JimC

Yep, and Gibson's conspiracy theories often don't stand up to detailed analysis. I know of four issues with the scissors gear in various sources, and of course they could all be true! Limp home on two cylinders after a failure, accuracy of valve events, Deeley's patent and valve setting as per Gibson. Personally I don't find any of them very convincing on their own, but add them all together... As for the inside Walschaerts, I've tried drawing outside Walschaerts for the Stars and Castles I can't make it fit, hence the 4 sets of gear on the first Stanier Pacifics. To have outside gear with rockers to drive the inside cylinders it either needs rockers in front of the cylinders, with all the valve timing issues from expansion, or else a complete reworking of the cylinder/wheel relationship as with the Duchesses. Only two sets, and being Walschaerts there were only two eccentrics plus the big ends, as opposed to four eccentrics and the big ends on all the thousands of inside cylinder locomotives with Stephenson's gear.

Probably fair to say, though, that a larger boiler and cylinders can be fitted on a ten wheel locomotive (even within UK loading gauge) than four driving wheels can provide adhesion for.

Pros and cons. Connecting and coupling rod bearings could be attended to without disturbing the valve gear. Loco preparation was a piece work task, so little saving by taking a few minutes off the job.

The coal merchants building in the model is in the same position on the 25" OS map on NLS. No sign of the staithes, but not sure if that is expected.

I'm confident I've posted this before, but its probably missing at the moment. Its basically the Great Bear truncated into a 4-4-2, lightly crossed with a Scott 4-4-2. It ought to have made for a more effective boiler. Factor of adhesion and weight limits? Err, lets conveniently gloss over those shall we?

Odd, isn't it. There were cut down locomotives for various highly restricted lines, but you'd think they'd start with an 850 or a 2021 for something like that.

They certainly vary. I have a lot of trouble with cab heights, they often don't seem to scale well on the drawings when you have a measured dimension. The dimensions I have for 645/655 are: K - 10'10 3/4 (equiv of M but 645 class) B28 - 11'4 5/8 B65 - 11'4 5/8 The others are scaling from the drawings I have, which are often distorted. I usually have boiler pitch and wheel centres and try and make those fit the measurements. The diag M was particularly difficult, I only have a photo with much distortion and had to manipulate more than am really secure with to try and make parallel lines parallel.

Enthusiasts often refer to this Wolverhampton built class as the 655 class, but the GWR usually described them as 1741s. Thirty-two were built from 1892. They were essentially similar to the earlier 645 and 1501 classes, but were just a little larger with longer overhangs front and rear. The bunker was actually the same size as the 1501 bunker, so the extra three inches of overhang presumably provided more room in the cab. Again they were built with T class boilers. They were numbered rather eccentrically: the first two, 655 and 767, were given numbers previously used by 645s that had been sold. The rest were numbered 1741-1750 and 1771-1790. Almost a subclass were the last 'large' Wolverhampton engines, 2701 to 2720, built 1896/7. The boilers were T class, but had small dimensional variations. Otherwise they were very similar to the 1741s. The 655/1741/2701s tended to merge with the earlier 645 and 1501 classes as time went on. They were fitted with the larger P class Belpaire boilers and pannier tanks. The majority were given enlarged bunkers. Around half were superheated at one stage in their lives and a number gained enclosed cabs. By the 1930s all four classes/sub classes were being treated as a single class. Some were scrapped in the 1930s, but most survived the war. Some twenty-one made it onto the BR books and the last were scrapped in 1950. There were five diagrams for the 1741s and 2701s, covering the variations in boilers and tanks. The last diagram, B65, covered 645, 1501, 1741 and 2701 classes, demonstrating how the classes had merged as they were updated. This first sketch is rather loosely based on diagram M, but the cab in particular has been amended from photos. A cab entrance with a single large radius as shown seemed to be something of a Wolverhampton thing. Swindon cabs usually had a larger radius on the bottom of the cutout than the top. This is the T class boiler, which was pitched appreciably lower than the later P class. Oddly the precise combination of dome position , firebox and T class boiler on the GWR diagram is not known to have actually been fitted to the class. Fortunately for my sketch the firebox top is hidden anyway. This is more closely based on diagram A18, the first diagram with the P class boiler The odd stumpy chimney was by no means universal on this variation. This sketch is based on diagram A42, which is an earlier pannier tank fitment with the P class boiler. And finally this is based on diagram B65, with a full length cab roof and a much extended bunker. The resemblance to the 57s is getting quite marked, but pre group Wolverhampton locomotives could always be recognised by the footplate valance and the shape of the front step. Its important to note that the sketches show just a few of a considerable number of variations. The Wolverhampton pre group classes are something of a modeller's nightmare, since Wolverhampton had their own style, but Swindon tended to put Swindon design features on locomotives that came into their hands. So photos, photos.

I'd be a bit nervous of the amount of metal dust flying around a running motor if you did it like that!

Nah, still bonkers, because the efficiency of electricity -> steam -> rail is a fraction of electricity -> electric motor to rail. Although you could make a case for bi-mode steam/electric it would still be far more sensible to use the sparks to run a motor rather than heat steam.

I found a nice works photos of one of the Ms as built, and decided that, with the dimensions in RCTS, gave me just enough information to attempt a sketch of the M Class as turned out by Stephensons. The main difference is a smaller diameter boiler, which I think is just different enough to lose some of the brute strength appearance of the other 20thC RR classes. But there's one little peculiarity I'd like to highlight. In this sketch the tank/cab and cab/bunker corners are both radiused, as are all 4 corners of the cab. This is as per the Stephensons' works grey photograph in wikipedia and other places as shown below. All these corners are also shown radiused on the GWR arrangement drawing for 106/47 when she was fitted with a GWR boiler. However all photographs of the class (with the later RR boilers) I have found show a 90 degree transition at bottom left of the cab door/window cutout, and between cab and tank, and a radiused transition between cab and bunker. Photographs of 106/97 with GWR boiler and bunker , however, clearly show both cab/tank and cab/bunkers with 90 degree transitions, whilst the cab window corner is hidden behind the cab shutter. So I've amended the GWR sketch to show what's in the photos rather than what is in the works drawings. RCTS doesn't record whether it was Swindon or Caerphilly factory who ignored this detail from the drawing office.

