Twin Sisters, using Romford / Markits parts

[What About The Bee]

The LMR locomotive Twin Sisters was a very early Robert Stephenson production.   Construction began in 1828, a mere 3 years after Active/Locomotion for the S&DR.  By 1829, Twin Sisters was hard at work, constructing the right of way.  Today, Twin Sisters would be termed a 'maintenance of way' engine.  

Twin Sisters was also pressed into early freight service, we have notice of such on 12 Feb 1831, when Twin Sisters was involved in a railway accident, running over one William Fewburn, rending him assunder.  Twin Sisters was termed "one of the oldest engines on the railway", which is not completely true.  Twin Sisters was the oldest, bar none.

On 12 Sept 1829, we have a newspaper report indicating Twin Sisters was hauling 50 to 60 tons of marl at 5 or 6 mph, with an empty speed of 10 mph, during construction of the LMR. Marl is simply dirt and rock, in other words excavated material.  We have investigated the common utility waggons that Twin Sisters likely hauled.  Hornby calls them "coal waggons", R60164.  Each capable of 4½ tons of marl, Twin Sisters was hauling a 11 to 14 waggon consist.

The same report indicates "There are two chimneys, through the sides of which openings are left to throw in the fuel".  This is truly an odd feature of the locomotive!

Issac Shaw presents us with the only drawing of Twin Sisters, to my knowledge.

There are some scaling issues here, as the individual with the wheelbarrow is drawn well over two feet tall, as he is in-between the rails, gauge 4'8½". If we accept the two adults further along the tracks as correct, the wheels are roughly 5 feet in diameter.

Another locomotive by Robert Stephenson, Lancashire Witch, was constructed at nearly the same time.  We have this marvelous mechanical drawing of Lancashire Witch, appearing in Coste, Memoire Sur Les Chemins a Ornieres, 1830.  

This has exquisite detail, such as the steam chest, eccentrics and valve gear.  When comparing the piston arrangement betwixt Coste and Shaw, great similarity will be found

Note the crosshead guide bar goose neck on each, drawn in the same convoluted way.  Such a distinct feature, lending support to the commonality argument.  Note that Lancashire Witch is shown on fishbelly rail.

Modeling

I will use Romford / Markits wheels and axles.  

Quartering is built into the axles, with the square boss on the axle fitting into the precisely sized square hole on the back of the wheels.  The round retaining nut sits in a circular bore on the front.  Shown are 20 mm wheels, or scale 5 feet, just as implied by Shaw.

Consistent with my practice, the wheels and axles were measured and place into CAD.  I insist on getting the details right in CAD, as this makes further refinement a reduction to practice.  Note the wheels are automatically quartered.

Crankpins, crankpin bushings and axle bushings are added.

The axle bushings, shown in the initial photograph, give a metal on metal bearing surface, yielding low friction and long life.

With one axle installed, multiply by three!  Shaw shows the wheels very close to each other.  I will retain that design feature, 0.5 mm apart at the flange tip. 

Notice that the crankpin on the right has two crankpin bushes.  One for the coupling rod, to couple the wheels together.  One for the connecting rod, to connect the wheel to the piston.  Stacked.

The classic Romford line offers a 60:1 worm gear arrangement.  In consideration of the top speed, a high gear ratio is called for.  The worm has a 1.5 mm bore, which matches the selected motor.  The upper shaft will go right up a chimney.

The wheels are turned off, for visibility.  This center axle will not move side to side in compliance for second radius curves. This will permit the gears to remain stable, on location of mesh. I do not have the gears on hand (yet) and there is dilemma not resolved by the specification.  If drawn to the spec, the gears interfere with each other, yet the gear to gear center distance is specified to two decimal places, making this a conundrum.   The gears are metal and have a long history.  The conundrum will be resolved later.

The coupling rods, connecting rods and crossheads are added.

These too are commercial parts.  There are 'universal coupling rods' available from Alan Gibson and others.  The double guidebar crossheads are a Markits item.

At last, we come to the first part I must make.  The crosshead guidebars.

