Via kettenkrad.de

"The Kettenkrad was designed as a small tractor (or prime mover) to tow a trailer or a small gun (20 mm AA or 3,7 cm AT). It carries a crew of three soldiers. The driver and two passengers. The passengers are facing backwards. The Kettenkrad is not armored and not armed. Some versions have three riffle holders to carry the riffles of the crew.

.NSU produced only one cylinder engines with up to 600 ccm, which were not powerfull enough for the Kettenkrad. To save the work and the time for the developing of an own engine, NSU took the reliable OPEL OLYMPIA car engine from its stock. The OLYMPIA car was in Wehrmacht use as well, so the mechanics in the field knew the engine.

The Kettenkrad steers like a motorcycle with sidecar, if you turn the handlebar a little bit, it turns only the front fork with the front wheel. If you turn the handlebar more, it engages the steering brakes of the tracks."