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If you couple two trains together, does this double the maximum speed?
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DenmarkRail
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No, the speed is not doubled.
trainmania100
Established Member
Because the diesel engines or traction motors can only turn so fast...
Take a look at how a car engine works, the faster the wheels go, the faster the RPM on the engine. It wouldn't work without blowing up
Take a look at how a car engine works, the faster the wheels go, the faster the RPM on the engine. It wouldn't work without blowing up
DenmarkRail
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There are many issues... Weight being one, line speeds, and others.
EM2
Established Member
They're trying to move twice the mass.
As well as the physical limitations of what engines, gearboxes, motors etc. can do.
hexagon789
Veteran Member
No.
If you have two trains of say 250 tonnes, each with say 4,000hp you don't double the potential speed simply by doubling the power to 8,000hp as you now also have twice the weight to shift - 500 tonnes in my example.
Richard Scott
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Need to realise that doubling the speed means 4 times greater air resistance (as is kinetic energy) even doubling power of one train will not double its speed because of this.
JamesRowden
Established Member
Doubling the speed does indeed increase the force of air resistance by a factor of four, which means that the power of the air resistance increases by a factor of eight (since work done equals force times displacement, which differentiated by time makes power equal force times velocity, or in other words, output force equals output power divided by velocity).
Roy Badami
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If two runners hold hands, can they run twice as fast as either of them could run alone?
JamesRowden
Established Member
That's a different situation since the energy required to move legs back and forth is the factor which primarily limits how fast people can run (and is why cyclists have a greater top speed than runners). So holding hands provides no benefit.
However, one multiple unit being in the slipstream of another is a benefit at speeds at which air resistance is dominant. So a 5+5 class 800 will have a significantly greater high speed performance in diesel mode than a single 5 car 800 in diesel mode.
randyrippley
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My ex-wife used to borrow the neighbours collie dog when she went running ...........when she had hold of its lead she definitely went twice as fast.
Is there a record for a dog-assisted marathon?
No, because physics. I'm assuming you mean using two locos. It takes much more than twice the power to double speed. Also, adding a loco means adding the weight of that loco as well. Coupling two multiple units won't make much difference to speed because the power to weight ratio stays the same.
Class465fan
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@VAR_Appeal
nope doesn't quite work that way mate.
nope doesn't quite work that way mate.
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