I've been approached by a local group who are interested in putting on some 'green' Christmas lights in the High Street this year using pedal power.I was sent a document outlining the idea but, unfortunately, it seems to be based on a lot of press reports of other schemes which I suspect have cost a lot more than their nothing pence target ...Now my background is electronics, so I've never had any dealings with generators other than the Miller dynamo on my mum's old bike (pre-war, 28" wheels, cast iron frame, no gears) which was handed down to me over half a century ago. Oh yes! There was also the little motor from my Trix construction set when I was about 10 which could be made to light a 2.5V torch bulb - just!I've stripped out all the 'why we should do this' and so on bits out and a lot at the end - which does mention the H&S aspect, by the way. What follows are the sections I've commented on - including my comments, of course.What does the team think? Has anybody ever got involved with anything like this before? And is my car alternator idea worth pursuing?The originator already confesses to having zero electrical knowledge, so I don't think that point needs further elaboration!=============================================================] PRECEDENTS OF PEDAL POWERED LIGHTSI do so love it when journalists get involved with technical matters ? they can be a constant source of mirth unless, of course, anybody makes the fatal mistake of taking them seriously!] - Belsize Park, London ] Doesn't say they managed it - just an appeal for bits. "We are currently looking for an old exercise bike, a small 12volt generator and a battery ..."] - Chorlton, Greater Manchester ] Better, but "The turbine costs £500 ..." etc.] - Copenhagen - UN Climate Summit:] sounds like one 80V 300W generator (see below) ... "a number of bikes are (each) connected to a different section of the tree ..."] - Video of Copenhagen (larger-scale than ours will be - but same principles)] you...

Exercise bike, either find one that the owner's bored with or through freecycle, longish v-belt from a local supplier, (Probably FOC if you out a plate on saying "Some parts supplied by...."), car dynamo and regulator (Not an alternator) from a scrappie, a couple of pulleys and an old car battery. If labour's free, you could even modfiy an old pushbike without too much trouble. You'll need a roof of some sort to keep the rain (And, hopefully, snow, if we get a White Christmas) off the pedaller (And, incidentally, the delicate bits), too.Protective earth via a spike made from a length of 6mm threaded rod between a couple of slabs, as they're mostly just laid on a sand bed in pedestrian areas. The hardest thing is going to be fastening it all down so it doesn't "walk". Even that could be done with a couple of Fischer fixings into a 2 metre by 1.2 metre by 100mm thick slab just laid on the floor. You'd need to borrow a lorry with a Hiab or equivalent to position the slab. Again, a...

and people who power stages at green festivalsuse magnets so there's no friction as in car alternators-but they're expensive.

Free electricity for Christmas?

Aug 15, 2011 25 Replies

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Andrew Gabriel 14 years ago

I'm miles off being a top cyclist, actually I'm quite out of shape at the moment, not having done much this summer so far, and nothing last summer.

Tried on an exercise bike last night and this morning... I can do 80W very comfortably for 30 minutes[1], and could probably do at least a couple of hours without difficulty at that rate. I can do 120W for 30 minutes[2], but probably couldn't keep it up more than that without a long break, although a fan would have helped. I can do a short burst of sprinting at 700W (could probably go a bit higher but the artificial wheel resistance doesn't go high enough).

So, where's the F.I.T. scheme for exercise bikes? ;-)

[1] equivalent to a Penguin biscuit. [2] equivalent to a Mars bar.

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PeterC 14 years ago

In the TdF, even over undulating terrain, they'll do ~25mph for 5h+.

Most are 3W; some are 5W. I don't know about modern hub dynamos - mostly 5W I think.

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Alan Braggins 14 years ago

Almost all are nominally 2.4W for front light only, or 3W for front and rear, but the hub dynamos are actually roughly constant current devices which will deliver 6W at reasonable cycling speeds if you give them twice the load.

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are secondary dynamo lights designed to be switched in at speed (with the switch shorting across them when not used), but there's less point with modern LED lights.

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Alan Braggins 14 years ago

It was relevent to TNP's "A TOP cyclist".

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PeterC 14 years ago

All of mine are 3W, usually run as 2.4W and O.6W, and most are modded systems to have LED rear and 3W front.

My only hub dynamo was a Sturmey-Archer, built back-to-back with a hub brake and with a Campag. rear QR axle all in the front wheel of a trike. Bloody good light front and rear! Modern hub dynos are much better. My Father had a Miller 12V dynamo on his tandem in the late '30s - cars used to pull in and stop as their headlights just weren't competitive!

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george [dicegeorge] 14 years ago

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