Planning Planet

[What About The Bee]

Planet is certainly on my Hornby wishlist. Yet a sensible person can easily see that Hornby will not be shipping a Planet model anytime in the near future. Maybe someday, but not soon.  

One option, then, would be to scratch build Planet.  

Planet, Liverpool and Manchester Railway #9, represents the first major step away from the Rocket-type locomotives. Planet was a railway revolution. The pistons and cylinders moved under the smoke box and were arranged horizontal to travel. This eliminated the Rocket-type's ungainly side to side wobble, due to the pistons working against the undercarriage springs. Further, the location under the smoke box pre-warmed the cylinders, which inhibits condensation upon initial steam admission, limiting hydrolock. 

One of the most visually defining features of Planet are the oscillating handles¹ on the footplate. Those handles are a Robert Stephenson design.   

What are those handles? What do they do? What is a steam locomotive without the operating mechanism to draw in the eye?  

They are quite noticeable in all the videos of the replica.  Link:

 Mr. Dawson provides an excellent explanation of how the Planet replica functions. I recommend this video unreservedly.  

The handles are indirectly connected to the slide valve rods. As the slide valve rods move, the oscillating handles follow. Slide valve rods also move the slide valves, which provide for the admission of steam to the piston.  

There is a pedal on Planet's footplate which selects the locomotive direction. If the pedal is up, the locomotive runs in reverse. If the pedal is all the way down, the locomotive runs forward. In either of these two positions, the timing of the slide valves, and therefore the positions of the oscillating handles, are controlled by the rotational angles of the eccentrics.

But if the pedal on the footplate is at the midpoint [there is a detent for this] the sliding valve timing is disconnected from the eccentrics and the slide valves may then be controlled by the handles!!! That is, the enginemen can admit steam to either cylinder, on either side of the piston, at will, via handle manipulation. This is their purpose!! The enginemen used the handles to shift the slide valves, to get the locomotive started in the correct direction. Once the locomotive was going in that direction, the enginemen would then move the footplate pedal to either up or down and let the eccentrics take control.

To better understand how this works, I decided to make a constrained mathematical model which functions as Planet would, albeit with numbers and equations instead of mechanisms and steam.

Link:

As the wheel turns, an axle mounted gear, red, drives a secondary gear, also red. The eccentric is the small yellow circle in the center of the secndary gear. Planet has the eccentric as part of the main axle, but for clarity and ease of modeling, I placed the eccentric on a secondary gear.

Note that the radius of the eccentric defines the travel of the slide valve and eventually the angular travel of the handles on the footplate.

In the side view, the yellow rod follows the eccentric around. This is connected to the slide valve rod, yellow, at the large red dot, representing a hinge. The slide valve rod drives the slide valve forward and back. You should see that the linear travel of the slide valve rod is defined by the radius of the eccentric. 

As the steam chest holds pressurized steam, there must be packing to constrain that steam from escaping alongside the slide valve rod. This constrains the slide valve rod to strictly linear motion.  

The slide valve rod protrudes out of the front of the steam chest. There is a Scottish Yoke² that drives a crank. A Scottish Yoke changes linear motion to rotary motion (or visa versa). The Scottish Yoke is depicted as two short vertical members in yellow on the slide valve rod, capturing the top of the crank.

A purple crank is connected to the front pivoting lever, brown. The pivoting lever pivots on the center of the three points. As the slide valve rod moves back and forth, the Scottish Yoke forces the crank to rotate, and as it does, it causes the front pivot lever to rotate. The angular travel of the front pivoting lever is therefore controlled by the radius of the eccentric. The angular travel in my model is +/-10°.

There are two blue rods that drive the rear pivoting lever, also brown. If you go back and examine the initial image "The oscillating handles", you can now pick out the blue rods and the rear pivoting lever, clearly depicted. The two pivoting levers and the two blue rods form a parallelogram. Whatever angle is created at the front pivoting lever, the rear pivoting lever will match it. So as the Scottish yoke in front drives an angle into the front pivoting lever, the rear pivoting lever is also driven to that angle.

Finally, a purple crank represents the handle on the footplate. It is connected to the rear pivoting lever. When the footplate pedal is either up or down, the motion of the wheel causes the purple lever on the footplate to oscillate, in time with the slide valve. Now if the pedal is at the midpoint and the eccentrics disconnected, you should be able to see that the enginemen can move the lever to manipulate the slide valve directly.

Link:

Nearly identical to the left side, the mechanism on the right hand side is for the right hand piston, slide valve and right hand footplate handle, this time in green.

