|
Main
- books.jibble.org
My Books
- IRC Hacks
Misc. Articles
- Meaning of Jibble
- M4 Su Doku
- Computer Scrapbooking
- Setting up Java
- Bootable Java
- Cookies in Java
- Dynamic Graphs
- Social Shakespeare
External Links
- Paul Mutton
- Jibble Photo Gallery
- Jibble Forums
- Google Landmarks
- Jibble Shop
- Free Books
- Intershot Ltd
|
books.jibble.org
Previous Page
| Next Page
Page 26
But we must not forget that such qualities are purely theoretical. In
practice the best machine is that in which the copper is best
utilized, that is to say, that which with a given weight of this metal
furnishes the most work. Now, this is certainly not the case in the
Pfaundler machine, for here half or more than half of the ring is
inert--a defect which is apparent at first sight. It results from this
that as soon as we propose to obtain an electromotive force, however
slight it be, we must get it with machines of large dimensions. Now,
it is permissible to believe that under such circumstances (taking
into consideration the complication of mechanical means that the
construction of such apparatus necessitates, and the great friction
that occurs) it would be impossible to obtain practical rotary
velocities. Comparing his machine with Gramme's, Prof. Pfaundler
expresses the idea that between them there is the same analogy as
there is between a constant pressure and an expansion engine. With
cylinders of equal diameters the work performed by the former of these
is greater than that done by the second, but in the latter the
expansive force of the steam is better utilized. This comparison seems
to us to be more ingenious than exact. Would it not be coming nearer
to the truth if we were to suppose a case of a hydraulic motor whose
performance continued diminishing with the height of the fall, and
would it not be advantageous under such circumstances to utilize only
a portion of the fall for the purpose of increasing the motor's
performance?
This machine, however, as before stated, has never as yet been
constructed, so that experimental data relative to its mode of working
are wanting. It is especially interesting as regards its origin, which
dates back to an epoch at which researches on the dynamo electric
machine were at their heat. It is in its historical aspect that it is
proper to regard it, and it is from such a point of view that we have
deemed it well to say a few words about it in this place.--_La Lumiere
Electrique._
* * * * *
BORNHARDT'S ELECTRIC MACHINE FOR BLASTING IN MINES.
We shall not attempt to pass in review the several apparatus that have
hitherto been devised for igniting blasts in mining operations, but
shall simply describe in this place a machine recently invented for
this purpose by Mr. Bornhardt, an engineer to the Grand Duke of
Brunswick.
This apparatus (shown in the accompanying engravings) consists
essentially of two hard-rubber disks, A (Figs. 2 and 3), keyed to an
iron axle, and of two rubbers, B, that are formed of skin and are held
against the disks by small springs, R; motion is communicated to the
axle, _a_, by means of a pair of gearings, _a_ and _b_, and a crank,
_f_.
[Illustration: BORNHARDT'S ELECTRIC MACHINE FOR BLASTING IN MINES.]
Each disk revolves between two metallic rings, _c_, provided with
points that attract and collect in Leyden jars, D, the electricity
produced by the friction. For discharging the condensers there is
employed a manipulator formed of a rod, mm, which can be acted upon,
from the exterior, by means of a button, _k_. Upon bringing the ball,
_m_, of the rod in contact with the ball, _p_, of the condenser, the
lever (which then takes the position shown by the dotted line)
continues to remain in connection with a small ring, _q_, through a
special spring. Another ring, _t_, is connected in the same way with
the external armature of the condenser. Upon connecting the rings, _p_
and _t_, by a wire to which cartridges are attached, any number of the
latter may be ignited.
The parts that we have just enumerated are inclosed in a tin box
covered with a wooden casing, P. Between the two there is inserted a
sheet of hard rubber in order to prevent a loss of electricity; the
whole is held in place by strong springs.
In order to show the normal state of the condenser, a scale consisting
of 15 metallic buttons to give the dimensions of the sparks, is
arranged at X. This scale is capable of being connected with the
rings, _q_ and _t_, by means of chains; when the spark obtained after 15
or 20 revolutions considerably exceeds the intervals of the scale, it
is a sure thing that the machine is in a proper state.
Previous Page
| Next Page
|
|