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Fitting nicer couplings to a Roco ÖBB 93

readingtype

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Today's activity, as it turned out, was to install Originalbügelkupplungen (OBKs) in my Roco H0 model of the Österreichische Bundesbahnen (ÖBB) Reihe 93 (formerly Reihe 378, see Wikipedia page (German, the English one has very little text)). More about the loco below; but to introduce them OBKs are a brilliant way to improve the look of an H0 model by replacing the large clumsy coupling. They simply disappear, while working perfectly with the conventional NEM loop coupling. You can just about see them in the photo.


This is a locomotive design I immediately loved when I first came across it. The 93 is a 2-8-2 classic allrounder tank loco, lots of small wheels giving plenty of torque for steep gradients and spreading the weight so it can run on lightly laid secondary lines. Although dating from the 1920s, members of the class were running right up to the very end of Austrian main line steam.  Regrettably for me, this event happened very shortly before I was born and so the first chance I got to see one was on a visit to the remarkable Strasshof depot not far from Vienna.

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Austrian locos have a look. It's hard to say exactly what it is, but the balance of elegance and steampunk is distinctive. Some locos had a brass ring around the chimney about half way up which is something like wearing a bandanna or a choker or ... I don't know. Many designs had truly wacky bits and bobs such as two domes with a pipe running between them (at least once through a sandbox in between), or the Brotan boiler which, well to be honest I don't really know what to say about that either. Looks disastrous but apparently it wasn't. Then there are cast iron disc wheels, found on all sorts of different low-speed locos, which most of the class originally had.

 

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There were two significant design constraints and these definitely left their mark. Firstly, Austria's supplies of coal were low grade. This meant thinking about how to make the best of what was available and on larger locos which rapidly chewed through fuel it there was a need for large wide fireboxes; this wasn't such an issue for a humble tank loco. Secondly, keeping weight down was important. Again, with six axles and a weight of 66 tons in running order this would not be a huge problem, but the ethos was there and of course the material saved was money saved up front and for every kilometer run. The desire to save weight led to frames with lots of cut-outs in them, generally rectangles with radiused corners to spread the stresses around them. On the 93 the boiler is raised fairly high and the alignment of the side tanks, cab and bunker leave open spaces which can be seen through. These are at a height where a standing observer can see through from one side to the other, sometimes through several intervening parts of the frame or thin supporting flanges and struts.

 

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The final distinctive feature, which this model has, is the Giesl Ejector -- including the narrow oblong chimney. This was designed by the Austrian engineer Dr.-Ing. Adolph Giesl-Gieslingen -- to Anglo-Saxon ears a rather grand name, but Giesel-Gieslingen seems to have been a genial and friendly as well as erudite man. He wrote an accessible history of the final years of steam designs in Austria, including trials he took part in (book details below). According to the British railway author O S Nock he was happy to roll up his sleeves and get involved when it came to trialling the ejector on various British locomotives. In Britain it wasn't considered a success but it apparently added a hundred horsepower or more to the Reihe 93. I believe that this success goes back to the fact that burning low energy, dusty coal is difficult partly because the fire won't burn nicely. I have read that really good blast pipe and chimney make a difference not by creating super-strong jets of steam but by being just right to keep the fire happily aerated so everything is burned without constricting the cyliders so the exhaust steam can't escape freely.

 

On with the task: fitting OBKs front and rear. The whole model strikes me as a brilliant example of commercial model loco design. Dismantling it reveals the experience of the design team, taking advantage of that common baseline running along the bottom  of the side tanks, the cab and the bunker. They were able to hollow out this space to place a circuit board for the DCC chip, the lights and the motor. The walls of the space are thick cast metal giving plenty of weight and a moulded plastic outer sleeve slides over the whole thing to carry the surface details representing the prototype. I caution anyone considering opening the model: take your time. It all comes apart very nicely but it offers few hints. The instruction booklet isn't very good on this point. Communication is entirely by diagrams, but I only discovered by trying for some time that is is not possible to remove the side tanks, bunker and cab until you have removed the boiler (screw hidden in the dome, that was clear from the diagram) and the cab roof. Naturally just after succeeding to carefully remove the tank, cab side and bunker moulding I broke a detail part through slight mishandling.


In common with many H0 models, if you remove the moulded coupling hook from the bufferbeam you reveal a slot exactly the right size for an OBK to go into. Behind the bufferbeam, things are a bit different. The design of this part of the model is extremely ingenious, and hard to describe. Both ends of the model use a similar component to bridge between the bufferbeam and the main chassis. The space under the bunker means the same design challenges are found at the rear as at the front. The part is a cast metal beam that carries the buffers and the NEM coupling at one end. At the other, it is anchored to the chassis with pins and then sandwiched in place so it cannot wobble or twist.

