HMT 8205

Description

From HMT (Hindustan Machine Tools Limited) in India there’s the 11 1/2 selfwindig caliber HMT 8205, a licensed reproduction of the japanese Citizen/Miyota 8205.

Unsurprisingly, construction and execution are practically identical.

The base plate is richly equipped with jewel bearings, even the minute wheel runs in a jewel-bearing.

The 1970s construction uses a directly driven (by the mainspring barrel) center minute wheel, which is beared under its own bridge.

The gear train is very extensive, as the normal gear train for displaying the time, the gear train for manual winding and the gear train for automatic winding are all housed under one and the same bridge.

For the time works, there are the mainspring barrel, center minute wheel, the third wheel, the seconds wheel and the center seconds pinion simultaneously and finally the escape wheel.

For manual winding, there’s the crown wheel and a slipping transmission wheel (at 10 o’clock), which in one direction engages with the ratchet wheel of the barrel, and on the opposite direction disenganges. Because of that, there’s no need for a breguet clutch on the winding stem.

The selfwinding mechanism consists of just two wheels, a transmission wheel that engages with the ratchet wheel and a clutch wheel, which consists of two wheels mounted on top of each other and transmits the power in one direction of rotation and disengages it in the other direction of rotation. A lever is required for this to prevent the lower wheel from rotating in the “wrong” direction.

To put six thin pivots, the mainspring barrel core and the two gears of the winding mechanism into the bearings of the gear train bridge, is not really trivial.

On the inner side of the gear train bridge, you can see the driving wheel of the ball beared oscillating weight, which engages with the clutch wheel of the selfwinding mechanism. This construction realizes a unidirectional selfwinding system.

Additionally, you can see the friction spring, which applies a little tension on the center seconds pinion. This should eliminitate an uneven run and jumps of the center seconds hand.

The HMT 8205 uses a two-leg Glucydur balance, which is beared in two Citizen Parashock bearings. Like the original, it beats with 21600 A/h and can be regulated at the hairspring key only.

The oscillating weight is screwed onto the ball bearing. It winds unidirectionally.

On the yet empty dial side, you can see the yoke winding system with its three positions. In the middle position, date and weekday indication can be quickly corrected.

The calendar mechanism uses already plastic parts.

More interesting is the quickset mechanism at 3 o’clock, where a lever, according to the winding direction of the stem, either advances the weekday disk with its gear on its inner side, or advances the date ring.

In this movement, just like the original, all springs are designed in such a way that they remain quite stable in the movement even without a cover and do not fly away at the slightest opportunity.

Just as the Citizen/Miyota 8205, the HMT 8205 offers a biligual weekday indication.

In the lab

Timegrapher result

Considering the poor condition of the movement, the rates ​​are still acceptable. In better condition, they should be similar to those of the Citizen/Miyota 8205.

Technical data

Usage gallery