< Bogie Truck Design Change 1 >
This month I have no progress except following design change of the bogie
Last month, during the rolling test on curved track, I also checked interference around the bogie truck and found that the cylinder tail rod box is interfered with the front leading wheels. In order to solve the problem, I have to cut off the bogie truck side play from +/- 15 mm to +/- 11 mm.
Due to the change of side play, I decided to change the bogie truck side control system from Coil spring type to Rocker type.
The following drawings show the rocker type side control system. The cyan part is bolster, the black part is truck body, and the magenta parts are rockers. The rockers and the bolster is connected by arms as the yellow parts. Due to side shift, the rockers are rolled as the drawings show. The rockers right (left) shoulder shapes circular arc of the left (right) foot. Therefore the top height of the rocker is constant at any roll.
Side control force is determined by the bolster bottom gradient. It is 1/3, so the force becomes 1/3 of the on-truck load. The force is constant at any side shift. The link pin's position have to be determined carefully so that the rockers always roll on the bolster without slipping.
In the case of model locomotive, excessive side control force possibly causes derailment. So I determined to decrease the bolster bottom gradient to 1/5.
The following drawings show final plan for my loco. I will report the details in future.