Watch as cars struggle to get up an icy Saltburn Bank in Saltburn by the Sea near Middlesbrough, UK. Then the Arriva bus just sails up the bank. Travel by bus, it's the safest way!
(thanks Cora)
5
comment(s):
Anonymous
said...
The bus has the advantage of several tons over the driven wheels. The cars do not.
The bus driver has probably also been trained not to use first gear on snow and ice, you can see that the driver of the Clio doesn't know that.
I'm not sure that weighing something like 8 tons would be an advantage coming back down the hill.
Whilst it's often advantageous to use a higher gear on snow and ice, it's unlikely that a clio could ascend Saltburn bank in second gear at a speed low enough to retain control on ice. More low rpm torque would be one of the bus's advantages too. Many modern cars fail to develop any power at low revs. I used to drive a landrover with a very low revving Perkins 4203 engine in it. In its lowest gear, with the Perkins at tickover, maybe 500 rpm it would climb anything. It would do an icy saltburn bank at snail's pace, providing it had decent tyres.
@soubriquet - torque is largely irrelevant. Simply because you are looking, by choosing a higher gear, to reduce the torque at the wheels for a given engine speed. The higher the gear the lower the torque. The reason you choose a higher gear in snow is to actually reduce the chance of torque overcoming what little traction you have.
A lot of people know to choose a higher gear, they just don't know why.
That being said with modern electronic engine control systems fueling and ignition is often so accurately controlled that it's often possible to use first gear. The trick is not to touch the throttle, but to gently engage the clutch and the ECU will keep you just above a stall. Works quite nicely as long as your clutch control is delicate.
If, however, I could choose any car to drive in snow it would be a Saab 96 V4. Never have I driven a better snow car.
You use a higher gear to reduce the torque at the wheels, that's true, since the effect of engine speed-changes to torque at the wheels is more abrupt in lower gears, more steadily spread in higher ones. We need to keep the force at the contact point between rubber and ice to a level where friction keeps the wheel from slipping and the car moving along. That can be achieved with forward momentum and a light torque on the level. But more energy is required when in addition to driving the car along, we are also trying to lift it as we climb the bank. We can get that power by accelerating, but if we do, the forces acting on that contact patch may overcome the friction available. A certain amount of power is required to move the car along, and on a level or downhill surface, the torque available at low engine revs in a higher gear will be sufficient. However, greater force is needed to do the extra work of ascending a gradient. Normally we would do it at a speed where the engine is in a useful power (or torque) range. However, I believe that in second or higher, the clio would be going too fast to keep a grip on the icy bends, and if slowed down would produce so little torque that the engine would be stalled by the gradient. Which is why my preference is for a bigger engine with a good low speed torque, running slowly.
I agree with you about the V4, it has a very smooth power delivery, and 've always had a soft spot for those earlier Saabs. I once drove a Saab 93, 2-stroke, 3 cylinder, 3 carburettor, from Oviken in Sweden to Trondheim in Norway, then up to Tromso in the Norwegian arctic, down the swedish/finnish border to Tornio, and back to Ostersund. It was early winter and the sound of a deranged lawnmower engine in the front, and the trailing cloud of blue 2-stroke smoke for close-on 1700 kilometres made for a fairly memorable journey. The car went flawlessly on packed snow and ice with steep climbs on mountain roads. But I also had a new set of Nokia Hakkapeliitta studded tyres.
I spent most of the nineteen-eighties in scandinavia, driving many thousands of miles on snow, ice, frozen lakes and many miles on the baltic sea. (Including ice-racing a Saab 99).
Wow, lots of tech talk about gears and torque. I've driven tractor-trailer/"semis" in snow and ice for 30 years. what matters most is friction with the road surface and inertia. From what I saw on the video (which was pretty boring I think) was that the bus kept it's inertia by not stopping or slowing down too much...Newton's First Law of Motion.
5 comment(s):
The bus has the advantage of several tons over the driven wheels. The cars do not.
The bus driver has probably also been trained not to use first gear on snow and ice, you can see that the driver of the Clio doesn't know that.
I'm not sure that weighing something like 8 tons would be an advantage coming back down the hill.
Whilst it's often advantageous to use a higher gear on snow and ice, it's unlikely that a clio could ascend Saltburn bank in second gear at a speed low enough to retain control on ice.
More low rpm torque would be one of the bus's advantages too. Many modern cars fail to develop any power at low revs. I used to drive a landrover with a very low revving Perkins 4203 engine in it. In its lowest gear, with the Perkins at tickover, maybe 500 rpm it would climb anything. It would do an icy saltburn bank at snail's pace, providing it had decent tyres.
@soubriquet - torque is largely irrelevant. Simply because you are looking, by choosing a higher gear, to reduce the torque at the wheels for a given engine speed. The higher the gear the lower the torque. The reason you choose a higher gear in snow is to actually reduce the chance of torque overcoming what little traction you have.
A lot of people know to choose a higher gear, they just don't know why.
That being said with modern electronic engine control systems fueling and ignition is often so accurately controlled that it's often possible to use first gear. The trick is not to touch the throttle, but to gently engage the clutch and the ECU will keep you just above a stall. Works quite nicely as long as your clutch control is delicate.
If, however, I could choose any car to drive in snow it would be a Saab 96 V4. Never have I driven a better snow car.
You use a higher gear to reduce the torque at the wheels, that's true, since the effect of engine speed-changes to torque at the wheels is more abrupt in lower gears, more steadily spread in higher ones. We need to keep the force at the contact point between rubber and ice to a level where friction keeps the wheel from slipping and the car moving along. That can be achieved with forward momentum and a light torque on the level. But more energy is required when in addition to driving the car along, we are also trying to lift it as we climb the bank. We can get that power by accelerating, but if we do, the forces acting on that contact patch may overcome the friction available.
A certain amount of power is required to move the car along, and on a level or downhill surface, the torque available at low engine revs in a higher gear will be sufficient. However, greater force is needed to do the extra work of ascending a gradient. Normally we would do it at a speed where the engine is in a useful power (or torque) range.
However, I believe that in second or higher, the clio would be going too fast to keep a grip on the icy bends, and if slowed down would produce so little torque that the engine would be stalled by the gradient.
Which is why my preference is for a bigger engine with a good low speed torque, running slowly.
I agree with you about the V4, it has a very smooth power delivery, and 've always had a soft spot for those earlier Saabs. I once drove a Saab 93, 2-stroke, 3 cylinder, 3 carburettor, from Oviken in Sweden to Trondheim in Norway, then up to Tromso in the Norwegian arctic, down the swedish/finnish border to Tornio, and back to Ostersund.
It was early winter and the sound of a deranged lawnmower engine in the front, and the trailing cloud of blue 2-stroke smoke for close-on 1700 kilometres made for a fairly memorable journey.
The car went flawlessly on packed snow and ice with steep climbs on mountain roads. But I also had a new set of Nokia Hakkapeliitta studded tyres.
I spent most of the nineteen-eighties in scandinavia, driving many thousands of miles on snow, ice, frozen lakes and many miles on the baltic sea. (Including ice-racing a Saab 99).
Wow, lots of tech talk about gears and torque.
I've driven tractor-trailer/"semis" in snow and ice for 30 years. what matters most is friction with the road surface and inertia. From what I saw on the video (which was pretty boring I think) was that the bus kept it's inertia by not stopping or slowing down too much...Newton's First Law of Motion.
Bill
Post a Comment