Shown in fushia, the length of these is quite critical.  Too short, and they do not support the crosshead over the full range of travel.  Too long, and the connecting rod interferes with the guidebars.  I was forced to compromise by providing a small radius to the end of the guidebars.  There is clearance now, but only just, a function of accurately measured parts and a reduction to practice.

How in the world did Stephenson resolve this same interference?  Consult the Lancashire Witch.  The crosshead is shown 

The piston rod and the connecting rod are NOT in the same plane as the crosshead.  In both plan and elevation views, this is quite clearly shown!  

With the mechanicals sketched in, it is possible to rough in the 3d printed plastic shell, and place the locomotive on a second radius curve.  Yes, there is room for axle compliance.

Note the pistons, which scale to 18" in diameter on Lancashire Witch.  Enormous for such a tiny locomotive.  The pistons are supported on triangular plates, similar to an array of Stephenson locomotives, such as Rocket.

The splashers over the wheels are included as implied by Shaw, with the crosshead going directly through the side mounted footplates.  A feature also found on locomotion.  

In general, the concept seems workable.  The majority of the mechanicals are commercially available Romford / Markits parts.  The only manufactured mechanical being the crosshead guidebars.  Brass bar stock will be readily purchased to fit the crosshead groove.  The details can be added to the 3D model to suit, a primary example being the cross mounted steam reservoir between the chimneys.

Before further progress can be made, the commercial parts must be sourced, measured and installed into CAD, not the least of which is the gear conundrum.

Bee
 

Edited June 20 by What About The Bee
Autocorrect corrected!

[What About The Bee]

Always so many details to discover.   

In the previous post, I didn't include this drawing of Twin Sisters from The Liverpool & Manchester Railway, R.H.G. Thomas, 1980.  

It appeared to be from a periodical known as "The Engineer", a non contemporary resource. This attribution was based on the font used, which is quite distinctive.  I am always very leary of non period sources and so skipped inclusion.

It turns out that Thomas got the image from Marshall, A Century of Locomotive Building by Robert Stephenson, published in 1923 and again, likely from "The Engineer".  Marshall's image is therefore well out of period, the build to scrap period for Twin Sisters being 1828 to Dec. 1831.

The choice morsel offered by Marshall, in 1923, is that the image in his book was "traced from the original undated drawing".  What?? 

I have investigated Marshall¹, and found other drawings, the most instructive being of Patentee, LMR33.  The drawing is signed by Robert Stephenson, dated June 12, 1840.  Patentee appeared on the railway in 1834.  Thus, these drawings are not precisely contemporary.  They may reflect remembrance by principals and therefore contain errors.  Yet they are directly from the firm of Robert Stephenson and Co. Ltd and thus authoritative.  Reviewed, apparently, by Stephenson himself.

The original drawing of Twin Sisters is labeled "Liverpool Engine C" on that drawing, but is clearly Twin Sisters.  It is held in public view by the Science Museum.  

https://collection.sciencemuseumgroup.org.uk/documents/aa110001922/liverpool-engine-c-drawing

Please zoom the Science Museum's image to see detail.  Title in upper right hand corner.

I have examined the drawing online, at high zoom magnification.  It is drawn at a 1:8 scale, as noted on the drawing.  

One concern of note is that of the drawing traced in Marshall, the scale added appears inaccurate.  Remember, these are "traced from the undated original". The scale is not drawn on the original, it is merely stated as 1½ inches per foot.   For example, when scaling² the original drawing, I obtain a wheel diameter of 4' 1⅛" +/- ⅜".    When scaling the drawing from Marshall, using that added scale, I obtain 3' 9" wheel diameter.  That is a significant delta of ~4".  Marshall's scale is not to be trusted³.

Yet, there are some interesting details revealed in the Stephenson mechanical drawing.

In the end elevation, the drawing specifies that the back to back is 4 feet, 5½ inches.  Further, that the back of flange to face of rail is 1⅜ inches.  5½+1⅜+1⅜ = 8¼, consistent with the known gauge 4'8¼".  Not something to reproduce in the model, but something that lends to understanding this early railway.

The valve gear is timed to the axle under the pistons, leading to the steam chest.  The valve gear is a detail not visible in Shaw but the steam chest is.  