Now a model need not drive the mechanism as illustrated. There are no slide valves to manipulate. There is no steam to admit. There is no pedal to engage, disengage the eccentric. I did think it meaningful to understand the oscillating handle mechanism Planet possess. The animated mechanism may take quite a bit of torque to drive, limiting my pulling power. The numbers, formulas and constraints operate without regard to friction, but the real world is a cruel master.

One alternative would be this simple crank.  Link:

The handles oscillate with almost the same motion. There is a small difference in the position of the handle vs time in cycle. This is due to the difference in drive between the Scottish Yoke³ and the eccentric levers depicted here. The number of oscillations is timed to the wheels, as before. I can either leave the unnatural handle extensions in plain sight through the footplate, or turn the extensions 90° and drive them into the firebox.  You would have to be very familiar with Planet to notice these extra extensions. Yet if I was to add the parallelogram levers, rods and then the front slide valve rod, the frictional component is nearly the same as before. The Scottish yoke and slide valve rod would still be present. The sliding friction would be as well. And I would be left with those odd handle extensions to offend my eye.  

What is a steam locomotive without the operating mechanism to draw in the eye? Nothing. Planet had oscillating handles on the footplate. So does Patentee. So must my models.

Thus, the planning begins.

Bee

¹ Patentee also has oscillating handles.

² This is the formal nomenclature for the mechanism. I do hope no feathers are ruffled by the use of proper nomenclature. This short video explains how a Scottish Yoke functions.  

Link:

To see the replica's Scottish Yoke, view Mr. Dawson's excellent video at 4:17. You will see the steam chest with the steam chest lid removed. The slide valves and rods are demonstrated. As the camera pans back, you will see the Scottish Yoke on the bottom of the screen and the front pivoting lever, as well as the parallelogram connecting rods.

³

[What About The Bee]

Interesting. Hyperlinks no longer have any color indication that they are links! They just look like bold text on my mobile device

Edit: same on my laptop

They function as links, but there is no indication that they are links.

Bee

[threelink]

Scratch building a 4mm scale planet would be a challenge in itself and doubly so if working handles are to be incorporated. I have been looking at the idea of building some early locos and, given their diminutive size, have been forced to the conclusion that it would be far easier to make a few powered carriages and wagons to push non-motorised locos - I do not think that tender drive is a realistic proposition.

[Rana Temporia]

There have been some early locos built using a tenshodo bogie or similar under the tender to provide the power. One option for the handles may be a cheap 12v N20 motor with side shaft from the gearbox and two eccentrics to make the handles rock backwards and forwards. If the drive was in the tender or a coach then there should be room in the loco. The eccentrics could be carved from two cogs designed to fit the 3mm D shaped output shaft.

I was looking at something similar a while back to power the vertical pistons on a vertical boiler loco I found a photo of in an industrial steam book but the only way I could see to do it would be to have the eccentrics on the axle. In a 4mm there isn’t a lot of room.

[threelink]

@RT

I thought about Tenshodo power bogies but have no experience of them. Are they of sufficient power to push a loco and haul a reasonable train of carriages? I discounted their use largely on aesthetic grounds - early locos and tenders are delightfully spidery in appearance, with much open work below the solebar. The Tenshodo type bogie would, I thought, block much of it whereas the good old X03/4 would be easy to conceal in a carriage, leave the under-solebar openworkon the tender tender readily visible and provide more than enough power for any train. I have an ebay purchase of a John Bull loco with a tender drive. The motor is so small that it would struggle to pull the skin off a rice puddding, yet still fills the tender. I intend to anglisize it and shall probably ditch the tender drive in favour of something more pleasing to the eye.

[What About The Bee]

Hi Rana 👋.

You have read my mind! Ha!

I've gone for Hanazono motor bogies, with spoke wheels.

Here is an image, comparing some 'generation three' tenders with the Hornby Lion tender.

[EDIT: corrected image below.]

The tender in back is installed on the top of a bogie, whereas the tender in front is not. The Hanazono motor bogie is displayed.

Will they pull or push much? Welp, they can certainly haul themselves around. I will try to propel a few carriages and report back.

Bee

[What About The Bee]

I have no idea why the image would be rotated, but I did notice this occurred previously.

I've processed the image, to see if I can correct the issue.

Hopefully this appears correctly. If it does, I can insure I won't get this issue again.

Apologies for the extra work mods.

