Category: Dates

Can still be saved with lasers?

Where there is air, there is life – sometimes a life of its own. This time the crankshaft. Does the welding machine help?

This article is about an engine like the one we find in the Puch 500 and Haflinger.

During the test drive, after starting the vehicle, the engine speed changed when the clutch pedal was pressed. This led to the suspicion of excessive axial backlash of the crankshaft, as this drives the ignition distributor and the associated ignition adjustment influences the engine speed.

The test by simply moving the pulley back and forth brought the certainty. Under certain circumstances, the V-belts have to be relaxed. A dial gauge confirmed the result with 0.8 mm. In the workshop manual we find 0.17- 0.29 mm, wear limit 0.6 mm.

A disassembly of the engine showed a still decent overall picture, but clear axial inlet marks on the crankshaft, also the crankshaft bearing to the flywheel has lost width.

The cause was probably an impetuous clutch foot.

A classic vehicle clutch must be operated as digitally as possible (almost) digitally, left the clutch pedal after changing gears and also carried out the engine start WITHOUT a clutch being pressed. These measures prolong engine life.

At some point, the simple adjustment option of the axial backlash of the crankshaft to target size via copper disc is over. This is now the case with about 70% of all engine revisions.

Major repair – weld on crankshaft

Today, with the help of laser technology, it is possible to repair run-in crankshafts. The applied material hardness can be selected. The running layer now has a hardness of approx. 60 HRC. Depending on the effort, we are talking about costs of 100-200 euros. After that, the surface must be sanded.

More information about laser application welding can also be found in this film.

…. for grinding it is now, will be resumed shortly

Small repair – add flywheel

If the crankshaft is still dimensionally stable, but still no axial backlash can be adjusted with suitable copper discs, the machining of the flywheel helps as a small solution.
With the milling machine, 0.1 – 0.2 mm can be removed very precisely. Mill because here the basic alignment to avoid impact is much easier in contrast to the lathe. Important here are two points:

1. The retention of the pass contour to the crankshaft, this radius must not be changed.
2. In order for the crankshaft to be able to rest really flat, the already existing hind stitch must be added to the lathe. In the area that the cutter has not reached.