While Toin and I are still fully occupied with building our 5-inch gauge Y14 steam locomotives, I could not resist the temptation to assemble the frames of the 7¼-inch gauge Stroudley Terrier. These frame plates were laser-cut about twenty years ago, but had never been taken any further.
Since the Terrier will be my next live steam locomotive project after the Y14, I spent part of last summer producing a number of drawings and component designs in SolidWorks. To get a realistic impression of the model's real size, I have also made a start on the buffers, drawhooks, and new buffer beams.
The buffer beams had likewise been manufactured many years ago, but a dimensional error in Don Young's Newport drawings became apparent: the specified centre-to-centre distance between the buffers was too small. A new buffer beam was made, incorporating the correct 219 mm centre-to-centre distance between the buffers.
With the help of AI, I carried out a verification strength calculation to determine the number of M4 bolts and rivets required to securely attach the buffer beams to the frame plates.
Assuming an estimated locomotive weight of approximately 80 kg, the maximum tractive effort that could be achieved, and only under very favourable conditions, would be around 20 kgf (about 200 N). With five M4 bolts and six 4 mm blind rivets per angle bracket, the assembly proves to be more than adequately strong. The joint is also capable of withstanding loads considerably higher than the maximum expected tractive effort.
Even in the event of a derailment, transportation in a crate or transport cage, or when lifting the locomotive by its buffers, the chosen attachment method is sufficiently robust to safely withstand the resulting forces.
