I'm sorry I didn't see this post earlier in the year, I'm afraid Yahoo have been bloody minded about letting me in and didn't send me any email notifications about any posts on here!. I'm hoping that's sorted now.
Turbines and Diesels
Q01: Yes, the Dales had been installed for some time by the WR tests. The 5th turbine APUs were moved forward and replaced by the Dales not long after Rebuild 1 that took place after the ASLEF blacking. I've tried to discover exactly when when they were installed but the APT-E Tilt System log books (which I still have....) don't have a broad enough view for that.
Q02: I have no idea, sorry, but they are the same as the ones fitted in the APT-Ps, and the two E-Train Dales were removed from the train once we'd delivered it to the NRM in 1976 specifically so they could be used for the first P-Train set. Rob Latham may know the exact model.
Q03: As far as I can recall the APUs,both gas turbine and diesel, ran at max power the entire time! Any time the test crew were aboard the 'house power draw' was very high, the only real change in demand came about when the four tilt packs were powered up or shut down, and we tried to run tilt active all the time, although some tests required that we ran tilt passive.
Q04: Counting from the cab rearwards Turbine 1 was right side forward as I recall, Turbine 2 left forward, Turbine 3 right centre, Turbine 4 left centre, Turbine 5 left rear and the APU right rear. But Turbine 5 wasn't really at the rear of the PC, it was just the rearmost turbine of the 5 and was mounted just forward of the Auxiliary Bay and mounted as a Tuned Mass Damper, thus the lateral hydraulic damper across the centre walk-way, designed to catch you precisely in the shins as you ran through the train!
The APU, whether turbine or diesel, was mounted right hand side rear, and it really WAS at the rear, the only part of the PC behind it was the bulkhead. All of these positions can still be seen aboard PC2 at Shildon to this day, apart from a big space where the Dale used to be.
Q05: There was one Dale in each Power car.
Q06: See above......
Q07 & Q08: Any of the turbines that were powered up on any one run all throttled together, according to the driver's power demands from his throttle handle. As far as I know the power output increased pretty linearly with RPM, but Alan Goodley would know that much better than I would. It was possible to run the train on any four of the turbines as I recall, but the performance was linted of course, and we did that quite often when max. power wasn't required, if only to minimise the fuel consumption.
Tilting
Q09: APT-E responded very similarly to APT-P in that the degree of tilt depended entirely on the lateral acceleration aboard each of the four vehicles individually. The radius of the curve that the train was traversing had no direct input to the tilt system, and the lateral acceleration depended on how fast the train was travelling, the sharpness of the curve radius and the amount of cant that was already built into the curve. It was wholly possible for the train to tilt OUTWARDS on a curve if it was travelling slower than the zero cant deficiency speed for any particular curve.
Q10: APT-E tilted at zero speed if need be, and this was very handy at stations like Wellingborough, which is on quite a sharp curve. If we stopped there the vehicle floors all adopted a truly horizontal position and we could step onto the platform with ease, unlike passengers boarding or alighting from Mk 1 or 2 coaches, which were 'tilted' according to the cant of the curve.
Aboard the train we didn't do anything other than switch the system on hydraulically and electrically. The degree of tilt was the province of the accelerometers and the control systems after that. APT-E had five accelerometers per vehicle, one in the roof and one under the floor, on the centre line of the Trailer Cars and above the Power Bogie of the Power cars. This pair was duplicated as the tilt system itself was a 90% 2-channel system, right down to the servo-valves, and the selection of the active channel could be decided by the operators, but was also automatically selected from the output of the fifth monitor accelerometer, which was also mounted on the centre line and under the floor. If it detected a large lateral acceleration the control system deduced that the active control channel had failed and would switch to the second channel.
While the four main accelerometers were very accurate (and expensive....) servo type units, the fifth monitor was exactly the same type of spirit level unit that David described as used on the P-Train. As no-one had ever done it before we didn't know how accurate they needed to be, thus our choice of the servo type units originally.
Q11: The short answer is no, such charts couldn't be plotted ahead of time as they'd be dependent on the train speed as well as any slight changes in the track profile. But neither would they be required as the system responded to the acceleration inputs in real time. No doubt some of our UV recorder plots taken during test runs could be described as 'charts', but they'd need knowledge of the specific calibrations active at the time to be of any use and they'll all long gone by now I'm afraid.
I hope that lots is of some use and once again I'm sorry for the huge delay in response.
Regards
Kit
---In Advanced-Passenger-Train@yahoogroups.com, <bob.digital@...> wrote :
Hello folks,
I have just joined the forum and have been reading old messages about the APT-E's gas turbine operation in Alan Coombes posts about digital sound. I was wondering whether I could take the topic on a bit further and ask some detailed questions about the Gas Turbine/APU operation and tilt on both the APT-E and APT-P?
The basis of my questions are related to reproducing the sound of each gas turbine in relation to the starting sequence outlined by Kit in posts going back to 2013 and in relation to their physical location in PC1 and PC2. The largescale model that I intend building would be as per the test trips down the GWR to Swindon so I do not know whether this would be pre or post rebuilding I.e. with or without the Dale diesel APU sets.
Q01: Would the Dale Diesel APU have been installed in the PC1/PC2 units during the testing down the GWR mainline?
Q02: If so, what model of Dale unit was used?
Q03: Would either the Gas Turbine Unit (GTU) or the Dale have run at idle powering the generator or would higher RPM's be involved reacting to the load on the generator? I.e. when the internal lighting, tilt pump sets and air compressors kick in?
Q04: Given Kits 2013 description of the engineers shouting out the starting 1, engine 1 running, engine 2 starting, ... etc How does the GTU and Dale engine numbering relate to the actual physical location within the PC1/PC2 power car bodyshells?
Q05: Was there only one Dale per APT or one in each power car?
Q06: Replacing the fifth GTU with a Dale seems to suggest that this occured in each power car?
In order to replicate engine running sequences digitally I am interested in how the GTU's were spooled up in relation to track speed and acceleration, either in RPM or as a percentage of total power output (Q07).
Q08: When driving the APT-E, did the GTU's spool up individually after each other in series or did they spool up all together in parallel when applying more power to accelerate the vehicle? I pesume that they spooled down together when the drivers power lever is moved back to idle or lower notches?
TILTING:
I cannot find the answer in specific terms but...
Q09: Did either the APT-E or APT-P use some form of graduated tilt dependent upon vehicle speed and degree of curve?
In modelling terms, the Hornby model tilts as the bogie follows the track curve, I suspect that the real APT's would not have tilted below a certain speed, if I am correct at what speed(s) did the onboard electronics (or operators) kick the tilt mechanism in and to what degree of tilt? (Q10).
Q11: Would the degree of tilt change based upon a combination of vehicle speed and the curvature of the line, do any charts documenting this profile exist anywhere?
Can anybody enlighten me on these issues? Many thanks in advance.
