My observations on running 39968 Flying Scotsman on a C track layout are as follows:

1. Runs comfortably through curves from R1, standard and long turnouts, cross overs and double-slips. I have catenary and signals etc and there was no fouling due to overhang.
You should check for any fouling of lineside objects on your layout.

2. Standard curved points are mostly OK but if there is a slight misalignment at the joint with ordinary rail (vertical or horizontal) the front bogie can become adrift.
I solved the problem by (either method may work alone):
Firstly lifting the track joints a few mm (cardboard or plasticine stuff) due to a dip at that point.
Secondly increasing the tension of the spring between chassis and front bogie by removing/replacing - bending the sprung brass sheet slightly in two places.
The bogie then tracked well.
I also noticed deeper flanges on carrying wheels.
By my measure (which may not be precise), the front bogie, trailing and tender wheels have normal Märklin deep flanges (1.25mm) whereas the driving wheels are 0.7mm on this locomotive.
I would say the deeper flanges on the carrying wheels definitely maintain the smooth guidance through turnouts and cross-overs.

3. The operating sound at slow speed replicates the 3 cylinder exhaust precisely, but at high speed it simply merges into one chuff which is too short and too long a space between chuffs to be realistic.
My experience of hearing locomotives at speed (70mph in NSW) was that the exhaust was just one giant roar of hissing with hardly a beat detectable.
I guess reloading sound is achievable if there is a better option. In my early CS1 there was an option to change the chuff rate and spacing, but the CS3 does not seem to offer that.

4. There are multiple options for lighting, most take time to figure out from the CS3 icons. My cab lighting does not work (i might not have figured that one out). No big deal for me because I rarely run my trains in the dark and I cannot see inside my tunnels.
5. The smoke generator is brilliant - I reckon it went for a full 5 minutes (and the smoke deflectors worked brilliantly lifting the smoke well clear of the cab ).

Summing-up this is a breath-takingly beautiful model and I am glad Märklin took the time to offer it.
There are very satisfying sounds from the wheels and chassis as it flies through turnouts, cross overs and slips, probably due to the 8 wheeled tender.
One more thing - the headboard in blue at the front of the engine smokebox was only used if the engine was to haul the Flying Scotsman train from London to Edinburgh.
That particular train left London every morning at 10:00, and I believe the opposite train left Edinburgh at around the same time (not sure exactly).

Now for some HO scale British coaches.
I have added polls (Poll 1, 2 and 3 in separate topics) to gauge the interest in HO scale British models.
I have deliberately restricted the poll because Märklin have started with an iconic locomotive, the 39968 Flying Scotsman as it is in era VI.
Using 39968 as a basis there are 3 options in the polls which Märklin may consider to be design-able and sale-able.

Kimball

Edited at: by user 07 December 2023 08:47:31(UTC)  | Reason: Added material

I have not opened the locomotive yet, but judging from the number of wires between the tender and locomotive I would guess that the SUSi module is integrated into the MTC Circuit Board (the PCB that has the 21pin mtc connector for the decoder). If that is the case it would take the Susi interface directly from the pins dedicated to the decoder SUSI interface. (e.g. it's possible to solder up Susi modules to the Pickup Shoe Changeover Circuit Board 60973). The decoder itself in the Flying Scotsman is a standard decoder (part no 347463).

Hi Kimball, I agree with you regarding the running of the loco over turnouts. The turnouts need to be perfectly flat, in fact all track needs to be flat - any dip at the track joints, the front bogie wheels will derail. Therefore, with my layout, this loco can only run on some of my circuits, and I'm extremely disappointed with it especially for the price. Another point that you didn't raise, was the paint finish - very cheap looking.

Regards
Greg

Hello Greg,
Do you think it would be better with more of a gloss?
That is my only opinion on that, otherwise as mbarreto says the paintwork is of an accepted standard.
regards
Kimball

Edited by user 21 November 2023 06:08:53(UTC)  | Reason: corected

Hello Greg,

Yes I see your point about having your Flying Scotsman only able to run on some circuits because of front bogie issues.
I have only one of my Märklin locos and one Liliput restricted from certain sections of my layout.
I take comfort from the fact that real railways also have to restrict locos from certain routes, usually due to the loading gauge or weight restrictions (overhead or under bridges, lineside structures etc).

The front bogie I fixed with a more positive bend in the shim brass in two places. It took a bit of juggling to insert it back into the bogie top.
No doubt workers in the Märklin assembly department would do it in 3 seconds flat from having practiced it thousands of times.
I hope they get paid well.

Kimball

Hello
Is your tender properly locked into the driving position?
This was a common and easily solved "problem" with the BR06
Regards

Hi Billy, I also had to put more tension on the front spring, however, it still derails on tracks that rise to another level. Therefore I have allocated it to a small very, very flat section of the layout, in fact it travels around the new c track turntable which doesn't work. So I have $2,000 basically doing nothing.

Greg

Hi Billy, from your comment about putting too much tension on the front spring, gives me the idea that it must have been too much for the Marklin team to get it right, or they are just plain lazy.

I agree that the loco is sensitive to poorly laid track, however, on my layout the loco derails when the track difference is around 1mm - this is a very small tolerance factor. Also, at the same time of buying the Flying Scotsman I bought the USA diesel 38440 and it also derails on the same section of track. The bogies are 3 wheels and are too long and when they go over these sections of track the front wheels lift off the track as the bogies have a lot of up and down movement. Again, this is another example of Marklin's inferior testing.

Hello
Today after a long customs process i was finally able to pickup my scotsman.
I must say again that is a gorgeous model that looks far better in person than in pictures. Did a running test over my R1-R2 M track layout with 5% grades and have no derailment issues at all. It nicely pulls 3 Fleischmann 5146-47-48 cars with no problems after ther wheels were properly gauged, equipped with Fleischmann profi couplers, i must get another pair, but right now they are scarce and expensive.
About turnouts, no problem on 5200 series ones, just a little loss of power in one 5207, but several locos have problems there so it must be more a turnout problem than a loco one. I gave up on curved turnouts long time ago since they are an endless source of troubles with many rolling stock.
A little video of it

Nice video. Loco runs well but probably needs track to be well laid.

Sorry for the late response - it's summertime down here and we have a very long holiday period.

What I did to make the loco stay on the tracks was to take care that the track was perfectly level. By this I mean that where the track pieces join together there is absolutely no variation in height. I placed a straight edge along the rails and made sure there was no gaps along the straight edge. I hope this helps.

Regards
Greg

Sure, you meant the modern models. But even the 3073 is more than 50 years old. The ugliest model ever.