Bee

[Rana Temporia]

I have used the Tenshodo bogies in plastic DMU kits and had no problems with them. I read a long time ago that someone built an MTK 6 car unit which was made of metal and needed two bogies to propel it. With a few early coaches and a small loco I would have thought they would be fine if it’s possible to get some weight into the tender. If you can get some additional pick-up from the loco that will help with smooth running, there are solder tags for this on top of the bogies. For your haulage test I would experiment with degrees of weight on top of the bogie otherwise the wheels might just spin.

I think the Hanazono bogies are virtually the same. I know people seem to prefer the black beetle type but I have no experience of them. The good thing about the Tenshodo is that it can have a variety of wheels fitted.

I did see one scratch built early loco in one of the magazines that was a 4-2-2 and a Tenshodo was used as the front bogie to allow the open frames to be unobstructed. Apparently it ran well.

In the previous version of this forum I posted a drawing of an early Bury (maker) loco from a 1960s Model Railway News. As the loco had the usual open frames the only real options for a motor would be the tender or a powered coach. I don’t know if that’s been transferred over yet.

[RDS]

@WATB

I quite often have to rotate images after approving them. Rather than have another post though with a correctly rotated image it is better to edit the initial post. (I can do it for you if you wish)

[What About The Bee]

Hi RDS

Now that I understand the issue is I can easily avoid it. Its at my end and can control the rotation quite readily.

Thank you kindly for the offer to rotate my image. I've simply deleted the strangely rotated image and let the corrected one stand. No sense in making extra work for you gentlemen! Difficult enough as it is.

Bee

[What About The Bee]

My results so far in the Hanazono bogie haul test.

The first result is to determine stall current. Stall current happens when the rotor of the motor no longer turns but draws current. I approached this in two ways.

Firstly, I simply measured the resistance of the motor. 24 ohms. The design voltage is 12 volts (DC). Therefore, stall current by this method is ½ amp.

Secondly, I applied a very low voltage to the motor, insufficient to get the rotor to turn. 0.407 volts. This was measured across the solder tags, in parallel with the motor under test. Next, I measured the current draw in series, without touching the position of the rotor. 0.018 amps. Using ohms law, I find the resistance to be 22.6 ohms and, when used at rated voltage of 12 volts, the stall current will be 0.530 amps.

Those results are close enough to be a meaningful result. I will use the more conservative ½ amp for stall current.

This will establish some limits as I add weight and perform the haulage test. I never want to exceed 0.250 amps continuous current, as this will lead directly to thermal failure. 0.200 amps continuous is acceptable but will shorten motor life. Ideal would be 0.125 amps continuous.

I ran the Hanazono motor bogie suspended in air, wheels up, such that the bearing surfaces, such as they are, were engaged as if the bogie was sitting on track. In forward, the motor drew 0.083 amps on average. In reverse, the motor drew between 0.096 and 0.120 amps, randomly. [Edit: not 0.96 amps!!! Hahaha] It was very inconsistent. Still, within ideal bounds, so I moved the wheels in both directions for ~20 minutes each.

Next step will be to service and lubricate. I will then test its ability to get around track while monitoring current. Add weights under self haul test, monitoring current, and then and only then, propel some carriages!

Bee

[What About The Bee]

Hi ThreeLink

You asked about Hanazono motor bogies and hauling power.

Today, I did the testing. Wow!

I installed the tender body onto the bogie such that the axles were NOT touching the bearing boxes. There is a screw attachment point on top of the Hanazono bogie, so the tender body was firmly fixed in place. I tested the assembly on its back, still drew the same current as before. This guaranteed that the axles weren't rubbing.

I weighed the assembly, 27 grams. I started out with 33 grams of weight, for a total of 60 grams.

Using this, I was easily able to haul all of my modern era 1 stock, to wit: 15 carriages/wagons. The current barely budged!

So I grabbed the three carriages in R796, the 1980s Rocket consist, now with fine scale pegs. No issues adding them! Still barely a murmur in additional current. Mind, (15+3) is more than any one of the Hornby locomotives can pull. 1980s Rocket hauls the three 1980s carriages and that is it. Lion can pull 15 modern, but needs double head help from modern 2020 Rocket.

The challenge was laid. I pulled out the 9 Accurascale Chaldrons. Lion can NOT pull 9 Chaldrons by themselves without assistance. Finally, I saw the Hanazono struggle. But it was all wheel slip.

I added another 33 grams, now 93 grams total for the tender. The Hanazono pulled all 27 carriages / wagons without real issue. The current was in the 0.160 amps region. Above ideal, but certainly not dangerous.

