T3 a Württembergische 0-6-0 loco

 

 

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3.5" gauge
railway: GER
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0-4-2 GWR 14xx class
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0-6-0 T3
7.25" gauge:  
railway:  Germany KWStE
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This is part 1 of the Württ T3: A model steam locomotive on 7.25" gauge (1:8 scale) of the German Württembergische Railway 0-6-0 class.

Ground level driving in Turnhout (Belgium)  is a wonderful experience, so much even that I finally started a 7.25" gauge locomotive.

 

The locomotive

This new project will be published on this site as progress gets along. The locomotive is a German Württembergische T3 which I'm designing with the aid of  3D cad software.  I've bought a model of the loco from Brawa. This H0 fine scale model, a book of the loco  and some photos of the preserved locos are the basis for this 7.25" design.

For this scale (1:8) it is a quite small loco, with the benefit that it hopefully still can be handled in my workshop. A larger loco on 7.25" gauge would be too much for my small workshop. And in my opinion most model live steam tracks in the Netherlands have the size of a branch line rather than a main line.
Although the small size of this loco there are several 7.25” versions of the Prussian T3 and they are all very good performers on the track. They are in main dimensions very similar to this Königlich Württembergische Staatseisenbahnen (KWStE) version and as in real live these is also derived from the Prussian T3.

With an overall length of just under 1.10 meter and a weight of around 100kg the model should be able to do some work on a ground level track and it still can be transported in our family car.

 

The choice of the model

   (Click on the small images to get a larger view)

It all started with the plan to build a small Stroudley Terrier A1 class 0-6-0 loco called New Port and designed by Don Young. A nice little engine on 7.25"gauge (184mm) as a next project after the 'Didcot'.
The wheel castings for this loco were (and still are)  however exceptional expensive at Reeves2000. Over 600,-- Euro for six wheels
, ex. postage & package.

I was talking about this with a German  model engineer, whom I'd met at the annual steam meeting in Den Haag Zuiderpark. Wolfgang told me he had some wheel castings,  drawings, cylinders, chimney and lots of other bits and pieces for a German 7.25" gauge  T3 (see this video)  he was not using any more.
An appointment was quickly made and within a few weeks I was the proud owner of a complete set of castings for
a 7.25" gauge locomotive. The drawings and castings came from Live Steam Service.

     

This Prussian T3  is very nice loco indeed, but in a small book I read about a variation on this design, the so called Württembergische T3 (89 3-4). All the parts could be used, only a new drawing had to be made. This gave me the opportunity to incorporate some ideas from earlier experiences with previous model locomotives and to get some hands-on experience with 3D solid modelling software like Inventor and Solid works.

          

I've started with the book of  "Die baureihe 89 3-4" by Werner Willhaus (EK-Verlag), which include a few very clear drawings and plenty of photographs of the locomotive during is existence. The first was built in 1891 for the Königlich Württembergische Staatseisenbahnen (KWStE). Luckily few are still preserved in Germany.

 

The frames

With Inventor 3D modelling software I set out the first sketches and the data was used for laser cutting the main frames. Measurements were taken from works drawings of the book and from the Brawa H0 model. Later on I took measurements from one of the preserved locos in the Landesmuseum für Technik und Arbeit Mannheim.     

The mainframe and frame stretchers are laser cut in 4mm steel plate. These were the first parts of the new locomotive project in the work shop. It took me 11 years to build the 'Didcot', so only time will learn how long it will take me to complete this locomotive.

The casting of the chimney was set up in the lathe for finishing the outside. The little square part on the front is for placing the steam operated bell. A typical German feature on small branch line locomotives.

        

Small steel angle profile (10x10x2 and 15x15x3mm) was used to erect the frames. Buffers are turned from mild steel bar, the coupling hooks are cut from solid steel bar. I always like to make these parts in the beginning, to get an impression of the size of the loco.

 

Turning of the wheel castings

The frame looked some what strange, with the unmachined wheel castings standing along side. So the next job to tackle was to turn the wheels. The castings are of a very good quality and they were easy to machine.

