Permitted Speeds for Steam Locomotives

As we are all aware the permitted speeds for steam locomotives on mainline charters is (i believe) based on Driving wheel diameter in the following blocks
Below 5 ft 50mph
5 -> 6Ft 60MPH
6fT + 75MPH

I do not think i am alone in thinking that this is a a bit of a rough and ready Yardstick as it doesnt consider Locomotive size, age, general design, balancing / track forces.... and in a few cases makes little sense.
Even the old 1mph/ 1 inch driving wheel diameter rule of thumb would mean that a Railtour is not unduly hampered if a Black five has to be brought in for a West country.

Tornado, god bless, is the first to challenge the upper speed limit. Tornado is a unique case in as much as its new and therefore should arguably be allowed to perform ' to design' and has undergone track forces testing, but if a derogation is granted the regulations can perhaps be challenged.... ?

Far from advocating that museum pieces should be allowed to hurtle round the network at whatever speed they
fancy, i think that Normal and Absoloute Max Speed recomendations should actually be worked out class by class
but absolouute max only permitted on the day and by individual vehicle.

Normal max speed recomendations could bebased on Wheel size only as a workable guideline even though this doesnt factor in , piston speeds, track forces and suitabilty of the original design which would be used to develop the Absoloute max

Actual speed of an individual loco on the day would be governed by - the wishes of the owners, the age and condition of the loco as determined at the fitness to run examination, and the discretion of the traction inspector on the footplate that there was the need to push the loco to its maximum.

EG On this basis say Clan Line might have a recommended speed 74mph but a Class max of 90mph. the owners might be happy for it to do this max speed but only if required to satisfy its customers, its noted as being in good condition having run in from a recent overhaul . to make up some lost time the traction inspector, in conjunction with the driver and owners representative lets it run at up to 85 mph for 20 miles on an easy stretch of track which enables it to clear that section ahead of a HST instead of it being pulled over to let it pass and everyone missing thier connections/ last tube home /whatever...

Its been suggested that Steam is a guest on Network rail and its best not to rock the boat, but that bit of flexibilty to run locos faster on easier stretches might mean less 'thrash' on harder sections and make allow steam to be less of a 'Nuissance' when inevitable slight delays/ hold ups happen... ?

 

An interesting thought Class8

I for one certainly agree that a Steam loco should be able to reach its max speed where ever necessary to avoid holding up service trains due to any circumstances that prevail, ie missing pathing slots etc.

It will be interesting to see what happens when Tornado is eventually passed for 90/100 mph running - will the owners/owning groups of the other mainline registered engines want their steeds to be able to perform at higher speeds for long durations on track that is immensely much smoother running than fifty years ago.

And what about the train operating companies, with Tornado basically tied to Steam Dreams, will they want a slice of that action, or will they be happy with what they already have?

To increase the line speed of loco's may also result in them being able to use all of the London termini on a more regular basis during the week so that they dont foul or get fouled by service trains.

Or are Joe Public more than happy with the current speed limits to amble along lines between 60 -75mph reliving the "glory" days of Steam/

 

Railway Group Standard GO/RT3440 Issue 2 defined the limits for steam engines based on driving wheel diameter as follows:

<5ft 0in max 35mph
<5ft 8in max 50mph
<6ft 2in max 60mph
>=6ft 2in max 75mph

Quite a few engines have derogations which allow higher speeds than these, but many owners are happy with current limits. Generally speaking, high speed=high maintenance cost. Another important factor to remember is that steam engine acceleration is a lot less than modern traction, so in many cases higher max speed doesn't always help greatly with pathing, unless it can be sustained over a long distance.

David

 

Interesting Dave

I wasnt aware that this existed (well having nothing to do with railways why would I !), and of course the harder you work a loco the faster things wear out - a la 60163 - and they want to go faster! (Iwill say no more on that subject).

Dave

 

Given that all these "museum pieces" were designed to run at high speeds day in and day out for many years, it does seem a little odd that the powers that be want to restrict them so much. They are all beautifully maintained by dedicated and committed support staff and, when you consider the likes of Ian Riley, Tyseley, etc, often with a highly experienced engineering base behind them. They run on far superior track to that on which they were built to run, so why not give them a higher permitted max? All the express passenger engines were designed and built to run at high speed, with wide open regulators and short cutoffs for maximum economy. The sustained, gentle draught on the fire, led to drifting steam obscuring the driver's view and streamlining / smoke deflectors of varying designs.

All the modern big 'uns, the A4, 3,1, the Duchess, the Bulleids and the Duke will have no problem running at 85 or 90mph for long stretches if the road permits. Anyone still doubting the ability of the GWR 4-6-0s to do the biz should read J. W. Street's book, "I drove the Cheltenham Flyer," where he is running through the Thames Valley on Brunel's billiard table with a Castle in the 80s and 90s, adjusting the cutoff from 23% to 17%, etc. - and this was before the War.


Regards,

jtx

P.S. Forgot to mention the Brits, they were goers as well. All the smaller stuff could go too. I was in the support coach behind 5000 when it was clocked at 88mph through Leominster a good few years ago...

