The Webra 2.5R was a glow-plug version of the far better-known Webra Mach I diesel. It was designed by Gunther Bodemann, who seems to have been influenced by seeing several British competitors using their own glow-plug conversions of the Mach I at the 1955 World Control Line Speed Championships in which Bodemann competed using a Mach I diesel. By early 1956 Bodemann had developed prototypes of the new model, which was released to the public later that same year.
The Webra 2.5R was highly unusual among racing glow-plug engines in retaining reverse-flow scavenging, a retrospective feature shared only by the Barbini B.40 TN. Although it never achieved any noteworthy success in the International control line speed category, the engine proved to be a dominant force in German free flight circles, a position which it retained for several years. My own tests have shown that a good example was a far better performer than the engine's reputation might suggest.
A detailed review and test of the Webra 2.5R will be found elsewhere on this website.