Not only is there a horizontally mounted steam reservoir, there are two other tanks mounted vertically nestled on either side, in between the large boilers.  Perhaps condensation traps or additional resevoirs.  This was made clear by the Stephenson drawing and once clear, became evident in  the Shaw depiction.  I hilariously missed these tanks in the first revision.

Not visible anywhere are the openings in the chimney for loading fuel, sadly we still just have the description.  Pity that, such an odd feature.

The Stephenson drawing does not show any body work at all.  It is merely a mechanical configuration drawing.  I trust that Shaw draws what he sees, and therefore, the body must be.

With the OO squish problem, details such as boiler diameter cannot be directly translated. However, the ratio between boiler diameter to chimney diameter & etc can be measured and installed, leading to a reasonable appearance in OO.

Examples:
Chimney : Boiler ratio = .239
Horizontal Steam Reservoir : Boiler ratio = .148
Etc.

My next task is clear. The CAD will be corrected to more closely match the Stephenson drawing, whilst including design cues from Shaw.

Bee

¹ The book covers locomotives right to 1923, for example:

Other modelers may wish to consult this book for details.  Who would not wish to model this beauty? 😉

²Scaling drawings is typically bad engineering practice.  It is fine for making models.  The wheel scales somewhere between 4' ¾" wheel diameter to 4' 1½" wheel diameter.  The imprecision is due to the Museum's resolution of  ~¹/₁₆" per pixel and my ability to precisely pick out which pixel represents the line.

³Note that this 4 foot wheel diameter makes the adults in Shaw terribly short, which leads us back to scaling issues in Shaw as well. 
 

Edited June 23 by What About The Bee
Italicized book titles for clarity

[What About The Bee]

A brief update.

Firstly, the author of the 1923 book is J.G.H.Warren, not Marshall.  When searching for the book, I used the full title and "Marshall" as the author.  Google found the book, and I never noticed I had the wrong author.  Whoops!

I've installed the scale 4 foot (16mm) wheels and adjusted the valve gear to match.  Various ratios were used to fine tune the model

After a great deal of thought and examination of the Robert Stephenson and Co Ltd drawing, I think I have a solution to the reservoir system.

In my drawing, it is clear to see that steam rises from the two main boilers and goes into the dark blue horizontal reservoir, via the pink pipe.  Its behind the chimney in the Stephenson dwg.

Yet in the Stephenson dwg, there are two vertical risers, internal to the horizontal reservoir.

Ah ha!  Steam may condense back into water.  If it does, it flows back down the pink pipe and into the main boilers.  It cannot flow up into the risers, water flows down, not up.  Steam does flow up into the vertical riser and down into the light blue vertical reservoirs, my drawing.  From there to the piston steam chests, not shown.

There is likely a blow down valve at the base of each vertical reservoir.  There will always be a little condensation.  Not terrifically relevant for the model, but helps to understand how Twin Sisters really worked.

Bee

 

Edited June 24 by What About The Bee
Grammar and clarity

[What About The Bee]

This update will focus on one particular component, the steam cylinder for Twin Sisters.  It is a prominent feature, and the driving mechanism of any steam locomotive.

1828 was a good year for Robert Stephenson and Co Ltd.  Robert had returned from South America and there was new demand from the LMR.

There was an order for their 11th locomotive, the Lancashire Witch.  The locomotive was delivered in June of 1828, to the LMR, who turned it over to the Bolton and Leigh. There exists a color image of Lancashire Witch, dated 1828.  You may observe the image on page 3 of this download, Friends of the Stockton and Darlington Railway 

https://www.sdr1825.org.uk/wp-content/uploads/2021/03/Pride-of-Newcastle-R-State.pdf

The 1828 illustration has been reduced to a line drawing, reproduced everywhere.  The cylinder has a distinct design.

Locomotive #12 was delivered to the Delaware and Hudson Canal Company, in the USA, in October of 1828.  It was called "Pride of Newcastle" by the company, renamed "America" by the D&HC, although there is some dispute regards the name.

This image appears in the Engineer and Railroad Journal, Vol LXVII, No 1, dated 1893.  The safety valve housing on the back of the boiler is a clear anachronism.  The nameplate is a fanciful addition. While I cannot vouch for the authoritative nature of a non-period drawing, the steam cylinder is definite, as you will soon see.

