[rwaudio]

Each turn of the pedals would turn the generator about 10 times. Depending on how I gear it. I could get as much as 40 to 1 but fear that pedalling would be much to difficult under any load. 60 pedals per minute is a standard leisurely amount I figure. That would be 600 rpms for the generator. That would add up to 48v at just a leisurely pedalling frequency. So the main question is the load capacity. It is a fairly high wind turbine motor that recommends a 75 amp blocking diode. The diode is supposed to prevent current from backing up into the generator. Would this prevent or at least decrease the load factor? Without the batteries, the speed of the pedalling would determine the speed of the tribe. That would make for a much simpler setup obviously. I've watched videos with this motor and 48v appears to give about 50 mph. Not bad for a leisurely cruise.

I have a feeling that you are leaving current out of the equation, 48v by itself is 0 watts 0 hp 0 in any measure of power, you also have to consider the current required to make that power, to get the theoretical 8hp (ignoring losses) you want that is roughly 8x746 = 5968watts/48v = 124 Amps

As per wikipedia on human power an average person can develop 200watts for over an hour. An elite cyclist can generate "an instantaneous maximum output of around 2,000 watts" the 200watts for an hour is far from the 5968 watts required for your 8hp and we haven't even considered losses in the system.

So in short, you NEED batteries to make up the other 120 Amps since you will be able to generate about 4Amps at 48V with a lot of work.
(I'm sure you wouldn't need the full 8hp at all speeds, however during acceleration and high speed you will need most of that power)

 

[rwaudio]

Sorry MikeK. I didn't mean to imply that your wife needed to shed a few pounds. That's certainly how it read though. I meant our wives in general. I'm starting to think the parallel suggestion seems like the way to go. I appreciate everyones help but still no answer to the blocking diode factor. Just wandering. If it's job is to block power from draining back into the generator, would it not block the load? Or some of the load?

A diode is a semiconductor device that only allows current to flow in one direction. There is a small voltage drop across the diode in the forward direction, between 0.2 and 0.7 volts depending on the type. The 75A rating is the amount of current that can pass through it safely, often this is a maximum rating that requires a suitable heatsink to achieve and it is usually better to stay away from the maximum for reliability. There will also be a reverse voltage rating which is the maximum reverse voltage that the diode can block. IE if the diode was on your generator the diode must block the maximum ripple voltage from the battery/motor system. So the diode will "block" a small portion of the power from the load if you want to look at it that way. There will be power disipated within the diode based on ohms law V=IR where v is voltage, I is current and R is resistance, P=IV is derived from ohms law where P is power, I again is current, and V again is voltage. The power lost/blocked/disipated in the diode can be calculated by the forward voltage drop of the diode times the current through the diode. So a diode with a 0.7 volt drop at 75amps will disipate 52.5watts, if the generator put out 48v as you had hoped the voltage to the battery would be 47.3v.

Sorry if it's a bit confusing and I jumped around too much it's been a long day I know how it works but I might not explain it clearly. Looking up diode in google or wikipedia might help you understand what it does and what it is used for. There are also many types of diodes with many applications and uses.

 

[rwaudio]

Well don't give up, just keep learning and you'll be able to build something that works nicely. I've been contemplating building a trike as well but it would definatially be a parallel hybrid to assist traditional pedal power.

Unfortunatially there's that stupid "law of conservation of energy" that says you can't create or destroy energy only transform it. That and "gravity" really can make our lives difficult sometimes.

I hear ya on the alien technology, I would like a new "battery"

 

[rwaudio]

Lithium will do nicely. It is the NEW battery.

How about a pack the same size as my gas tank with even 1/4 or 1/2 the range of the ICE version. With 20C charge/discharge rating, not to mention a source from the "grid" to charge at that rate.
Ya that's dreaming

However I will probably be buying TS 200ah cells for my Porsche, and I'm sure I will be happy with them.