A charming little video of the innards of one
- posted
9 years ago
A charming little video of the innards of one
alt.horology added
I've now got inside this and a bit more info beyond that person's video. That strange white splurged numbering is real, not wear, in conjunction with a static black segmented mask gives an odd visual effect between true minute digit forms. The teeth are stripped from the 19.6mm diameter plastic cog driven by the worm drive on the motor. Owner (given in early 1970s and used continuously since) reported it running noticeably fast before packing up totally. The finesse of this escapement is probably that the spring unwinds a specific number of turns , and so specific time, until the 2 timing cams align and the motor comes on for that specific number of turns. So the escapement consistently runs between 2 specific spring tensions and so on average is more accurate than simple wound clockwork. So no fusee required,and independent of fading battery power until exhausion point and no more motor turning. I suspect the motor became engaged continuously and so winding the spring to maximum and so running the escapement fast. Whether preceeded by tooth stripping or that came after motor jamming , don't know. The motor runs well, now not jammed or constrained by worm and cog train. The escapement drive cog off this spring seems to take 6 minutes to back off 1 turn. I cannot work out the double cam action for the motor switch, whether every 6 minutes of even say 10 times that, 1 hour, that I don't know. I suspect the whir of the motor once an hour would be the designed repeat rate , rather than every 27 minutes 22 seconds or whatever. For every 6 minutes would not require the double cam mechanism, just a simple single cam. So if I get this working again it would be a matter of over-riding the motor switch a bit and measuring the escapement until the 10 spring turns is in the right range, I suspect something like 20 turns available in total, but some residual tension has to be there at all times. Plus the balance wheel spring adjuster for final adjustment. Just as well I salvaged "useful parts" from scrapped cassette audio tape machines. A plastic cog of right tooth pitch and axle size is available to replace the broken one, just requiring a hole made in the disc to take the spring anchor hook. There is condensed nicotine goo on the balance wheel etc. I own a small ultrasonic bath, use that? immersed in what chemical/s to clean off the nicotine?
Anyone know of a repair guide for these clocks,? generic name for this battery driven clockwork mechanism?
Comes apart very easily, under the dust cover
Can't help with the repair, but wow that thing is weird. I recall a similar "mechnical" type digital clock that had a complex mechanism to move shutters back and forth in a 7 segment patterns to display the time. It lacked the big wheels like this one. I have no idea what company made this type of clock or when.
I know little about clocks but my favourite escapement is the Congreve, shame it is the most useless for timekeeping. Dunked clockwork and motor switch in 3 minutes of meths in the ultrasonic bath and the obvious nicotine gloop disappeared. The escapement needs a minimum of 80gm of force on one of those 6 spigots (6mm radius) to maintain function = 4.7x10^-3 N-m ?. So 150gm minimum for that 8.5mm ext diameter torsion spring looks achievable with plastic cogs. I suspect an earlier version used the 3 arm trip that moves the minute drum, every 1/3 turn,to reset the motor. There is a blanked off section that protrudes into the motor section which otherwise is not required in this model. Perhaps for some reason they had to move to a self-timed motor on-off timing and so that double cam mechanism in this version
I've had it running for over half an hour with one charge of motor wind, without the double cam system in place. Sounds healthy enough tic-toc, so I'll next have to see if the once-a-minute rewind mechanism works. Cannot check the timing of it without that in place , not prepared to cound tics
Has now been running consistently for some hours, with the once a minute motor drive. With balance wheel spring adjuster mid position and main spring fairly loose but enough to drive the escapement, about 2 sec per minute slow. With the mainspring tight , so having a regular cylinder form, rather than the sloppy looking form when loose, gains about 1sec per 5 minutes.
Operating on battery overnight , so now just fine timing adjustment. Strange being in a room with a ticking clock. A third/fourth function of that double cam system, if the battery runs down then the drive to the escapement is delatched, so the turns on the mainspring are not run down. Insert a new battery and the motor spins up to recharge the spring, 1/6 turn and the escapement is reengaged. Microprocessor designers have it easy these days . The wonky digits are so that you get a large room display without requiring large display rings and so large clock.
With some final sub-5 degree adjustments to the balance wheel tensioner , for one thermal time of year , could probably get it to 5 seconds per day accuracy. What with the 1/6 of one turn of the mainspring used only and independent of battery state of charge. I reckon as 40mA of current use one second per minute then with a 4Ah D cell the clock would run for
9 years. The replacement plastic cog is fibre reinforced so perhaps that one will last another 40 years. Even the alarm works. Would originally there have been active flourescent or radioactive numerals? no sign of any "Glo" with no room light, only illumination is if you switch on the internal lamp. Just had summertime clocks change here, could not be easier to adjust this clock, just turn the small knob on the side 6 turns forward or back.
From a horologist at Combe Mill centre
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