I have on old "digital" clock from the 1930s that I found in the rubbish in San Fransisco. At first it ran slow, until I cleaned it and lubed it. Now it keeps accurate time.
Interesting that the UK is already doing pumped water storage generation. IMHO that is a much more doable way to cope with the wrong time effect of wind and solar power, than all these battery systems and hyperspeed flywheels you see in the news. There are plenty of dams that could be run backwards in this country, some near hot, sunny deserts, but as usual nobody is using their brain except the entrepreneurs looking to make a fast $. Natural gas, the energy source (and weather driver) of the future. Keep your UK gas pipes for heat, you will have tankers docking like Japan does if your own shale gas projects don't work out.
I had an old fifties clocks that would start backwards as often as forwards, but Dad threw it away. I had no idea then how clocks were supposed to start forwards: the 1954 GE clock would, this one wouldn't. It was interesting, a hideous bronze cowboy in hat and chaps twirling a shiny brass lariat, a design that screamed 1953. Mother won it in a raffle at a movie.
I had an old fifties clocks that would start backwards as often as forwards, but Dad threw it away. I had no idea then how clocks were supposed to start forwards: the 1954 GE clock would, this one wouldn't. It was interesting, a hideous bronze cowboy in hat and chaps twirling a shiny brass lariat, a design that screamed 1953. Mother won it in a raffle at a movie.
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Dinorwig is 1728MW
https://en.wikipedia.org/wiki/Dinorwig_Power_Station
whereas Cruachan is 420MW and Foyers is 300MW
List of power stations in Scotland - Wikipedia, the free encyclopedia
Clearly my earlier post
https://en.wikipedia.org/wiki/Dinorwig_Power_Station
whereas Cruachan is 420MW and Foyers is 300MW
List of power stations in Scotland - Wikipedia, the free encyclopedia
Clearly my earlier post
is simply wrong. Sorry.
So they can run very slightly slow which seems intuitively correct.
Oil and gas is to precious to burn in power stations imo. We depend on it for plastics and a whole host of materials and uses. And when its gone, its gone.
No problem. I hadn't specifically heard of those you mention tbh
The link showing the outputs of the various hydro schemes was interesting.
Synchronous motors run at a constant speed but change the amount of power they use by changing current draw for diferrent torque. Until they reach there max power, then they slow down. If you push on the motor while its spinning at speed it becomes a generator.
I magnaged to stall the output shaft, but only after I had turned to AC voltage to very low. There is a very preceptable OUT of Synchronous LOCK. It just suddenly stops.
Everytime I released the finger clamping force ,the motor ran in the opposite direction from which it had been. Three times in a row.
The "bounce back" of the anti-reverse mechanism seems to be proved, even though I was at the wrong end of the compound gearbox.
Gave me a new idea on my proposed ratchet.
It does not need to be "on the motor" shaft. It will be easier to fit it to the next gear in the train. The backlash and the flexibility in the plastic gears should help with the "bounce back". Part 2 starts today.
Everytime I released the finger clamping force ,the motor ran in the opposite direction from which it had been. Three times in a row.
The "bounce back" of the anti-reverse mechanism seems to be proved, even though I was at the wrong end of the compound gearbox.
Gave me a new idea on my proposed ratchet.
It does not need to be "on the motor" shaft. It will be easier to fit it to the next gear in the train. The backlash and the flexibility in the plastic gears should help with the "bounce back". Part 2 starts today.
I don't believe synchrous motors "can run slow".
On no load, they will be almost in phase with the driving waveform.
As load is applied the rotor will increasingly lag in phase behind the driving waveform. That lag must do something to the magnetic coupling and that in turn will draw more current.
But the motor is still "locked" to the waveform. It does not slip (as with induction motors). The phase changes with loading. And catches up again when the load reduces.
On no load, they will be almost in phase with the driving waveform.
As load is applied the rotor will increasingly lag in phase behind the driving waveform. That lag must do something to the magnetic coupling and that in turn will draw more current.
But the motor is still "locked" to the waveform. It does not slip (as with induction motors). The phase changes with loading. And catches up again when the load reduces.
Plastic gears and lots of torque sound like a potential problem, particularly as it relies on stalling the motor to kick it the other way.
In the early days of home video, the Sanyo Betamax 9300 used a massive synchronous motor for both capstan and head drum (and everything else). You can see the size of the thing here, bottom left in the picture,
http://www.palsite.com/tech.py?model=vtr10300tech.html
Although it was a synchronous motor it still had to have the speed altered within fine limits (actually always slowed, you can't speed it up) by a servo and this used an eddy current brake controlled by a TIP41 transistor.
https://en.wikipedia.org/wiki/Eddy_current_brake
In the early days of home video, the Sanyo Betamax 9300 used a massive synchronous motor for both capstan and head drum (and everything else). You can see the size of the thing here, bottom left in the picture,
http://www.palsite.com/tech.py?model=vtr10300tech.html
Although it was a synchronous motor it still had to have the speed altered within fine limits (actually always slowed, you can't speed it up) by a servo and this used an eddy current brake controlled by a TIP41 transistor.
https://en.wikipedia.org/wiki/Eddy_current_brake
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No, you have misunderstood.
