April 2nd, 2023

Engineering Report 2nd April 2023

Wheelsets Update

As previously reported, all our wheel castings have been delivered to Riley & Son for assembly. As the original design had a one piece forged crank, it was decided that a fabricated crank was the best option for manufacture and cost, this meant an expensive one-piece forging was not required and subsequent expensive machining/grinding wasn’t required. Our design will be based around the J15 style crank axle and, along with the expertise of Riley’s, a suitable design will be quoted and constructed.


View of the J15 crank used as a basis for our design. CME Elliot Powick.

Once the crank axle has been verified, all additional material will be ordered and Rileys will commence work starting with the leading and trailing axles as these are the quickest sets to attack to enable getting the loco on its wheels. Once these are done they will be closely followed be the driven and trailing drivers.

The radial guides are still at the machinists and are due to be delivered some time in April, once they have arrived they will accurately set up fitted into the frames.

The design for the main radial truck casting has been finished and will be put out for quotation for manufacture. These are quite complex castings and the trust is looking at utilising some modern 3d printed patterns to produce high quality castings, the process that has been successfully used to produce some very complex castings for several other preservation groups. This isn’t a cheap process but compared to traditional patterns they will hopefully come in way under the cost of traditional patterns alone.


One of the big ticket items yet to be attacked are the driving wheel hornblocks. Prior to our CME’s & TLW’s involvement the frames had been cut to the original design to accept the wedge style hornblocks as shown below.


View of original design hornblock dated 1933.

It was decided that this elaborate wedge system really wasn’t required in modern preservation times so a simplified version needed to be deigned to alleviate this. The main problem was that the frames had already been designed and cut to accept it and to save welding in corners and subsequently machining, it was decided to design the hornblocks to “fill the gap”. This has meant the design of 4 different patterns (leading & trailing, left and righthand side) have needed to be created. The beauty of this design means that, as the original design would’ve needed four patterns too, we’ve reduced the number of components required considerably, thus saving a considerable cost on the final assembly, not to mention ease of maintenance once the loco goes into traffic.

The main importance for this is strength of the assembly as we build. Once the locomotive is on its front and rear radial trucks, the frames will have a lot of stress on them, increasing as parts are fitted. Naturally the hornblocks are needed prior to the fitting of the driving wheels but they also supply added tied in strength to the frames, especially with the keeps fitted too. This will all go towards keeping any undue stress to the frames to a minimum as the build moves forwards.

Shown below is one of the hornblock castings (right rear). Before manufacture full FEA (Finite Element Analysis) will be carried out on the new design and any additional strengthening added prior to manufacture.


Hornblock casting CAD model. CME Elliot Powick.

Rear hornblocks shown in place and secured with fitted bolts. CME Elliot Powick

The Importance of CAD Modelling.

There are several reasons behind producing 3D CAD models of the assembly as the build progresses. The CAD work can be used in the manufacture of patterns (poly patterns for the cylinders saving on the costs of tradition patterns) and also for the ratification of the design, especially when parts come together.

These locomotives were designed and built over 100 years ago and mistakes were a regular occurrence, especially when it cam to assembling the kit of parts. To keep manufacturing down to a minimum and to try and achieve a 0% failure rate, the design is regularly checked along the way.

The design of the hornblocks is no exception and when the design was looked at it became apparent that, once the boiler was fitted, the firebox came into close proximity with the hornblocks, not only this but you have to take into account the fact that, whilst in steam, the boiler will expand by a certain percentage. Doing the model shows that, although the assembly is very close, once assembled and the boiler fitted, there won’t be any issues with clashes between the two.


Elliot Powick CME.

This shows just how close the rear corners of the firebox get to the rear hornguides, not much wiggle room in there at all (some bolts drop within ¼” in it’s “hot” state).

Addition Parts

 Whilst the aforementioned parts have been addressed, TLW has been continuing in manufacturing all the associated suspension gear whilst waiting for the radial guides to return from machining, all these parts will go together to assist in getting the loco “on its wheels” for the first time.

To survey how you might be of assistance to the rebirth of GER 789 please click on “How you can help”