   

The first operation was to turn the outer rim clean. Now it could be held on this rim in the chuck and the front face and tread were 'cleaned' also. By 'cleaning' only a small amount of material is removed, just enough to get rid of the rough surface of the casting. Once this is done, the wheels have a so called reference side or face, on which they can now be hold to turn the back of the wheel. In this operation the wheels get there final width dimension. In the same setting the hole for the axle is drilled and bored to final close fit dimension  of 18mm (tol. 18.00 - 18.02mm)

  

Profiling the tread is done is various settings. The wheel is therefore clamped  on the faceplate with the aid of a mandrel which is hold in a collet. The wheels tread is 3 degree coned. These wheels are, with a diameter of 138mm, even a few millimetres smaller than those on the "Didcot".

    

The wheels are fitted on 22mm axles. I've took one to the club track of the SMMB in Tilburg for testing.

A quick set-up in the milling machine was made for drilling and reaming the crankpin holes. No complex jig is needed, only a pin of (in this case) of 18.01 mm, that has been screwed and fixed in T-groove on the table. The wheel is clamped on the table and machined.  Without moving the table of the milling machine, all wheels were treated in the same manner.

 

 

Designing the axle boxes, horn blocks and springs

     box up side down in the vice

The axle boxes are the so called split type. The upper bearing is made from bronze, the lower part from brass and the axle box from mild steel. Of course everything could be made of bronze, but I had no material available in this size. One could ask if the split bearing type is necessary, but I would like to able to remove the bearings, without removing the wheels from the axle. I must state that I’ve this type of axle boxes on the “Mona” (3.5” gauge) and “Didcot” (5” gauge) as well………and I had never to remove the boxes jet.

  

Due to the relative small wheel diameter (138mm) there is not much ground clearance for the spring hangers. If I would use the same design as with the Mona and Didcot, there is a possibility that in case of a derailment (not uncommon on 7.25” gauge ground level track I’m told) that these spring hangers would get seriously damaged.

I could have made a design with the springs on top, but that would coincide with the boiler.
 

So I’ve drew up a system on which the springs are positioned inside the frame
beside the axle box. The springs are fixed between a bar on top of the horn blocks and one bar below.

 Milling of the horn blocks from square brass bar.

This construction is quite strong and the lower bar acts like some kind of skid plate in case of a derailment. 

For the necessary oiling of the axles, each axle box has a milled recess on the top, which has a drilled hole that is in connection with the bearing below. 


Tribology theory taught me that it is unwise to feed the oil to the axle on the top. There is a
hydrodynamic lubrication: This form of lubrication occurs more or less naturally in properly finished, sized, and lubricated holes and shafts. Essentially, rotation of the journal causes it to drag lubricant into a wedged-shaped channel generating a load-carrying pressure. The lubricant in this wedge creates sufficient pressure to keep the journal riding on the oil film. This form of lubrication is generally preferred because it is simple and dependable.
An oil feed hole on top would partly destroy this build up of pressure. So why use it anyway? There is a quite simple explanation, I found in a reprint of an old German locomotive handbook.
Indeed the oil film
build up of pressure is not as good as it could have been, so most of the wear of the bearing would take place on the top………just were you want it. The locomotive “would sink deeper in the bearings” and that is easy compensated by the springs. The wear over the horizontal line of the bearing however will be less, because the oil film is there not interrupted by an oil feeding hole. And exactly on that position are, on a steam locomotive, the greatest forces due to the movement of the driving rod and movement it translates from the piston to the frame. 

 

On top of the axle box I’ve made a small lid, which can be opened and closed with the tip of the spout of an oil can, which conveniently fits through the spokes of the wheels from the outside. The lid should prevent to get dirt and grid in the oil reservoir, which is always around when driving on ground level track.
The lower part of the axle box has a milled groove, in which a piece of felt will be fitted. This should make sure that, even in the event that the oil reservoir is running empty, a small quantity of oil will keep the bearing lubricated.

 

The manufacturing of the axle box is a straight forward milling job.

The boring of the hole for the axle was done in the lathe. The set up for machining this hole was done in the 4-jaw-chuck. To get the hole exactly in the middle, a small pilot hole was first drilled in the milling machine (with the aid of an edge-finder this is precise and quick). Once the job is transferred to the lathe, a fixed centre point is put in the pilot hole and the centre is supported with the tail stock. A dial test indicator is put on the centre, and by adjusting the jaws the reading of the indicator can be set to zero.

