gas -alternator powered 250watt

GoldenMotor.com

BarelyAWake

New Member
Jul 21, 2009
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lol post 3 times and then you'll be "active" - which ofc you just did ;)

It's to help with the evil spam...


|.o
 

deacon

minor bike philosopher
Jan 15, 2008
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north carolina
you can post like you just did... for a while you can't hot link that is prevent people from joining just to post a link to their website.. and then never participating again The people here don't want to run a cataloge business.
 

professor

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Oct 14, 2009
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Buffalo ny area
OK- update.
I tested a Ford alternator ('86 which has a remote style regulator), NOT using a regulator, on the bench, hooked up to my drill motor (up to 2200 rpm. Energized the field windings with a 12 volt source. Connected the alternator DIRECTLY to the 24v 250w scooter motor.
The volts would go up to around 25 and the motor followed right along. I was surprised at how slow the alt. could turn and still the motor would turn too.
Unfortunately, the little direct drive weed wacker motor's tiny shaft output diameter would not take the strain of inertia ( or my attempt at a coupling) twisting a mild steel square piece or shearing a hardned square. When it did run the vibration was awsome- then all of a suden it ran great- minus the alternator.
I am thinking about waiting for the 2.5 hp HF four stroke engine to go on a bigger sale than right now. The thing needs a belt drive. The "Gen set" would be on the back.

I almost bought a I-zip until I saw a vid on youtube and the poster mentioned how loud it is. Really seems to scream to me - It would drive me nuts.
New York made electric assist bikes legal recently (It's nice to see them do something right) so I looked into electric, BUT the batterys are the big bugaboo. Why not displace them with a gen-set?
From my experiment, you have 2 controls:
The amount of current you give the field and engine rpm. NO controler needed. One small battery needed
I would like to tap off the alt. output with a diode (so current can only go TO the battery and a regulator to send some current to the battery when the alternator is outputing.
I want to power the pedal crank, so as to keep the motor in an efficlent range and still have full gears. I pedal at around 50 rpm. It would spin the pedals by itself along with the back wheel, but that is not a biggie to me.
 

geeksquid

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Feb 14, 2008
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What do you mean displace the batteries with a gen-set? I'm glad you're experimenting but there's just no way around having to use batteries, usually SLAs. You can spend upwards of $800 for the li-ions but that's insane and they can poop out on you at anytime and most likely, there will be no warranty to protect your investment. Until one of the many promised miracle batteries that are "just around the corner" materialize, we're stuck in the stone ages. Yes, the Currie motors scream like a siren. Some MBers would love the attention that such a noise attracts, but I find it embarrassing. Other than that little problem, the ezip is a great, durable bike.
 

jdcburg

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Jul 9, 2009
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massachusetts
Hi Professor – Your experiment sounds interesting. You know you need a battery to energize the alternator field but it could be a small one. If you’re not storing a lot of electricity (batteries) then you will be running the engine the entire time – probably just as noisy as the Izip. The laws of physics tell us that the energy required to power the e-motor (250 watts) will show up as “drag” on the alternator. Put a load on your motor and see if it doesn’t slow the drill. There are lots of videos on YouTube showing experiments with a bicyclist pedaling a stationary bike hooked to a generator or alternator. It looks like they’re not working at all. As soon as they put a load on the generator (lightbulbs, a resistor, etc) the bicyclist bogs right down like they’re riding in mud. That’s how those exercise bikes hooked to generators work – higher resistance makes harder pedaling = more exercise. Another thing to think about is: 250 watts is about 1/3 hp. You’re talking about using a 2.5 hp engine to generate 1/3 hp. Seems like a waste to me. Probably much more efficient to hook the g-engine directly to the crank.

Finally – please rethink the idea of powering your unmodified cranks. If your foot slips off and gets caught between the crank and the ground or you are leaning into a corner and a crank hits the ground, the results will not be pretty. There are several places that sell freewheels that fit between the crank sprocket and the crank so you can use a motor (e or gas) to power your chain without forcing the crank to turn. SickBikeParts sells a kit as well as individual parts, or you could look into crank freewheels designed for tandems - jd
 

professor

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Oct 14, 2009
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Buffalo ny area
Jdc- I hadn't thought of that. Good call. I will be looking at a way to separate the pedal power from electric.
Geek- The deal is, here in New York, it is now legal to motorize a bike with a 250 watt limit electric motor (no gas jobs).
I fully considered a gas powered super- covert (meaning quiet and hidden) but then I thought, I could still use gas power, only, it would supply juice to the electric drive motor. Most little weedwacker motors make about a hp, so even with the losses involved, there should be enough power to easily drive 250 (or more) watts.

