Wow that’s pretty wild then! I had heard one of the Mach DI’s who did their training down in Cardiff say that they were told “this is where you’d go into emergency on a 150 to stop, but don’t brake yet” might have even said the same about the 175 but I can’t quite remember now!
I use the same braking points for 75mph in a 150/153 as from 90 in a 175/197. There's a lot to be said for disk brakes/engine brakes over brake blocks!
I have heard it takes a bit of getting used to the brakes on them and they’re a bit more tricky than units!
I didn’t know that they didn’t have light loco speed restrictions though!
67, 68 and 88 are all exempt - as far as I know they're the only ones.
Surprising as I would have guessed 197’s beat them like that but I suppose once you’ve got all that mass going, there’s a lot of power available to keep it going !
Also electric transmissions can put full power down over a wide speed range once moving, something I doubt the mechanical transmissions of the 197 can do despite having 5 ratios?
Yes I would assume that once you have enough speed to sufficiently reduce the back EMF in the motors and therefore reduce the current draw then you can pretty much apply full power and you continuously have ‘full power’ actually applied to the motors as opposed to a mechanical gearbox, as you say in the 197’s case it is a ZF 5 speed gear box which is much more like a car where you would take full power but the revs increase and drop as the gears change meaning you’re not always getting ‘full power’ applied.
With an electric motor as well, power peaks around 50% of its rated RPM whilst its efficiency is highest at around 90% RPM. The diesel engine can also run at a constant speed if full power is applied unlike with the mechanical gear box.
All in all, does make a lot of sense !
The climb to Llanvihangel being a case in point. Their mid range acceleration is pretty good. I recall an early run on one from Reading to Paddington with 12 mark 1s. Start to stop was 25 minutes, very similar to HSTs at the time.
197s acceleration at a low speed is fantastic, but that tails off as you go through the gears. Having multiple gears is a big improvement over the previous 2 stage transmissions on the older DMUs for hill climbing.
Going up Llanviihangel, a 150/153 will normally clear the summit at around 55, a 158 58, a 175 63, a 197 somewhere between 68 or 76 depending on which power mode is selected, and a 67 around 73. The difference is the 197 will get up to that speed fairly quickly, then the acceleration will fall off a cliff in top gear. The 67 will take a while to get going, but when it does it'll keep on accelerating relentlessly.
Traction motor fault on 67012. 1 Traction motor now isolated to allow it to remain in service.
Says a lot for 67s that they can still stay pretty close to time even on 75% power.
Didn't know that Holyhead drivers work all the way to Swansea!
They don't. Only Cardiff crews work 67 services between there and Swansea.