Velodyne, works great at high speed, but worth a go on a broken road — the spotlight begins to fade. The reason is lack of frequency of rotation of the rotor of the generator at low speed. To bring the revs back to normal, I advise those who do mostly ride the bike at low speeds, to impose on the Dynamo shaft instead of the standard clutch with knurling buy gear with an external diameter of about 15 mm. you can Secure it between two suitable nuts.