tank.As opposed to the laws of kinetics in which both the mass and the velocity subject the formula are exchanged for energy which just smashes and/or melts the armour.
On that note if you agree the 10t + load retains its kinetic energy,that being 40 mph’s worth in the case of the truck load and anyone’s guess in the case of the space station.How can you then only rate the load security based on 1 g of deceleration only supposedly exerting a force on anything in its way that’s only equal to its static weight.
When surely at least some of the formula should be based on the laws of kinetics and inertia.
On that note I’d guess that a race car 4 way safety belt system and anchorages or for that matter even a standard car system has a lot more strength than just that needed to suspend the static weight of a person above the floor ?.
IE their whole case is that a 10t + lump of metal travelling at 40 mph contains no kinetic energy at all,so long as it’s supposedly stopped from moving relative to the load bed,by supposedly applying an opposing pull equal to its static gravitational weight. 
Which seems to defy all the laws of kinetics to me.