second hand on escape wheel?

[kc092755]

Hi guys,
Just finished cleaning a fusee lever with sub seconds movement , but the second hand of this watch is attached directly to the escape wheel and it take 15 seconds for a round!
Could someone tell me is this normal and why?
Thanx!
kevin

[kc092755]

Hi guys,
Just finished cleaning a fusee lever with sub seconds movement , but the second hand of this watch is attached directly to the escape wheel and it take 15 seconds for a round!
Could someone tell me is this normal and why?
Thanx!
kevin

[Keith H]

Hi Kevin
Is it possibly a rack lever escapement? I believe some of them had a fifteen second dial?

[Keith H]

Hi Kevin,
I've tracked down a 15 second rack lever on http://www.antiquewatchstore.co.uk The Antique Watch Store Pocket Watches...
No 24423. described as :- a very good example of a 30-tooth rack lever watch with 15 seconds dial. ...
It would not allow a link to be made so if you go to the site and enter 24423 in the search field it should take you to the watch.
Hope that is of some help
Regards
Keith

[kc092755]

Hi Keith,
Thanx for the informations!
I found an explanation:

"THIRTY-TOOTH
ESCAPE WHEEL

A fashion of the years 1805-1825. The fourth wheel is omitted and the escape-wheel, which takes its place and carries the second-hand, has thirty teeth rather than the usual fifteen, so that the hand makes a complete circle in fifteen seconds.
A watch with this arrangement (usually a rack-lever) can be recognised at once because the seconds dial is numbered only 5-10-15."

but mine is an English lever not rack lever movement and the numbered is 10-20-30-40-50-60(probably a wrong dial)!
Do you know why they made this kind of watch?
Thanx!
Kevin

[mch]

Hello Kevin,

A lot of these Liverpool three wheel trains were made with Massey lever escapements, and some Swiss ones are pretty funky. A late Roskopf three wheel train had a seconds bit that rotates backward. I have seen several types with the 4 RPM seconds hand, but numbered with a 60 second dial. The following text was already around, so will throw it in as a quick explanation.

Elimination of the fourth wheel is a simple cost saving, best known from Liverpool watches made between 1790 and 1820, and called a three-wheel train (the great wheel is ignored). A 30-tooth escape wheel is located where the fourth wheel used to be, although many such watches have no seconds hand on the dial. Having a lower overall gear ratio, escape wheels are reduced from their standard speed down to four RPM, so that when a seconds bit is used, the seconds hand rotates every 15 seconds around an appropriately numbered dial. Three-wheel trains are very occasionally found in Swiss pocket watches, including a low-grade example having a glass dial and 30-toothed cylinder escape wheel. A precursor to Roskopf watches, Chamberlain illustrates a three-wheel train Swiss watch from perhaps the 1820’s, having unusually high gear ratios for faster beat, and a pin pallet escapement. It constitutes an attempt at a reasonable quality inexpensive watch, and Roskopf, who thoroughly researched his designs, must have been aware of such mechanisms.

The traditional three-wheel train suffers several problems. Its 30-tooth escape wheel at four RPM implies a balance rate of only four beats per second, precluding this gearing from timekeepers of appreciable quality. Early American industrial watches beat 4.5 per second, and five beats per second becomes standard over subsequent years for more stable timekeeping. Another difficulty is that traditional three-wheel trains use six leaf pinions in order to achieve escape wheel speed with fewer gears. Unless well made, such low count pinions operate poorly and can bind the train. Coarse trains in early American industrial watches use eight leaf pinions, followed by improved fine pitch trains having ten leaf pinions. Free of size limitations, precision clocks use higher tooth counts for smooth low-friction operation. The traditional three-wheel train layout is basically a conventional configuration, with the second wheel rotating once per hour in the center of the watch and another wheel simply eliminated.

Roskopf’s variation on the three-wheel train is ingeniously non-conventional,

Blah, blah, blah, you can get the picture. I love these things. Do you have the whole watch?

Mike

[kc092755]

Hi Mike,
Thank you for this nice article!
Sorry, I don't have the whole watch, just the movement!
Kevin

[Tom McIntyre]

I have one in my on-line collection, but you really cannot see much of the mechanism.

http://www.awco.org/European/Tobias/front.jpg

Tobias web page (http://www.awco.org/European/Tobias/tobias.htm)

[kc092755]

"A lot of these Liverpool three wheel trains were made with Massey lever escapements...",

Could someone tell me the difference between English lever and Massey lever(III), is it only the difference of the roller jewel position?
Thanx!
kevin