The discussion in the 68+Mk5 thread suggests not, as DRS are expected to want the 68s for their own activities, and there isn't yet any alternative motive power.
Designed for 100 mph running, same speed as a 170.
But they are LHCS, so cannot use HST differentials which apply on significant portions of some Scottish mainlines.
HSTs are really LHCS, it's just their duplicated 'locomotives' are single-ended, and were carefully engineered down to a ~17t axle weight so 125mph running met the approval of civil and permanent way engineers. The complete HST trainsets' braking capability was also specified to be able to stop from 125mph in the same distance as previous trains could stop from 100mph, allowing higher differential speeds to be permitted without widespread respacing of signals.
Mk5s are still not so passed though.
According to Wikipedia(!), Mk5A cars are permitted a maximum of 125mph, on suitable track and given something better to haul them. The class 68 locos however are limited to 100mph and have an axle weight a little in excess of 21t. With new locos or power cars, the carriage sets might plausibly be reformed into something a little faster than they have achieved so far on Transpennine Express.
Mk5s are really an unpowered multiple unit. They are difficult to split and cannot be used with other BR carriages.
Yes, the Mk5A are a 125mph design and the 68s are 100mph capable and quite decent at acceleration compared to a DMU such as 158/170. They still cannot use HST differentials and that will affect running times, particularly Edinburgh to Dundee and Dundee to Aberdeen.
My point is that the locos might be the primary reason the sets as currently formed couldn't take advantage of higher speeds HSTs have been allowed historically in Scotland. Pair the coaches with a new power car with a lower axle load and that could change, plausibly. Maybe a re-signing of the routes concerned could allow something higher but not as high as the HSTs. HST as a label is becoming anachronistic now anyway with the trains gone from LNER, soon to disappear from XC and in due course from Scotrail.
running higher than 100mph in Scotland would need a whole new safety case. (other than hte stretches of track on the ECML and WCML where it is already authorised). So the use of class 67s (125mph capable) or 93s (110mph) makes it a moot point.
Maybe if the Grand Union London - Stirling route goes ahead but they can't use the bi-modes, 93s & Mk5a & DVT or 93 (?) would work. Just temporary storage would be needed so probably not.
Why would they need new locomotives? Most of the diffs on the relevant lines are sprinter-only, so the HSTs get very little advantage anyway. The timings are also largely set for 170s, which stagger up hills like a middle-aged smoker on their first marathon. 68s would be fine, if not quite as good as the HSTs, which are in any case going nowhere.
any hint as to which manufacturer / products would be preferred for these options?
Is this speculation or from an internal source(s) at SR/TS?
Yeah and be a damn sight more reliable than the current offering! I’m led to believe the training is nothing like what was required for the HST so should be much simpler to achieve.
