Mount alternator on top of back tire?

Hi George - Of course you CAN try whatever you want. But you asked us "Whadyathink???" I think it's not going to be very efficient either, but that is not really a priority for you. One thing I would suggest is that you think about doing this on a trike or quad. I think you're going to have serious balance and braking issues with all the weight you are talking about. Then you could sit down low in a comfortable seat and carry lots of weight too (groceries, etc) There are lots of trikes and quads out there (both pedal and powered) for you to look at. Let us know how it all comes out. jd

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In theory there is no difference between theory and practice. But in practice, there is - Yogi Berra

We pretty much all know most states allow 48cc and about 2hp gas engines and they also allow certain size electric motors as well. The other restriction we face generally is 20 or 30 MPH...that being said the thing I think most would like to improve on is torq to start and pull steep hills...be nice if one could use magnetic resistance to generate power going down a hill rather than hitting the brakes much as a jake brake (engine brake) works. I doubt very many if any here are riding a bike to get that 100-150 MPG it is more icing on the cake. I would think most here would be happy to get 80 MPG if it meant little to no peddling. I want to go hybrid for other reasons as well...be nice to have an inverter to run my laptop anywhere I go for one. I have AT&T broadband aircard so I could pull over at a picnic table and surf away. You wouldn't have to have big car batteries you could use motorcycle batteries such as Amazon.com: PowerStar PM12-7L Motorcycle Battery: Automotive
these weigh 6 pounds shipping so that would be 18 pounds total battery weight. someone suggested a motorcycle alternator but the post I made on hybrid with a link shows a fully dual power motor and generator in 1 unit still in developement. I gotta wonder why someone would develope something like this with no potential. I guess they could be catering to dreamers like me. I guess I could just be trippin and not dreamin LOL I don't mind being wrong I've been wrong many times before just as long as nobody is investing too much time or money I figure there's not much harm.

If you ran a second (as in ,harbor freight Greayhound motor/to alternator)motor t power the alt.,???

There is no disputing any time you convert one energy to another you loose efficientcy.

If you can capture energy like water flowing thru a dam and IMHO wheels that are spinning anyway seems to me you would benefit.

I keep hearing about the amount of friction that has to be overcome by an alternator at high output...the only time there would be a high output is when you are using the stored up energy you hopefully built up it the 100 miles you just ran on gas and for a short time if you ran the batteries way down.

I am not proposing to take fire from the magneto I am talking about an alternator's pulley resting on top of your tire.

Someone said maybe my math was off here's my formula for approximate rpm: 1 mile = 5280 feet I am assuming an alternator pulley is less than 1 foot in circumference. Your tires be they trailer 10 inch or bike 26 inch still cover the same distance.

Surely the friction of my 245 pounds on the tires grabbing at the pavement makes that alternator pale in comparison.
Have ya ever seen how hard the guy pulls down to test a load on an alternator at the auto parts store?

So if my numbers are correct 5280 feet times let's say average 20 MPH equals 105600 feet of distance divided by 60 minutes in an hour equals 1760 feet per minute hence 1760 RPM which is enough to produce nominal amps and volts from the alternator.

What would be great is if you could put a controller that would increase the amps load output from the alternator to increase if you went over say 25 MPH as you would be surely coasting downhill and restrict the load output to zero when engine rpm is low.

Here's someone who kicked this idea around in a race car...he had a switch to turn off connection to alternator during 1/4 mile race:

Switching off alternator during hard acceleration Text - Physics Forums Library

I was really just doing the armchair engineering thing but I think I'm gonna try this some day when I have more funds...unemployed and obviously boored at the time now.

Hi George – What some of us referred to in earlier posts as frictional losses are really the magnetic drag you mentioned in a previous post. There are friction losses of course but they pale in comparison to the magnetic drag the generating device (alternator) would cause. As long as you realize you need the gas motor (or pedaling) to get you up to the top of the hill or to coasting speed or to turn your alternator, you will be fine. My question now is – why bother with the alternator at all? A brushed motor will act as a generator if it is being spun and isn’t drawing power. There are controllers made that have a regen circuit so they can redirect that power into the battery. In a regular car, that’s what the voltage regulator does automatically – it senses the voltage in the battery and charges it if necessary. In a hybrid car, regen can be used to slow the car. The magnetic drag can be that strong. You will already have an electric motor attached to the bike, so why add the extra weight and complexity of an alternator? Just use the motor that will already be turning and available for generating electricity to keep your battery pack charged. If you have an adjustable regen circuit you have electric brakes as well.

There are a few things you can think about that might help you plan things. 750 watts equals about 1 hp. Volts times amps equals watts, but you can turn that around into watts divided by volts equals amps. A 750 watt motor at 36 volts will draw just below 21 amps at its rated wattage. I’m pretty sure a 20 ah (amp-hour) battery pack would run that for just under an hour. There are meters you can put on your bike (Watts Up, Cycle Analyst) that can tell you how much power you are using. I don’t have one but I have run my 350 watt ebike on a 24 volt 12 ah battery pack for 15 miles/90 minutes pedal-assisting all the way and had battery left. 350/24=14.6 amps, so obviously I wasn’t drawing full power. You should probably think about how fast and far you want to go on battery so you can figure how much epower you need. Then you can figure the motor and battery size. The weight of the rig will also figure into that.

Also, you could be thinking about a way to disconnect the gas engine from the driveline when you are on electric power. A freewheel sprocket will do that, but then you will have to figure a way to start the engine. Electric start would work but will add weight. A manual clutch would let you jump-start it but I don’t know if they make them. You could use belt drive with an idler pulley. Friction drive would seem to be perfect for that. Drop it down while you’re moving to start the engine and run on gas. Lift it up for electric. Also you could pull the hinge pin, disconnect the throttle and pull the whole unit off, leaving just the electric if you wanted. A brushed hub motor probably spins easily when not generating but would act as a brake when regen is activated, so that’s what I’d think about for electric power. I’d probably want both gas and electric powering the rear to avoid any possibility of an end-over or “fork-torque” issues. As I suggested before, I’d seriously consider a trike or quad. For stability, if I was thinking trike I’d go with 2 wheels up front and front steering. More complicated but much safer IMO. Rear drive would work but then you have the motor right behind the driver’s head, depending on how low the driver sits. Lots to think about… - jd

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In theory there is no difference between theory and practice. But in practice, there is - Yogi Berra

I think this is a great idea and look forward to see you get it done. I am 'estupid with math so I have to build some thing to find out what I don't know, I don't know. Ya know? lol

Just thinking and typing out loud here, but instead of st8 up friction, how about a MB sprocket/ rag joint on the front wheel and mounting the alt above? Easy mount options.

I can't find it, but have a thread (or mabie just a post) rack mount some thing like this, Building your own generator. then use a standard ebike kit

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I want 2 ride my bicycle

the word of the day is "entropy".

Used in a sentence:
Due to the entropy encountered when I was peddling my fat arse up a hill I felt compelled to make my bike have more redundancy by turning it into a hybrid.

The reason why they changed over from GENERATORS to ALTERNATORS in the old days,is because alternators will charge at LOW rpms. ATTN;This is common knowledge.A car engine that is idling is NOT high r.p.m. If your alternator in your car is not charging while the engine is idling,then IT IS BROKEN!! the FAULTY DIODE inside the alt.must be removed and replaced with a new one.If the voltage regulator is faulty,then your battery goes dead, and your car does not start.

If the system could be set up to run only while your going downhill or even with a wind, possibly it would be feasable.