MÁV Class 325 Steamer Model Design

General

When choosing the Class 325 as prototype for my next model its exclusivity was most tempting. I have not seen any of these engines in their active life, they were not stationed close to Budapest and all were scrapped by 1962. There are not many pictures available showing a Class 325 loco. I do not know about any small scale models of this engine, but it can happen that one or two exists.

Fortunately the Budapest Transport Museum possesses a 1:5 scale model of this loco. A 1:5 model is practically an exact replica of the prototype, you can find every small parts correctly shaped and positioned. These engines supposed to be able to heat up and operate but nobody ever tried to do this with these extremely valuable models.

On the other hand they were no rarity locos. Many of them were in service before WW1 and they were characteristic engines with their huge cylinder blocks and large size flat sliding valves. They had a very nice Walshaert valvegear, two different types. As they were present in the late '30s, the era I model, they are excellent modelling objects. As I always build two similar models, it is natural to consider one model with old type valvegear, another with the new type. The new type looks a bit easier to build, thus I start with this.

I had no opportunity to visit the only survivor of this Class in Serbia.

When choosing this prototype I faced with a series of problems.

There is not too much of documantation available. The number of pictures is limited. This has several reasons. Before WW2 these engines were unimportant, not very present. After WW2 it was forbidden to take photos about railway equipment in Hungary. Most pictures are form before WW1 and there are a few photos in accident reports. I found a nice photo from the famous Hungarian railway photograph, Mr. Béla Fialovits in the Hungarian Motive Power book. This was the base. In 2003 I got a copy of a few engineering drawings showing an engine with old type valvegear. I used this drawing for my design. Unfortunately the drawings do not show a few very important details. The Budapest Transport Museum 1:5 replica models a loco with new type valvegear. The model is placed in the Museum on a very badly arranged shelf, almost on floor level in a dark corner. No possibility to take usable photos, but I made a number of skeches in my notebook about many interesting details. (Museum guards were wondering what I was doing sitting on the floor in front of the shelf!)
The drivers made me a big headache. The prototype had a driver diameter of 1440mm, a rather common size and the German standard size 1400mm is also close to this. But the Class 325 had drivers with 13 spokes! As far as I know, no German loco had 13 spoke drivers, thus no model manufacturers offer this. Neither Austrian, French, Italian or American locos had drivers with 13 spokes. It seems the only source might be the British model maker Sharman Wheels, who offers wheelsets with the required diameter and number of spokes.
I wanted to avoid to make a tender drive. As the prototype's tender was practically the same (except for the air brake) as those of the Class 326 I could simply copy that solution. But I am not really satisfied with the drivetrain of the Class 326 model. Thus I decided to build a loco drive, similar to those of the Class 342. That, however, is housed inside a rather large tank loco below the integrated boiler-tank box. In the Class 325 the boiler is shallow and lies well visible above the frame. The only solution is to put a small diameter motor intruding into the longboiler and put the whole gearset into the firebox. Fortunately the firebox is as long as it almost touches the rear wheelset axle. The gearbox will be thus a delicate design.
Until now all my models were equipped with a "moustache" type current collector. The only exception was the exeprimental solution for the second Class 326 with its internal ring. This is, however, impossible for the Class 325. Its drivers are all around visible below the rather high mounted footplate. A moustache wire would be very eye-catching there. Another solution is required.
The Class 325 had a very emphasised cylinder block. This was due to its two-cylinder compound engine. The low-pressure cylinder was rather large and in order to have a nice symmetric frontside appearance the shrouding of the smaller high-pressure cylinder was made to the same size. There was a flat sliding valve in slanted position on both cylinders with a rather special shape. As this block and its shape contributes much to the "face" of the loco it needs a special attention.

Let's see how these design requirements could be satisfied.

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