(first posted 7/8/2017) Don’t let people tell you British Rail was a slow, stodgy and conservative organisation, unable to adapt and change with the times. Well, not all the time. In 1976, it gave us the 125mph High Speed Train, still in frontline service today, and still unmatched – a true transport great. And just five years later, we could travel on the first practical tilting train in the world, and it was capable of 155mph. But learning that development of the Advanced Passenger Train was started before the HST suggests it isn’t a simple story.
By the mid-1960s, British Railways (BR) had come a long way from nationalisation in 1948. Steam was almost gone, replaced by a very mixed bag of diesel power and with just one modern electrified route – the West Coast Main Line from London Euston to Birmingham, Manchester, Liverpool and Glasgow. The network had shrunk by a third, as surplus and duplicating routes were ruthlessly eliminated. But passenger traffic was dropping, as motorways and domestic air travel began to steal business. Something was needed to get speeds above the 100 mph of the WCML electrics and the mighty Deltics never mind the paltry 90mph achieved elsewhere, if intercity passengers were to be won back.
Unlike Japan and France who built new lines just for high speed passenger trains for the famous Shinkansen (‘Bullet’) and TGV (Train a Grand Vitesse) trains, Britain lacked the funds and political appetite to develop a new high speed network, so faster trains would have to be accommodated on the existing infrastructure.
But how to get speeds up without building new lines?
First, the physics. The biggest constraint on the average speed of a modern train isn’t power, it’s curvature. A train can’t take curves like cars or bikes, because of the centrifugal force that tries to push it outwards, with disconcerting effects for passengers well before the train gets thrown off the rails. This can be tackled in two ways – reduce speed, or raise the rail on the outer side of the curve above the inner one, a technique called ‘super-elevation’, as seen here.
But super elevation is a compromise. It must be enough to allow faster trains to avoid disruptive slowing, but not too much to give passengers on slower trains the sensation of being tipped inwards to the curve. So, in the mid-1960s, even with super elevation and electric acceleration, expresses on the West Coast Main Line faced frequent speed restrictions, not just on the 200 notoriously sinuous miles between Preston and Glasgow but also on some of the sharper curves further south. These constrained London – Glasgow times to a minimum of 5 hours, at an average of 80mph, which wouldn’t be enough to compete with car and plane into the 1980s.
The seemingly obvious answer to that dilemma is to tilt the train into the curve, to keep the effect of the train’s mass in line with the track. This was the solution put forward by a specially recruited research team in BR – a proposal for a train that would tilt through corners, thereby increasing cornering speeds by 50% and thus able to reach and sustain higher cruising speeds. No conservative bogged down by tradition thinking here
Tilting has downsides of course. Because of the restrictions of the standard BR loading gauge (the envelope of length, height and width that a train must fit within), the body of a train that tilts (blue in the drawing above) would need to be narrower above the waist than conventional trains (yellow) – without the distinctive inward slope, APT would collide with bridges, tunnels, platforms and other trains when tilting. And then there was the worry about nausea induced by the tilting motion – a big concern for many people before they travel on a tilting train, and for nobody afterwards, as it doesn’t happen if you remain aware of your surroundings.
BR aimed high; speed through curves was to rise by 50%, while maximum service speed would rise from 100mph to 150mph, on existing track with existing signals and no extra track maintenance, whilst maintaining current levels of passenger comfort. Quite a tall order. Clever calculations came up with the proposition that track, train and passengers could safely and comfortably withstand a tilt of 9 degrees from the vertical, which would be enough on most curves to get the desired speed increase. So, in 1964, BR, with government funding, began the serious development of a tilting train capable of 155mph.
BR had assembled a special team of engineers for the task of designing and developing the APT. Many had aeronautical backgrounds, which allegedly influenced the extensive use of lightweight alloys in the structure. Gas turbines were chosen for the power cars – their only use on Britain’s rails, bar a brief experiment in the early 1950s. There was a purpose-built development laboratory and engineering centre at Derby, one of Britain’s great train building cities since the earliest days of the railways. And even a dedicated 13 mile test track, on the trackbed of a closed secondary line, conveniently close to Derby and with a good mixture of curves and straights that was ideal for testing a tilting train – this was a test vehicle built to experiment with tilt
The development programme was where it began to go wrong. The original plan had been for a prototype to be ready in two years, but this was hopelessly optimistic. With funding issues, and delays in selecting and proving the gas turbines, it was 1969 before the design was settled.
