Railperf
Established Member
- Joined
- 30 Oct 2017
- Messages
- 2,944
Loco engines are massively detuned compared to a car engine. A HST engine for example at full power is only running at 1500rpm. Not sure what Class 47 engines max speed was.The engines would be practically cremated because, my friend:
The top speed on level track is 95mph. 10% overspeed - 104.5 mph. Engines are probably screaming hot.
117mph is a 23.5% overspeed of course the engines won't handle it that's over double the "intended" overspeed the loco was meant to handle
The engine is turning a generator shaft. The generator supplies electricity to the motors. Therefore whether you are running at 5mph or 95mph, the actual engine is running at the same maximum speed. The only difference is the higher back EMF from the traction motors and it is working against the current coming from the generator. That's why there is a balancing speed on level track. But downhill the balancing speed is higher due to the effects of gravity aiding the loco - despite increased aerodynamic resistance. Give the 47 a more aerodynamic pointed nose, and it would probably go faster than 117mph downhill.
At seriously high speeds the motors, wheel axles, wheel bearings and other equipment starts to move beyond design limits and are more likely to fail due to overheating and stresses. The engine and generator seem to be the least likely items to fail at higher than designed speeds.