I stalled with output saft with great difficulty, but it then dawned that I was forcing the Bounce Back due to the flexibility and backlash through the whole geartrain.
I had been looking at fitting the bounce back ratchet to the motor shaft. Due to the very small diameter, only 10 teeth, that ratchet is quite difficult to get right and as reported my first attempt failed.
I now realise that the ratchet does not need to be on the motor shaft. I think it can work on the second gear in the train, That second gear is above a clear area of the motor chassis and there is room to fit a better ratchet.
Trying to stall, or at least not allow to start in the wrong direction, at the end of a 150:1 compound gearbox would involve enormous forces for those tiny gears. I would expect destruction in very short order.
At the second gear the reduction is only 5:1 and I suspect that the forces and springyness (compliance) will not lead to damage for the few times that the anti-reverse activates, at 50% probability, after each power failure.
I stalled with output saft with great difficulty, but it then dawned that I was forcing the Bounce Back due to the flexibility and backlash through the whole geartrain.
I had been looking at fitting the bounce back ratchet to the motor shaft. Due to the very small diameter, only 10 teeth, that ratchet is quite difficult to get right and as reported my first attempt failed.
I now realise that the ratchet does not need to be on the motor shaft. I think it can work on the second gear in the train, That second gear is above a clear area of the motor chassis and there is room to fit a better ratchet.
Trying to stall, or at least not allow to start in the wrong direction, at the end of a 150:1 compound gearbox would involve enormous forces for those tiny gears. I would expect destruction in very short order.
At the second gear the reduction is only 5:1 and I suspect that the forces and springyness (compliance) will not lead to damage for the few times that the anti-reverse activates, at 50% probability, after each power failure.
It's not completely clear to me, but the description seems to differentiate between "motor" and "drum".
The drum is slowed by the servoed brake.
The motor continues to be "locked" to mains frequency.
This would make some sense in that mains frequency variations would lead to motor speed variations that would be outside the tolerances for video recorder syncronisation with picture and line rates.
A drive belt, say, between motor and drum would allow a bit of slip. It seems to me that the servo is varying the slip in the belt drive to maintain drum speed accuracy to the tolerances required by the video.
I'm trying to think back... as far as I remember the drum and capstan were mechanically locked and it relied on using the eddy current brake to get the drum speed 100% correct and hence line rate correct knowing that the wide pull in range of the TV's frame sync circuit would always cope with any slight error in frame sync timing. That's how I remember it. There was certainly no friction devices or anything relying on slippage, that just wouldn't work for something as critical as a TV signal.
That's pretty much how the Revox motors worked.
And if a synchronous motor can't run slow, why did my mains powered clock run slow until I cleaned and lubed it?
And if a synchronous motor can't run slow, why did my mains powered clock run slow until I cleaned and lubed it?
Sorry.
It's motor driven from the mains. I don't think they did oscillator clocks back then, at least not for home use.
Attachments
Lesser things than that have been called digital. Its quite nice actually.
Don't know when quartz oscillators came on the scene although I would guess when divider chips in LSI form appeared. I don't think a triode astable would cut it somehow 😀
Synchronous motors can *not* run slow, its in their basic function principle. They run synchronous until the load is larger than their torque, then they just drop out of synchronity and stop.
Your clock did not 'run slow' in a continuous way, I think. The sticky mechanism imposed a too large load on the motor and it probably stopped for a short period from time to time, until the repeated starting attempts (in both directions) succeeded to overcome the friction. Averaged over hours or days, this would appear as 'running slow'.
Rundmaus
Thanks Rundmaus. So you don't think there could be any slippage? I.E., the motor trying to follow sync but not able to quite keep up?
My Rek-O-Kut turntable has a speed adjustment that is done by pressing the pinch roller tighter onto the platter. Perhaps the motor is not synchronous? I had a Thorens with an electromagnetic brake for speed adjustment. Always thought the motor was synchronous. Maybe not?
My Rek-O-Kut turntable has a speed adjustment that is done by pressing the pinch roller tighter onto the platter. Perhaps the motor is not synchronous? I had a Thorens with an electromagnetic brake for speed adjustment. Always thought the motor was synchronous. Maybe not?
A synchronous motor spins as long as its rotor is moving (with a load-dependent lag) along *synchronously* with the rotating magnetic field created by the stator. That's where its name comes from.
If you mechanically brake it, it loses synchronity and stops. If the load is intermittent, it might 'catch' again after a few missed field periods, without coming to a full halt, but that is no stable slowdown in its usual sense - something more like a repeated 'stall and restart' process. Should be very noticeable, as the available torque drops to zero the moment in loses synchronity. Trying to adjust the speed of a synchronous motor by braking should lead to a very unstable, fluctuating speed and torque behaviour.
Rundmaus
If you mechanically brake it, it loses synchronity and stops. If the load is intermittent, it might 'catch' again after a few missed field periods, without coming to a full halt, but that is no stable slowdown in its usual sense - something more like a repeated 'stall and restart' process. Should be very noticeable, as the available torque drops to zero the moment in loses synchronity. Trying to adjust the speed of a synchronous motor by braking should lead to a very unstable, fluctuating speed and torque behaviour.
Rundmaus
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