Paul kidger

PFMJI - Just as I forgot, we might have talked about that in old CS Trainnet Forum, but ... as there are several rebuilt versions of class 86, I'd presume the high access charges are for cl.86.0 (if any are left over) with plain nose- suspended AEI type 282AZ traction motors in cl.85 bogies, definitely not for the 86.1 with springborne GEC G412 AZ motors and flexicoil susopension, but maybe for 86.2 with flexicoil suspension, but few (if any left) with resilient wheels and AEI type 282 BZ traction motors, all axle-hung (hence the resilient wheels on some of the class - or all ??). Or cl. 86.3, derived from 86.0 sans flexicoil suspension, but fitted with resilient wheels ("MR" 06/07-1980)? What of these are in use with Anglia ?

What do the high access charges refer to, otherwise? "Reliability factor", or the like? I deem the 1960ies experiment with nose- suspended traction motors is suitably reflected by increased access charges. However, the track damage ought be different for the sub-classes, thus the charges. BTW, I still wonder why the effects of nose-suspended tm-s are deemed irrelevant with diesel-electric locomotives, at least the high-power ones. AFAIK, the cl.67 have been provided with springborne motors and flexible drives, like the HST power cars. Or haven't the 67-s, and some are more equal than others in Railtrack's view of physics ?

Kind regards, CTW (whose information is some 23 years old )

CTW, DE-Goslar

One intersting point is the way in which the power requirements are calculated. AEA technology, which seems now to have taken over much of the BR research function, has developed a series of algorithms to predict the power consumption of electric trains based on operating parameters. It would be interesting to have an insight into these equations but I fear that may ne be possible.

Regarding the Access charges, I've always viewed this as being the charges associated with running on the tracks and is a payment directly related to the cost to railtrack (or its successors) of having that train on that track and must pay for wear of the track, signalling etc....a mixtrure of fixed and variable costs. There is the additional cost of electric power for electric stock.

Sorry, but I am unable to comment on the Class 67, I am not very familiar with the technical details on that loco.

Paul Kidger

Well, I'd then presume this means a "wear factor of unity", and, given that cl. 90 had previously been designed as a project for "cl.87.2", using the very same running gear as 87 101, I'd suspect class 87 ranks equal to this. However, class 91 with APT-type cardan shaft drives and correspondingly low unsprung weight must then get sorts of a "bonus", even if taking into account the long wheelbase of its bogies.

BK Cooper's "British Rail Handbook" (IAN ALLAN, 1981) on p.132 gives
unsprung masses as follows:

cl.55 (Deltic): 3.25 tons per axle
cl.253(HST-pc): 2.16 tons per axle
cl.370(APT-P-pc):1.38 tons per axle

We can just guess that an unmodified cl.86 is an "extremist" in excess of 4.5 tons (the motor is rated at approx. 800 kW, vs.400 kW in a cl.55), and that a cl.91 is somewhat more substantial than in a cl.370, at 1.7 tons. Would sound pragmatic to me, at least.
My guess also is that cl.87 is "somewhere near 3 tons", hence also cl.90; not quite twice the unsprung weight of a cl.91, but close.

I also see that cl.67 with 650-kW-traction motors could not be much below 3.8 tons unsprung weight if fitted with 4 axle- hung, nose- suspended "tramway" drives (the Deltic distributed the same power over 6 smaller traction motors !). At a top speed of 125 mph, this would be a bare massacre to the infrastructure. So I presume cl.67 *IS* fitted with flexible drives like HST and the later electrics.

Another aspect of that story is the recent US crash near Washington DC. These passenger units at 2.9 MW (4000 hp) may have three-phase asynchronous motors, which are approx. 0.6 times the weight of a dc trction motor, but even so, the nose-suspended, axle-hung machine on passenger units ought be banned and abolished. I wonder if the train would have made it over the irregularity with flexible drives, instead of spreading the rails. I have no problems with freight units, but IMHO passenger locos are different in their speed profile, thus flexible drives are an absolute must, otherwise it will hammer the permanent way to less permanent pieces, despite 135 lbs rails and all that stuff, nice to match near-static axleloads at low speeds.

Kind regards, CTW

CTW, DE-Goslar