Fortunately for BR (and everyone else), other engineers in BR had foreseen this slow progress, and in 1970 they persuaded the Board to authorise a second project, which became the HST. Initially presented as an interim solution pending squadron deployment of the APT, the HST (seen here in prototype form, alongside the APT-E at Swindon) was running in under two years, in service within six and is still running at 125 mph 40 years later – the fastest diesel train in the world. Truly a remarkable piece of engineeerring, even if past its stylish best now.
When it finally emerged in 1972, the APT-E (Advanced Passenger Train – Experimental) looked like no train before or since – perhaps a small jetliner on wheels is the closest description.
It was built of lightweight steel, and the two power cars and the two trailers between them were carried on articulated bogies, where one bogie supports the trailing end of one vehicle and the leading end of the next, again to reduce weight.
Power came from five Leyland gas turbines, each of 300hp. This power unit could trace its lineage back through those used by Rover in experimental car installations in the early 1960s to Sir Frank Whittle’s wartime experiments. It was chosen as it provided plenty of power without the weight penalty then typical of diesel engines, and allowed the APT-E to operate away from electrified lines – it was always assumed the production train would be electric. Overall, the four car train was styled to suit its purpose – a striking pointed nose, a high single central windscreen, and a silver-grey finish offset by a BR blue stripe that ran over the roof at both ends. Overall, it was a remarkable vehicle.
Tilt was achieved through accelerometers on each bogie detecting lateral movement of the vehicle as it entered a curve, and initiating the movement of two hydraulic jacks (one on each side of each bogie) to deliver the required degree of tilt. The target was to generate tilt at 5 degrees per second. This shot, with one tilt mechanism jammed, shows what that looks like.
APT-E was not designed for passenger service, but was strictly for experimentation to prove the concept and research the problems of high speed tilt and high speed braking. The trailer cars were equipped as mobile laboratories to monitor and test systems to aerospace standards – although contemporary film shows slide rules at every work station!
And APT-E proved the concept; after early arguments with the train drivers’ union about there being only one seat in the cab, and reliability issues with the gas turbines, the performance began to improve. In August 1975, it set a UK rail speed record of 152.3mph near Swindon, and averaged over 101mph between London St Pancras and Derby – today, over 40 year later, the fastest trains average around 85mph.
APT-E was retired from its testing career in 1976, as development of the prototype APT-P began. This was to be an electrically powered train, of up to 14 coaches, powered by two centrally located power cars. Stylistically it was a big advance from APT-E, partly because of the more attractive nose treatment (and seats for two drivers) and the new dark and light grey with red striping livery, which soon appeared on the HSTs as well. And just as the HST was officially the InterCity125, APT became InterCityAPT.
Unlike the APT-E, APT-P was designed for passenger service, and the coaches were fully equipped for seating and catering use. The upholstery (in first class top, and second class) may look a little dated now, but the layout still looks better than on many modern trains, with larger windows and better seat spacing. Partly, that reflects better crash protection through a stronger structure in 21st century trains, and partly the need to cram in as many seats as possible nowadays. But it certainly looks better than a Pendolino inside and out to me (but a Pendolino is structurally very strong indeed).
A big weakness with the APT-P was the need to locate the two power cars adjacent to each other in the centre of the train, with one pantograph serving both, which effectively made it two separate trains as there was no passage through the power cars. Contemporary rules prevented the cables for the 25kv electricity being fed through the passenger vehicles, and it was believed the overhead power line would be so disturbed by the pantograph on the leading power car that the trailing one would be out of alignment, and damage would ensue if the power cars had been located at the two ends, as on the HST and the APT-E. There were also concerns about the dynamics of 8,000hp pushing a train if the power cars were both placed at one end, so the mid train position was the unhappy compromise result.
