Saw a Biomass train at Edge Hill last week. Had two 66's on the front. The coal train in front had one 66. This happened two days on the trot. Anyone think of a reason the Biomass train had two up front both times?
I am assuming it was this you noted? The two GBRf Class 66's were probably 66716 and 66736 on the Tyne Dock - Tuebrook Sdgs - Drax PS "Trial" Biomass Hoppers which happened over 3 days beginning 16 April 2014. For reference they were hauling
27 hoppers hence two Class 66's.
Likewise if you noted a DBS Class 66 on a Coal train then probably only consisted of 19 hoppers as that is the standard load for a Class 66 out of the docks. The DBS - FFPS coal sets consist of 23 HHA hoppers and Class 60's are required when they are fully loaded (2100 tonnes). A Class 66 can hauled one of those sets but you will find that 4 hoppers will be empty when leaving the docks.
I have known a Class 66 (FLHH or DBS) to haul 21 loaded hoppers from the docks but they have struggled as you must bear in mind they are starting from a dead start and attacking a 1 mile 1in60 reverse curve climb upto Bootle Junction. If the conditions are not right they will grind to an almost halt!! Likewise, I have seen especially FLHH Class 66/5's struggled up the Whiston incline on a loaded coal set which is approx two miles on a 1 in 100 climb with the Class 66 screaming like hell to maintain any form of movement!
This is why DBS use Class 60's on the coal trains out of docks with FLHH preferring to use Class 70's on similar trains (19/21 hoppers). The GBRF Biomass trains are lighter loads so a Class 66 is sufficient. HTH.
(As an afterthought - DBS trialed the Class 59's on the LBT coal trains and they did not fare any better than the Class 66's - basically they could not compete with the Class 60's. The 59's used on the trains in that short period were unreliable and really not suitable in hauling the trains from a dead start, some drivers could not wait to see the back of them!! As a guide and going back further - when we had the old HAA wagons, a Class 60 could take 45 loaded HAA's (2200 tonnes), so could four Class 20's, two Class 56's or 66's but when it was a single Class 56 or 66, it was generally a maximum of 35 HAA's).