craigybagel
Established Member
- Joined
- 25 Oct 2012
- Messages
- 5,820
I can't speak for other drivers here, but I know my own driving style very much depends on the circumstances. Give me a 75mph unit on a 100mph diagram, or a big delay along the route, and I'm going to get to full power from a standing start a lot quicker than if we're on time. I'll still work through the notches as per our PDP, but what will change is how long I dwell in each notch.
Meanwhile if we're running on time, I'll shut off earlier, brake more gently, in some cases not even use full power between two stations. It all comes down to learning your route and your traction and working out what you need to do at any given time
I did hear talk that the London Overground 172s originally had the top gear locked out as they never went fast enough to need it, might it be that that's causing confusion? I would assume that's been rectified now they're regularly doing 90mph + at WMR.
Meanwhile if we're running on time, I'll shut off earlier, brake more gently, in some cases not even use full power between two stations. It all comes down to learning your route and your traction and working out what you need to do at any given time
I take it the loco was leading? Keeping it smooth with the loco pushing is a bit more of a challenge. In either direction it's never likely to be as good as it is with a 91 on the back, as it's relying on the emergency chain coupling and not the buckeye.I was impressed recently how smooth the 67 hauled 'Gerallt' service I took in north Wales was, I was expecting something a lot 'joltier'
No negative comment on drivers intended!!
The 16x suffer from the Perkins issue of not moving until notch 5 - I always get paranoid about what people must think of my driving style in a Perkins 158 going to such high revs so quickly, but often it's necessary!On 16x there’s a delay in power delivery, as with 15x, although 15x have far more lower down torque. As far as I’m aware, if you notch up straight to 7 in a 16x, the revs are restricted initially to notch 5 (only for a few seconds). Not sure if that’s what you’re alluding to?
The 172s and 195s definitely have 6 audible stages in the transmission (in that it sounds like it's working through 6 different gears).Seems to be that (dependant on throttle setting), the torque converter operates up to ~15mph, then into first gear
1800rpm, which is lower than some hydraulic DMUs, which go to 2100/2350rpm.
I read that somewhere they don't use the top gear.
But I decided to read in more detail.
On reading the spec I found out that the transmission ZF 5HP902R, is a five-speed gearbox with torque converter and integrated braking retarder. The first digit in ZF transmission description codes is the number of gears, the R on the end means Retarder fitted.
So, either the design has more gears but for this application the sixth is locked out OR "six-speed" includes the torque converter as a "speed" and there is no sixth gear.
I did hear talk that the London Overground 172s originally had the top gear locked out as they never went fast enough to need it, might it be that that's causing confusion? I would assume that's been rectified now they're regularly doing 90mph + at WMR.