Sorry to report, but first test already failed.
FreeCAD 015.4250 on Windows 7 64 bit (SGROGAN Build
FreeCAD 015.4276 in Linux Mint 13 (daily PPA).
Both with same results.
Old_Car is small "Assembly" done with Part Module Workbench.
Axle is inserted three times, Tires are Ignored.
Everything exported as ONE Object, not desired ...
Look at FreeCAD File, Picture attached.
Look at Kerkythea Result.
Tested with Kerkythea 200 Echo V2.0.19.
Do you have to mark your Solids for Export in Tree View ? ... I didn't do that ...