Lastly, we have the Twin Sisters, Robert Stephenson and Co Ltd # 13 Started 1 December, per a letter by Robert Stephenson.  Delivered in July of 1829, per the LMR Board of Directors.  8 months, start to finish. The drawing of the steam cylinder is by Robert Stephenson and Co, so I think we can trust this.

So what of the steam cylinders?

These three cylinders for the three sequential locomotives are compared in one image.  I think you will agree that they look to be the same cylinder.  Two bands divide the length into 3 parts.  There is a stepped down diameter around the piston rod and packing.  There is a protruding plate on the back.  

The casting for this cylinder would be quite complicated, with internal steam injection ports and exhaust ports.  Expensive to design, expensive to make.   We are looking at a relatively small time frame of sequential locomotives. It makes sense that the cylinder would be the same for all three locomotives.  

But here is the absolute cherry.  In Warren's book, there is a picture of an artifact held by the Smithsonian Institution in Washington DC.  

This is the cylinder from Pride of Newcastle / America.    This is the actual part, not a replica.  Notice how this compares to the drawings. I would call it a match.  

There are details in that image not present in the drawings.  

Example: the slide valve internal to the steam chest.  

Example: the nut to press the packing around the piston rod.  

Example: how the piston mounts to the plate.  Those flanges are simply not shown in the Stephenson drawings, yet the mounting arrangement is used generally for a long series of locomotives, to include Rocket (Robert Stephenson and Co Ltd #19) and the Rocket-Class locomotives on the LMR, all the way to Northumbrian LMR7. 

The critical detail offered by the photograph is the location of steam admission port to the steam chest.  This permits the path of the plumbing from the vertical reservoir to the steam chest to be logically construed.  Look again at the Lancashire Witch line drawing to see the steam piped to the steam chest.

Shaw

Shaw may not have captured every detail.  It's a sketch, not a photograph. Twin Sisters wasn't even the focus of the image.  Yet the sketch appears to show a pipe leading from the vertical reservoir to the steam chest.  This could be a leg for a support bracket for the crosshead guide bars, but where are the other three legs?  The steam admission port is just behind the flange, moreover, the pipe would be mounted to the plate.  It would be mostly hidden, given the perspective of the drawing.

With such exquisite detail available, it is installed in CAD for OO Twin Sisters.  Perhaps not in every feature, it is tiny after all.  I will eventually touch it up to more closely resemble the real thing.

Bee

[threelink]

Super stuff as ever, Bee. Please will you post a photo of the finished article, when you have produced it. These early locos, especially the more implausible specimens, are a source of never ending fascination. The same is true of early stationary engines, especially those produced by diy smiths and engineers, often working for some small out of the way and probably impoverished concern. I recall finding the fragmentary remains of an ancient Newcomen engine at a long abandoned brickworks. It had been modified to incorporate a condenser knocked up from an old engine cylinder, the open end blanked of by a wrought iron sheet and plumbed in with an heterogenous selection of mismatched piping and valve work. It was horribly corroded but I was able to make a preliminary sketch plan. Sadly, when I went back to carry out a more detailed survey, the whole site had been bulldozed.

[81F]

This thread has just got me thinking, I wonder if anyone has compared the remains of these ancient Stephenson locos to see if any parts are similar. Although all "hand built" some things like cylinders would have been cast using patterns. As these can be used more than once, would there be a chance that more than one loco would have the same cylinders. Also the tender of twin sisters looks pure Rocket.

[What About The Bee]

Hi 81F

I did check to see if Rocket had the cylinders illustrated in this thread.  Rocket was Robert Stephenson and Co Ltd 's locomotive #19, with Twin Sisters at #13.  So relatively close in sequence.  Rocket did not use these cylinders.

It is very likely that there was commonality among Arrow LMR2, Wildfire LMR3, Dart LMR4, Comet LMR5, Phoenix LMR6 and North Star LMR8.  These were ordered by the board as a group, after the success of Rocket at the Rainhill Trials

Note: these are different artists, but the images do show commonality betwixt engines.  The first is Phoenix, the second is North Star.

