Gas powered electric motor

Hi all,

I've often thought of getting a gas or electric powered bike to make it easier to get around.

I've had an idea which I assume is not new, but I do need some advice.

I want to use a elation or cyclone 200watt mid-drive kit to provide legal assistance to a bike, and take advantage of the gears.
But I don't want to use battery's as they are expensive. I would prefer to fix a small gas powered motor to the bike which would spin an alternator and provide electricity to drive the electric motor. The motor I'm thinking of is a honda gx25 which is the smallest gas motor that honda make. Details of the motor here : http://engines.honda.com/models/model-detail/gx25 the motor can be purchased here in australia for about 327 dollars : http://www.haughton.com.au/product/engines/dompethor/HO0022.html

Does anyone have any advice as to how I would do this ?
By the way, the motor produces 720watts of power at 7000rpm, so I need a way to limit the amount of power that gets to the motor.

I don't think batteries are more expensive than motor + alternator. Are they? I just paid $47 at hobbyking for 23V and 5Ah of lithium polymer battery (that's 5 miles of range for me...)
And you'll still need a battery or lots of capacitance to ensure the output is steady enough to run the motor controller....
It will be an interesting project though!!!

I have a similar idea on the back burner until I get my current project going, but I think a small gas engine could power an R/C motor to then charge the batteries and increase range. I have thought long about this and if you get it right, it could be a real cool design, it has to be small and light and easily removable from the bike to be applicable. I think maybe a seat post mounted rack with the whole shebang mounted on it and you just plug it in and fire it up when needed... I think it would be super cool for those of us not wanting 50lbs of battery on our bikes that only need that whole thing once in a while. I BET it would be cheaper than the additional batts to get the same range too!

i 've had this idea for a while too, only gx35 or 50, for a 750 or 1000 watt drive. i mentioned it pretty extensively in my first thread about efficiency and hillclimbing. http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=29924

here's the site that got me thinking it was pretty viable...

http://translate.google.com/transla...l=en&safe=off&sa=G&biw=1206&bih=753&prmd=ivns

the one thing i can't figure is the reason why most generators run about 65% efficiency. but even with that, you get about 3600 watts per gallon of gas, which imo makes it pretty comparable to the direct drive gassers. the decreased weight and increased range is what interested me about it.

YERY cool indeed! I was thinking of using an even smaller engine that spins higher RPM and a higher KV motor so I can spin the motor up to maybe 4-5000 RPM and get the 50V of charge power I would need with hopefully 500-1000 watts continuous output. If that can be done, it will WORK! Heck, if you could get it to put out around 2000 watts, you could use it on an electric motorcycle as a range extender!

A series Hybrid always stacks inefficiency.

If you're going to have a gasoline engine on the bike, make it power the bike by a chain/gearbox etc.

This gives you the lowest weight, lowest system complexity, highest efficiency, and best performance.


If you want to do electric, power it by batteries.

LFP, how did i know you were gunna say that, lol... the problem is, then it's a motorized bike (406a) and requires registration, a license, motorcycle helmet, and all that crap. AND, it might be just as efficient, to run the motor at whatever power level you actually needed, instead of whatever rpm the tire rpm dictates. you could go through the gears though, and then the gassers would maybe get closer to what electric is getting, in terms of efficiency.

and whiplash... the RCGF15, imo, is the ideal match, 1500-15000 rpm, 2.1 hp, and 2 lbs. gotta add oil to the fuel though, and i can only imagine what it sounds like, but i was thinking of sacraficing some hp to quiet the exhaust. i got started with the ecycle motorcycle. the original pages or links are gone, but, in a nutshell, it was hybrid, electric motor for 0-12 mph, then a small diesel kicked in. wicked cafe styling, and supposedly 180 mpg, with pretty good 0-60 and top speed (i think around 100).

Yeah, I have a 35something cc pocket bike motor I got for 20$ Maybe that would do it right? Maybe LFP is right just have a gas motor that can come off quickly??

why have it come off? i mean, LFP's right, if you want to bump it up to motor vehicle, running it direct is much less complexity, the weight is less, the cost is less, but i still think the efficiency is going to be close, running the engine for only what you need. i have seen a real hybrid motorized bike, can't remember where, but the guy had it run through a jackshaft setup and through the gears. it was like the ecycle, it'd take off on electric motor, and get you up to speed enough to kick the motor over and gas away, two throttles and everything, lol. the ecycle just had fuel injection that would kick in at 12 mph, but the motor spun any time you were moving iirc. in my setup, i was just thinking the generator would start the motor, and they have electric start blowers and weed eaters now, they just haven't figured out to have the motor recharge the battery that goes with it. won't be long methinks.

The generator will not be much better than 50% eff, even if U could get close to 80% ur still loosing 1/5th the potential energy. A hydraulic drive system w/ an electric motor and ICE(gas to the layman) would more than make up the diff w/ high (<80%) regen braking.

