NSWGR M40/Z11 Class 4-4-2 Tank Locomotive

[hartleymartin]

Hi everyone. I'm looking at scratch-building an NSWGR M40/Z11 4-4-2 Tank locomotive. The superstructure isn't going to be a problem, as it is a pretty straight-forward prototype. My questions at the moment relate to building the chassis.

In particular, I am wondering about the arrangement for a front bogie and the trailing axle. I believe the prototype had some form of radial axle. Should I build it basically as a 4-4-0 and have the rear axle free-floating?

 

*edit* I will be building this in 7mm scale, 32mm gauge, GOG Fine Standard.

 

Builder's photo from Wikipedia and article linked here: https://en.wikipedia.org/wiki/New_South_Wales_Z11_class_locomotive

Edited December 13, 2019 by hartleymartin

[Michael Edge]

The bogie can be sprung or compensated with the driving wheels but the trailing axle does need radial movement to work properly. In my experience simply giving it some sideplay doesn't work very well. This is the arrangement I use for 4-4-2Ts - thsi one is of similar size to yours.

This has an internal pony truck with the pivot at the same radius as the radial axlebox (I have tried building radial axleboxes but there seems to be too much friction in 4mm scale for them to work really well). Note that most radial tanks had narrowed frames in this area. This 00 gauge frame with no cutouts for bogie swing (yours has acutout for the leading bogie wheels) runs happily round 28" radius curves.