Perhaps the tender is a clue about the time the image of Twin Sisters was created.  During the construction of the LMR's right of way, Twin Sisters was kept very busy.  She was a star.  Her boiler, it is noted, was filled / refreshed with already boiling water so there was no waiting to raise steam.  Therefore, not much need for a tender.  After Opening Day, as more powerful and quicker locomotives came on line, Twin Sisters was relegated to luggage (freight) service, and due to her slow speed, only at night.  In the image, Twin Sisters is on a siding.  Its daytime.  And she has a tender.  I think, therefore, that the image was created after Opening Day, Sept 1830 and before she was scrapped in Dec 1831

Yet barrel tenders were a Stephenson practice.  In the early 1820s, George produced locomotives for the Hetton Colliery.  Tredgold, 1825, presents us with an image of one of them

Tredgold specifically uses the word "tender" for the carriage behind the locomotive which carries "water for supplying the boiler, and coals...for the fire".   

Hedley's Puffing Billy of 1813 also had a barrel tender.  Seen here in the 8 coupled drive wheel version.

I give a quick pictorial reference of tender development here.  There are three phases.
 https://community.hornbyhobbies.com/forums/topic/31950-bee-what-do-you-think-about-rockets-tender-being-used-for-tigers-wagons/?do=findComment&comment=340276

Bee
 

Edited June 29 by What About The Bee
Clarity

[What About The Bee]

Hi @threelink

Of course I will update with the completed article, but we have have long way to go yet.

The CAD stuff here is much more complicated than simple waggons or carriages.  Its motorized, with working coupling and connecting rods. 

It needs electrical power distribution and pickups.  I have some ideas, but nothing has been installed in CAD, a major task.

I think of this CAD model as a proposal drawing, because many of the purchased Romford and Markits parts are not on hand.  So I have "guessed some of the dimensions" which will need correcting when they are on hand

The good news: I think this model quite feasible.  It can be made.  I do not need to invent technical solutions, like my prior locomotive design.

Bee

[threelink]

So far as concerns the early tenders I would suggest that they were created by installing a cask on a standard wagon - simple and inexpensive using items readily available. 

[threelink]

Technically I think the "barrel " would have been a tun, a standard container used for shipping liquids, usually wine or beer, and with a capacity of approximately 250 imperial gallons. Pretty much the shipping container of its day, so readily available new or used 

[What About The Bee]

A gallon of water weights ~8.34 lbs

250 gallons × 8.34 pounds/gallon = 2084 pounds

1 tun weighs ~1 ton

Which, per the internet, is where the word "ton" is derived from: "tun"

Thanks Three Link!  Learned something new today.

Bee

 

[Dukedog.]

That would be us gallons then uk is 10LB to the uk gallon 

uk gallon 4.54 litres

us gallons 3.78 litres

[threelink]

Have since discovered that in1824 that tun was amended to 210 gallons as a measurement specifically of wine. 

You are right about the ton, Bee. A ships carrying capacity by reference to the number of tuns it could accommodate gave us the more recent reference to a ships tonnage. 

[threelink]

It's surprising how often booze crops up in measurements. The dimensions of Barlows Saint Pancras train shed undercroft (where the shops now are) were based on the size of a barrel of Burton beer so as to accommodate the maximum number of barrels with no waste of space. The Midland Railway carried staggering quantities of beer from the Burton on Trent breweries to slake the thirst of Londoners (and others) 

[What About The Bee]

@Dukedog.

Hi Duke

The tricky bit will be the weights and measures standards, for the time.  Let's just say that things weren't exactly defined or observed.  Exactly how long was a yard?  How much, precisely, does a pound weigh?  Those questions are far deeper than they appear on the face of it.  Traceable standards are accepted today, but it has taken quite a bit of effort to get here.

The metric units you quote were a system used in France but not on the LMR, where it was still the imperial system.  The barrels on the tenders appeare quite large in comparison to the individuals working the locomotive, Three Link is most likely correct in referring to them as "tuns".

To sum it up, however, we are looking at an ancient unit of measure called the "tun".  Like a chaldron (weight of coal), these had loose meanings which only acquire firm definition in a more modern era.

