In search of an alternative for the Be4/6 and Ce6/8 in 1929 the SBB made an advertisement. Out of approximately 20 drafts the 11801 was one of 3 prototypes which were built. The 11801 had a length of 34 m and a gross weight of 240t. The identical loco halves had apiece four drive axles and three carrying axles. The outer carrying axles and the first and last drive axles were combined to a Java bogie, the inside 3 axles were arranged buoyant. So the loco had the ability to drive through turns with a radius of 100 m without any problems.
The model has a reproduced Buchli-gear (picture 3), which drives all eight drive axles. The Buchli-wheels are mounted fixed in the locomotive frame, whereas the drive axles are spring mounted. Every Buchli-wheel has two equalizing levers (picture 4), these are connected by two pins in each case with a wheel of the drive axle.
- Delivery status 1931 dark green
- Status 1957 lime green