WPM


Mechanical Lifting of the Blade

There are in principal two mechanical solutions available for a scale front attachment unit which are using the lifting cylinder directly and thus eliminate unsightly leverage systems: the pistonrod can be connected directly to the servo with a joint, or indirectly with a lever like at the Pistenking models. We built a fake extension of the tub for our PB600 on Graupner chassis. The fulcrum of the lever would be outside of the Graupner tub, and two long slots would be necessary in the tub, which we didn't want.

Therefore we built the first solution with a directly connected piston rod. A slot has to be milled into the pistonrod, so that it is hold in position by the bolt. This slot weakens the rod, which is also strained by a bending moment at this point. We therefore chose steel, and a short calculation showed a maximum deflection of 0.3 mm, which is absolutely acceptable.

Kolbenstange
Pic: Steel pistonrod with milled slot

Hubzylinder
Pic: Lifting cylinder

The lifting cylinder has to be open for the pistonrod at the upper end. This eliminates the usual connection with a ball joint. To keep it in place a small brass bracket is glued to its side. This will hardly be noticed lateron, after being painted black and mounted on the inner side.

The following pictures show the front attachment unit in the lowered and raised position, as well as the corresponding servo positions. After everything is painted black, the trick with the extended pistonrod is hardly visible.

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