Bee

[threelink]

The pre- 1824 tun as a unit of volume was stated to be, in respect of wine, the equivalent of a cylindrical vessel with both height and diameter of 42 inches. The physical shape of the tun as a container would be different with a "belly" to allow for the accumulation of sediments (ie the traditional barrel shape as on the Hornby Rocket). Taking these factors into account the size of the vessel on contemporary tenders indicates the use of tuns to carry water. 

[What About The Bee]

I decided to install the chimney cable stays.  There are quite a number of stays in Shaw's drawing of Twin Sisters.  Kind of bewildering.  Being a careful lad, I traced each one, identifying where the stay came from and where it attached to.  

And what to my wondering eyes did appear?  The door in the chimney, perfectly clear! 😉

Firstly a review of the statements, this published 12 Sept 1829, 6 weeks after LMR takes possession of the locomotive.

"This engine has two cylindrical boilers, placed vertically on 6 wheels, with a fire-place¹ in each, having a conical tube passing up through the centre of the boiler.  There are two chimneys, through the sides of which openings are left to throw in the fuel."

From this, we can know that the openings in the chimney are very likely below head height.   For poking the fire, the engineman needs to see in, to see what he is poking.  To permit fuel to be "thrown in", the opening would certainly be low enough such that an engineman could reach it.  So the opening was likely head height or lower.

We also have this statement from George Stephenson to the Chief Draftsman at the Robert Stephenson and Co Ltd  works in Newcastle, in a letter  dated 13 Aug 1829.

"....I have put to the coke engine² a longer exarsting pipe, reaching to nearly the top of the chimney, but find it does not nearly do so well as putting it in to the chimney lower down..."

If George had his way, we would call it the exarsting pipe and not the blast pipe.  A blast pipe causes a venturi effect to draw the fire.  The exarsting pipe cannot draw the fire with a large opening in the chimney, the air would be drawn from the opening, not the firebox.

From this we know there must be a door, so as to close that opening in the side of the chimney.   If the opening was above the exarsting pipe, it would not require a door.  But George states that he experimented with the location of the pipe, placing it at the top of the chimney.  This is well above where an engineman could reach.  There must be a door.

When I think of a door, I usually envision hinges on the side and the door swinging around a vertical axis, like the front door to your home.  That is what I expected on Twin Sisters.  That turns out to be a terrible assumption.  

As I mentioned, I was drawing the cable stays.  That's odd, I said to myself, that particular cable stay has a sharp bend in it.  A line with a sharp bend in it.  That isn't a cable stay, full stop. 

Shaw has other prints which we have examined.   

In examining this drawing by Shaw, the rearward facing guard, who is nearest us, has a brake handle directly to his right hand side.  Take a moment to look at the image and find the brake handle.  It is a crank handle.  Drawn as a line with a sharp bend in it.  It blends into the rock lines, but once you see it, trace the line down the front of the carriage, leading to the brake assembly.  Definitely the brake handle, conveniently placed for the guard in charge of the brake.

Ah HA!  There is a crank handle in the superstructure, mounted to the chimney on Twin Sisters.

So what does that crank handle do?  Here is my solution to the door. 

The central series of short repeated horizontal lines are a rack.  The crank handle turns a pinion, which engages the rack.  The long vertical lines are the guides for the door as it is raised and lowered by the rack and pinion.  Naturally, the guides must be longer than the door is tall.

I've sketched this up in CAD, to make crisp three dimensional objects from the lines drawn by Shaw, shown side by side with Shaw.

On the other chimney, I've turned the crank handle, raising the door to expose the opening. 

This particular chimney does not have the motor shaft running straight up inside.  I am sorely tempted to leave the door up when 3D printed, perhaps with added firebox glow!

I am convinced.  But have I convinced you? Let me know.

Bee

¹firebox.  

² Twin Sisters.  Recall the Stephenson dwg says "Liverpool Coke Engine".  In LMR Board minutes, the engine is referred to as "The Sisters".  Referenced in the press as "Twin Sisters".
 

