musical bicycle
Posted: January 15th, 2025, 12:35 pm
Some of those in the DIY group already know about me having made an indoor bicycle trainer that generates the electricity needed to run an audio system. I have recently changed the system from CD based to LP. And with this I needed a new amplifier with phono. So I thought I would share this amusement with the rest of the group. First and foremost to anyone who thinks they are paying too much for power, they should try to generate their own power. Believe me, for the amount of power you get for pennies you will have to work really hard if you had to generate that with your own body. I summarize the components that I have made with a series of pictures. To run this system I need to supply an average of 60 watts going into the inverter. There are additional losses not counted here in the generator and mechanical chain linkages that my legs need to generate. I would estimate these additional losses at around 20% of the power delivered.
First is a general view showing a protective bag with noise-absorbing materials. Second picture gives a back view with the two chains and generator. If I pedal at 85 RPM on the cranks the generator spins at around 1500 RPM. The generator is 3-phase and I run it typically at around 70 volts output, but the useful range I use is 50 to 100 volts depending on my leg speed. A front-mounted display, not shown, shows amps, volts, watts, and energy in watt-hours. Next a view of the amplifier. This is a 6 wpc ZOTL complete with tube phono section. I could have made the pedaling easier by making this SS, but I needed a challenge physically and mentally to make the most efficient TUBE amp I could. The output tubes are 6DL5/EL95 types. The plate-to-plate loading is around 73 k for an 8-ohm speaker. The ZOTL can do this whereas it would not be possible to wind a full-bandwidth output transformer to do this. The average plate voltage is 560 V The next picture gives a view from the front where the amplifier and turntable are shown.. Next up is the inverter. This is a custom made unit with crystal frequency control and a low-distortion 120 V sine wave output. It can regulate from 50 volts in to over 100 volts in. Finally, a large energy storage bank of capacitors is needed. This gives an important fly-wheel effect to the pedaling. Without this the pedaling is very jerky.
First is a general view showing a protective bag with noise-absorbing materials. Second picture gives a back view with the two chains and generator. If I pedal at 85 RPM on the cranks the generator spins at around 1500 RPM. The generator is 3-phase and I run it typically at around 70 volts output, but the useful range I use is 50 to 100 volts depending on my leg speed. A front-mounted display, not shown, shows amps, volts, watts, and energy in watt-hours. Next a view of the amplifier. This is a 6 wpc ZOTL complete with tube phono section. I could have made the pedaling easier by making this SS, but I needed a challenge physically and mentally to make the most efficient TUBE amp I could. The output tubes are 6DL5/EL95 types. The plate-to-plate loading is around 73 k for an 8-ohm speaker. The ZOTL can do this whereas it would not be possible to wind a full-bandwidth output transformer to do this. The average plate voltage is 560 V The next picture gives a view from the front where the amplifier and turntable are shown.. Next up is the inverter. This is a custom made unit with crystal frequency control and a low-distortion 120 V sine wave output. It can regulate from 50 volts in to over 100 volts in. Finally, a large energy storage bank of capacitors is needed. This gives an important fly-wheel effect to the pedaling. Without this the pedaling is very jerky.
