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Dingdoc

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Joined: 23/09/2009
Location: Australia
Posts: 76

Posted: 04:53am 06 Oct 2009

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I�ve recently made a couple of hand cranked F&P alternators as demo units for the school science labs (where I work as a Labbie). They have proven to be extremely effective in demonstrating energy conversion and alternator/generator principles in the science curriculum.
The students (and teachers) have been surprised how much effort is required to produce around 100w to light the lamps and it gives a good appreciation of energy �production�.

To mount the F&P motor on the heavy particle board base, I cut the bearing hub out of the plastic tub using a reciprocating saw, keeping a fairly large radius to act as a mounting flange. The steel shaft was cut by hand with a hacksaw just below the rib near its centre and re-fitted to the bearings before screwing it to the base board.

The stator was re-fitted after re-wiring it for 12v as per the instructions on this website.
IMPORTANT : I WOULD NOT RECOMMEND USING THE STATOR WITH THE STANDARD WIRING CONFIG AS IT IS CAPABLE OF PRODUCING LETHAL VOLTAGES.

The crank handle was cut from a short length of 90 x 45 pine with a 42mm hole cut in one end using a hole saw. This proved to be a tight fit over the slightly ground down plastic nut on the motor. A long wood screw near the outer end of the arm into the rotor helps to stop it slipping when turned. A long 6mm bolt and piece of drilled broom handle finished the job.

Each of the 3 output phases was connected through a toggle switch to a 12v 35w lamp mounted on the baseboard. This way the load can be progressively increased while turning the handle. It takes quite a bit of effort to fully light the 3 lamps.

When time permits I hope to add bridge rectifiers and meters (V & A) to enable calculation of power output.

Will try to upload some images soon.
Trev

Dingdoc

Regular Member

Joined: 23/09/2009
Location: Australia
Posts: 76

Posted: 06:22am 06 Oct 2009

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Here are the pictures -

daveames
Newbie

Joined: 19/09/2009
Location: United States
Posts: 30

Posted: 11:07pm 11 Oct 2009

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hi trev,

that looks like fun. let us get this straight-you, as a lab tech get to build this stuff and play with it all day long and they pay you to do it! where do i sign up for a gig like that?

really, that is a super demo you put together there. i would not be 100% sure of less than lethal voltage potentials though, even rewired for 12 volts that output is still wild and might be higher than we think. (exposed wiring) we may find that adding the bridge will smooth things out a bit and even out the unbalanced phases. also we might be surprised at what we think is 100 watts output is more like 40-50 watts. our 12 volt 35 watt bulbs might be running at about 30 volts and 10 watts or so.

there are some nice pre packaged in line watt hour meters that can go in after the rectifers for real time info. check out the "doc wattson" and others. of course that takes all the fun out of the power calculations though.

all in all a cool project there. thanks for giving us a look.

kind regards, dave

Dingdoc

Regular Member

Joined: 23/09/2009
Location: Australia
Posts: 76

Posted: 05:30am 12 Oct 2009

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Hi Dave
Thanks for the kind comments.

Yes, the job is pretty good, although I did most of this build at home. I was a Science teacher for 30 yrs before becoming a labbie so its been a bit hard to shake the habit of doing extra work at home!!! The job's certainly a breeze after teaching.

I have checked the no load AC voltage output and it hasn't gone up much over 18v, even with fast cranking so I reckon its fairly safe.
Have also checked the output under load and it has been possible to get to 12 volts but VERY hard work with all 3 lamps switched in and not sustainable for long. I am also building a wind turbine and this generator has given me a good 'feel' for how hard the blades have to turn to produce power.

Another interesting 'trick' was to connect another F&P rewired motor to the 3 phase output and have it turn with the power generated - didn't seem to start on its own, but with a push start its speed of rotation matched the speed of the handcranked alternator and it had a reasonable amount of torque.

Regards
Trev

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