[threelink]

Hi Bee. I am sure that you are right about the doors in the chimneys. The real question is their height above the running plate. Head height would make operation of the crank and the charging of coke though the door very difficult so I guess that the doors would be no more than waist height to a crewman standing on the running board unless the crewman stood on top of the boiler to charge in which case the door could be correspondingly higher. I suspect that the latter was not the case - there seems to be what could be a shovel handle protruding form the loco in front of the nearer boiler, suggesting the possibility of a coke store at running plate height. Fascinating as it is, the Shaw print is not much help because his perspective is all over the place The engine shed to the left of the drawing and all other buildings appear well drawn as does Twin Sisters herself, but the tracks are not, creating the impression that the track bed is higher to the right than to the left, never mind the track gauge being questionable. The two figures to the right are out of proportion (too small) and Twin Sisters' tender is badly drawn, giving the impression of a behemoth of a thing with the frames higher to the front than to the rear (rear being taken as the barrel end). I could almost believe that the main elements of the drawing were done on site and details such as the figures and possibly the tender were added in the studio. Naturally one has to make allowance for the fact that Shaw and others were drawing cutting edge technology  with which they would be wholly unfamiliar but its a thundering nuisance that reliably accurate details cannot be obtained from their drawings. Oh to have a time machine...

[LTSR_NSE]

If the tender barrel was full of water & front of tender devoid of coal - that could account (a bit) for the tender’s tail-heavy appearance.  Equally if the sketch is a composite, with initial (more distant) sketch of scene & a separate more detailed sketch of loco + tender (from closer) - that could account for (some of) the scaling/perspective inconsistencies.

[What About The Bee]

Hello ThreeLink 

I am pleased that you find the chimney doors as I do.  I was very excited to find them, as we know they existed.  Such an odd feature.

As to the height, I was trying to portray an upper limit.  Perhaps that wasn't clear. That the door could be no higher than head height.  I fully agree that the doors should be lower, to facilitate use.  How much lower?  It depends on how much credence we apply to the height of the footplates drawn by Shaw, noting that the Stephenson drawing shows only the mechanicals, not any body work.

I too have noticed the tool.  For the benefit of others 

I suggest that we see the top, because an engineman would place the tool with the handle up, for convenience.  I make it to be a T-Handle.  

It is a long tool.  Based on orientation and placement, it very likely extends completely across the cavity.  How long?  Ask Shaw.

We do not see the working end of the tool.  It could be a shovel.  I make it to be a tool to poke the fire, through the door, which is entirely speculative. 

As to loading fuel through the door, as specified by the press?  There are two doors, and the solution would likely be the same for both.  Certainly, a long shovel could reach the tender and the door nearest the tender, but what of the door between the cylinders?  That doesn't work.  I would propose a bucket of fuel, placed on the top of the boiler by the chimney door.  An engineman would simply pick up a lump and 'throw it in', as stated in the press.  Poking the fire with the long tool. Again, entirely speculative. 

About the perspective and scaling issues?  Its all wrong, and I have noted this throughout this thread as well.  For example: length.  Twin Sisters has 3 axles of 4 foot wheels.  The absolute minimum is that Twin Sisters is 12 feet long.  Yet the tender is drawn equally as long.  This is the barrel tender of the period, built on the common utility waggon.  Simply put, no, its not that long.  

@LTSR_NSE

Your solution makes sense.  The axles were sprung and this could upset the balance.  Reasonable and logical. The tender could be out of level based on load.

I do agree that the sketch could have been drawn in different places or at different times.  This could just be a working sketch, in preparation for a more carefully drawn subsequent presentation, a known practice of artists.  Certainly, Twin Sisters was a unique engine, and as Three Link points out, the entire railway was novel.  It may have confused Shaw, who perhaps only had a small time frame to make the sketch.  We really will never know.  I  accept the Shaw sketch for design cues and thank the heavens for the mechanical drawing in the Robert Stephenson and Co Ltd archives.

Bee
 

Edited July 1 by What About The Bee
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[threelink]

There is another possible explanation for the doors namely that they were soot doors ie doors open to allow sweeping of the chimneys but this would, of necessity, imply some firehole door in the boilers. I have to say that the practicality of charging the fire from the chimney is a notion I find difficult to comprehend. 

