Engine driven electric power

[safe]

Heck, if you can get a constant speed gasoline engine that is able to cruise along at a moderate pace and have a governor that automatically adjusts for motor load and at the same time be able to vary the alternator field strength to control bike speed, then you have it all worked out.

So the basic points are:

Gasoline motor with automatic load adjustment by governor. (mechanical)

Alternator that goes from zero volts output up to the maximum you need for a 250 watt motor all controlled by a simple field current. (should be from 0 - 24 volts output)

Throttle that acts to control the field current of the alternator.

Electric motor to drive bike which is directly connected to the alternator output.

...you will need a battery to supply the field current, just like with a car, but it would likely not need to be that big as long as you have the ability to feed some of the alternator power back into battery charging. This is what the standard voltage regulators do on cars already... so if you just salvage the voltage regulator from a car and use it then you are set.

This will be interesting... be sure to include digital images on this thread to record the progress. (we want to watch you build it)

 

[professor]

Safe, when I get done with the off road bike, I will start on the gas/electric.

Was talking to the sparkey guys at work who gave me some tips also.

Here is how the alternator works - the diode bank turns the AC into DC.
The field spins, the field becomes a bunch of magnets as you send current thru their slip rings.
The amount of current you send thru detirimines the output that comes off the big wire to feed everything. The regulator controls the amount of voltage the whole thing puts out.
The faster you spin the thing - the higher the voltage would be IF it wasn't regulated somehow. At full field current (3 amps of 12 V or so) I saw 25 V @ 3300 rpm. Spun at 5000, it is said, voltage goes up to 110.
It sure looks like a goverened engine (3500 rpm) would work real well to just leave it there and tweak the field from zero up to what you need to get 24V.

For my application, I will be setting the field current at some level, probably with something like a dimmer switch and limiting engine rpm under load @ 24V.
For idling another switch would be at the throttle lever somewhere to cut field power until the throttle is opened again.
It would be great to be able to find a car-type regulator that would have it's preset level at 24. My friends tell me that a regulator is available to take a range of input voltages up to around 38 and get a fixed output of one to three amps 12V (dependong on which regulator I get- there are a lot of them and they do not cost much) This could not be used to set field current but could be used to charge the battery while running.
So far everything looks viable.
One of the guys is doing a windmill. He disassembled an alternator and placed rare-earth magnets in the part that spins- eliminating the need for energizing that field section electrically...he is wild about that set-up, but it would need a clutch to use it on a bike.

 

[safe]

Once I made the mental connection of "throttle" and "field voltage" it all made sense. The idea seems very good... you use the variable field strength as your way to control the electric motor.

No need for a PWM controller... it's sounding very good.

Throttles are usually either Hall Sensors (most ebikes) or Potentiometers. (Magura) The dimmer is actually some type of PWM using some really basic circuit which I don't know much about. Dimmers are for AC household 120 vac to my knowledge so I'm not sure if they will work with DC or AC that isn't 120 volts.

The field voltage is a DC voltage, not AC.

Are you sure about the dimmer idea?

 

[professor]

I did use a rotary devise that looked like a reostat. It was from a car and it did change the power to the field, thus dropping voltage. I am thinking the dimmer switch controls current the same way.
BUT, I have been studying alternators. One of the connections on the back is the "S" terminal (on Delcos) and on Fords the "S" spade on the remote regulator, in both cases the "S" stands for "Sensing". This line feeds system voltage to the regulator.
When the regulator receives lower than (a built in standard refrence) voltage- the regulator sends more juice to the field, to bring that voltage up to the standard refrence point.

I am now thinking- what if that line would have a resistance built into it? Could be a resistor, reostat, or light bulb?.
Wouldn't the regulator fire up more juice to the field until it got it's end of the sensing line to register 14.5 volts?
But in reality, the alternator is putting out my desired for 24 volts. The alternator would be functioning totally normally- limiting voltage- except that now the limit is where I want it.
At this point, being that the voltage is now set and limited to 24, engine throttle position would detiriimine output.

There is one unknown to me and that is- the wacker may need to rev more than the alternator. In this case, I would fool the regulator again by placing a resistance on the field line as it goes to the alt. Not a big deal, the engine then would rev higher to make the desired output. Far as I know the wacker can rpm real high but I only want to rev as much as needed to get full power to the drive motor.

Battery charging would be able to be done with a different regulator which takes alternator output and sends a set amp signal at 12v to the battery. But 12v would not charge the battery, it needs a couple more.

Have been looking at the weedeater engine/ means of mounting and driving the alternator. Don't see any problem here. The engine weigns about 6#, the ford alternator 6, drive-motor 2or 3, jackshaft and chains/guards about 3. Mounts, a rack and small battery, maybe 10#, the bike was 34. A quiet muffler and a milk crate to cover the generation rack.
Should be under 60 #.

 

[safe]

Light dimmers are Triacs:

http://en.wikipedia.org/wiki/TRIAC

This results in a bidirectional electronic switch which can conduct current in either direction when it is triggered (turned on) and thus doesn't have any polarity. It can be triggered by either a positive or a negative voltage being applied to its gate electrode (with respect to A1, otherwise known as MT1). Once triggered, the device continues to conduct until the current through it drops below a certain threshold value, the holding current, such as at the end of a half-cycle of alternating current (AC) mains power. This makes the TRIAC a very convenient switch for AC circuits, allowing the control of very large power flows with milliampere-scale control currents. In addition, applying a trigger pulse at a controllable point in an AC cycle allows one to control the percentage of current that flows through the TRIAC to the load (phase control).

So it does tend to suggest that you need AC current for a generic "dimmer" to work...

 

[safe]

"Must See" Internet Forum Thread

http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=13343

...uses an AC Induction motor and will be using a gasoline engine to power the batteries. (similiar idea to the hybrid here only different in a lot of ways too)