In an effort to see if I could push the current up to 0.200 amps (40% of stall current), I kept increasing the velocity. Eventually, it was flying around the layout, hovering around 0.190 amps. Just a pinch more I thought.

The weight fell out of the tender, and there was a horrible train wreck. No damages incurred but it was spectacular!!

So 27 carriages / wagons at warp speed could not get me to 40% of stall.

This is by far my strongest puller.

Next to determine the volume of lead for 66 grams and see if I can get it under a coal load.

I recommend the Hanazono, without reservations.

Cheers

Bee

EDIT: Best crawler of the lot as well. Slower and more stable at slow speed.

[threelink]

@Bee

Fascinating post, as ever. The Hanazono sounds to be first class. Does it obscure any openwork below solebar level?

Threelink

[What About The Bee]

Hi ThreeLink

You asked about the open work below the solebar.

The answer is yes, it obscures, the Hanazono is a rectangular block that sits between the wheels. If you go back a post or two, I show the Hanazono without the tender. Here is a view of the tender I used for test

Pay no attention to the wire, that was just to test current draw during axle alignment. I attempted to take a square on, track level image of the tender. The Hanazono can be seen, but you have to look mighty hard, as it is black. From a normal viewing angle, it is mostly invisible. I can live with this, but I respect that your opinion may differ.

I went and measured the coal bin area. Treating it as a rectangular cavity, I get 14.9mm × 11.9mm × 23.9 mm or 4.238 cm³.

Density of Lead is 11.29 grams/cm³, so if I was to fill the cavity with a (very unrealistic) rectangular block, it would be 47.8 grams. Of course, if I hack away at the lead, I can create a more realistic shape and glue on a layer of coal. Say 30 grams total.

I could use other elements. I will of course avoid radioactive or toxic materials.

Osmium is 22.6 grams/cm³ but is ~ $38/gram. Too expensive.

Tungsten is 19.35 grams/cm³ and only ~$1/gram. Unfortunately, very difficult to cut. I do have a large diamond chop saw which would work but would make a lot of tungsten dust and therefore waste. Maybe.

Tantalum is 16.65 grams/cm³ and is ~$2/gram. Tantalum can be machined, unlike Tungsten.

In the end, I have to consider how many carriages/wagons I intend to haul and what the prototype offers. There is this period image of Planet, which appears in Walker, 1831. Note the horizontal cylinders under the smokebox. This image has been stolen and redrawn many times with many variations, but this is the grand daddy of them all. The original depiction. I get 10 flat wagons with freight.

Do I need 66 grams, so that I can haul 27 wagons? Probably not.

Bee

[threelink]

Thanks, Bee. I shall keep the Hanazono in mind but shall meanwhile, when I can find time, continue with the powered carriage approach. There's plenty of room for weights and it preserves the openwork on the tender. There may be buffing and coupling issues but nothing insurmountable. Powered wagons are feasible too so long as there is sufficent load to hide the motor.

Regards,

Threelink

[threelink]

@Bee

I just had a thought about the weight issue and the potentially unrealistic appearance of a weighted tender on the Planet. Some time ago I modified an old Triang Lord of the lsles (with turned down wheel flanges and tyres) to run on code 75 nickel silver track by removing the Magnadhesion weights and substituting lead blocks. It was not enough to give sufficient traction to the single driver so I weighted the tender and put a short spring on the loco drawhook. Part of the tender weight was then transferred via the spring to the back of the loco. A thin balancing weight (lead sheet) under the front of the loco running plate evened out the weight distribution. It hauls very well with no loss of traction. A similar arrangement in reverse, whereby the Planet loco is weighted and arrranged to bear down on the motorised tender, may well be a solution worth considering. On the Lord I chose to reduce the gap between loco and tender and introduced a fall plate to hide the modifications to the drawhook but that was simple enough and the fall plate improved the appearance no end, so it was win-win.

[What About The Bee]

Hi ThreeLink

It was with great interest that I studied your solution to the Lord of the Isles traction issue. From my understanding, you transferred the load from the tender onto the rear of the locomotive. This lifting the front, you added weight to balance the load over the center driving wheel and thus increased traction.

How clever of ThreeLink, I thought to myself, that indeed will function. And then the penny dropped.

