From Newsgroup: uk.railway

Many years ago, one of the late Andy Breen's last contributions to this
group was on the topic of early locomotives, specifically their operating procedures and metallurgy. In the great tradition of usenet thread drift,
the thread was titled "Welding aluminium"

Accordingly, I think the group may be interested in this post from "On Historical Lines" Facebook page, which is the work of railway historian
Anthony Dawson. <https://www.facebook.com/share/p/16Uk2mvZ7T/>

I'm not sure whether it's visible without a Facebook login, so I'm sure he won't mind me repeating the text here:

<quote>

So now that the dust has settled from celebrating the bicentenary of the Stockton & Darlington Railway, and with the epic run of the "Locomotion" replica on the mainline, I think it's worth taking a quick look at the performance of the replica in 1975, 2025 and compare that with the
original.

To start off with, it has to be remembered that the replica of "Locomotion"
is not a replica of the locomotive as it appeared visually or mechanically
at any stage in its working life. It is a replica of a collection of parts
put together by William Bouch at Shildon Works in 1857 essentially creating
a sculpture of a locomotive: it was never intended to be a working
locomotive and it was never intended to operate. There is no evidence it
has ever been steamed, but did have the driving gear moving through steam supplied by an external source at a very low pressure.

Despite Ernest Forward in the 1940s and Brian Reed in the early 1970s
noting that "Locomotion" was built was nothing like the preserved
locomotive, Mike Satow and his team copied what they saw in Darlington. Amazingly it worked, but only just.

One of the problems of the replica which stems from the "preserved"
locomotive is the position of the flue: due to using longer stroke
cylinders intended for when it had a return flue boiler, it means that the single large diameter flue is place very low down in the boiler. This
really impedes heat transfer. When the 1975 replica was lit up it was noted that the top of the boiler you could fry eggs on, but the bottom was only
luke warm. Water circulation and heat transfer was poor - largely due to
the position of the flue so low down in the boiler barrel.

Because of this it took several hours to raise steam: fire lit at 11.00
first pressure at 14.00 working pressure (50psi) at 15.00.

Prior to draughting modifications, in 2025 the replica also presented
similar issues - despite being fitted with a short bank of tubes. In fact
the tubes presented more of a hindrance than a help as the gas flow through
the boiler was so low, and the fire temperature equally low, that any ash
or soot just clogged up the tubes and coal was not combusting fully leading
to un burnt coal clogging up the flue. Eventually the tube cluster would be sufficiently clogged either through steam raising or under way as to cause
the engine to run out of steam. Fewer, larger diameter flue tubes would
have been preferable. In 1975 running down hill under load the fire was
prone to clinkering becuase of poor gas flow and the low temperature of the fire.

The poor gas flow was likely due to a mistake made by Stephenson back in
1825, but one which is understandable given availability of materials and ability to roll ironplate. Stephenson's locomotives used a large diameter (24inch OD) flue tube which passed through the boiler and emerged with a
large diameter cylindrical chimney. No attempt was made to cone or taper
the flue or the chimney to improve gas flow. This is odd given that
Blenkinsop & Murray in 1812 used a tapered flue and chimney, so too John
Buddle with "Steam Elephant" in 1815. They recognised the need to imrpove
gas flow and clearly understood that. But at Killingworth colliery,
Stephenson may not have recognised this, or thought it was unimportant. It
is likely Stephenson also lacked the skill or means to roll these
complicated tubes. It's also worth noting that Stephenson's first
locomotive, "Blucher" really only just worked and was shy of steam until
the exhaust was routed into the chimney via a coned pipe to improve the gas flow, transforming its performance. But from 1814 to 1825 George stuck with
a cylindrical flue and chimney of pretty much the same diameter which must
have presented many problems in steam generation.

The other problem was that in 1857 William Bouch replaced the 1834
return-flue with a replica straight flue. But because the return-flue had
been smaller, and the locomotive had had longer-stroke cylinders fitted, it meant that there was insufficient space to locate the flue tube higher up
in the boiler barrel without it fouling the cylinders. Thus the flue was located very low down, which lead to poor water circulation and uneven
heating through the boiler. And, because the post-1857 condition of "Locomotion" was replicated, it means the replica also has the same inaccurately located flue tube, with the corresponding detrimental affect
on steam raising.

On the replica a steam blower was fitted and the chimney was sleeved
internally to reduce its diameter which had an immediate effect of
improving steaming.

But, it still only just works. In 1975 and 2025 the boiler was undable to maintain pressure against the water pump. When the firebox door was opened
the sudden inrush of cold air chilled the fire with the boiler pressure
visibly dropping. It has been suggested the loco was bascially 'boxed up' before setting off but would need regular periods to stop for a 'blow up'
which with the replica were aided through the use of a blower, which the original guys didn't have.

