Dynamo (pedal) power

[whiteoaks7]

Needing to maintain my excellent level of fitness (;-) while on a cruise around the coast I was thinking of rigging up the bikes on a stand on deck and driving the screw (no - delete) a dynamo to provide a load to cycle against and put some trickle into the battery at the same time. Bike dynamos are no good (and have you seen the cost!!!) so I was thinking of an old car one. It needs to be a dynamo (generator) not an alternator because of the fixed magnets so any idea where I can get one? Even the scrappies don;t seem to have anything other than alternators these days.

BTW if you see my boat going round and round in circles it's obvious that I'm pedalling like mad with the bike hitched to the prop and the magnet in the dynamo pulling the compass around.

Ho hum - another bright idea . . .

 

[sarabande]

The typical average continuous power that can be generated by pedaling is about one-sixth horsepower or 125 watts, more or less, depending on the weight, strength, and endurance of the person pedaling. The maximum power obtainable through hand cranking is more a function of strength than of weight, and is typically about 50 watts. Enough to keep a coolbox coolish.

There are a couple of devices already on the market.

http://www.windstreampower.com/humanpower/hpgtech.html

 

[DaveS]

Can't help you source a dynamo, but why can't you use an alternator? Given that the idea is to charge a battery, then by definition there's a battery available to energise the field winding.

Pedalling as a source of energy is not an entirely daft idea. It should be possible for a person of low to moderate fitness to maintain 50 to 100W for an hour - which will put around 4 to 8Ah into the battery. Fit cyclists can maintain much higher outputs. I suspect (but haven't actually done the sums to prove it) that for a given energy content, cheap carbohydrate food (pasta, potatoes) costs less than (taxed or otherwise) liquid hydrocarbon fuel. And, given that most of us have a weight surplus that we'd prefer not to have, going a bit "calorie negative" should probably be regarded as a benefit rather than a cost. /forums/images/graemlins/smile.gif (Consider the money people pay to gyms etc.)

All that is needed is a practical design to allow efficient cycling to continue when the boat is moving about (consider no wind following rough weather)...

 

[Salty John]

I remember a device called the Wesson Pedal Power Generator. It produced a claimed 5 amps at 50 RPM. The inventor claimed he could get 6 hours of light from a fluorescent bulb for one hours pedalling. Probably had muscles like Popeye.

 

[shmoo]

[ QUOTE ]

I suspect (but haven't actually done the sums to prove it) that for a given energy content, cheap carbohydrate food (pasta, potatoes) costs less than (taxed or otherwise) liquid hydrocarbon fuel.


[/ QUOTE ]

I remember seeing, years ago, a table (graph?) of energy content against cost and being taken with the fact that dry cells had approximatly the same energy/cost ratio as dry martinis.

Not important, I know.

 

[davies]

The vision of everyone pedalling furiously up the Solent every summer weekend is delicious.

 

[DaveS]

Well, looking at dear carbohydrates (because I've a packet in front of me) a packet of Pringles costs around 70p (assuming BYGOF) for 3.757 MJ which is about 67p / kWh. Now buying 1 kWh off the grid would cost about 12p and generating your own from diesel would cost about 30p, so in energy terms Pringles are poor value. However, that's highly processed "food". A sack of rice or bag of tatties would work out much cheaper.

Mention of dry martinis... That's another of my hobby horses. Why isn't the energy rating of drink quoted on the labelling? Everyone knows that if you drink too much you get fat, but there's a terrible lack of objective data around. I have absolutely no idea what proportion of my daily energy intake is derived from alcohol; I rather suspect it's too high, but how to tell?

 

[macd]

"I rather suspect it's too high, but how to tell?"

When you fall over, it's too high (borrowed tenuously from WC Fields).

 

[Superstrath]

[ QUOTE ]
Mention of dry martinis... That's another of my hobby horses. Why isn't the energy rating of drink quoted on the labelling? Everyone knows that if you drink too much you get fat, but there's a terrible lack of objective data around. I have absolutely no idea what proportion of my daily energy intake is derived from alcohol; I rather suspect it's too high, but how to tell?

[/ QUOTE ]

Don't forget that it's easy to consume your "Five a day" in the form of barley and hops. I don't understand how, with this much energy and good stuff coursing through me, I'm not the healthiest guy around. Must try harder.

 

[shmoo]

[ QUOTE ]

The vision of everyone pedalling furiously up the Solent every summer weekend is delicious.


[/ QUOTE ]
Given that conversion of energy from one for to another is ineffienct, pedalos would be best.

 

[RIMCOas01]

I remember from childhood days of a TV-series science program that "proved" three Smarties replaced the energy expended by a man pedalling for ?? minutes that produced 20w. Now if only we could invent a machine that directly converted Smarties to electrical energy ... it would one hell of a smart machine ;-))

http://www.los-gatos.ca.us/davidbu/pedgen.html
http://www.webpal.org/b_recovery/3_alternate_energy/electricity/electricity.htm
http://www.humboldt.edu/~ccat/pedalpower/josephSP2004/index.html

 

[Heckler]

get a stainless vessel. put in some waste matter, dead food, beans, etc and get it fermenting, the methane generated could then be piped to a small petrol gennie and away you go!! google on biodigester to get the idea.
Stu

 

[Wunja]

Very slightly off topic...
Wouldn't it be a good idea if all those exercise machines in gyms were conected to the national grid?
Or are the owners of gyms already suplimenting their incomes?

 

[Appleyard]

Re: \"any idea where I can get one?\"

You will definitely be able to get one if you go to an autojumble..(like a boat jumble but for old cars) There are usually heaps of them for sale for a few quid.

 

[Guest]

To answer your question you need to look for a brushless DC motor and put a diode bridge on the three phases. Exactly what they use for home made wind turbines.

 

[Heckler]

No, not off topic, the man asked how to get smarties to produce power without eating them!
Stu

 

[fishermantwo]

What about the dynamo that is fitted to Kubota's. Its just an overgrown version of a push bike dynamo. I have a spare one in the workshop and have often wondered how it would go with either a towed set up or a wind driven setup.

 

[richardandtracy]

Use an alternator. A home grown one. Take a look at Hugh Piggot's 'Brakedrum Windmill' book or its replacement 'How to Build a Wind Turbine' see http://www.lindsaybks.com/bks10/wturb/index.html. In there are all the calculations necessary to make a custom alternator. Could easily fit to a bicycle rear wheel.

Regards

Richard.