Steering head
The steering head or control head is a highly loaded part of the chassis of a two-wheeler or trike , in which by means of two rolling bearings , the fork is guided and is rotatably supported. It forms the bearing point for steering or the fixed tube for building this bearing.
A thick short tube ( steering tube ) with a machined upper and lower bearing is welded to the frame almost vertically, with a slight incline of approx. 70 degrees in the side view, then fitted with the steering head bearings and provided with the fork for wheel guidance.
A steering head must be precisely machined, i. H. mechanically precise and welded in a stable position in a precise position, because the safety of the user depends on its good construction and manufacture .
As the most complex part of the frame, the steering head on motorcycles often bears the chassis number and “in front of the head” (here in the literal sense) also the type plate .
There are alternative designs that either do without a steering head ( e.g. wheel hub steering ) or provide the steering head only for the lower forces of the steering movement itself, but not for the force-bearing connection between the front and rear wheels ( axle pivot steering from Yamaha ).
Handlebar weights serve to reduce natural vibrations .
Check of operational safety
The perfect functioning of the steering head is just as important for driving safety as the functioning of the entire front axle in multi-lane vehicles. Typical weaknesses are part of safety checks such as the general inspection and should also be checked by the driver when taking over unknown vehicles. In general, the front wheel is lifted into the air and the handlebars moved:
- Bearing stiff (due to rust, dirt, insufficient lubrication or screwing that is too tight): Steering maneuvers can fail due to the effort required, in extreme cases the steering can lock, resulting in a fall.
- Radial bearing play: the fork “flutters”, at higher speeds the vehicle can no longer be controlled.
- Axial bearing play: When braking, the bearing moves in an axial direction ("hits"). This creates pressure points. The design of the usual steering head bearings as angular contact roller bearings also gradually creates radial play.
- Pressure points: The balls or needles of the bearings have pressed holes in the bearing rings in the middle position. They can be recognized by the "cracking" sound when turning the handlebars around the middle position. These pressure points create radial and axial bearing play. In extreme cases, the turning of the handlebar is hindered.
literature
- Fritz Winkler, Siegfried Rauch: Bicycle technology repair, construction, production . 10th edition, BVA Bielefelder Verlagsanstalt GmbH & Co. KG, Bielefeld, 1999, ISBN 3-87073-131-1