Maximum speeds of steam on the mainline today

[Kris]

Raised in the topic about the future of main line steam was the speed that the locos can run at (max 75mph or less loco dependant). I know that the maximum speed is based on the wheel size but what I'm not aware of is how this maximum speed has been decided and why it is lower than the speeds these locos were achieving during their working (pre preservation) life.

[EddieB]

I'm no expert, but current maximum speeds for main line steam are tightly regulated and in most cases the locomotives are well capable of exceeding their "safe limits".

 

Speed is a function of power, which itself is related to the thermal efficiency of the locomotives firebox, boiler and cylinders. In order to keep those large driving wheels turning at higher revolutions, the locomotive boiler needs to be supplying sufficient quantities of steam to the cylinders (and not to lose too much heat and pressure in those cylinders).

[Edwin_m]

Sustained running at over 75mph was actually relatively rare in steam days, except perhaps on the very top expresses before WW2. Tornado is cleared for 100mph I think - there is no problem with going faster if you are willing and able to make the safety case to Network Rail!

[Lady_Ava_Hay]

I think this has more to do with packing in a tight schedule based on practical experience. If you watch DVD's of real steam main line running, it is quite common for the steamer to be pulled up for a faster ( 100mph + ) train to pass.

 

It would be unwise to schedule a steamer for 100mph running continuously as the fireman would be completely unable to keep up and the frequent stops for water would negate any savings.

 

Bear in mind as well that apart from Tornado, none of these steam locos has air brakes so they need to plan stops many miles ahead and adjust speed slowly. Bear in mind also that all of these steam locos and the stock they are pulling are hugely expensive to run and maintain and continuous high speed running will increase these costs and shorten the life of the running gear.

 

So I think it might be a sensible operating decision of both the owner and the railway track authority to limit the speed. Expediency rather than imposition, I believe.

[The Stationmaster]

Mechanical condition (some bits are even difficult to assess with x-ray gear etc), reliability (of both men and machine), enginemen not at all used to working on - and stopping - steam locos travelling really fast steam, and a dose of commonsense for all the preceding reasons.

 

Having said that the fastest I have travelled behind a steam loco in the 'mainline steam era' was 85mph through xxxxxxxxx behind 'xxxxxxx xxxxxxx' back in the days of the universal 60mph limit some xx years ago - the loco is still about so I won't name it, the man who was driving that evening died last year and the Traction Inspector who was on the footplate has long since retired but I won't be so rude as to name him. All I will say is that in that place in that era speeds that high were not uncommon with certain locos in tip-top condition but everybody kept their mouths shut. Similarly there was occasionally some fast running during a certain event in 1985 (honest) but as I had to explain when being hauled over the coals following one 'sparkling' run we had not exceeded 60 mph (although I didn't add that it was the start-to-stop average speed). The difference back then of course was that we were using enginemen who had past day-to-day experience of steam operation including plenty who had worked on fast timings and who were prepared and happy to have a go if they got the nod - all far more tightly regulated nowadays.

[PenrithBeacon]

I remember reading somewhere that there are concerns about the visibility from the cabs of steam locos. This is based not just on the possibility that the exhaust might get in the way of the drivers vision but that the boiler itself is an obstruction. It may be worth noting that Cl20 diesels are always operated cab rather than bonnet first, AFAIK.

 

Regards

[mikemeg]

I'm no expert on the mechnical constraints, real or potential, which have resulted in the general imposition of the 75 mph maximum for main line steam, but I do seem to remember reading that modern permanent way, with its much greater rigidity and continuous welded rail of a much deeper section, was and is one reason for the imposition of this limit.

 

Apparently (and again this is what I have read) the much older chaired bullhead rail, in sixty foot panels with fishplates joining the panels, tended to even out any sideways oscillation which locos, especially two cylinder locos, would develop.

 

Hammer blow from steam locomotives was always a consideration in the Civil Engineering Depts in the days of steam. Clearly modern traction does not produce those hammer blow stresses and I wonder whether the 75 mph limit may be Network Rail simply trying to avoid any damage or wear to the permanent way from these stresses?

 

Someone commented that 100+ mph running was quite rare in steam days. Being old enough to remember the days of steam and having travelled behind steam many times in the 1950's and 60's I can only ever remember one 100+ mph run. This was an Easter excursion (1962) from Hull to Newcastle where, on the return run, 60002 Sir Murrough Wilson was the locomotive. The train was twenty minutes late out of Newcastle but arrived in Hull slightly early, albeit on a Sunday.