Stephenson had the same issue with Planet. The tractive effort was affected by the force of the driving wheel v track. He understood, quite properly, that Planet had some of that force deducted because the idler wheels in front. The weight was distributed over all the wheels, not just the driving wheels. Patentee was the logical outcome. The front idlers and rear idlers were sprung such that they balanced the load over the driving wheels. Increasing tractive effort.

This is not to deduct from your solution ThreeLink, but rather to commend you for finding the identical solution as one of the true giants of locomotive development. Attaboy!

Bee

PS. Always had my eye on Lord of the Isles. Beautiful loco. Just not my era / railway.

[threelink]

@Bee

Thank you for your kind comments. However I cannot claim to have invented the idea - I read an article about weighting problems many years ago. All I did was adapt one of the suggestions discussed namely the transfer of tender weight to the loco. Clearly, Stephenson got there very early on: a genius in all respects.

LoI is indeed a beautiful loco. Even the old Triang version can be made to look very well - turned down tyres and flanges, finer wheels substituted on the tender, buffer beams lowered to scale height, screw link couplings, lamps and other detail and a careful paint job transform a toy into a nice looking model. It's not to scale but it is a very believable pastiche and looks well at the head of a rake of clerestories (more Triang products jiggered about with). The work involved may sound complicated but it was not: the wheels were turned down using a power drill and a file, the buffer beams were lowered by slicing them off, sticking on 2 mm thick distance pieces and sticking the buffer beams to the underside of the distance pieces. With the distance pieces dressed off to merge with the body and suitably painted, the trickery is not immediately apparent. I have modified umpteen Triang locos and items of rolling stock in this way so that they can be run with modern products having scale height buffer beams. The only Triang items that have defeated me are the wagons with cast mazak chassis. They are easily modified with pinpoint wheelsets and three link couplings but reducing the height of the buffer beams is very difficult. I gave up trying to do it and run the overheight wagons in fixed rakes with a converter wagon at either end. The converter wagon has a lowered buffer beam at one end only. This allows the rakes of over height Triang wagons to be coupled to and buffer shunted with stock and locos having scale height buffer beams. Surprisingly, the trickery is not apparent at normal viewing distance. The advantage of all the faff is cost: old Triang wagons are dirt cheap and my labour is free. The work is also most enjoyable.

[What About The Bee]

As I pondered loading the tender so as to get better tractive effort, I have slowly come to the conclusion I may only get ½ the volume filled with lead or under 23 grams. The practical nature of installing exotic materials makes them unlikely. Dejected, I tabled the issue.

I was having a play with my new locomotive, Tiger. It runs well. I tried to double head it, and that is when the penny dropped. Why not double head Planet?

I've artfully(?) dressed up a locomotive as a tender. Planet, as I have currently envisioned, is a tender drive system. This depends on the friction between Planet's wheels and the rails to drive the oscillating handles. Hands up if you have ever seen a steam locomotive skating along in front of a tender drive.

The penny? Put a DC motor into Planet and now I've effectively double headed the system. Locomotive #1 would be Planet, with an onboard motor. Locomotive #2 is Planet's tender. BING!!

Okay, so what motor? How will I effectively speed match Planet's motor and 20mm wheels to the Hanazono motor and 10.5mm wheels. The smart lads know the answer, but I did not. Off I went on a madcap tour of small DC motors. This was nothing but a fools errand. The voltage to speed and speed torque curves are not published.

And then the other penny dropped. What motor matches a Hanazono motor? A Hanazono motor. The characteristics of any one sample Hanazono to any other Hanazono will have only tiny differences. 

But will it fit? Rectangular 10mm×13mm. ~25mm long, including one worm. ~29mm long if both worms are there. The short answer is yes, it will fit!! Exciting!

But what about the wheel size difference? Both Hanazono motors will have near identical velocity over the voltage range. A simple gear ratio change will suffice to make the larger wheel rotate slower than the small wheel. The forward linear travel, assuming no wheel slip, is a function of circumference and then gear ratio. Match them to each other by changing the gear ratio.

Viola!  

Bee

Note: I've seen some excellent motors which I may take advantage of in the future. Hanazono motors are expensive because they come with gears, drive train and wheels. A full kit. That isn't ideal.

[81F]

@Bee,

My profile image shows a tiny 009 Ruston Hornby loco which Shapeways 3d printed for me. My initial test print used a fine detailed plastic which looks like the one used in your post of the tender. This proved much too light. I therefore got Shapeways to print it in natural brass (or bronze) to add weight. You might want to consider this option.

The only draw backs was that I needed to slightly thicken up some of the finer detail and the cost was significantly higher but running quality was much better.

