My and Albert(Dietrich) tried the Gruapner speed 480 race bb motors, also the Grupner 480 standard motors. pulled to many amps,even for my double fan cooled Rx18, the Gruapner 400 race series have been in my Tiger S13 for over two years,the torque is very strong,20lbs tank Asiatam Lower hull,Asiatam 3/1 metal not brass gearboxes,12tooth pinion,have also run the 11tooth pinion.The 12 tooth is perfect,I have cable tied my Jagdpanther with metal tracks,sprockets and the Heng Long black top motors,metal gearbox.
Started the JAGDPANTHER,The distance between the tanks was about 18inches max. As the Jagdpanther started moving the Tiger backwards,on level ground,solid dirt surface. After allowing the Jagdpanther to gain traction,I ENGAGED the Tigers Drive,the tracks spun a little brock traction but as I slowly applied power the Tiger dug in,the Jagdpanther broke traction and never regained it.
The Tiger dug in,and slowly at first but gaining speed pulled the Jagdpanther backwards as it spun tracks,the torque and power of the 400 series motors,the proper weight (extra weight directly over the fender/tracks using auto motive wheel weights) the Tiger just kept dragging the Jagdpanther behind it at a constant speed, my motor wires were pretty warm yet they did not over heat,the fans cooling my board kept the heat down,and this as much as the motors,gear-boxes,pinion and battery 3300MHA are he correct combination.
My Tiger has not ever failed me,to this day my best tank,better than both Tamiya King Tigers with their brass gearboxes. My point is this package,and the added weight,the fan cooling of the RX18 are the best combination for a powerful tank,that acts,drives and looks the part. But one problem,the Gruapner speed series are no longer available? But the same torque can be achieved using the JAMARA series if the tank is weighted properly,and the board is elevated with a small intake fan on top and a large fan on the bottom drawing the air from top to bottom,the heat is pulled away and blown into the metal lower hull which the steel tends to be cooler so the heat seems to disapate faster. My method,but it works

- Grossdeutschland Early Tiger S13 PHASE i

- Elevated RX-18 Double cooling fans

- RX-18 Housing