Construction of Class M7
1981 “BRUSH” diesel engine of Sri Lanka.
CHASSIS CONSTRUCTION
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This page shows the start of the M7 project with the selection and acquisition of materials for manufacturing this 7¼ inch scale engine. Having obtained 24, A3 size works drawings the basic engine dimensions were inserted into an Excel data base so as to arrive at the real working engine sizes. Both drawing sizes and actual sizes have been used (or adjusted) to make this model
The size data then allowed the purchase of materials needed to start construction.
Some of the A3 drawings were enlarged to ensure that the scale data would actually produce an engine that would be large enough to represent the full model size which would then permit assessment of the component sizes and fitting of standard available components.
One of the major problems with making such a model from scratch is that delivering a real working model is often a compromise between having a nice looking model and one that actually looks about right and performs within the models design parameters that have been worked out initially. Getting the balance right is often more important than exact scale.
Works designs can change during construction of a new engine, liaison between the workshop and the office may well take place in order to accommodate changes needed that may affect other parts of the working components when the engine is tested, or may arise during track trials. Having lots of actual detail pictures helps sort this out.
A picture can do what a thousand words cannot, it provides the builder with small details that could otherwise be overlooked. It may also be necessary to modify your own sketches to take account of any anomalies seen and allow you to arrive at a workable compromise thus ensuring that you end up with a good working model. What might work on the full size engine may not on a scale or semi-scale model.
Detailed panels or parts can be flimsy and fragile and susceptible to damage when being demonstrated and operated, for these reasons it might be prudent to avoid (making or) fitting such parts to the engine when being operated.
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 Plan of chassis
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 chassis deck plate
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 main frames added to deck plate
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 buffer beam plate work (upside down).
Note:
In order to ensure that the model would be square, flat and true it was mounted and constructed on two heavy box section steel parallel bars bolted together to form a rigid construction base.
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SLM7 – Chassis – stage. i