DrWhat ;
the placque gives his birth year as 1680 . the hourglass in the other . as his death date is well known but not inscribed , that signifies to me that his time had not run out yet and placed there while he still lived . but i could be wrong . just ask Stewart !!!
Thanks JC. for posting the pictures . they were a real eye opener .
Prague Astronomical Clock
Moderator: scott
-
docfeelsgood
- Aficionado
- Posts: 819
- Joined: Thu Dec 01, 2005 7:38 am
re: Prague Astronomical Clock
Doc. quote:
I think your trying to say, the hourglass presence itself provides proof that the header was built before his death, therefore that it was inscribe after his death.
tks
Time to give them spectacles a good cleaning ;)as his death date is well known but not inscribed
I think your trying to say, the hourglass presence itself provides proof that the header was built before his death, therefore that it was inscribe after his death.
tks
- Attachments
-
-
path_finder
- Addict
- Posts: 2372
- Joined: Wed Dec 10, 2008 9:32 am
- Location: Paris (France)
re: Prague Astronomical Clock
I return back to the key-stone located above the door of the bookstore in Karlshafen.
If we have any doubt on the creation date of this object, it's not useful to discuss further on the angels sex.
But if this object has been created by Siegfried Kretschmer, at this time a famous sculptor, having perhaps some undisclosed and unpublished data, an examination of the engraved details can be interesting.
What's strange in this engraved portrait are the mechanical parts behind the head.
The presence of a crown with some teeth is the first surprise (so many people said they were only simple rods, not mentioning the presence of any gear nor crown in the inner of the Bessler wheel). But in addition and most important I was really surprised to see the shape of the teeth: they are squared.
BTW my question is: if the presence of any crown and gear is confirmed, for what purpose Bessler used squared teeth instead the convoluted teeth normally used by the clockmakers?.
IMHO a possible answer is: this particular shape allows not only a rotary motion but also in addition a mechanical linkage between the two rotating parts.
Remember the secret of the Antikythera mechanism was in the shape of the teeeth.
Or may be another linkage with an additional part.
Any comments?
If we have any doubt on the creation date of this object, it's not useful to discuss further on the angels sex.
But if this object has been created by Siegfried Kretschmer, at this time a famous sculptor, having perhaps some undisclosed and unpublished data, an examination of the engraved details can be interesting.
What's strange in this engraved portrait are the mechanical parts behind the head.
The presence of a crown with some teeth is the first surprise (so many people said they were only simple rods, not mentioning the presence of any gear nor crown in the inner of the Bessler wheel). But in addition and most important I was really surprised to see the shape of the teeth: they are squared.
BTW my question is: if the presence of any crown and gear is confirmed, for what purpose Bessler used squared teeth instead the convoluted teeth normally used by the clockmakers?.
IMHO a possible answer is: this particular shape allows not only a rotary motion but also in addition a mechanical linkage between the two rotating parts.
Remember the secret of the Antikythera mechanism was in the shape of the teeeth.
Or may be another linkage with an additional part.
Any comments?
- Attachments
-
I cannot imagine why nobody though on this before, including myself? It is so simple!...
-
path_finder
- Addict
- Posts: 2372
- Joined: Wed Dec 10, 2008 9:32 am
- Location: Paris (France)
re: Prague Astronomical Clock
After review of several dedicated web sites to the mechanical gears, it seems that the squared teeth are not used for the meshing gears.
If the shape of the teeth on the keystone is really squared, this is an important clue, leading to one of these designs:
- 1 - The squared teeth are empty on the engraved keystone but could be earlier a receptacle for some (orthogonal?) insets realizing a crown of pins.
see the URL: http://nptel.iitm.ac.in/courses/IIT-MAD ... df/2_1.pdf figure 1 page 2.
- 2 - The squared teeth on the crown are used by a clutch mechanism (ratchet or clock like escapement)
- 3 - The crown was linked to an helical worm, assuming in this case a high ratio of rotation, where the additional worm had its axle orthogonal with the crown central axis and located in the plane of the crown. For what purpose? that's the game. But Jim_Mich (wich is a specialist of the gears) will for sure explain this better than me and perhaps suggest a proposal.
On the same document (in the above referenced URL) look at the page 6 the picture J (copy hereafter) and page 20. This is similar with the upper gear in the keystone.
Strange?
If the shape of the teeth on the keystone is really squared, this is an important clue, leading to one of these designs:
- 1 - The squared teeth are empty on the engraved keystone but could be earlier a receptacle for some (orthogonal?) insets realizing a crown of pins.
see the URL: http://nptel.iitm.ac.in/courses/IIT-MAD ... df/2_1.pdf figure 1 page 2.
- 2 - The squared teeth on the crown are used by a clutch mechanism (ratchet or clock like escapement)
- 3 - The crown was linked to an helical worm, assuming in this case a high ratio of rotation, where the additional worm had its axle orthogonal with the crown central axis and located in the plane of the crown. For what purpose? that's the game. But Jim_Mich (wich is a specialist of the gears) will for sure explain this better than me and perhaps suggest a proposal.
On the same document (in the above referenced URL) look at the page 6 the picture J (copy hereafter) and page 20. This is similar with the upper gear in the keystone.
Strange?
- Attachments
-
I cannot imagine why nobody though on this before, including myself? It is so simple!...
re: Prague Astronomical Clock
http://mysite.du.edu/~jcalvert/tech/oldgears.htm
If you look into Hoover's translation of Georg Bauer's De Re Metallica ("On Mining Technology"), you will see woodcuts of machinery, or millwork, used to apply the power of water wheels, treadmills, and horse whims to pumping and other mechanical processes in the processing of ores, as it was done in 1556.
(I have 1950 copy of Hoovers translation.)
Madrid Ms. I (BNM), fol. 118v (detail)
Square tooth gear;
Leonardo states that these are among the most commonly employed and describes their characteristics: "The distance from the middle of the bottom of one tooth space to the other shall equal the length of a tooth."
Ralph
If you look into Hoover's translation of Georg Bauer's De Re Metallica ("On Mining Technology"), you will see woodcuts of machinery, or millwork, used to apply the power of water wheels, treadmills, and horse whims to pumping and other mechanical processes in the processing of ores, as it was done in 1556.
(I have 1950 copy of Hoovers translation.)
The primitive shape of the teeth on a spur or crown gear is rectangular, with straight flanks, which are the sides of the teeth that come into contact on meshing gears. Lantern gears used cylindrical teeth, with circular flanks. Therefore, the straight flank of a driver tooth had line contact with the circular flank of a driven tooth.
Madrid Ms. I (BNM), fol. 118v (detail)
Square tooth gear;
Leonardo states that these are among the most commonly employed and describes their characteristics: "The distance from the middle of the bottom of one tooth space to the other shall equal the length of a tooth."
Ralph
-
docfeelsgood
- Aficionado
- Posts: 819
- Joined: Thu Dec 01, 2005 7:38 am
re: Prague Astronomical Clock
Ralph ;
that is a exellant choice of books . i have a copy on my shelf also .
that is a exellant choice of books . i have a copy on my shelf also .