The first power car was completed in June 1977; the first trailer cars a year later, but a complete train did not run until May 1979, such was the complexity and lack of resources afflicting the project. There was some good news in December 1979, with a new UK speed record of 162.2 mph – not broken until 2002.
And APT-P had some cutting edge features beyond tilt. Hydrokinetic brakes, which are basically water turbines, were used to ensure the train could slow from 155mph within existing signal distances, while an early transponder system called Control-APT gave the driver in cab display of the maximum permitted speed in the centre of the driver’s panel, surrounded by a blue mounting
But by now, the winds were turning against the APT. A new government, led by the famously anti-rail Margaret Thatcher, was demanding a return on its investment in BR, while the decision to move to electric power meant the APT was confined to just one route, the WCML, as there were no funds for more electrification. The perceived failure of the APT stood in stark contrast to the runaway success of the HST, and BR was forced to take a huge risk to try to save the project – the prototype had to go into passenger service.
So, in December 1981, at 6am on a cold murky Glasgow morning, one of the three APT-P sets (from an original plan for eight) set out for London Euston, full of journalists and BR engineers. London was reached in 4 hours 15 minutes at a maximum of 125 mph without incident except for overhung journalists suffering from the tilt motion once the sun came up.
But the smooth running didn’t last. December is a cruel month for testing heavy engineering in public, and APT-P suffered a spate of problems (frozen hydrokinetic brakes, door problems, you name it).
https://www.youtube.com/watch?v=oSMSSdL2yeo
But BR really tried. They made this film, presented by the BBC’s Peter Purvis, to fightback at the naysayers and the critics. It was an uphill battle, as the train was obviously not yet ready for regular service. Public service ended after less than three weeks, and the APT-P was taken away for a thorough review and modification.
It returned in1984, with no publicity, and slowly earned a reputation for reliability. But it was not used at high speed, and just mixed in with the WCML 100 mph electrics. Clearly, APT was not the train of the future anymore. But it did record the first sub-4 hour London – Glasgow journey – 3 hours 52 minutes for 400 miles of railway built for Victorian steam engines was a real achievement, and stands as the fastest rail trip between the two cities to this day.
It was finally quietly taken off the mainline in 1986; two sets were scrapped and the third sits at a private heritage centre just outside Crewe station; if you’re lucky, you’ll spot it from your Pendolino. Plans for an APT-S (Squadron) production version were quietly dropped.
Today, APT-E rests at the National Railway Museum’s Co Durham outstation, Locomotion, alongside another great express prototype, Deltic.
You might think that was the end., but the technology lived on. Much of it was used in the 4,830hp class 91 electrics built for the East Coast Mainline in 1988, which copied the APT’s unusual body (rather than bogie) mounted electric motors, which significantly reduces the unsprung weight and thus track impact. Designed to reach 140mph, or 225km/h, they were known as InterCity225 – the APT name had lost its credibility; but, despite their 140mph capability, they only reach 125mph, as the signalling improvements needed failed to materialise. The accompanying mark IV coaches were designed to accept a retrofitted tilt mechanism, and thus copied the APT’s distinctive sloping profile. Now nearly 30 years later, these trains are still the ECML’s frontline, but they don’t tilt and never will.
Ultimately, BR sold the rights to the APT tilt system to FIAT, who then developed a series of tilting trains that now run across Europe, using the Pendolino name. And, in 2001, Virgin Trains introduced a fleet of tilting trains on the WCML, built in Birmingham by Alstom with FIAT tilting technology. Yes, Richard Branson’s pride and joy is based on APT’s pioneering engineering of a quarter centrury earlier – not that he’ll tell you.
So maybe BR wasn’t an old fashioned, unadventurous and uninspired organisation. Perhaps it was 20 years ahead of everyone else, but we just didn’t appreciate it.
Wouldn’t the tilting put enormous stress on the wheel sets?
