Using a car to generate emergency electricity

[Mad Scientist]

Is this what you think happens in power stations, M-S ?
We use a black box.

Well I would hope so. In my case I just designed and built one, except I have it in a green box.

[ElectricMick]

Well I would hope so. In my case I just designed and built one, except I have it in a green box.

A green box is better still. Do you want to release the circuit? If a carb is being used (gas as opposed to diesel), we will need a torsional solenoid to control the butterfly valve unless there is a better way to do it. The idea of a device acting on the accelerator pedal (or the velocerator, as Monty Burns would have us call it) might be easier to implement but crude and possibly a bit dangerous. (There could be an overspeed cutout).

[Mad Scientist]

Do you want to release the circuit? I.

Not a problem. The basic operation is the engine is started with the accelerator in its idle position. This gets its juices flowing without any load and allows it a chance to warm up a bit.
Then the regulator circuit is switched on and to its horror it senses that the generators voltage is way to low so it turns on a motor that pulls on the accelerator cable to increase the speed. This motor will run until the correct output voltage is reached.
If a load is plugged into the generator this will cause the voltage and speed to drop. The regulator sensing the drop in voltage restarts the motor to bring the engine back up to speed and also the output voltage.
Conversely if the load is unplugged this will cause the speed/voltage to increase. The regulator then reverses the control motor to slow down the engine.
Turning the regulator off causes the engine to return to its idle position.

So here is what the circuit looks like.



The circuit is powered by the engines 12V battery, this regulated down to 5Volts. The output of the generator is also stepped down through a small transformer. Whose voltage is rectified and further reduced to be within the working range of the 5V supply. However at this point the 5 or so volt change in the generators output, that I am trying to maintain, proportionally is quite small.
Thus IC4 is wired as an amplifier (gain of 10) to get the change in voltage up to a point where the comparator circuits (IC1&2) can easily detect the changes.

If the sense voltage is low IC1 turns on a relay to “up” the engine speed.
If the sense voltage is high IC2 turns on a relay to slow down the engine speed.

Alright you now have a motor that can run forward or backward depending on the output of the generator. But now you need to convert that rotary motion into a push/ pull for the accelerator cable. Here is how I did it.



A gear motor, mounted to bottom of plate and slowly turns crank which moves lever. (Scottish yoke) Accelerator cable is run through a hole near the pivot end of the lever and is held in place with a screw.
The motors control relays are mounted on the angle bracket to the right.



On the bottom there is a cam that operates the high and low limit switches.

[wrtner]

...so it turns on a motor that pulls on the accelerator cable to increase the speed. This motor will run until the correct output voltage is reached.

Very interesting post, M-S.

But what about the frequency? What looks after that?

Is it true that when you buy a generator head, you specify the
voltage and the frequency. Then, so long as the rotational speed
of the shaft is adjusted until one of these is true, then the other will
be true as well?

[citfta]

Constant speed is the key

Hi wrtner,

Yes you are correct. If you maintain the proper speed then the frequency and voltage will be correct for a given generator head. As the load "current" increases the engine or moving force must supply more power to maintain the speed and thus keep the voltage and frequency in the proper range.

Just consider a small portable generator with a gasoline engine. The only control on the engine is the mechanical governor. All it does is make sure the engine is always running at the same speed. Yet the small generator can handle varying loads up to the limit of its design.

I believe MS could have taken the sine wave signal of his generator and converted it into a stream of pulses and feed them to a regular cruise control for a car and accomplished the same thing based on frequency instead of voltage. Either way will still give you good control. I suspect he had some reason for doing it the way he did. Maybe he will share that with us later. He has certainly done a great job on his design and build!

Very interesting post, M-S.

But what about the frequency? What looks after that?

Is it true that when you buy a generator head, you specify the
voltage and the frequency. Then, so long as the rotational speed
of the shaft is adjusted until one of these is true, then the other will
be true as well?

Respectfully,
Carroll

[Mad Scientist]

V Then, so long as the rotational speed
of the shaft is adjusted until one of these is true, then the other will
be true as well?

Correct! However with a small generator it is virtually imposable to precisely maintain either one. But then for all practical purposes it does not matter. Most appliances can easily tolerate a 10-15% variation in voltage. If you are running a motor a change if frequency will cause a corresponding changes it the motors speed. But aside from running an electric clock this will not have any noticeable effect nor cause it any harm. Matter of fact if you have any machine tools that need to run at varying speeds a “variable frequency drive unit” is a common way to achieve this. Frequency changes from half of the motors rated frequency to double it are considered normal.

A car with a cruse control would be a convenient way to control the engine speed. However the car that I purchased did not have that as a option and even if it did it probably would not have been working.

Regardless consider this, if a car is to be used to run the generator because of the differential the wheel speed will be first reduced by the axle ratio then if one wheel is on the ground and not turning the other one will run twice its normal speed. With a direct drive to the generator this is probably going to be too slow without revving up the engine.

