Repair of a vintage motorcycle seat
(BMW R 100 S)
The initial situation
This application example shows a fatigue fracture on a hinge of the seat
of an old BMW R 100 S.
Spare parts for such old vehicles (in this case 47 years old) are hard to come by and repairs are often the last chance to keep the assemblies ready for use. In this case, welding makes it possible to continue using the old seat bench.
The preparation
The first step is to thoroughly clean the parts and deburr the breakage points where necessary. In some cases, some grinding is required to position the parts correctly.
In addition, careful cleaning and degreasing of the welding areas are essential work steps before starting any welding task, e.g. with acetone, brake cleaner or in an ultrasonic device.
The implementation
We used our Micro Arc Welder. The Micro Arc Welder is Lampert ‘s most powerful micropulse welding machine and is best suited to this task.
First, the fractures on the upper side are welded in the areas with good contact to each other, and then any remaining defects and indentations are filled with welding wire filled in.
This task is started with the standard welding geometry; when applying welding wire, a separate welding curve offers good performance for a homogeneous welded joint.
As the exact material designation cannot be determined in this case and a steel alloy can be assumed, our easy-flowing welding wire CMS (Ø 0.4 mm) is used for this task,
Art. no. 304 320), and with the help of the welding wire-WIRE PEN feeder.
On the lower side, a relatively large gap can be seen in the area of the intended fillet weld. This must be filled with the same welding wire to achieve the necessary stability. Start with the pre-set welding curve for joint and angle situations. When applying welding wire, you can then switch to the specially designed welding curve with the recommended parameters for power and pulse duration.
The larger the gap between two components, the more complex the welding generally becomes and the more time it takes.
The post-processing
The processing of the weld seams is limited to the bare essentials and does not take up much time.
The weld does not need to be finished at the fillet weld to avoid unnecessarily weakening the barely visible joint.
The back of the hinge is ground flat as little as necessary and lightly rubberized to achieve good contact with the base plate of the seat bench.
The result
The seat is now back in its correct position and has the desired functionality. The old hinge can still be used after welding and the seat has a stable seat again.
