Added February 2020
Since writing the original piece about weight distribution, we have built another nine locos. Here is a complete list of all engines and their weights. All measurements are in grams.
I have also devised a method to measure their effective drawbar force. This consists of a length of small chain, which rests on my small scales on the floor. The chain is attached to the loco with a length of thread over a pulley. With the engine on a metre length of track, it pulls the chain upwards until the loco starts slipping and cannot lift any more chain. The difference in weight between the whole chain and what is left resting on the scales is the drawbar force. The diagram should make this clear.