In my model I have some forklift fleets which started out as simple Resources, but I decided to improve the model by replacing them with free-space Transporters.
My problem is that this seems to lower the simulation speed drastically in virtual time mode even if nothing is happening - the forklifts need to unload/load trucks and often a couple hours pass by between truck arrivals.
The forklifts do not seem to jam when they are at their home location, they are completely still. Also there are 15 forklifts in the model, so the fleet size shouldn't cause performance issues either. The simulation is using about 15-20% of the allocated memory.
Is this a natural consequence of using free-space transporters or is it possibly a mistake on my side? I tried switching the model time units from seconds to hours but it did not help significantly.
Yes, these forklifts lower your computation speed a fair bit. They constantly re-evalulate stuff, even if not used.
If you do not need the specific capability of an advanced object (like a forklift), you should always revert to a simpler approach within a model.