[Rana Temporia]

If the fire was charged from the chimney how would the ash be cleared out from the bottom of the boiler? I would be more tempted to look at some of the other vertical boilered locos either standard or narrow gauge and look how they were/are fired or even a VB Sentinel. The door may have been to control the draft up the funnel while the fire was being lit? However, with this being a very early loco maybe some of the problems weren’t ironed out and they did feed the fire through the door, ash and clinker being expelled up the chimney. The fire would have needed air from somewhere. 

Whatever the doors were for and however the loco was fired I want to see the finished article, looking forward to it. 

[What About The Bee]

I totally agree.  Charging the fire through the chimney is very strange indeed.   How can fuel be added through the firetubes?  Answer: there were no firetubes!  Henry Booth famously suggests firetubes for Rocket at the Rainhill Trials. Twin Sisters predates Rocket.  Indeed, competitor San Pariel was a return flue boiler, sans tubes.  

So how can we be sure the fuel was added via the chimney?  The newspaper report is indisputable.

"There are two chimneys, through the sides of which openings are left to throw in the fuel."
Verbatim Quote¹

There may have been other uses as you suggest, but this was the reported use.  That same newspaper report states that 

 "...having a conical tube passing up through the centre of the boiler..."

There must be a grate on the bottom of that conical tube, so as to support the coke while it burns and to permit air to flow into that conical tube.  Otherwise, the conical tube has a sealed bottom, only open to the chimney.  That will make it hard to sustain a fire.

My purely speculative cut away sketch of a Twin Sisters boiler

We have a cutaway of a vertical boiler in Janvier 1838, which does include firetubes.

http:// https://community.hornbyhobbies.com/forums/topic/33593-railway-oddities/?do=findComment&comment=361804

Bee 

¹ I did not record the name of the newspaper, thinking that the website would retain free access to the data. Liverpool Albion?   It is now behind a paywall.  I did capture the image, read the entire report here

 

Edited July 2 by What About The Bee
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[threelink]

I entirely take your points, Bee, and on reflection realise that there is an existing example of fuel charging via an opening in a chimney in the form of a furnace at the Blists Hill museum, Ironbridge. It is used to melt iron in the foundry where cast iron products are made for sale and for repair/renovation projects. Fuel lime and scrap are charged through an opening in the chimney. There are videos of this operation - I saw one on You Tube. I imagine that Stephenson will have been very familiar with furnaces of the day and may have experimented with their application on locos. 

[What About The Bee]

 

21 hours ago, threelink said:

 I imagine that Stephenson will have been very familiar with furnaces of the day and may have experimented with their application on locos. 

Accurate assessment.

The foundational document of Robert Stephenson and Co Ltd is signed by four individuals

The first two will need no introduction.  Take a careful look, these are authentic signatures, the document dated 23 June 1823.

The next signature is Edward Pease.  He was the main promoter of the Stockton and Darlington Railway.  His biography is quite impressive, Google away!

The last one is Michael Longridge, co-owner of the Bedlington Iron Works.  With his engineer, Birkinshaw, the developer of wrought iron fish belly rails.  With decades of experience by 1823.  Supplier to the Stockton and Darlington Railway as well as the Liverpool and Manchester Railway. 

So absolutely, yes, a Robert Stephenson and Co Ltd principal knew a thing or two about furnaces!

The Twin Sisters boiler is wildly inefficient.  Without firetubes, the heating surface is limited to the conical area within the firebox.  Most of the heat shoots straight up the chimney.  It is hard to examine Twin Sisters without the lens of two centuries of knowledge.

It is one thing to polish a design, when a vast body of emperical data exists.  Engineers like Stanier could stand on the shoulders the giants who came before.  A tip of the cap to that type engineer, one who squeezes a bit more efficiency out of an existing design.  Much harder than it looks.

The early days did not have that body of data.  What worked?  What didn't?  What was efficient?  Who knew anything.  No wonder Rocket overcame San Pariel.  The Booth firetubes were remarkably efficient compared to the return flue.  Twin Sisters didn't even have a return flue.  Essentially a teakettle in a fireplace.  

Bee