Deutsche Bahn (German Railway) has several tilting trains (some diesel, some electric) for the past thirty years. One issue that kept showing up is stress fractures on the axles. Hardened wheel sets alleviate the problem, but the speed and tilting angle have been severly restricted ever since.
Of course, some people are sensitive to the tilting motion: similar to car or sea sickness. The passenger comfort is due to two factors: how sharp the curves are and how fast the train set tilts into and at the end of curve.
Two train sets, particularly the ill-fated Deutsche Bahn Class 611 and its successor, Class 612 (called RegioSwinger), have maximum tilting angle of 8°. Both trains serve the regional routes, which have lot of meandering curves with tighter turning radius. The tilting motion is often jarring and can be very disorienting for some passengers. Eventually, maintenance cost and passenger comfort reduced the tilting angle and speed.
I ride ICE-T (InterCity Express with tilting capability) many times between Munich and Berlin. Ironically, ICE-T tilts at 8°, but it doesn’t feel jarring and disorienting because ICE-T travels on high speed trunk routes that have wider turning radius.
Israel Railways, as a part of trying to modernize the ancient Tel-Aviv to Jerusalem line (which follows the original, Turkish Ottoman Empire route), leased a couple of VT611s for evaluation purposes. The trials were successful and led to an order of 8 Pendolino sets. However – after rethinking the financial and engineering-related factors of the purchase – the order was cancelled. Eventually IR came to the conclusion that a better solution would be represented by constructing a completely new route, and the new (fully electrified. See more: https://en.wikipedia.org/wiki/Tel_Aviv%E2%80%93Jerusalem_railway) line, which relies on a number of bridges and tunnels in order to avoid curves, will use conventional stock. Ultimately however – due to many unforeseen difficulties and delays – it probably would have been cheaper to stick to the original plan…
That’s one of the VT611 which were tested in Israel, still in service in Germany…
The tilt rotates around the centre of gravity so the weight distribution is no different tilted or upright. Indeed it was found on test runs that the flanges on APT rarely touched the rails. The whole APT programme actually grew out of research into the fundamental properties of steel wheel/rail interaction, largely as a result of a number of freight train derailments in the late ’50s/early 60s as an increasing number of wagons with power brakes began to drive up their speed.
I rode APT in 1984 (Euston-Preston) and had no problem with the tilting, in fact rather enjoyed it, standing by the buffet watching the scenery speed by at implausible angles, though I admit I’ve never really suffered from sea-sickness either. The interior was nice and bright and airy, not dissimilar to the HST’s Mk.III coaches, though the ride was slightly softer. The reduced profile was a serious concern during development and a lot of mock-ups were made (including some built into existing coaches) to ensure they didn’t feel too claustrophobic, unlike the Pendolino where some of the so-called ‘window’ seats are in fact just a blank wall. Sadly all modern Standard class seating is sardine-like regardless of the type of train.
At the time the train was built Tartan was kind of in fashion for car seating too.
https://static.cargurus.com/images/site/2009/02/28/18/36/1978_vauxhall_chevette-pic-16901-200×200.jpeg
Maybe I blinked and missed it, but where are references to the Talgo train [Spanish, I believe] in active service for years, including on Amtrak’s West Coast rail service between Van BC and Portland Ore. I read about them for years before my first ride! Train buffs- make the pilgrimage while we still have them! [The scenery is also fantastic]
The Talgo Pendular of 1980 has a passive tilt system rather than active, just swinging out like a pendulum. This does, have the effect of shifting the centre of gravity outwards on curves overall. Such passive tilt systems were used at least as far back as the 1940s.
The acela here in the US runs a tilting system as well. Never bothered me. The also tested an ICE train here in the 90s before Acela. The Acela route in particular the part here in CT are very curvy and reading the issues raised in the post mirrors the issues for high speed rail here.
Fascinating writeup – was not aware of these at all. I’ve ridden the Shinkansen from Kobe to Kakogawa. Was fun, but as I’m given to motion sickness, I think I’d probably pass on a tilting train given the opportunity.
