The 200-300 Watts claim is true but tat's very demanding.
500 Watts + is also true of top top athletes.
Far
Far more in selected cases - such as in flying across the English Channel
Gossamer Albatross - 1st man powered flight across the English Channel June 12th 1979. . !!! :-).
About 300 Watts continuous in still air and no turbulence. "Rises rapidly" with turbulence.
Another day at the office for Bryan Allen. (day job ) -
I can do 500 Watts for about 10 seconds, after which my legs turn to jelly and I'm utterly exhausted.
Best is an AcAC alternator - preferably 3 phase or more. As shown below, a 3 phase waveform does not drop to zero at any stage. Rectifying this and filtering produces an even smoother result. More than 3 phases gives an evneven better result but is rare. A DC generator is an AC alternator in which the the rectification is provided by a commutator and brushes - as the voltage levels change a new winding is selected by the commutator rotating a new winding contact under the brushes. While the principle is similar to using an alternator with diodes, with brushes you generally get more mechanical drag and losses than with an alternator. Most generator (DC) offerings will be DC moors being driven as generators - the two roles are interchangeable but a machines designed for one will tend to be less optimised for the other.
The rime poweredrim-powered motor based dynamo which you cited is OK in principle but likely to be horrendously inefficient in practice due to mechanical issues. As a child the many rim dynamos that I saw were all terrible so I was surprised to see modern units which do this reasonably well - it's a matter of actually knowing what you are doing mechanically with shaft alignment, gearing, surface friction etc. A "dynamo" of sort will typically produce 1 to 10 Watts output. With an efficient system, you'd notice 10 Watts when cycling and would almost not notice 1 Watt except under very light load conditions or coasting.
The 200-300 Watts claim is true but tat's very demanding.
500 Watts + is also true of top top athletes.
Far more in selected cases - such as in flying across the English Channel !!! :-).
I can do 500 Watts for about 10 seconds, after which my legs turn to jelly and I'm utterly exhausted.
Best is an Ac alternator - preferably 3 phase or more. As shown below, a 3 phase waveform does not drop to zero at any stage. Rectifying this and filtering produces an even smoother result. More than 3 phases gives an evn better result but is rare.
The rime powered motor based dynamo which you cited is OK in principle but likely to be horrendously inefficient in practice due to mechanical issues. As a child the many rim dynamos that I saw were all terrible so I was surprised to see modern units which do this reasonably well - it's a matter of actually knowing what you are doing mechanically with shaft alignment, gearing, surface friction etc. A "dynamo" of sort will typically produce 1 to 10 Watts output. With an efficient system, you'd notice 10 Watts when cycling and would almost not notice 1 Watt except under very light load conditions or coasting.
The 200-300 Watts claim is true but tat's very demanding.
500 Watts + is also true of top top athletes.
Far more in selected cases - such as
Gossamer Albatross - 1st man powered flight across the English Channel June 12th 1979. . !!! :-).
About 300 Watts continuous in still air and no turbulence. "Rises rapidly" with turbulence.
Another day at the office for Bryan Allen. (day job ) -
I can do 500 Watts for about 10 seconds, after which my legs turn to jelly and I'm utterly exhausted.
Best is an AC alternator - preferably 3 phase or more. As shown below, a 3 phase waveform does not drop to zero at any stage. Rectifying this and filtering produces an even smoother result. More than 3 phases gives an even better result but is rare. A DC generator is an AC alternator in which the the rectification is provided by a commutator and brushes - as the voltage levels change a new winding is selected by the commutator rotating a new winding contact under the brushes. While the principle is similar to using an alternator with diodes, with brushes you generally get more mechanical drag and losses than with an alternator. Most generator (DC) offerings will be DC moors being driven as generators - the two roles are interchangeable but a machines designed for one will tend to be less optimised for the other.
The rim-powered motor based dynamo which you cited is OK in principle but likely to be horrendously inefficient in practice due to mechanical issues. As a child the many rim dynamos that I saw were all terrible so I was surprised to see modern units which do this reasonably well - it's a matter of actually knowing what you are doing mechanically with shaft alignment, gearing, surface friction etc. A "dynamo" of sort will typically produce 1 to 10 Watts output. With an efficient system, you'd notice 10 Watts when cycling and would almost not notice 1 Watt except under very light load conditions or coasting.
More soon
The rime powered motor based dynamo which you cited is OK in principle but likely to be horrendously inefficient in practice due to mechanical issues. As a child the many rim dynamos that I saw were all terrible so I was surprised to see modern units which do this reasonably well - it's a matter of actually knowing what you are doing mechanically with shaft alignment, gearing, surface friction etc. A "dynamo" of sort will typically produce 1 to 10 Watts output. With an efficient system, you'd notice 10 Watts when cycling and would almost not notice 1 Watt except under very light load conditions or coasting.
Some form of battery storage is almost essential. A laptop or tablet etc will have its own unless removed. Towards the lower limit, a more than usually netbook of tablet may get 6 hours from 3 x 18650 LiIon cells. Say 3.5V mean x 2 amp hours x 3 = 21 Watt hours. So operating over 6 hours = 21/6 = 3.5 Watts. Big laptops may get as low as 2 hours with 6 or 8 or 9 or 12 cells so say worst case 20 to 30 Watts. The rate they will charge their battery packs at is not directly connected but obviously a bigger pack takes more energy. A larger charger may specify 19v x 5.5A = 110 Watts. A single 2 AH 18650 LiIon cell (as used in combination in most laptop batteries) requires about 10 Watts peak to charge (4.2V x 2A + some "headroom") so the above 110 Watts is about right for the very largest of battery packs (12 cells). This is for about the first 40 minutes of a charge cycle from fully "flat". After that the cells go into a constant voltage tapering current mode.
More later if needed. Sleep calls alas ..
More soon ...
The rime powered motor based dynamo which you cited is OK in principle but likely to be horrendously inefficient in practice due to mechanical issues. As a child the many rim dynamos that I saw were all terrible so I was surprised to see modern units which do this reasonably well - it's a matter of actually knowing what you are doing mechanically with shaft alignment, gearing, surface friction etc. A "dynamo" of sort will typically produce 1 to 10 Watts output. With an efficient system, you'd notice 10 Watts when cycling and would almost not notice 1 Watt except under very light load conditions or coasting.
Some form of battery storage is almost essential. A laptop or tablet etc will have its own unless removed. Towards the lower limit, a more than usually netbook of tablet may get 6 hours from 3 x 18650 LiIon cells. Say 3.5V mean x 2 amp hours x 3 = 21 Watt hours. So operating over 6 hours = 21/6 = 3.5 Watts. Big laptops may get as low as 2 hours with 6 or 8 or 9 or 12 cells so say worst case 20 to 30 Watts. The rate they will charge their battery packs at is not directly connected but obviously a bigger pack takes more energy. A larger charger may specify 19v x 5.5A = 110 Watts. A single 2 AH 18650 LiIon cell (as used in combination in most laptop batteries) requires about 10 Watts peak to charge (4.2V x 2A + some "headroom") so the above 110 Watts is about right for the very largest of battery packs (12 cells). This is for about the first 40 minutes of a charge cycle from fully "flat". After that the cells go into a constant voltage tapering current mode.
More later if needed. Sleep calls alas ..
