Shaw S Hunter
Established Member
I remember someone making the observation that a 170 (being designed for 100mph) spending the day on the Harrogate line will never exceed 65mph and therefore never get out of hydraulic transmission into direct drive. Prolonged use like this doesn’t do the transmission any good. Given the maintenance facility is at Hull Botanic they must be cycled through other duties but then this doesn’t support good timetable performance at Leeds if one route can import delay to another, etc.
For comparison a 158 will ‘change gear’ at between 53-60mph depending on the power notch, so they don’t have the same problem.
For anyone in the know - is there a limit to how much time a 170 can be diagrammed to remain on sub-70mph duties?
No, and there are very little issues with the transmissions. It is largely a problem that has been 'invented' from the characteristics of the unit.
I have mentioned this before but I believe it bears repeating. When 170s were first used on the Harrogate line they quickly gained a reputation for unreliability due to overheating. Seemingly the issue was (is) exacerbated by an unfortunate aerodynamic "incompatiblity" between 170s and the interior of Bramhope Tunnel, ie the airflow around these units at this location does not provide the expected amount of air-cooling. Remember that Leeds-bound trains face an adverse gradient of 1 in 94 through the tunnel and then turn round in Leeds before having a chance to cool down.
The short-term solution was to ensure that daily diagramming of the class kept the units from more than a couple of days at a time on the route. Longer term greater attention to detail during maintenance has largely dealt with the problem ie keeping underfloor areas free from debris and ensuring radiator circuits are in good order and properly topped-up with coolant. Sadly this sort of problem is not new, the HST Valentas had major cooling issues for a while and the Coradia family units have shown a propensity to self-combust due to lack of engine bay cleaning. It seems it's easy (for some) to forget the importance of good quality maintenance.