Sweden has a similar tilting train, the X2000, launched in 1990. It has a similar set up with shared articulated boogies, but only one power car, up front. Except for extremely small rural networks, most of Sweden has been electrified since the early 20th Century, so we didn’t have the same kind of problems as the UK and USA concerning coal/diesel and the electrifying of old lines.
The X2000 replaced the old intercity lines as the fastest way to travel between Swedens three largest cities, though it was intended as a business oriented travel at first, with substantially hiked ticket prices to lure the plebs off. The trade off is that a smaller demographic has to pay the investment off with higher prices, instead of doing as France with their TGV and have the ticket prices intentionally low to increase volume.
Funnily enough, the old intercity-line cars are still in service, now under private contractors, run by modern high speed engines on the same lines as the X2000, but without a tilt. It is actually the same cars from the 50’s and 60’s that I grew up with in the 80’s, only slightly refreshed. And with those new high speed engines speed has more than doubled upwards 200 km/h, only slightly less then the X2000. I must say it is a little scary travelling in those old cars at that speed, but the ticket price is absurdly low, the cost is less than a taxi ride to the airport. O tempora, o mores!
https://en.wikipedia.org/wiki/X_2000
Great article – as always very informative. Jim.
Until reading this I thought all the interesting experiments ended with steam. Thanks for something really unexpected.
Great article, as yours always are. I read these English rail pieces with immense jealousy. In Victoria, Aus, the state was once spiderwebbed with train lines, peaking in about 1920 or so. The largely Victorian-era system was so overbuilt and expensive I believe it was not paid off fully until the late 1980’s! (Victoria is the same size as the UK, but pop of less than 6 million). Many of those lines were exceptionally scenic. Victorian Railways was a large and proud govt organisation. Now, just a handful of privatised, poorly maintained lines run, slowly. The “fast” trains recently introduced to one regional city should do about 90mph – they never do. Sigh. Sure, cars made a lot of it all uneconomic (I suspect a lot of it never was even new) but the remnants of these beautiful lines and services and faded classy rolling stock were there and closing during my childhood. We caught special steam train trips on them as they went, and I absolutely loved it. ( I saw an actual, working steam loco doing shunting work in the country in 1972, must have been the very last). That era can never return, for me or rail, but it’s downright absurd we can’t have at least 3 or 4 actually fast trains to our country cities. Sadly, in my time, Aussies have seen rail as a very sub-standard, poor persons way to move about, and state politicians defunded it accordingly. I have always laughed, BigPaws, at English people whingeing about the “bad” Brit rail services. Hopefully, at 125 mph, you can’t hear ’em…
Oh boy, you are not wrong. It is amazing how bad the govt is at expanding infrastructure of all types when new areas are developed, road, rail, schools, etc. It has been improved since (but not very much?), but years ago I rode the train from Bendigo to Melbourne, which had to slow to 40 km/h in some sections due to the tracks needing maintenance.
There is a tilting train up in Queensland, but I’ve never seen it.
Special interests are pushing real hard to get a bullet train built in Texas from Houston to Dallas. The two cities are all for it; the dozens of communities and counties it would impact are not. For a state that’s always bragging about local control and individual rights, Austin sure knows how to make laws that take away local control and determination.
They did the same when Denton outlawed fracking and Austin took self-determination away from the municipalities….
Train fight: https://www.texastribune.org/search/?q=train
Fantastic read! Thanks for that.
Maybe it’s ‘cos I grew up on the east coast and so all childhood trains were ECML trains, but I had no idea the APT was ever in active service.
I knew the story of the run with the hungover journos making much of how sick they felt from the tilt (as you rightly say, all in the mind which you quickly realise as soon as you actually ride a tilting train) but somehow thought it ended there. The ’82 vintage film with Peter Purves shuttling down from Glasgow Central is a real gem. Can’t help but wonder what might have been had we not had such an adamantly anti-public-service administration back then…
The APT-P was never intended for passenger service but purely to find and fix problems. The trailer cars were going to be used in the APT-D (development) sets only the power cars were going to be retired. All service units were planned to have one power car and one driving trailer as was used in the 225, the “D” would have passenger driver trailers from the P trains and not goods. The APT-U (ultimate) was going to have two power cars at each end and non articulated bogies (as were used in the 225 only without the tilt) so would have been a electric tilting version on the 125.