 

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Very fortunately, the OBK's shaft slides straight into the slot on the rear bufferbeam which is deep enough to accommodate its full length. The front bufferbeam needs more work; here the guide for the coupling mount is positioned so that the slot cannot be so deep. By drilling out some of the material that forms this guide and by shortening the coupling shaft slightly, the one can be made to fit in the other. To others wanting to follow: just remember to go very slowly, remove material bit by bit and keep trying the fit. Have you read that ever before?

 

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Finally: a note on the superb replacement wheels. These are to RP-25 profile and were done by Holger Gräler who offers re-wheeling as a commercial service. Here, he has put new nickel silver tyres onto the original Roco centres. Impressive.

 


Dr.-Ing. Giesl-Gieslingen's book is: Die Ära nach Gölsdorf. Die letzten 3 Jahrzehnte des österreichischen Dampflokomotivbaus, Verlag Slezak, Wien 1981
OBKs come from H0fine: www.h0fine.com

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Allegheny1600

Very interesting stuff, I may have to try this coupling.

I'm sure I have heard of it before but never really considered it. I take it you're using the OBK108, loco coupling hook? Have you used the wagon couplings, please?

I like your description of the Roco OBB Rh93, I only wish the Roco DB/DR/KPEV BR93 was so good, this is one of their rare 'dogs' but then, the prototype should have been a 2-8-4T imho.

Cheers,

John.

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readingtype
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8 hours ago, Allegheny1600 said:

I take it you're using the OBK108, loco coupling hook? Have you used the wagon couplings, please?

 

These are H0fine's OBK138. There's also 139 which is for vehicles with a deep bufferbeam or front 'skirt' -- small diesel shunters and railbuses for example.

 

Yes, I have fitted the wagon couplings too. These have a loop of nicely magnetic steel wire that comes pre-bent. It would be a total pain to make! I thought the cast nickel silver ones were a little OTT (how dreadful to treat wagons as second rate, but there are more of them to work on). The plastic OBK120s fit the bill pretty well and are not that difficult to assemble; there is a central hook/turnbuckle/shaft silhouette laser cut from something vaguely acrylic and either side are triangular reinforcements that vaguely resemble the shackles that are cut from a similar plastic. The assembly work is slotting three 0.4mm n/s wire dowels into holes in the profile and sliding the triangular reinforcements over each side.

 

You fit them through the convenient hole left by the moulded coupling hook if you are lucky enough to have a wagon made that way; otherwise careful drilling is needed and a 3D printed plug that turns a drilled hole back into a rectangular one (to stop the coupling rotating around its shaft) is available. It is made to look like the flanges above and below the prototype coupling hook. There's a jig (Einbaulehre) that is very helpful. In fact there are two, and the first one I got has lines marking the correct buffer height. Don't put the buffers of anything by Fleischmann or (deeper breath) Märklin against that without knowing what you are doing :-) The second can be fitted with a projecting knitting needle to stab a proffered bufferbeam at the right spot to start drilling.

 

In theory OBKs should be used with sprung buffers. If you think about this, it gives a couple of mm at most of 'grace' on a sharp curve. Other things may well not be going well for the wagons involved by the time this is needed. I prefer to let the couplings project a little futher; if you fit them as designed you get a lovely close coupling and another mm doesn't really harm the appearance. R1 curves, forget them. OF course there were and are some very sharp curves out there in the world but vehicles are not always coupled together wherever they go ...

 

Speaking of the appearance, what you can do with both the loco and wagon couplings is completely lose the NEM pocket. Have a look under the vehicle after this has been done and you soon realise how much realism can be gained by taking things away!

 

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(In the photo above the hook should actually be behind the buffer heads rather than in front).

 

Final point: the plastic is not mega strong and I have already suffered some broken ones (the obvious weak point is the neck where the shaft enters the buffer beam). Etched metal would be more resilient.

Edited by readingtype
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readingtype
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Final final point, despite being a little delicate these couplings were designed for serious use, specifically at FREMO meetings where running longish trains and doing lots of shunting is important. They couple and uncouple brilliantly if the height is correct and don't snag as much as the conventional NEM design.

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Allegheny1600

Many thanks indeed!

This is very encouraging information, it gives me all sorts of pleasant ideas.

Cheers,

John.

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readingtype
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Update from Austria: 931403, which is at Heizhaus Strasshof north east of Vienna, was repainted 2019-2020. See this photo of the loco in the Heizhaus. Thanks to @Michael W on the Kleinbahnsammler forum for this news!

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