The hole for the axle is on this loco 22.04 mm. First the hole is drilled up to a diameter of 20 mm. The last 2 mm are turned with a boring tool. Reaming is also possible, but I didn’t had a parallel reamer in this size and find that the lathe boring tool gives a better and more controled finish.

 

The cylinder castings

These are the cylinder castings that came with the set of locomotive parts.
(They are 90mm long and and have an out side diameter of 66mm. The finished bore is 40mm).




It is the first time for me that I’ll incorporate cast iron cylinders, all my previous locomotives are fitted with bronze cylinders.
During manufacturing of the cylinders there is not much difference with bronze, but the usage of cast iron cylinders on the finished locomotive will be different. This material depends on good lubrication with first grade quality steam oil. Otherwise rust will set in quite quickly. Also all the condensated water has to be removed via the drain cocks after the run I'm told.

  

This cast iron is of a good quality (no hard spots) and machining in the lathe was done with carbide cutting tools.  Although they are large, they could be clamped in the 3 jaw chuck. This made turning a straight forward job.

After boring out the cylinder to the correct diameter (in this case 40mm, which is small for a 7.25” locomotive) an automotive honing tool was bought and used for finishing the bore to a smooth surface.
I’ll be using Teflon piston rings of the same design as used in the Mona, Dacre and Didcot. In these locomotives they proofed to be successful and never needed any maintenance
yet.

      

The cylinder port face on the original Prussian T3 (for which these castings are intended)  has an inclined angle. In my design this will not be incorporated, so the shaping machine was put in action to remove the surplus of material. The shaper leaves the port face with a very flat surface. The machining marks, left by the tool, are all parallel and in straight lines. This will be near to perfect to take up a small oil film, on which the valve can glide. The slide valve it self will also be machined in the shaper, but the set up will be arranged so that the grooves left by the cutting tool will be 90 degrees to the ones in the port face. I’ve used this method before with the other locomotives and the slide valves and port faces still look very good after years of service.    

The cylinders partly finished, with the covers in front. These were made by Wolfgang years ago and can be used without any problems.  

Cutting of the steam ports. They are 4 mm and 8 mm wide and were cut with a small 3.5mm cutter. You'll see no chips in the picture, because I've used a vacuum cleaner to remove them after every cut. This way I kept a clear view on the process and the chips would not clog up the relative deep ports during the cutting process.

Drilling the connection holes from the cylinder bore to the ports is still a job I have to tackle. 

 

The smokebox

This is a classical design, with the flared out front plate. The Stroudley A1 Terrier locomotive has the same kind of smokebox shape.  That loco was from the same period (1880’s).

     

I used a piece of steel pipe (160mm diameter) on which the front plate is silver soldered. The door is a combination of a steel turned disk and a curved steel plate, also silver soldered on. I’ve used the standard dart design for closing the door, because I couldn’t figure out how this worked on the original Württ. T3.

The hinge is made from a steel bar, that was first reduced to thickness of 2 mm in the shaping machine. You’ll see in the photo the 8mm square lumps, that became the eye of the hinge. This job has been done by filing.  

 

The Solidworks drawing

I started out with Inventor software for the 3D modelling of the loco. At my work at Fontys University of applied sciences, I have made to change to Solidworks because we got better support with this software. To get familiar with the 3D modelling CAD software, a 3 day starter course isn’t enough; so I had to get some hand-on experience myself.

    

What better way than to make your own drawings. Designing the locomotive in 3D is great to do. You’ll get an instant view and ‘feel’ of how things will look on the loco. In the assembly drawings, all the parts can be fitted and checked on the virtual locomotive. Even the total weight of the loco can easily be determent. The valve gear can completely be tested in forehand; so when I start to cut metal in the workshop, I know the parts will fit. From every 3D modelled part a 2D workshop drawing can be made very quickly. A change in the 3D part will be automatically up-dated in the 2D drawing.   

 

Part 1    

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GWR 14xx class loco and the new T3 frame at the model engineer exhibition at the Rijnhal  Arnhem november 2008


The Solidworks assembly in october 2009


A cross section view of the virtual locomotive