Initially one, now two class 90s are now on hire to cover for 91 non-availability, they seem to be going through a program of works visits for overhaul at present.
The 90s are limited to the shorter distance stopping services to Newark / Leeds to limit effects on timekeeping making use of there better acceleration.
Also, only Kings X drivers have been trained to operate them, which effectively limits there operation to that anyway. Although KX crews do work as far as Newcastle, they'd be unlikely to be working the same set back, and there's very few Newcastle terminators now anyway, with no-one to work them further north.
Comparisons between the 91s and other traction are interesting, although they appear slow when observed starting away, once they do (eventually) get going they're certainly not the sloaths generally imagined. Two points to bear in mind, firstly as mentioned, as they're geared for high speed running tractive effort at low speed needs to be limited. it's rather like starting your car in second or third gear. Secondly, with all traction, particularly diesels, acceleration tails off markedly as maximum speed is approached, the 91 however is designed for a 140 mph maximum, so approaching the max permitted 125, the 91's still not approaching it's maximum and wants to keep going - acceleration's still high.
91 v HST; leaving Darlington southbound (virtually unrestricted) an HSTs much quicker starting off, the 91 very slow starting then not really getting going till about 60. The HST will take virtually to Northallerton to reach 125 though, the 91 will do so around Cowton (roughly half-way). The 91 can then stop at Northallerton, make it's lethargic start, and still pass Thirsk at 125!
91 v Voyager; again the Voyager appears to be faster accelerating. You'll often see them leaving York Northbound immediately ahead of a 91, which has to wait till it's cleared the first section (past Siemens depot) before dispatch can commence, so by time it's ready to leave and makes it's labourious start, it's usually on a green, which makes the voyager around Skelton Bridge, well clear of the 60 restriction and accelerating into the distance while the 91s making it's slow start. Once the 91s clear of Skelton and getting into it's stride though, the gap reduces to the extent that if the voyager's one that stops at Northallerton, the 91s standing at the signal behind it.
91 v 185; the TPE 185 units again have a rapid initial acceleration. As a Southbound 91 receives 'ready to start' at York, a 185 passes leaving from an adjacent platform, rapidly up to the permitted 30, then is clear of Holgate and the restriction as the 91 just starting off and accelerating into the distance as the 91 gets going... as the parallel Main and Leeds lines diverge at Colton Jn, the 185's being passed with the 91 up to 110
On the question above about Grantham to Newark, remember it's also downhill all the way from Peascliffe
Also the 185 can’t accelerate straight away on the Leeds lines having to traverse point work. 90 mph starts soon after Holgate Jct on the up main.
Class 90 on the ECML
in UK Prototype Questions
Posted
Also the 185 can’t accelerate straight away on the Leeds lines having to traverse point work. 90 mph starts soon after Holgate Jct on the up main.