Sulis and Sarum Express - 60163 - 24/03/18

Sean,
I bow to your far greater knowledge of your railway between Dr Day's and Horfield Summit. Not having been a railway enthusiast until the mid 1980s, mine is non-existent and wholly restricted to what's in the Gradient Profiles Book, W12, that shows a dip at 1in132 for less than a 1/4 mile directly after Stapleton Road leading onto the 1in75. Probably just an average of numerous short sections. Out of interest, where does your detailed info come from???

 

Filton bank is my back yard and I helped piece together the current RPS mileage chart, trying to nail down distances for the various bridges in the absence of visible mileposts.

This included cycling out to each one to check official info stencilled on them. No, I'm not doing that for the ECML...

This was before the ABC infrastructure website had this info.

Data then checked using local gps fixes, google earth etc.

Around this time I asked around for distance and gradient info the within RPS, partly for my own interest but mainly as the local Councillor campainging to reopen local stations, for which derogation and/or expensive earthworks may be required as 1:75 is way off Network Rail standards for new stations.

I understand the 1:75 starts at MP 2, but ends just before MP4.

Would be interested if someone involved with tbe current four tracking project could confirm gradient info on Filton bank?

 

Sean, superb performance recording and respect for being able to concentrate closely for the whole journey - i used to do a lot of timing and I know how draining it can be. Thank you for sharing your impeccable work.

Mike

P S My daughter lives near Horfield and messaged me to say she had heard a noise that sounded a bit like a steam train....... probably others heard it too!

 

Totally concur with that. I do every quarter milepost visible on the side I'm seated and sometimes use middle windows and stand if they aren't on my side and it's on track worth recording them. And that's nowhere near as many recording points as Sean takes. Filton always has been an annoying bank for accurately identifying the gradients. I can only base it on the experience of riding on all manner of trains up the bank back to South Wales and onward and timings always show a decent speed pick up off the end of Stapleton Road. As Sean said, it would be good to know from NR what the surveys showed. There were enough modern versions of ye olde theodolites on show when the surveys were being done.

 

Deep ballasting has changed some historic gradient profiles, as has lowering track under bridges for electrification.

My GPS shows altitudes to nearest metre. It works off changes in air pressure. Analysis of track log shows no dip in the Stapleton Rd area.

Some of the reports re possible stations on Filton bank quote 1:76 not 1:75.

 

It does not. You might have an instrument that includes both a GPS receiver and a barometric altimeter but they are wholly different measurement systems. Incidentally your barometric altimeter requires regular calibration but even high end systems with GPS receivers, temperature sensors and barometric altimeters are not accurate to a metre. You would have to spend a lot of money to get to 3m accuracy and still have to recalibrate the altimeter at hourly intervals.

 

My (very cheap) GPS is reasonably reliable on speed, but the altimeter seems to be consistently 40m out so is only realistically usable as a 'rough guide'.

Sent from my SM-J330FN using Tapatalk

 

Yeah, mine GPS is always a bit out on altitude - I think on this trip, while sat at Chemtenham, it thought we were slowly rising (by 20m in the end) and at Hampton Loade on the SVR, next to the river Severn, it had us at 25m below sea level... so they’re not always a great guide

 

Yes I do appreciate all of that. I usually calibrate the GPS at start of each day and am fully aware it will be affected by changes in air pressure during the day e.g. passage of a cold front, characterised by steady fall in pressure then rapid rise as the front passes. As air pressure rises the GPS will show a lower altitude and vice-versa. On 24 March 2018 weather conditions were relatively benign, with a gentle south easterly flow with a low pressure centre off SW England. So no rapid changes of pressure as Tornado climbed Filton bank.

Over a short time frame, say 15 minutes, even if the starting altitude is wrong, adjacent altitudes will be will wrong by the same error factor. So whether I'm looking at the GPS on the day, or analysing the track log afterwards, I'm not finding a dip at the foot of Filton bank. I've looked at the track logs of Tornado and Galatea from March 2017, and a recent IET, which confirm the same.

I'm not doubting Shireman's source - the Ian Allan profiles - and indeed the 1949 WR timetables show a 1 in 132 fall between Lawrence Hill and Stapleton Rd. But I am advised that's not what a more recent survey shows.