The only real downside was that it looks so nice in Brass it was a shame to paint it!

[What About The Bee]

Hello 81F

I've always seen the Ruston in your icon, of course. I could tell it was unusual, but did not realize it was one of a kind. Its a tiny locomotive, well executed.

I took on board your comments vis Shapeways and 3D printed metal. Yes, the tenders are in the fine scale plastic. This was selected for dimensional stability more than anything else. They are very light indeed.

Before I commit to a metal print, I investigated the process. In the end, I think its sintered metal. The process by which they get to sintering is 'binder jet', which glues the shape together, pre-sintering.

I would like to ask you about two artifacts about this process

1) How did you deal with the shrinkage issue? ExOne, the company Shapeways uses, is explicit that the part will shrink "up to 20%" during sintering. Did you create sequential prints until the process was accurate? Did you engage in machining post sintering? Getting the tender to fit will not be an issue. Its a bolted on detail. Yet multiple parts in Planet will not be as easy.

2) Sintering creates an inherently porous metal. This will have a rough(er) surface, pores and internal voids Did you fill the pores to get a reasonable finish? Polish post fill? Did you fill the internal voids to eliminate trapped air volumes?

I hope to understand your process a bit better, so I may achieve a like result. Thanks!

Bee

[81F]

The brass and bronze prints i have ordered from Shapeways are made using the lost wax method of casting with the wax being 3d printed see Shapeways: Wax Casting and with more info here

Although I was worried about shrinkage, I've never had a real problem with it, although some of the fine detail plastic parts of mt Ruston were a tight fit and a little trial and error was needed with some parts.

I also produced a GWR 517 class loco body in fine detail plastic with brass smoke-box door tank fillers and tool boxes. All seem to fit OK without any signs of differential shrinkage although I do tend to make holes that parts plug into very slightly larger than the item that fits into them (usuall around 0.1 to 0.2mm).

Hope this helps

As an aside, have you seen the Bachmann 'John Bull'. It looks a little Planet-like but I think the prototype original was designed as an 0-4-0. This is tender driven although the huge "garden shed" of a tender means there is plenty of room for a motor.

However,their 4-2-0 Lafeyette is loco driven see

[What About The Bee]

Hello 81F 👋

Thank you for the correction. I assumed the binder jet sintering method. The lost wax method you utilized appears to be far superior, with much higher dimensional stability and certainly superior weight for a given volume. A clear winner.

If I may ask, since you executed the Ruston Shunter in both fine detail plastic and in metal, what was the rough price multiplier? Was it 3×, 10x or 30x the price? Not the absolutes, just the relative values.

I have indeed seen the John Bull and others. I had a complete list of all manufacturer Era 1 models. Almost all are HO scale, not OO. John Bull is a member of the Samson-class and should have a boiler ~7'3" long. Rocket's boiler was only 6 feet long. Yet when Sam shows us the 2020 Hornby Rocket head to head, John Bull looks diminutive. To each his own, of course, but I find mixing scales to be quite glaring.

Once again, thank you for sharing your expertise with me. Greatly appreciated

Bee

[What About The Bee]

Hello All

I thought to give an update on this project, so as to keep motivation high.

As I plod thru the Armengaud drawings, I am struck by the dimensional accuracy. I have found each pixel is 1.3 mm, this on an overall length of 5.056 meters. That is an astonishing 1 part in 3800+.

Presented here is my CAD model. It is drawn 1:1, not 1:76.2, as the model will come after the full scale representation of Planet

The sandwich frames are shown with the metal in purple, the wood in gray. The metal wraps around the corners and on the outside, is let into the front wood member.

The front corner brackets tie the frames together. There should be rear corner brackets, but as these will be buried under the footplate, I saw no need to model them. Similarly, no effort will be made on internal boiler tubes, even though Armengaud shows those as well.

The rear draw pin bracket is two parts, the outer member wraps around the rear frame, and is let into the wood on top.

The front and rear plates are different in more than just height, to my great surprise! Modern standards would require commonality of design and therefore commonality of parts. Stephenson did not feel so constrained. In any event, all 8 plates are present and accurate to Armengaud.

A dilemma presents itself. It occurs because the Planet Class was quite large and widespread over many railways. Armengaud shows the front springs BELOW the frame

Yet the Stephenson drawing, used in the animations, shows the front springs ABOVE the frame.

Finally, the replica shows the front springs ABOVE the frame.

Above the frame they shall be. This is relatively easy to do and will be consistent with Stephenson.

Bee