Pedal Powered Prime Mover Maximum Human Power Experiments
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After a year of generating power with the PPPM, I decided to see what the
limits of my 52-year-old body were for generating power. While my
daily rides are a great workout, the goal of those rides is to produce steady
power for a long period of time, not to sprint. The PPPM as it is currently
designed is optimized for those rides, not for generating maximum power.
To set up for this experiment, I took the generator off of my daily rider PPPM and cabled it up along with the new version of the PPPM I assembled recently for further experiments. Both generators were connected through cables to the Power Board, with all power flowing into the board through a single Watt's Up meter.
The Power Board is equipped with a Maxwell 58 Farad Ultracapacitor, and for this experiment, that was the only "load" I had attached to the Power Board. My plan was to pedal power into the Ultracapacitor and monitor the Watts being produced as the voltage increased.
Zachary was on hand to hold the second generator against the PPPM flywheel to enable the single flywheel to drive both devices. An interesting situation arose when all the cables were attached. There was no diode in the circuit for the second generator, as there is for the PPPM, so the second generator began to "motor" just from the power stored in the Ultracapacitor from the last experiments, which took place more than a week ago!
Prior to the beginning of the movie below, I have pedaled the Ultracapacitor up to 12 volts. At that level, the Ultracapacitor is three volts below the maximum voltage listed on the case. The movie begins with me "holding" that voltage by pedaling just fast enough to generate 12 volts, but essentially zero amps. As the movie progresses, I increase pedaling speed and force, and the Watt's Up meter displays Watts in real time, which I announce. I stop pedaling quickly after I feel maximum power is reached, as the Ultracapacitor has been driven to almost 16 volts by the surge of power! That is beyond it's design limit.
I could have sustained that power level for at least five seconds, and maybe longer. I was definitely developing an "oxygen debt" so I could not have sustained that rate for more than half a minute or so. In my morning workouts, as of December 2006, I can sustain 110 Watts of output without going into oxygen debt, so my sustainable maximum in this condidtion is somewhere between 110 Watts and 265 Watts.
At the end of the video, you may hear me ask Zachary to keep the second generator pressed on the flywheel. At that point I begin to resist the pedals, which are still beinig driven by the motoring effect of the second generator, to quickly draw the power from the Ultracapacitor back out through the generator and reduce the voltage to safe levels.
For this configuration, with only one practice run prior to the movie, the peak output reached was 265 Watts. That is a little over one third horsepower. With some additional preparation, and careful attention to tension on both generators, I believe that power level could be exceeded, but probably not doubled, at least not in my current physical condition.
I learned a lot from this experiment. The current generator selection for the PPPM is probably just about perfect for sustained workouts at a steady pace of 120 Watts or less. It is not the right choice for higher power levels, as it requires RPMs beyond the level the PPPM flywheel and generator drive pulley can comfortably produce. To re-work the PPPM for short bursts of higher power, or for superior athletes, a generator capable of a higher power output at the same RPM's would be required. The alternative, as seen in the movie, of using two "standard" generators is certainly possible, but I would expect one large generator, with two ball bearings, to be more effecient than two small generators with a total of four ball bearings. On the other hand, splitting the power being produced between two drive rollers may be safer from the point of view of limitations of the materials involved. When driven hard, the polyurethane rollers begin to desintegrate from heat and mechanical strain.
The basic PPPM is well tested (more than a year of daily power generation rides) and the design is stable. Experiments like this one show how the current design could be modified to acheive different operating parameters. I have no doubt that the PPPM is capable of more than I have yet imagined. The experiments will continue.
Update Sun Aug 9 13:02:47 PDT 2009 - today I had an opportunity to try my maximum power output again, after several more years of daily workouts, and this time I Pedaled 301 Watts Peak Output Power! That is approaching one half horsepower - quite a bit for a Human Being!
Order the plans, and see how much power YOU can generate!
The Max Power configuration is an example of the PPPM System - a tested, matched set of devices selected to maximize Human power generation.