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After the expensive 1½-Deck-Bus of the last year for 2005 a simpler model was built: A
steam engine with governor.
Firstly a MÄRKLIN-solenoid was to build into the generous dimensioned cylinder; because of the intended governor and the number of involved rotating parts from the outset 2 solenoids were used. The first trial was made with parallel mounted coils which were switched at the same time and whose cores were coupled by a perforated strip. But the weight of this construction at pulled cores generated a large tilting effect, which considerable influenced the operation because of friction. The following experience was made with serial mounted coils which also were switched at the same time and whose cores were coupled by a threaded rod. In this case the core is very long and the tilting effect doesn´t cause significant friction. The piston connecting rod is realized with a 14 whole perforated strip. Because this mass doesn´t support the rotation, it was built from aluminium parts. A further benefit is that only a small balance weight is required which doesn´t increase the large inertia anyway. The construction of the governor was made according to existing plans. Also for this some aluminium parts are used for this reason that the governor can work at preferably low rotation speed. With accelerating rotation speed the sliding contact lifts and so it avoids a further increasing; this corresponds to an ordinary speed control. The rotation speed is determined by the presetted level of the flyballs: The lower the flyballs are placed in the resting state, the former they will travel and the lower is the rotation speed of the engine. The spring contacts from bronze are soft springs how they are used in the EMC-technique (electromagnetic compatibility). After the first tests could be demonstrated that one solenoid probably would be sufficient because of the very smooth running mechanism. 2 solenoids however offer a generous power reserve. So the presetted nominal rotation speed of 150 rpm can be reached at a supply voltage of 8 Volts with the benefit, that the coils will not become heated excessively. Heat increases the ohmic resistance, because of this decreases the current and also the magnetic field strenght; indeed in practice the engine at 8 Volts works better with cold coils. If the engine is operated with a higher voltage the rotation speed remains constant, and if the engine is loaded the rotation speed will be maintained within a defined range - with this the operation of the automatic control can be demonstrated very well.
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