Class 91

[badger1badger]

A technical question - when the London trains are about to set off the fans start then a second later there is a short blast of compressed air can anyone tell me what this is for ?
Cheers
Paul

 

[rail-britain]

First set of fans are to cool the traction motors
The second noise is to release the brakes

 

[networkrail1]

Do you mean like this.

http://www.youtube.com/watch?v=b9y9P2fAp3g

0:13 door interlock engages.
0:25 driver puts reverser into forward and takes power. (start up)
0:37 driver releases brakes and off he goes.

All the best.

Simon

 

[Eng274]

this may seem a dim question, but when a loco like the 91 is at rest, what is the humming, almost crackling noise, would that be the transformer? its a common thing ive noticed on other AC locos like 86s, 90s etc.

 

[TGV]

Can't speak for other traction but on our trains (373), the main noise is the transformer cooling fans in harmony (!) with the traction motor blowers. When stationary, you'll hear the hum of the transformer with the quieter sound of aux inverter cooling fans. When it starts off, there is the staggered spooling up of oil pumps and the aforementioned cooling fans and blowers.