Monica
💫 Summary
Trains struggle to move uphill due to the limited tractive force and grip on the tracks, while downhill poses the challenge of preventing runaway trains. The weight, tractive effort, and aerodynamic drag play a crucial role in determining a train's speed and ability to overcome gradients.
✨ Highlights📊 Transcript
Trains can go uphill, but they are not very efficient at it.
00:01
Human beings can climb gradients of around 80 degrees.
Cars can manage gradients of up to about 30 percent.
The steepest mainline gradient in Britain is 2.65 percent.
Trains struggle to find grip on a level piece of track due to the lack of friction and the narrow contact area between the wheels and the rails.
01:14
Trains produce very little friction because the wheels and rails are made of steel.
Train wheels are narrow and only a small part of them rests on the track.
The contact area between all the wheels and the track is about the same as two coins, explaining why trains struggle to find grip.
Trains are able to move uphill because the weight of the train presses the wheels down into the rails, creating grip.
02:29
The tractive force of the train has to overcome the weight of the train, friction, and aerodynamic drag.
The maximum speed of the train is reached when the aerodynamic drag is equal to the tractive force.
Weight is important for generating tractive effort, so a heavier locomotive can generate more effort than a lighter one.
Trains face problems going uphill due to the added drag from the gradient and weight, potentially causing the wheels to spin or the train to come to a halt.
03:46
The drag created by the weight of the train is increased by the gradient.
Powerful locomotives may experience wheel spinning, while weaker ones may grind to a halt.
Trains face an even bigger problem going downhill, as all the braking force is concentrated in a small area where the wheels meet the rails.
Steep inclines, heavy trains, or slippery rails can cause trains to run away downhill.
00:01hello and firstly my heartfelt thanks to
00:04all of those who have subscribed to head
00:07squeeze it really is genuinely very
00:10important to us it's also rather
00:12flattering and now why can't trains go
00:16up and Hills
00:17now the smarter ones amongst you will
00:19have recognized already especially if
00:21you're a qualified railway engineer this
00:23is a bit of a trick question because of
00:26course trains can go up hills they're
00:28just not very good at it
00:30which when you think about the
00:31topography of most of the world is
00:32clearly a bit of a problem human beings
00:35can admittedly rather sweat early
00:38motivate themselves up a gradient of
00:40around 80 degrees or one in one and a
00:43quarter you do it every time you climb
00:46the stairs cars can manage gradients of
00:49up to about thirty percent or one in
00:52three before their tyres start to lose
00:54grip or their gearboxes explode into
00:57oily shards but as only 1950 school
01:01board would tell you the steepest
01:02mainline gradient in Britain is the
01:05fearsome licky incline in Worcestershire
01:07that is a gradient of just two point six
01:11five percent or one in thirty seven and
01:14a half in the old money and yet that was
01:17considered so terrifying in the days of
01:19steam that a train would often have to
01:21be pushed from behind the banks to use
01:24the technical term by up to four other
01:26locomotives the problem is one of
01:29traction or rather tractive force
01:33because for all their size and immense
01:35weight trains really struggle to find
01:38grip on a level piece of track a train
01:41is a very efficient thing the wheels are
01:44made of steel and so are the rails if
01:47you rub two pieces of Steel together you
01:49will find they produce very little
01:51friction much less than you'd get
01:53between say a tire under road or even
01:57much less than you get between your
01:59finger and a piece of glass train wheels
02:02are also very narrow and profile in such
02:04a way that only a tiny part of them
02:06rests on the track if you take a typical
02:09twelve wheeled locomotive with a weight
02:11of a
02:12120 tonnes then the size of the contact
02:15area between all those wheels in the
02:17track is about the same as 250 pounds
02:20pieces which the people watching in
02:23countries outside Britain is two coins
02:25roughly so big which explains why trains
02:29are so good at slicing the hands and
02:31feets off distressed damsels who have
02:33been tied to the railway line by
02:35Edwardian ruffians it also explains why
02:37trains are able to move at all the
02:39entire weight of the Train presses the
02:41wheels down into the rails and create
02:44grip even though it's steel on slippery
02:48steel the tractive force has to overcome
02:50the weight of the Train friction and as
02:54it starts to go faster aerodynamic drag
02:56there comes a point where the
02:58aerodynamic drag has built to a point
03:00where it's equal to the tractive force
03:02and at that point the Train has reached
03:04its maximum speed because weight is so
03:08important to the generation of tractive
03:10effort it is possible that a fatter less
03:14powerful locomotive can generate more of
03:16it than a lighter but much brawny r-1
03:19the upshot of this is that on a nice
03:22straight level flat piece of track a
03:25train can reach a surprisingly high top
03:28speed despite a limited power output the
03:31Eurostar only generates something like
03:3322 brake horsepower per tonne or less
03:37than a small city car with five fat
03:39blokes and a month supply of pies on
03:41board and yet the Eurostar can do 200
03:44miles an hour the car will struggle to
03:46crack 70 partly because of the
03:49inefficiency and the drag created by its
03:52big rubber tyres but on hills which the
03:56car will crest gracefully probably in
03:58second gear then the train will run into
04:01problems because the gradient will add
04:04to the drag created by its weight but
04:07the tractive force remains the same if
04:11it's powerful locomotive it might well
04:13start spinning its wheels if it's a puny
04:15one it will probably just grind to a
04:18halt and then the guard will come on the
04:20Tam I blame the
04:22stoppage on operational difficulties or
04:24something like that but the net result
04:26is the same you miss you dinner but the
04:29trains Hills cause an even bigger
04:31problem which is how to get down them
04:34because then all the braking force is
04:36concentrated in that same tiny area
04:39where the wheels meet the rails and if
04:41it's a particularly steep incline or a
04:43particularly heavy train or even if the
04:46rails are very slippery then your train
04:48can run away so you know those excuses
04:51we've all mocked over the years mud on
04:54the line leaves on the line the wrong
04:56kind of snow it's all true actually
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FAQs about This YouTube Video

1. Why do trains struggle to move uphill?

Trains struggle to move uphill due to the limited tractive force and grip on the tracks. The weight of the train combined with the incline creates a challenging environment for locomotives to overcome.

2. What makes downhill movement challenging for trains?

Downhill poses the challenge of preventing runaway trains. The weight and momentum of the train, combined with the downward slope, require effective braking systems to ensure safe and controlled descent.

3. How do weight, tractive effort, and aerodynamic drag influence a train's speed?

The weight, tractive effort, and aerodynamic drag play a crucial role in determining a train's speed and ability to overcome gradients. A heavier train requires more tractive effort to achieve speed and combat resistance from aerodynamic drag.

4. What are the factors that determine a train's ability to overcome gradients?

A train's ability to overcome gradients is determined by factors such as the weight of the train, tractive effort, grip on the tracks, and the effectiveness of the locomotive's propulsion system. These factors collectively determine the train's ability to maintain speed while ascending or descending gradients.

5. How do trains optimize tractive force to overcome challenges?

Trains optimize tractive force through advanced locomotive designs, improved traction control systems, and the use of additional locomotives in challenging terrains. By maximizing tractive force, trains can effectively tackle uphill struggles and maintain control during downhill movement.

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