 

jtx now you've let the cat out of the bag I knew it had gone well over the limit but no to what extent and, that according to the Bridgnorth guys it was a rough 5 nowhere near as smooth as 5110.

I still believe the BR way was good, if you are on time stick to the limit if you are behind try to make up time if possible.

The current regulations show startling similarities to the Knee jerk limits that were proposed after the 90mph 9F's.

Didn't 4930 go through Abergavenny at 77mph on one trip?

Cheers Dave

 

Whilst perhaps it would be good for steam to be able to exceed the 75mph limit for maybe a short gallop to make up time or to clear a certain section, I do not want to think of engines being thrashed for mile upon mile just to please the enthusiasts.

With the exception of "Tornado" all locos are now old ladies and so we should treat them with respect.

Just my thoughts.

Stan

 

the speed limit should be flexible to a degree , so that with in reason and as long as its safe a loco should be able to run above 75mph to make up time, or to clear a path for operational reasons up to a top speed of 90 which is the limit for Mk 1 coaches i believe , but i dont think its good practice to run at a higher speed all day long, unless its a one of such as the non stop run last year which could have ran at 90 to make it really special
should all engines have this flexibility?, it should be only allowed where the engine is known to be in good condition and the maintance regime is reconised as being suitable for high speed running for instance would you trust running a worn out engine at 90 thats nearly at the end of its ticket? where as an engine thats well looked after and well run in could do it with no problem

 

The trouble is that modern rules/security regimes demand hard and fast limits. Flexible limits tend to be abused. From what little I understand of this stuff I suspect it would make more sense to be able to run at a constant steaming rate and run faster downhill and slower uphill for an average of 75, but I cannot imagine the regulators (that's people, not locomotive controls) coming up with a way to make it work.

 

But I would wonder whether a loco would be thrashed harder to accelerate as quickly as possible to a maximum, than it would be to accelerate slightly more gradually to a slightly higher maximum? What I mean is whether a higher top speed does more harm than hard acceleration? Same overall section time in both instances. I'm no engineer so the comparitive merits I have no idea about, but just my thoughts.

Playing devil's advocate, suppose the class 8s had dispensation to run at 90mph. What actual difference would this make in terms of mainline running? Will the opportunities available on the big railway to fully exploit a higher top speed really justify any extra costs and wear to running the loco? With the costs involved with running a loco on the mainline already so high, would there even be any owners willing to take that risk?

Interesting stuff, but in my mind top speed isn't the bee all an end all of loco performance. 45407 at full regulator on the West Highland line was epic back in August, but the speed on the entire journey probably never surpassed 50mph.

 

I think being allowed to run up to a higher maximum at the request of the Traction Inspector with R.O's permission to solve pathing issues and delays would be useful. There must have been many cases where a good run was blighted due to a missed path and the dreaded "now following the stopper" situation was invoked. These forays into extra-speed would not be regular, lengthy episodes, so wear should be minimised.

 

Surely the increase in rotational forces due to the motion thrashing around that bit faster would add stress, and that is down to increased speed regardless of the state of the loco (i.e coasting or applying traction)

 

There are many factors at work here. Most important is the design specification of the locomotive. Then there is the general condition of individual engines of a particular design. Thirdly comes the financial consideration.

There are some locomotive owners who are quite happy for their engines to run according to their design specification, say running in the high 80s and low 90s in easy ecconomical conditions. Other owners are more conservative and are quite happy with a 60 mph limit - their charges have some 30mph in hand but that is the way they choose to operate their charges. Interestingly some of the former group have about 30 mph in hand too.

In the past some engines have worked a little beyond their natural limit, 13809 for example, but this was not for long and little damage was done and why should it have been given the engines condition?


If your motion is thrashing then you need to get some work done on it - you shouldn't be out on the mainline.

 

I think track damage is a non starter with regard to steam.

Mr Bob Burkhardt covered this when he was boss of EWS.

He said that the passage of steam trains on todays railways is so infrequent that they cause no harm, compare this to the steam age when there was a constant stream of steam trains.

Quite logical when you think of it this way.

Cheers Dave

 

I think I read somewhere that one of the reasons for the speed limits relating to wheel size was something to do with 'hammer blow', ie the more revolutions a wheel makes the more likelihood of damage to the track.
Hopefully someone on here will be able to explain it better.
Also the speed limits imposed are not absolutes, I can't remember the exact figures but I believe it's somewhere in the region of 10 - 12% above permitted speeds to take account of the fact that a steam loco's speedometer needle will bounce about a bit at high speed due to the motion of the loco.

 

The out of balance force is calculated as F= MxRxV^2, where F is the Force; M is the Mass (weight); R is the distance of the imbalance from the centre of rotation, and V is Rotational Velocity - squared. So at low speed, even a large imbalance has little effect; but at high speeds, even a small imbalance has a large effect.

It should be realised though that with multi-cylindered engines the out of balance forces largely cancel each other out.

 

Oh dear salty, did you really say this?
I would have thought with the experiences you've had and the organisation you have been involved with you should have known better than this piece of absolute *******.