I am NOT looking for speed. I ride around 10 mph on my bike, often using the sidewalk. It would be nice to go a tiny bit faster, or take hills easier, or go to work ( weather permitting) without being a sweat-ball when I arrive.
 

motor_head

New Member
Dec 18, 2008
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iowa
nice the electric drives it so your within the guidlines but it's gas so just fill it up no waiting to charge batts prolly last longer than batts too
 

professor

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Oct 14, 2009
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Buffalo ny area
You got it Motor.
Update- After many hours adapting the weed wacker to drive the alternator- the wacker has not enough torque to run the alt. I could not even start the thing with the belt connected.
I have a rain check for the 2.5 hp engine from HF and should be able to pick it up this friday. Only issue is the 23# it weighs! But it will have torque. I am looking at a full up weight of over 70 pounds for the Mongoose with all the drive stuff. Heavy, but no heavier than some electric bikes.
Yes, the engine will be running at all times with varying rpm. The engine and alternator will go on a rack. As for noise level, I will make a muffler and sound attenuate the deal later. It WILL be quiet.

I just ordered a sprocket and attachment to the back wheel. Real unsure about drive ratio, I have 5.2 from the electric scooter to the jackshaft (which is a rear hub from a single speed 20 inch bike with the freewheel side having the scooter sprocket and the other side as small sprocket as I can weld on), the wheel sprocket I ordered is a 44 and the sprocket I welded to the "Jackshaft" is about 2.5 " - maybe 2.5 to one. Can go bigger on the rear sprocket if needed.

I have had a bunch of stuff to do lately (winter preparation-snow tires, rustproofing wife's car with oil/cosmoline........) and will be able to do some more on the bike, especially since rain is forecast fo the next several days.
What is unique to me, is that as far as I know, no one has done this kind of set-up.
If it wasn't for the NY law making 250 watts legal- I would not have attempted it.
If the thing works out, it could be repeated in places like Austrellia (spell?).
 

TheE

New Member
Jun 26, 2009
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Canada
I was reading that a weedwhacker engine goes anywhere from 7.5k-12k RPM wide open. That's a pretty high frequency electrical output!
 

popcornsutton

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Aug 9, 2009
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NY
What is unique to me, is that as far as I know, no one has done this kind of set-up.
If it wasn't for the NY law making 250 watts legal- I would not have attempted it.
If the thing works out, it could be repeated in places like Austrellia (spell?).
I hate to rain on your parade and people here generally avoid being nay sayers, but there's a good reason "no one has ever done this kind of set-up". It's because it just won't work. There's plenty of good reasons car alternators aren't ever used in bicycle setups. They're super inefficient and you can't possibly spin it fast enough with small gas engines to do anything. You're defeating the purpose at every step you take. But on forums like this, every single day, someone comes up with a brainstorm of "hey, what about a car alternator"!! "Hey, I can charge the batteries while I drive"!!! "Hey, I can put magnets on my bike rims and generate electricity while I drive!!" You cannot possibly charge batteries that power an electric motor that powers the bike while the bike is running under that power. If you add a heavy gas engine to charge those batteries, you just added a ton of weight to rob you of any efficiency that you might have gotten in the first place. You seem to be thinking you're coming up with a new invention no one ever thought of. You're not by a long shot. And you can't silence a weedeater motor. They are the loudest of all gas engines. If you DID manage to silence one or another small gas engine, it would mean you blocked most of the air coming out of the exhaust and you'd lose most of your power if it would even run at all. You obviously have money to burn to find out eventually what I say is true, but you'd be much better off to just use a traditional electric bike motor and traditional batteries and be done with it and accept that your range will suck because of what we have available to us. There are plenty of choices of bike motors available to you. There are few choices on batteries. All this stuff about a heavy gas engine turning a car alternator on a bicycle is hogwash and you'll find this out in the end. But on the positive side, you'll have another contraption we can add to the Rube Goldberg archives. And I have no idea what you meant when you topped it all off with the "Austrellia" comment. What does this have to do with motorized bikes in Australia?
 

