Except they reverse at Edinburgh so require a run round anyway.
No comment on the Class 93 thenI'm quite sure GBRf know exactly what flows they are going to be used on without rail enthusiasts trying to second guess.
The Class 90s are usually paired, albeit with a power limit on them. So that suggests that, yes, that output is a good idea on the 99s.
Can it haul an intermodal up Shap and Beattock at 75mph?
They have to run in pairs for Freightliner, a solo 90 won’t keep to timings. DBC, before they ceased using them, also used them in pairs. However it is worth mentioning that GBRf only seem to have one daily intermodal over Shap and Beattock.
But could win more contracts in the future
A maximum length 1800t intermodal going up a 1% gradient needs an 18t tractive effort = 180kN. At 10m/s (22mph) that requires 1.8MW of power. So a class 90 with 3.7MW could keep going at 44mph up a 1% grade. 66mph would require 5.4MW. The 6MW Class 99 should be able to get up the same slope at around 70-75mph.
No mid-high 60s is more realistic, your expectations of container train resistances at high speed are bit off and the gradients are steeper than 1%. Almost but not quiet as good as a pair of 90s.
Careful not to get TE and power conflated. The relationship between TE and power is not linear as TE is compromised by poor adhesion no matter what the power provided.
The pairing is presumably less about power than about adhesion.
However AC drives have better control so poor adhesion, whilst still an issue, will be less prominent with a 99.
I seem to recall there is also contingency if one 90 fails. Network Rail prefer double headed freight over Shap to reduce chances of a broken down train blocking the line
That only applies at low speeds. At the higher speeds, power becomes the limiting factor, and the tractive effort that the locomotive can deliver falls away so it will be much less than the limit of adhesion.
Isn't a pair of 90s in multi restricted to about 7500hp to reduce load on the power supply? Originally by isolating one traction motor on each, then electronically after Freightliner started routinely operating them in pairs.
0. Electrical engineers have not used horsepower for longer than I've been alive. Don't use hp and then you can't get confused by them!
There’s ‘prefer’ and ‘require’. I can’t see that any such ‘preference’ would have any influence anyway. If it’s not a documented policy it’s best filed under wibble.
A 92 has better traction equipment than a 90 and 2 more axles.
Effectively NR as it is the worst a supply should be able to support per train in the worst case and usually should be much better. The trains are then effectively limited to the infrastucture worst case (unlike modern 3rd rail units which adapt to power supply condition in various ways)
Route the sleeper via the sub at Edinburgh
How do the 88s perform? I've not seen much comment on them, but it would be relevant to the 93s and the 99s ...
Why does that make a difference?
Routing via the Sub would avoid a reversal. It would still need splitting into three though
Ok, doesn't solve the 1500V supply issue, though, so currently a non-starter anyway.
The 88s perform adequately on the Tescos but, when the adhesion’s low, they are double headed by another 88 or a 68. A 93 may be slightly more powerful but is higher geared so probably performs the same as an 88 on containers up Shap but a 99 has an extra two axles with which to lay down its increased power so should perform better especially considering its lower gearing.
That's not encouraging for the 93s. According to wikipedia, they deliver less tractive effort (290kN) than an 88 (317kN). But that discussion is for another thread. The 99 will be far superior with 500kN when it matters.
This is not the limiting factor when adhesion is low.