It needs to operate at full boiler pressure or as close to it as possible.
At 48psi the safety valve starts to feather which causes a considerable reduction in pressure - this would have been even more pronounced with a lever-arm safety valve bouncing away. Its no wonder S&DR crews were in the habit of tying the lever arm down! On the replica the valve fully lifts at 50psi and only re-seats at 45psi and on such a low pressure that's 20% of
your pressure - and power - gone. It's easy to see why Hackworth rebuilt
the engine with a double-return flue and return flue boiler to increase the heating surface. But the big problem with a flue tube boiler is the lack of depth for flame development to enable the fire to burn at its hottest -
hence the firebox proper being a crucial break through. With its return
flue boiler the engine would have a larger capacity to make steam and would likely be less prone to being "winded" but would likely be just as fussy
over fuel type and firing.

Crucially, however, the return flue tapered. So not only was there are a
larger wetted area, but it would have helped improve gas flow. This wasn't
a break through by Hackworth - he was going back to the earlier designs of Trevithick whose locomotive at Pen-y-darren had used a double return flue
(two chimneys at the same end as the firebox) as "Locomotion" would later
use, and indeed, one of the Blenkinsop & Murray locomotives also used.
Indeed, after Trevithick the next locomotive builders to adopt the return
flue were Blenkinsop & Murray, but I digress. The Stephenson boiler with
its cylindrical flue and chimney were crude in comparison to what others
were doing and would have created problems with steam raising and gas flow,
yet he stuck with them largely because they were simple and easy to manufacture.

Through both valves being worked from a single eccentric it means the valve timing isn't perfect and the locomotive is a bit 'three legged' with a pronounced dead spot for about 1/8 of a rotation when it loses power.
Audibly it's noticeable that there were three strong beats and one weak
one. This poor valve timing is exacerbated through the valve rod for the
rear piston being cranked around the boiler barrel and thus being longer
than the leading one. Furthermore, with everything anchored to the boiler,
as soon as the boiler is pressurised and it expands it throws all the
geometry out. So too the vertical forces from the piston in the cylider.
It's probably as good as it could be got.

In terms of performance, on a falling gradient speeds of 9 - 10mph could be reached with a trailing load. On a rising gradient, however, things could
be more difficult. Michael Bailey and Peter Davidson's analysis of
"Locomotion" demonstrates that the engine worked, but like the replica,
only just. On a falling gradient it only needed about 9psi to move an 80
ton train (Shildon to Stockton), with the driver building up sufficent
speed and momentum on the falling gradient to help him ascend any rises -
and rising gradients are where the replica came unstuck in 1975 needing
time to blow up. With full boiler pressure the engine could have generated
34HP which would have been sufficient to pull a load of empties back up
from Stockton to Shildon. Head winds and poor weather would also have a detrimental effect on its performance.

As Davidson has previously noted, "Locomotion" only just worked, but
despite these problems was fit for service because it was able to put in
more work than a horse or horses could in taking waggons down to Stockton
and back. Crucially it was also much cheaper than horses in terms of the
cost of purchase, fodder, and care and thus even though it only just
worked, presented cost-savings.

What is abundently clear, is that the Stephenson "Killingworth Type" was
good enough: good enough for working low speed trains, initially over a
short distance, over gradients which favoured the load. "Locomotion" was
the utlimate expression of the type. And whilst it opened the first mechanically-worked public railway, it was entirely unsuited for a
timetabled, mainline railway. Yet, in just under five years the locomotive
was completely revolutionised largely thanks to Robert Stephenson and the demand of the mainline railway.

"Locomotion" works but only just - but it's fit for purpose.

</quote>
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From Newsgroup: uk.railway

Anna Noyd-Dryver <anna@noyd-dryver.com> wrote:

<quote>

So now that the dust has settled from celebrating the bicentenary of the Stockton & Darlington Railway, and with the epic run of the "Locomotion" replica on the mainline, I think it's worth taking a quick look at the performance of the replica in 1975, 2025 and compare that with the
original.

To start off with, it has to be remembered that the replica of "Locomotion" is not a replica of the locomotive as it appeared visually or mechanically
at any stage in its working life. It is a replica of a collection of parts put together by William Bouch at Shildon Works in 1857 essentially creating
a sculpture of a locomotive: it was never intended to be a working
locomotive and it was never intended to operate. There is no evidence it
has ever been steamed, but did have the driving gear moving through steam supplied by an external source at a very low pressure.

