Metal Construction

 
Steam Engine with Governor

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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.
The idea for this provided a plan from one of the very old instruction books.
But because this model doesn´t work self-acting it was modified in different ways.
Plan of the Steam Engine
The original


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.


Opened cylinder
The opened cylinder
The best result was reached with serial mounted coils which were switched alternately and whose cores work against each other.
This configuration generates a bi-directional force with the benefit of a better smooth running. Furthermore of course this behaviour corresponds to a true steam engine.
Disadvantageous is that 2 sliding contacts are necessary which increase the friction a little.


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.

As flywheel hub a MEKANIK cogwheel is used which allows a 60 degrees pitch without more ado.
The flywheel itself was made from the large MÄRKLIN ring, which because of the outside lying mass has a large inertia in relation to the other hub discs.
Piston connecting rod and flywheel
Piston connecting rod and flywheel


Drive of the governor
Drive of the governor
On the other side of the engine the drive of the governor is installed.
To realize a preferably small installation height the power transmission was to change to a lower level. The total gear reduction to simplify matters was chosen to 1


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.

To the lower, on the shaft relocatable (selfmade) guide of the governor the sliding contact for switching of the coils is mounted. Thereunder 2 spring contacts are situated which are connected each with one coil.
If the contact is closed the coil is switched to ground and magnetises the core.
Governor
The governor


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).


Total view of the steam engine
Total view of the steam engine
The wall of the cylinder is realized with corrugated card which is excellent qualified for this purpose.
To uncover the inner parts the front side cap of the cylinder can be removed by loosening of only one screw.


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.

And finally we present a Video of the Steam Engine with Governor (60s / 3,72MB).


Data of the Steam Engine with Governor:

Length:51cm
Width:21cm
Heigth:20,5cm
Weigth:2,2kg
Number of Parts:not yet counted

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