First work with designed chassis was not very succesfull. I installed Rokuhan Shorty engine but there is too much friction on the boogie and shaft is too tight. I also experiment with original Shorties - this looks very promising:
3D printed German origin Bromberg car with some parts od chassis and boogies from old 4 axle Marklin tank car:
Second approach to EN57 chassis. It is based on universal chassis to be used with Shorty. I found it on e-bay: It is still prototype to be improved but the concept of using oruginal shorty mechanism works fine:
The military trucks are really wonderful! And I like the growing grass between the concrete plates. You are a master modeller!