Bauhaus-Universität Weimar

L. E. Knott Apparatus Company: Scientific Instruments, Catalogue 26
Knott, L. E.
No. 97-115 
The Gramme Machine represents a type of generator 
now generally used in large units for power and lighting 
stations. The Gilley Gramme Machine is a modification 
so worked out that the lines of force may be easily plotted 
by the compass and filings method. 
No other apparatus has yet been designed with which 
it is possible to show the lines of force in a working model 
of the dynamo and motor with the armature in position 
and in actual operation. Both the field and armature are 
designed and made in flat form, so that the upper surfaces 
of both are level, permitting the paper or glass upon 
which the lines of force by the filings method are to be 
mapped, to take a smooth horizontal position. The lines 
arrange themselves under no other influence than that of the magnetic force existing 
Dissectible Features. Fig. 2 shows the three basic parts of the apparatus — the armature with the commutator, 
the field magnet with base, and the brush-holder. The instrument is readily dissected, as the illustration shows. 
Each part can be studied separately, as will be noted from the following list of experiments. 
We desire to call attention also to the fact that the field coil is easily removed from its base and the base so 
designed that 6-inch permanent magnets can be substituted for the field coil, thus teaching the fundamental principle 
of the magneto. 
No. 97-115 
of force are thus permitted to 
in the armature and field. 
Experiment 1. Study of the field mag¬ 
net in an electromagnet, the lines of force 
being mapped out either by compass or 
filings method. 
Experiment 2. To show what effect the 
soft iron ring of the armature has upon field 
magnets. The value of this exercise is greatly 
increased by using the filings method of map¬ 
ping the field and comparing the field with 
results obtained above. 
Experiment 3. A detailed study of the 
armature, showing that it is wound in sec¬ 
tions and where the ends of each section are. 
Experiment 4. A detailed study of the 
commutator by passing the current into the 
armature magnet through the brushes, show¬ 
ing by this method the exact position of each 
section when polarity is reversed. 
Experiment 5. The method of answering definitely why the armature of a motor rotates. The action of the 
lines of force as indicated by the filings method will make this clear. 
Experiment 6. A study of the magneto generator and its relation to the regular commercial dynamo, showing 
definitely why the current is generated when the armature is rotated between the poles of a magnet. 
Experiment 7. A study of the magneto and its relation to the dynamo, also why the armature in a magneto 
machine rotates. 
Experiment 8. A study of the dynamo using electromagnetic field and armature. Determining the relation 
of the armature to the field coils and the speed of the armature to the strength of the magnetic field. 
Experiment 9. The study of different types of dynamos and motors depending upon whether the armature 
and field are connected in series or in multiple, and what are the conditions regulating the method of connecting in 
any given machine. 
Experiment 10. To show what the result will be if the armature is removed and a permanent bar magnet 
mounted on the same bearing. This experiment teaches clearly the reason why the armature must be an electro¬ 
magnet and not a permanent magnet. 
PRICE, $14.50


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