Also so whatever load is placed on the generator that load/torque is also applied the other wheel, via the differential and which will be trying to move the car! Then if by chance the car has a limited slip differential it will move the car and that might tend to get a bit exciting

[wrtner]

Also so whatever load is placed on the generator that load/torque is also applied the other wheel, via the differential and which will be trying to move the car! Then if by chance the car has a limited slip differential it will move the car and that might tend to get a bit exciting

This reminds me of driving into muddy conditions when one wheel
in a mud pool, spins wildly as the other, on terra firma, stays still.

I think the problem will increase as the generator load increases. At
10kw, it is possible it may not be an issue.

As the power drawn off increases, we could think of two 12" chocks
and a thick webbing strap to secure the other wheel. (I am not sure
what to say about limited slip diffs. Work needed).

[Allcanadian]

@wrtner

But what about the frequency? What looks after that?

Is it true that when you buy a generator head, you specify the
voltage and the frequency. Then, so long as the rotational speed
of the shaft is adjusted until one of these is true, then the other will
be true as well?

This conversation brings back memories of the 1st year Power Engineering lab at college. Everyone had to pass a "stress test" in which we were required to bring a big old "D" type boiler on line, fired on oil no less, then bring the steam turbine generator on line and synch it with the city power grid. To make matters worse the instructor would make something go wrong during the run up and we had to determine what the problem was and correct it.

I remember a few students just grabbed their hard hat and threw it on the ground and walked out, cursing as they left, a little too much stress,lol. The first thing they teach you is to think on your feet, don't get too excited and work the problem through, that is sheer panic is not a sign of professionalism.

We used a Synchroscope, to synch to the grid which is a relative measure. That is we do not aim for 60Hz because the grid is never at exactly 60Hz so we match the generator frequency to the grid frequency wherever it may be. My instructor said one operator dropped a generator online without synching properly and it snapped the 6" hardened steel shaft of the generator cleanly within a second. Mind you that was 30 years ago and most everything is now automated however there are some very old systems still in operation.

As easy way to synch would be two 120v to 5v transformers driving an op amp or comparator(differential amplifier). If the two inputs, generator and grid, are synched or equal then the output is zero. Basically when the dummy light goes out your synched and we close the switch to the grid, no brainer.

AC

[ElectricMick]

We used a Synchroscope, to synch to the grid which is a relative measure. That is we do not aim for 60Hz because the grid is never at exactly 60Hz

A great anecdote, AC. In the UK, there is another method to feed back to the grid with a black box. no idea how it works. But if this idea got taken further and this was to be done (I think fuel costs would get in the way unless someone had a gas solution based on bio-mass or similar - potentially HHO), your experinece tells us thast we need to be careful. -EM.

[wrtner]

Just consider a small portable generator with a gasoline engine...

The only control on the engine is the mechanical governor...

Don't forget that the fuel can be untaxed - red diesel
for diesel engines. (I don't think there is a petrol equivalent
- very unjust).

Where do we go for retro-fit mechanical governors? Hard to find.

[wrtner]

Tornadoes - Many in Texas needs electricity.

Tornadoes cutting off mains power:

Thousands lose power after deadly Texas tornadoes | khou.com Houston

Are there any people in Texas to put a big push on this
project to get power to the people (if they have cars,
generator heads and a few more bibs and bobs?).

What is lacking?
1. interface between the wheel and gen head
2. governor
3. differential issues and what happens to the other wheel.

Paul-R

[inventionmaster]

Hi

Interesting project. I like

[ElectricMick]

Now Oklahoma is being trashed. theres gonna be extensive power outtages.

Massive tornado slams Oklahoma City area - CNN.com

Never have our ideas been more needed. i will look into governors. we need someone to work out how to join the gen-head to the wheel flange - or the wheel itself if it can be left on with longer wheel studs - to act like a flywheel.

[wrtner]

Now Oklahoma is being trashed. theres gonna be extensive power outtages.

Massive tornado slams Oklahoma City area - CNN.com

Never have our ideas been more needed. i will look into governors

I wonder if we should shelve this and, for the first
implementation, start with a vehicle with cruise control.

The urgent issue then becomes interfacing the generator
head and the wheel. The industry seems to like tapers
which I see as quite annoying.

Paul-R

[ElectricMick]

I wonder if we should shelve this and, for the first
implementation, start with a vehicle with cruise control.

The urgent issue then becomes interfacing the generator
head and the wheel. The industry seems to like tapers
which I see as quite annoying.

Paul-R

Lets leave the wheel on.

A load of these gennies are designed for a drum and belt arrangement which could have a huge benefit - of giving a "step up gearbox", the step up being the diameter of the wheel divided by the dia of the drum on the genny shaft. This means the car can run at a more comfortable RPM.