how to repair split cogs?

I don't think its a case of performance for the cogs, its that some trains use 12 teeth and others 14. Its how the gearing is set up in the motor.

As a business running repairs are a necessity . We find it is the Tomy engines as the trackmaster ones are different material. We were lucky in sourcing some brass cogs and made a rig to enable the installation of the new cogs onto the axle . Once a cog is broken and fixed with glue it will always have a weakpoint.