I've googled for small generators and found the smallest to be about 750 watts. I'm wondering if such exists < 100w? The application being to charge batteries from AAA, cell phones, to car or device batteries in the bush. How about running on a small butane, propane or gasoline? How about the thing weighing in at 5 pounds or less? It seems there would be a good market. I wonder if I could rig-up an RC gas engine with a bicycle generator. I hate it when my electric fishing reel line stripper dies and have to do it by hand.
I'd suggest a storage battery and a small solar panel to keep it charged. I rigged a panel on top of my "Yankee Flipper" squirrel flinging bird feeder about five years ago to keep the nicad batteries which power it charged and it's worked "slicker than snot" since then.
Years ago at a formerly local power equipment place, I saw a Honda generator that I thought was a model at first. The thing was about the size of a tissue box and was actually a real functional generator rated at something like 200W. I've never seen it since and it isn't in Honda's current lineup.
For small jobs like charging phones and small batteries, the solar chargers seem to be about it these days. You might consider a thermocouple based unit if you had to make a fuel powered one. That way you don't have a lot of moving parts or noise, same concept as the heat powered fans they sell for use on wood stoves.
There certainly are RC engines that can deliver 100 watts (0.134 HP). Check Tower hobbies. (You didn't mention budgetary constraints.) You'll want an 0.9 or larger engine.
An RC engine will cost more and may not run as long as a weedwhacker engine, but it will be smaller and lighter weight.
A DCPM (permanent magnet) motor will produce DC. Look for a motor that is rated at 12 volts or so, 8 amps continuous, and a speed compatible with your choice of engine. It will probably be about the size of the motor in a cordless drill -- about half the size of a can of frozen orange juice. In fact, it might be a whole lot like the motor in a 12-volt drill if you can match up the speeds. They won't be far apart, both somewhere between 5000 and 15000 RPM.
I'd start with cheap 12V to 18V cordless drills from HF, or even better, drills found with dead batteries at garage sales or flea markets. Ignore the rated speed, the speed you're after is the motor speed before all the gear reduction inside the drill.
A bicycle generator won't do it because 100 watts of steady output for any sustained period would tax a cyclist in good condition.
A weedwhacker or small chainsaw engine could do this while loafing well below max speed, which should make speed matching real easy.
You didn't mention anything about noise, right?
100 watts of solar cells will be quite large, and probably a bit fragile, and of course it only works when the sun is shining.
You'd probably want some sort of voltage and current regulation elex. I can help with that if you can build simple electronic circuits.
PS, Tom, the guys I shoot with liked my XD .40 trigger job so well I didn't get to shoot my XD for the first 45 minutes at the range. I'll bet there are guys in MN tonight disassembling their XD's in paper bags -- you know why they're doing it in a paper bag.
Get a PM DC motor. Turn the shaft. If you want a good one - try hobby shop - those under glass - for Gliders. Cobalt magnets - with or without gear reduction.
Martin
Mart> I've googled for small generators and found the smallest to be about 750
Why not a 4 stroke model engine driving a dc motor. They are quiet and use very little fuel. Better still might be a small diesel model engine. The fuel is mostly kerosene with some oil and ether mixed in. These have been made to run so lean that 6 ounces of fuel can last for 3 hours.. no glow plug. Belt drive the dc perm mag and viola.. Google up P.A.W engines. I think I'm gona try this since I have a few laying around in boxes
Miracle of miracles, I found the motor I once took out of a $1.50 fleamarket 14.4 volt drill -- with very dead battery.
This motor is about 1.5" dia, 2.5" long, weighs 8.2 oz. Stall current with 1.8 volts applied is 10 amps, which makes the armature resistance 0.18 ohms. This implies a 12-volt stall current of 67 amps, which would certainly smoke it -- but the point is that while drawing (or delivering) 8 amps (96 watts at 12 volts) it'd be dissipating only about 11.5 watts. It could probably do that for quite a while without overheating.
Don't know what the 12-volt speed is, but I suppose it wouldn't be too hard to kludge up a way to measure it. It's fast, probably quite compatible with a small RC or weedwhacker engine.
14.4 volts is pretty close to what you'd need to charge a 12 volt lead-acid battery. So, it seems that a 14.4 to 18 volt drill motor might do ya just fine -- and you'd still have over 4 lb for the engine and whatever mounting and packaging means you might devise.
***Don't they have a trained bandsaw?*** The trigger gets better and better as it wears in and you get more and more used to it.
I think one necessary feature would be the ability to charge a car battery even if it takes a number of hours. (don't ask) I imagine charging a laptop enough to play a DVD and wet cells to power a big flouresent lantern while out fishing. Even the smallest genny I've found is too big and heavy for fly-ins. On those trips, gasoline would be the most plentiful fuel. I'll bet we haul in ten pounds of spare batteries for everything especially the sonar units, they EAT batteries. The weight payback is there. I like the idea of a RC engine but how long can they run? I can always handle noise one way or another. Budget wise, all those batteries are expensive and how do you put a price on MP3s and DVDs in the bush, not to mention plenty of light?
The RC model engines that I'm familiar with run on nitromethane fuel, basically methanol (it is a blue, water soluble liquid that smells just like denatured alcohol, if a little less potent) and use glow plugs to start. They shouldn't be too hard to hook to a small motor for generator power. Another idea, if you could get the gearing/speed issue worked out, would be a medium sized Stirling engine. That could be powered off of a regular camp/cook stove or other burner. They would have to be geared. I'd bet you could even use a model steam engine. Just heat the water and away you go.
If this is for fishing trips on running water, then hydro-power is the only reasonable way to go . I'm thinking about something like those SE Asian river launches with a 12 foot long prop shaft attached to a gimballed engine on the stern of the boat. Since the shaft would be in tension it could be quite slender, perhaps even aircraft cable, in which case it would be much like a taffrail log. Of course a cordless drill motor wouldn't be a good speed match for such a rig, but the right slo- syn motor might do.
Check out ebay item 230067379458. I have no knowledge of it beyond what I read in the auction, or affiliation with the seller. So take it as buyer beware etc.
That's a stirling engine that turns its rotor at 1,000 rpm, if we are to believe the seller. That's quite suitable for attaching a pulley driven DC motor generator. Converting its output to clean DC for battery charging is not very complicated.
Probably produces a few watts of power. Enough to charge little batteries.
A doctrine fostered by a delusional, illogical liberal minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
I wound up with a brand new 12vt DC prop spinner for RC aircraft. Hook it to a battery and it spin starts your RC motor. About the size of a small air die grinder.
I would assume that could generate something, if externally spun, if anyone wants it.
Personally, I go up country to get away from all that crap. Have you ever considered that you don't have to have man made noise 24/7 to have a good time?
You might be able to handle the noise OK but I hope you don't have any neighbours. I can think of few things worse than someone running a high revving chainsaw motor, RC motor, weed wacker etc in a campsite within my hearing. If you're in a private camp in the middle of the boonies, different story.
FWIW my people built such a device but IIRC it was a bit more than 5 lbs. It was used to charge batteries etc on a sub-Antarctic island. In essence it was a PM generator ratted out of a motorbike coupled to a Honda powerhead a la weed wacker. It worked but the noise made it pretty unpopular.
There are some pretty neat fuel cell powered devices available. And they're *quiet*.
Model engines will run just fine on alcohol and oil mix. The nitro does boost output but in some parts of the world it is not allowed. The diesels only use a kerosene oil and ether mix and no glow plugs. There are simple kits to convert glow engines to spark ignition.
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