I think there are two things that could be done to evaluate it a bit. The first is to burn a tiny little bit which would tell you whether its plastic or natural fibre, and the other would be to see if a similarly printed tape is available contemporarily.

Another observation is that they appear to have simply removed the brakes rather than create a new arrangement. So may we guess the idler wheel is one side only and this was a very quick and dirty short term experiment?

In that case may I challenge one of you to produce an image of 4-4-0 trailing wheels with balance weights as small as that:-) I didn't think there was a chance of that tiny weight doing anything useful vis a vis a coupling rod, but was successfully proved wrong a couple of posts down!

I hunted out some other photos of the Samsons. Most have coupling rods down, but on the others it seems to me evident that the tiny balance weight on that locomotive is far smaller than they were on the coupled locomotives. Just big enough to balance the off centre crank web perhaps?

Having lined up sketches in different ways, If you line up the driving wheels then the cylinders, boiler and cab also line up, but the rest of the wheels have moved. The other two driving wheels have moved back 6 inches, the front buffer beam and leading pony wheel back 2 inches and the trailing pony wheel back 6 inches. The rear buffer beam, of course, was something of a moveable feast anyway. I think the 4'1.5/4'7.5 wheels is interesting, because the 4'1.5 wheels were well established for branch etc with the 850/1901/2021 classes as against 4'7.5 on the larger 0-6-0Ts. You'd think they would have known what the limitations were. I wonder if there was something of a speeding up of trains?

They're even more different than that. If you look at the weight diagrams the entire relationship between chassis and superstructure is subtly different: look at the cylinder positions relative to the wheels and the overhangs front and rear. There must have been a considerable redesign done: it was anything but a straight rewheeling. The relationship between the front of the water tank and the leading driving wheel is worth noting too.

Quite agree. But then even Webb just tried it as an experiment and never built another. It started life as a 2-4-0, so presumably the [grief, cant think of the word, not crank] place where the rod was connected is under the valance.

There's friction and friction. As a general rule friction is purely parasitic and best avoided. But what's going on here is effectively a clutch using friction in much the same principle as a clutch on an internal combustion engine. So provided the clutch is working fully effectively with no slippage there isn't any more loss than on a motor car clutch. That's the good news. The bad news? I don't suppose the tiny little contact area of that friction drive has any more chance of working efficiently without slipping than I have of winning a tug of war with a GWR 2-8-0 tank engine...

"an attempt to meet Brunel’s virtually impossible specifications." Its interesting isn't it. There's nothing particularly unusual, even these days, about a prospective client coming up with utterly unrealistic specifications, but a competent supplier should work out a way to agree a deliverable product. In those days, I suppose, with the whole business of heavy engineering being so new, perhaps it was more difficult. I doubt Brunel was an easy client too, but oh to be a fly on the wall for the discussions of the actual locomotive designers. Did they have grave doubts, or did they really believe - or hope - their interpretations of the specifications would make for useful locomotives? I well recall a situation in my IT career. I worked for a central IT department, but the divisions of the organisation had complete power to purchase their own systems. The IT manager of department X put together a concept and specification for a new system that on paper looked as if it solved all sorts of problems, but in practice was clearly going to be impossibly complex and nightmarish to run. Somewhat Brunellian really! Anyway the in house team put together a proposal with their normal external partner that discarded all this horrendous complexity and proposed something that would actually work. Meanwhile ICL (you can tell this was a long time ago) put together a proposal that met the specification closely and won the contract. At the centre we were awaiting with great interest to see how on earth they were going to make this confection work. At this point ICLs clearly highly competent technical sales people stepped in. They 'worked with' the customer to make some 'minor changes' to the design which actually totally discarded Dept X's IT manager's castles in the air, and replaced it with something that was very close to the proposal the in house team had worked up, with a few fancy features that were of little benefit or disadvantage, but made it look as if it had some relation to the original concept. I've always admired their superb customer management, and tried to emulate it...

I don't know about an actual map, but there is certainly a text list - 6 pages in the 1936 General appendix to the rulebook.

I'm sure I've heard of parts stamped 111, but these are surely more likely to date to her rather longer career as a Castle.

I have absolutely no connection with the running of this site, but a fair bit of experience with recovering broken IT systems. It's in the nature of these things that we (as in IT people) don't really have any idea how long a complex one off process is going to take until it finishes. This is especially the case when it's an intensive background process that will take processing power away from the main business of running the site, because if it causes too much of a performance hit then it has to be slowed up. There's also an age old dilemma that doing the work required to find out how long a recovery will take diverts resources from doing the recovery, so the engineer has to decide whether its more important to get the system back as quickly as possible, or whether to accept a slower recovery in order to give the users a better sense of when full service will be resumed. So pragmatically, at this stage my uninformed opinion is that it's sensible to assume it will be a few weeks, and consider whether there's any material that is so much referred to and so important that it's worth you taking some time to reload - and maybe review the content at the same time.

Its interesting too that the word is being used of an actual existing mechanism that is nothing at all like Capek's artificial humanoids, and in no sense mimics limbs or other human function.

Also begs the question of whether it would be advisable to recreate something that was demonstrably not that great in the first place.