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Watch Escapements
MASSEY TYPE 4 ESCAPEMENT
This is one of two versions of the detached lever escapement designed by Massey, in which the safety action is provided by the points of the lever, next to the slot at the fork.
It is also worth noting that there are four different Massey rollers which, following the nomenclature given to them by Alan Treherne, have come to be known as types 1, 2 3 and 5. Type 1 is the earliest used by Massey, followed by type 5 and then by types 2 and 3, though there was much overlapping in use and changes of roller have and continue to occur.
Massey's type 4 escapement is usually to be found with a type 3 roller, the main difference in the escapement being the fork end of the lever having three notches allowing the balance a maximum of just under fours turns before banking. The balance would usually turn between one and one and a half full turns.
The escape wheel and pallet frame are also different than normal, with extended, dead-beat pallets and upright escape teeth. This allows each pallet a much deeper engagement with the wheel should any added momentum to the balance take it to near the full four turns.
This and other line drawings of watch escapements will shortly be posted on my web-site and visitors are welcome to view and use the site. If, however, anyone wants to use any of them commercially, please get in touch with me before doing so. |
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