BarelyAWake

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Jul 21, 2009
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There's a couple of lil differences that sets professor's scheme apart from the dreaded perpetual motion babble.

1: As far as I understand it he's not lookin' for "free" power, he's goin' for more the hybrid setup.

2: He's actually experimenting and building stuff - not just "armchair engineering".

Now - while I'm not sayin' it'll work, but I for one am glad he's trying. One BIG thing he did prove beyond a doubt is that a weed whacker engine doesn't have the cojones to push an alternator!

professor said:
Update- After many hours adapting the weed wacker to drive the alternator- the wacker has not enough torque to run the alt. I could not even start the thing with the belt connected.
That quote alone is worth it's weight in gold. Regardless of what is thought of the project itself - I have massive respect for those that'll break out the tools and try! Who knows? He just might surprise us all! :D
 

professor

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Oct 14, 2009
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Buffalo ny area
Well Popcorn, I already did silence the wacker motor with a muffler I made. It is on the other forum. Went from 90.5 db to around 85. Large diameter tubes = no loss in power.
An alternative to the alternator would be another DC motor, however, that would mean having a clutch on the engine to cut drive to the actual drive motor when you want zero forward movement.

I do not know how locomotives work in detail, but they have a diesel driving a generator which drives the wheels. This is the concept I am after.

I do agree that alternators are not real efficient. They are real durable and inexpensive though.

By the way, I hadn't mentioned, that the only battery on board will be a small 12 volt one to energize the field, switched on with throttle opening. I want to tap off the big power to put charge into the battery while running with some kind of regulator and a diode.
I doubt I will need anywhere near the full 2.5 hp the engine is rated at to run it.

Thank you, Barely awake, for your comment.
 

BarelyAWake

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Jul 21, 2009
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Those big diesel-electrics are far more common than some may know: Diesel-electric transmission - Wikipedia, the free encyclopedia

While a liveaboard I looked into a scale version for my application, the numbers work out great for a slippery displacement hull and a battery bank - the concept goes way back: Elco History They even had fuel gennys onboard with similar thoughts in mind - of course they were steam or naphtha lol

I see yer bike as just yet another scale down. I dunno if it'll work out - the math gets troublesome the smaller a vehicle it is, land vehicles also have variable demand considerations that boats do not (hills and traffic driving).

Yet the tech is proven for what you wanna do - those WWII subs wouldn't have got very far w/o it lol
 

skjjoe

Member
Mar 9, 2009
393
1
18
Boerne Texas
hey professor ive got an old craftsman 500 watt genset in the garage that i tried to get going. but the carb was so jacked up there was no getting it going. and and there are no more parts available.the genset works and ive still got the power panel . it is belt driven and the motor is only a 1 hp. Do you think that might work ? it does have a 12v out put on the power panel
 

professor

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Oct 14, 2009
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Buffalo ny area
The problem is we want 24 volts to the drive motor (or maybe more since some scooters go higher) I guess if you had a 500 watt drive motor and you run it on 12 volts, you will have 250 watts of output. You would be pulling a bit over 22 amps to do it. That is more than house outlets I think

I have sucessfully put different carbs on small engines- especially the Techumseh. I like the carbs with the primer bulb. Main jet is on the side of the bottom plug that holds the bowl on- they get full of junk and stop flowing. Thus, we find free mowers often. A guitar wire or welding tip cleaner and some compressed air fixes them. REAL simple carb.
 

nathandance1996

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Aug 24, 2010
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bognor regis, UK
I was thinking the same, I am building one of these for use in england as you can't strap an engine on a bike, but can use a 250watt motor at 14 years old, why don't you use 2 brushless motors, both same watt rating and voltage and use a small weed eater engine to provide power and use a diode bridge to convert the ac made by the motor (a DC motor makes a good alternator) into DC for the motor to use. also make sure to put a silencer on the engine so you don't have to worry about being pulled over by police.
 

ferball

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Apr 8, 2010
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NH
Why not use a pocket bike motor to run the alternator/generator a ton of clutch option, and some even have electric starters....the combination could be fun....