what has been modified on 47851 + maybe others?

[truckman060473]

I was at Cardiff on Saturday, where 47851 "Traction Magazine" was started up at the station for an ECS movement to Canton. There was no initial starter motor whine. It caught me out, by just quietly bursting into the classic Sulzer tick over. Even an MTU class 43 gives an audible starter motor noise as a warning it is about to fire up. The noise of 47851's exhaust also sounded quieter than I remember the class to be.

 

[Vulcan]

Don't they used compressed air to start the engine, and the electric starter motor only when theres no compressed air available? I'm sure I remember someone telling me this.

 

[truckman060473]

I'm looking at my phone camera video again and it is almost as if nothing happens. Hardly anything heard on fire up, and not even the usual plume of black smoke normally associated with a vintage loco

 

[Turbostar]

Yes, 47's start up more or less straight away. I've noticed this when they used to be on the XC & RES services from Plymouth. Can't explain why, obviously have a different way to starting compared to other classes of loco's. Have a look on YouTube as well, there's 47's starting up on there, & they do start up straight away. Someone with more tech knowledge on here will hopefully be able to explain why.

 

[mainframe444]

The class 47, like all generator fitted diesels, starts in the following way....
Battery on, direction selector to EO.
The triple pump then starts, this brings the oil pressure up, the water circulates, and diesel is pumped to the fuel racks on the engine.

Once this has happened, the start button is pressed. This uses the loco's generator as a motor to turn over the engine and start it. The engine will not turn over if the oil pressure is not high enough.

This is fairly quiet as it turns over, the noise only starts as the engine starts to fire.... and clag!!!

Later locos fitted with an alternator instead of a generator, and those modified to have a generator (refurb cl 37, e.g.) have starter motors fitted as an alternator cannot be used in this way.

Its possible that this one started relatively quick as the oil pressure was still fairly high in the engine following shutdown.

MainFrame