Several concepts were drawn and worked on which would cover the entire U.K. network as electrification continued. But the project was poorly managed was riddled with in fighting and conflict of interests. Maggie has enough, she hated trains and hated the project, long term, we bought trains with our own technology back instead of selling trains.
APT-P still holds the speed record, but lost the HP record to Eurostar.
The central power cars made it easy and cheaper to test with one or two cars with the formations and was only intended on the P train for trails of the project and helped with Passenger service designs.
The APT-P was never intended for passenger service but testing. After E train proved successful the project was handed to BR engineers who set about building the prototype for further development and used their own designs hardly any technology from the E train featured on the P train.
The trailer cars of the P train were intended for being used in the D train (development) only the central power cars would be retired.
The service trains were intended to have one driving power car and a driving trailer as used in the 225 project only the D trains would have passenger driving trailers from the P trains.
The Ultimate (U train) would have a driving motor at each end and no articulated bogies and this car was developed and used in the P train project.
The intention would be that all intercity trains would be a version of the APT.
But in fighting and poor management with conflicting interests and eventually a government that lost faith along with a brutal press saw the APT get savaged and killed off.
Sadly it was never praised for being successful in service nor that the three prototypes were never intended for public service but for research and fault finding and fixing, the prototype Concorde never carried passengers in service despite having a full set of seats. The press decided it was going to fail, they did not like being kept waiting, got drunk then the return trip had technical issues and did not complete the run, they had found their next victim to kill. Plus Maggie was very anti trains.
But the project lives on in the 225, Eurostar and pendelino.
I understood that P train still held the speed record but lost the hp record to Eurostar.
Wonderful piece. However, I am extremely doubtful about the alleged 1982 sale of rights from BR to FIAT
Why? Because FIAT had already developed the first tilting railcar – name Y 0160 – in the end of the 1960s with all the components crucial to the Pendolino family, gyroscope included. Moreover, in 1975 the ETR 401 (a four car trainset) entered regular service between Rome and Ancona and thanks to the gyroscope (which employed the elevation of the outer rail to detect the start of a corner) most passengers felt no discomfort at all. The APT as you know never had such device and in fact the tilting had to be discomfortingly abrupt.
If the sale ever happened, I could imagine it might have had to do with processor and microelectronics technology but that was absolutely marginal to the Pendolino’s success, if relevant at all.
Unfortunately it’ s a tale so widespread on English speaking media (even Wiki iirc) that the only explanation I can give is that the Brits had to cope somehow and no one bothered to check 😀
In some ways the subtext of this article is the continuing inability of most countries in the English-speaking world to take high speed rail seriously.
I’ve made a number of trips on Spain’s network over the past few years, and it’s hard to convey to people who haven’t experienced modern high-speed rail how fast, spacious, quiet, and just pleasant these trains are. Plus of course they go city-centre to city-centre, eliminating the whole to-and-from-the-airport ordeal, and the lengthy and soul-deadening airport experience as well.
Walking 20 or 30 minutes from a downtown hotel to the station, and then walking again to your hotel at the end of the trip, was a revelation.
“Walking 20 or 30 minutes from a downtown hotel to the station, and then walking again to your hotel at the end of the trip, was a revelation.” robadr, I truly believe that if every other obstacle to high speed rail in America were eliminated, that the prospect of walking 20 or 30 minutes from hotel to station just once and most certainly twice per trip would discourage most Americans from ever giving high speed rail a chance. Why? They simply aren’t in shape to do it.
Although APT had its own teething troubles, it seems much of it was down to Britain’s on-going difficultly in modernizing the railway network and falling behind others from the Technological Revolution to the present.
It can be seen too in the UK’s various unbuilt railway and road/motorway plans both pre/post-war.
It’s amazing to learn how British Rail was ahead of its time with this project. Even though it faced many challenges, the APT’s technology paved the way for modern high-speed trains. Thanks for sharing this fascinating and detailed story!