 

Leaning out of the carriage window, the sight and sound of that locomotive running south from Darlington to York was one of those very special and very rare experiences which are 'the times of ones life'. I swear everything but the firebars were issuing from that double chimney. A chance conversation, by one of the alighting passengers with the driver, elicited the statement that they had touched 105 mph along the racing stretch.

 

Cheers

 

Mike

[Bon Accord]

Whilst I would agree it would be lunacy for NR to actually time a mainline steam excursion to run at speeds above 70/75mph, I do think it steam locos should be allowed to have a higher max speed (say 85-90 for an 8P) which would allow them to make up (some) time should the need arise.

If you're running late and there's a path available, the bobby is far more likely to give you the road if he knows you have the capability to 'make haste' when required.

[Kris]

Some interesting comments and thoughts here, thanks for them.

[spamcan61]

 

Hammer blow from steam locomotives was always a consideration in the Civil Engineering Depts in the days of steam. Clearly modern traction does not produce those hammer blow stresses and I wonder whether the 75 mph limit may be Network Rail simply trying to avoid any damage or wear to the permanent way from these stresses?

 

Cheers

 

Mike

 

That's always been my assumption as to the primary reason for the limit, damage to the track, although axle hung traction motors presumably aren't too kind to the track either, with considerable unsprung weight.

[Guest stuartp]

That's always been my assumption as to the primary reason for the limit, damage to the track, although axle hung traction motors presumably aren't too kind to the track either, with considerable unsprung weight.

 

I remember being told in 1993 by a senior PW bod that some kit had been fitted at Ais Gill to measure hammerblow, and that the Traction Inspector responsible for that weekend's southbound run over the S&C might like to take this into account if an assault on the Blue Riband was planned. He was concerned that he was only maintaining the track to Sprinter standards (this was during Regional Railways' "maintenance holiday" era) yet 8Ps were belting up it every weekend.

[Michael Delamar]

quote from Campbell Highet's book, All Steamed up "A record of fourty years service in motive power depots of the LMSR"

 

this was near his retirement at Bank hall Liverpool as a motive power officer.

 

"In the 1960s the effects of the introduction of flat-bottom rail as the BR standard began to be felt in the riding, and the mechanical condition of engines which normally ran at fairly high speeds. A number of sections of this track were laid within our breakdown area, and on several ocassions, when the district engineer's assistant was present at derailments, I discussed this matter with him, ably supported by Tom Walker, the mechanical foreman. One had only to look along a rail, supposedly well-established since the speed restriction had been taken off, to see what a succession of dogs legs it appeared to be. My argument was based on experiences when riding on the footplates of class 5mt and 6p engines. I held the opinion that the unbalanced forces which tended to cause tail wag at the rear of the engine, caused the the trailing wheel pair to travel laterally until the flange struck and bounced off the rail, travelled to the opposite side and did the same there, ad infinitum.

On bull head track much of the flange-thrust was asbsorbed by the assembly of rail, chair and key, wheras flat-bottom track was of heavier and more rigid construction and did not absorb the shocks to anything like the same degree, so that side to side movement was more pronounced.

Tom Walker got out some figures showing that a greater amount of wear had developed in the trailing axle boxes, and at greater frequency, since flat bottom rail was introduced.

Moreover, there was a considerable increase in the use of bearing springs.

I took an opportunity of expressing these findings of several ocassions, but of course, it was rank herasy.

Flat bottom rail had come to stay, and so long as we had steam locomotives we had to put up with the worsened condiitons".

[298]

I remember reading somewhere that there are concerns about the visibility from the cabs of steam locos. This is based not just on the possibility that the exhaust might get in the way of the drivers vision but that the boiler itself is an obstruction. It may be worth noting that Cl20 diesels are always operated cab rather than bonnet first, AFAIK.

 

Regards

Wardrobes are allowed to run bonnet first, as long as the loco is manned by two drivers.

 

Sometimes the top speed is less relevant compared to acceleration, and even then it depends on the route. 86101 is on a tour on the WCML tomorrow and the timings are very slack, even for it and 100mph stock, and I'm sure a 75mph loco could keep to them.

[The Stationmaster]

I'm no expert on the mechnical constraints, real or potential, which have resulted in the general imposition of the 75 mph maximum for main line steam, but I do seem to remember reading that modern permanent way, with its much greater rigidity and continuous welded rail of a much deeper section, was and is one reason for the imposition of this limit.