</quote>

Two further things of note:

200 years ago the locomotive was called Active, not Locomotion; it was
renamed in 1834

The current condition of the locomotive and replica, do not actually
represent a condition in which it originally existed prior to preservation.
A handy set of diagrams of its changing appearance can be found here: <https://x.com/1825steam/status/1974790810978984420> and here <https://x.com/1825steam/status/1974942692045119974>

--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.railway

On 07/10/2025 14:46, Anna Noyd-Dryver wrote:

Anna Noyd-Dryver <anna@noyd-dryver.com> wrote:

<quote>

So now that the dust has settled from celebrating the bicentenary of the
Stockton & Darlington Railway, and with the epic run of the "Locomotion"
replica on the mainline, I think it's worth taking a quick look at the
performance of the replica in 1975, 2025 and compare that with the
original.

To start off with, it has to be remembered that the replica of "Locomotion" >> is not a replica of the locomotive as it appeared visually or mechanically >> at any stage in its working life. It is a replica of a collection of parts >> put together by William Bouch at Shildon Works in 1857 essentially creating >> a sculpture of a locomotive: it was never intended to be a working
locomotive and it was never intended to operate. There is no evidence it
has ever been steamed, but did have the driving gear moving through steam
supplied by an external source at a very low pressure.

</quote>

Two further things of note:

200 years ago the locomotive was called Active, not Locomotion; it was renamed in 1834

The current condition of the locomotive and replica, do not actually represent a condition in which it originally existed prior to preservation.
A handy set of diagrams of its changing appearance can be found here: <https://x.com/1825steam/status/1974790810978984420> and here <https://x.com/1825steam/status/1974942692045119974>

Many thanks for posting this.
--
Colin

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From Newsgroup: uk.railway

ColinR <rail@greystane.shetland.co.uk> wrote:

On 07/10/2025 14:46, Anna Noyd-Dryver wrote:

Anna Noyd-Dryver <anna@noyd-dryver.com> wrote:

<quote>

So now that the dust has settled from celebrating the bicentenary of the >>> Stockton & Darlington Railway, and with the epic run of the "Locomotion" >>> replica on the mainline, I think it's worth taking a quick look at the
performance of the replica in 1975, 2025 and compare that with the
original.

To start off with, it has to be remembered that the replica of "Locomotion" >>> is not a replica of the locomotive as it appeared visually or mechanically >>> at any stage in its working life. It is a replica of a collection of parts >>> put together by William Bouch at Shildon Works in 1857 essentially creating >>> a sculpture of a locomotive: it was never intended to be a working
locomotive and it was never intended to operate. There is no evidence it >>> has ever been steamed, but did have the driving gear moving through steam >>> supplied by an external source at a very low pressure.

</quote>

Two further things of note:

200 years ago the locomotive was called Active, not Locomotion; it was
renamed in 1834

The current condition of the locomotive and replica, do not actually
represent a condition in which it originally existed prior to preservation. >> A handy set of diagrams of its changing appearance can be found here:
<https://x.com/1825steam/status/1974790810978984420> and here
<https://x.com/1825steam/status/1974942692045119974>

Many thanks for posting this.

What he said!

Sam
--
The entity formerly known as Sam.Wilson@ed.ac.uk
Spit the dummy to reply
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From Newsgroup: uk.railway

Sam Wilson wrote:

ColinR <rail@greystane.shetland.co.uk> wrote:

On 07/10/2025 14:46, Anna Noyd-Dryver wrote:

Anna Noyd-Dryver <anna@noyd-dryver.com> wrote:

<quote>

So now that the dust has settled from celebrating the bicentenary

of the >>> Stockton & Darlington Railway, and with the epic run of
the "Locomotion" >>> replica on the mainline, I think it's worth
taking a quick look at the >>> performance of the replica in 1975,
2025 and compare that with the >>> original.

To start off with, it has to be remembered that the replica of "Locomotion" >>> is not a replica of the locomotive as it appeared

visually or mechanically >>> at any stage in its working life. It is
a replica of a collection of parts >>> put together by William Bouch
at Shildon Works in 1857 essentially creating >>> a sculpture of a locomotive: it was never intended to be a working >>> locomotive and
it was never intended to operate. There is no evidence it >>> has
ever been steamed, but did have the driving gear moving through steam

supplied by an external source at a very low pressure. >>>
</quote>

Two further things of note:

200 years ago the locomotive was called Active, not Locomotion; it

was >> renamed in 1834

The current condition of the locomotive and replica, do not

actually >> represent a condition in which it originally existed
prior to preservation. >> A handy set of diagrams of its changing
appearance can be found here: >> <https://x.com/1825steam/status/1974790810978984420> and here >> <https://x.com/1825steam/status/1974942692045119974> >>

Many thanks for posting this.

What he said!

Sam

There is a YouTube thing about this at
https://youtu.be/pP44h0CduWY?si=E803ClKMhffz3a4l
(Locomotion Mythbusting: The TRUTH About the Infamous 1825 Locomotive
| Curator with a Camera)

This says some of the above, with vague pointing at the engine itself,
that be of limited may help.
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