 

Cheers

Mike

 

You may be right there Mike as the civil engineers certainly had a hand in agreeing the speed limits. As many people will know the BR original limit was 60 mph but as time went David Ward (who was head of the Inter City Special Trains Unit - responsible for steam specials for many years) fought a long and hard campaign to get the limit raised to 75mph for selected locos. From what I can recall the only 'special' locos I ever heard mentioned were all multi-cylinder designs.

[St. Simon]

Hi,

 

I seem to remember that Network rail imposed a new set of resctrictions on speed on the main line based on the diameter of the driving wheels? Something like the 8F No. 48151 being restricted to 45mph, but was allowed to go faster?

 

Not sure when, but a couple of years ago.

 

Simon

[t-b-g]

Sustained running at over 75mph was actually relatively rare in steam days, except perhaps on the very top expresses before WW2. Tornado is cleared for 100mph I think - there is no problem with going faster if you are willing and able to make the safety case to Network Rail!

 

There was talk of the Tornado people trying to get clearance for 90mph running but that seems to have died down. So it has the usual 75mph limit.

[phil-b259]

There was talk of the Tornado people trying to get clearance for 90mph running but that seems to have died down. So it has the usual 75mph limit.

 

I was under the impression Tornado's maximum was actually 85mph and this extra 10mph increase was all the powers that be would agree to, even though Tornado herself is perectly capeable of more.

 

As others have indicated, the current maximum speeds are determined by wheel diameter which is actually a rather crude way of assesing the hammer blow effect on the track. Quite why modern track is less tollerent is something of a mystery to most but I understand that p-way tollerences, specifications, renewal procedures and indeed the whole science behind modern trackwork is very different from that used in the days of steam.

 

Oh yes and because every loco has to be fitted with OTMR these days, speed limits have to be adeared to at all times so gone are the days when you could run at a high speed for part of the journey then slacken off later so as to get an average figure of 75mph.

[Tom Bayford]

Hi,

 

I seem to remember that Network rail imposed a new set of resctrictions on speed on the main line based on the diameter of the driving wheels? Something like the 8F No. 48151 being restricted to 45mph, but was allowed to go faster?

 

Not sure when, but a couple of years ago.

 

Simon

 

48151 is fiited with counter balances so she is cleared for 60 or that is atleast what i have heard

[Bon Accord]

48151 is fiited with counter balances so she is cleared for 60 or that is atleast what i have heard

 

Is it not 50? Regardless, she has run MUCH faster.

Anyway, she is indeed balanced for faster running, denoted by the star above her cabside number - one of a number of 8F's similarly treated by BR.

[5944]

From what I can recall the only 'special' locos I ever heard mentioned were all multi-cylinder designs.

 

Now if we're being pedantic, aren't all steam locos multi-cylindered?

[The Stationmaster]

Now if we're being pedantic, aren't all steam locos multi-cylindered?

 

[t-b-g]

Now if we're being pedantic, aren't all steam locos multi-cylindered?

 

To be really, really pedantic, no they weren't! I recall that one of the industrial firms made some single cylinder shunting locos, with a lever arrangement to drive the wheels on both sides. There may have been others. They appeared on a "unusual loco" website or suchlike (might have been called loco locos!). I love pedantry!

[Bon Accord]

Didn't the LNWR have a single cylinder 4-4-0 which carried a large 'jemmy' bar as part of the toolkit?

The idea being that when the loco was TDC/BDC, the Fireman would jam said jemmy bar under a wheel and exert pressure in an attempt to get said loco under way.

[Christopher125]

Bear in mind as well that apart from Tornado, none of these steam locos has air brakes so they need to plan stops many miles ahead and adjust speed slowly.

 

Some major misconceptions in this thread. To be absolutely clear, Tornado is NOT the only loco with air brakes - 71000, 70000, 45407, 6233, 6201, 34067, 5029 and 60019 to name but a few... Its also wrong to suggest that Vacuum brakes massively increase braking distances.

 

was under the impression Tornado's maximum was actually 85mph and this extra 10mph increase was all the powers that be would agree to, even though Tornado herself is perectly capeable of more.

 

Tornado is a 75mph loco - she ran at 10% overspeed during her initial testing, and there are aspirations for 90mph running, but that is it.

 

Chris

[melmerby]

Didn't the LNWR have a single cylinder 4-4-0 which carried a large 'jemmy' bar as part of the toolkit?

The idea being that when the loco was TDC/BDC, the Fireman would jam said jemmy bar under a wheel and exert pressure in an attempt to get said loco under way.

 

Wasn't that one of FW Webb's non-coupled compounds (strictly a 2-2-2-0 or similar)? - Where it could end up TDC/BDC and not move!

 

Keith