Understanding what potential energy is, would be a great start to this project.

what, like 36,635 watts per gallon? and most generators i've seen are in the 65% range, nearly all of them. at an ICE of 15%, a gen of 65%, that gives us 3572 watts. at 15 wh/mi, that gives us 238 mpge. so, what about all the power you're wasting at cruise, just because the ICE has to spin at that rpm, even though it only needs 1/4 of the power? hydraulic would be similar to going through the gears, allowing the motor to run at an idealic speed as needed, not dictated. and i've not seen too many regen systems capable of any great amount of recovery. i don't think hydraulic is any better than chain, but it does allow for variable motor speed. when you say electric motor and ICE, are you saying parallel hybrid? my thought was series. where the ICE is just an energy source, not a motive source.

Remus said:

By the way, the motor produces 720watts of power at 7000rpm, so I need a way to limit the amount of power that gets to the motor.

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that's an easy one, it's called a throttle, lol. of course, it's not THAT easy, i would think you need to provide the right voltage and amperage as well. the way i was thinking, was to go through a battery. at first i thought, oh, just ship it to the motor, but going through a transformer, or using pwm, would probably have it's own issues. going through the battery probably has issues too, maybe use the battery as some sort of "supplement".

LFP, how did i know you were gunna say that, lol... the problem is, then it's a motorized bike (406a) and requires registration, a license, motorcycle helmet, and all that crap. AND, it might be just as efficient, to run the motor at whatever power level you actually needed, instead of whatever rpm the tire rpm dictates. you could go through the gears though, and then the gassers would maybe get closer to what electric is getting, in terms of efficiency.

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Personally I think if you are riding around with a gas powered motor going, regardless of whether it is connected to a drive train, you are going to get pulled over by the police, and you are going to get booked (in Australia this would be the case guaranteed anyway). You might get the charges dropped when you go to court (after proving that you were riding around with a running gas engine, not actually connected to your drive train), but what a hassle to go through, when you can avoid all that to begin with, by using a battery and an electric motor.

The whole reason the cops (here in Australia anyway) don't bother you with an Ebike (regardless of its wattage), is that they can't hear it, and it just doesn't bother them or attract their attention (unless you are pulling 80km/h weaving through cars). The minute you have a noisy gas engine running on your bike, the Po will be on you like honey to a bee. You will be standing there arguing about how its just a motor connected to an alternator, and the Po man is just going to want you to take your noisy attention attracting motor away, and he will book you (leaving it to you to attend court and argue your case).

Maybe cops in the States are more interested in technical legal definitions than Aussie cops, but basically Aussie cops just want to "keep the peace" at least by appearance, and a guy with a piston firing engine attached to his bike is not meeting that criteria.

This is one of the reasons I am not into RC bikes, I think so many parts of them are attractive, but that whiny jet noise (which sounds cool) would have my local Po all over you like a rash. But my HS35 makes virtually no noise at all, so the cops couldn't care less.

Wouldn't an alternator and ICE engine cost more than even 20S of Lipo? 20S of Lipo on any hub motor will get you up pretty much any hill, with no noise. For me the tradeoff in desiging a bike is finding the absolute limit of how much batteries I can fit, without adversely affecting handling, or attracting too much attention (by looking clearly unlike a bike), the motor/stator/hybrid would fail both those tests immediately I would have thought.

My two cents.

i agree, make a lot of noise, and you're gunna get looked at. my philosophy there was that an insane muffler might be in order. i'd even give up some hp to do it. and ya, it'd be a tough explanation to dumbass cops, who just want to make a buck and a mark. the reason i'm looking at it is hillclimbing, but also, and maybe more importantly, range. i'm looking at keeping at 20, so i won't be weaving through cars, lol, unless there's some gridlock. 20s would be what, 370 watts? not a lot range in the mountains. 60s might do it, but now we're talking about $350. that's about the breakeven point i think. gx35 is $250, little motor and controller about $100. and if i want to do even more range, it's like an extra 2 pounds of gas, quick, and available on the road.

When I say "20S" I mean 20S of Lipo, so 84v. So at say 40amp battery, that is 3,360W. Range is just a question of AH/how many in parralell. But I run 20 ah of Lipo, and I have never wanted for more range (if I did, i would just add it).

I guess what I mean is, I agree with the other posters who say if you are going to add a gas engine, just make it a gas bike. The argument that you will then have legal/compliance problems is bogus, because you are still going to have those same problems with a hybrid, even if you are able to eventually argue your way out of them. Spending months to get before a magistrate to argue that your hybrid bike is not in fact a ICE bike - despite the fact it was noisily exhausting its way down the road (which you could still possibly lose - the law is haphazard at best), is in my opinion, not an ideal path to go down.

Just like other disciplines, where there is pure theory, then what we see in the world, the law is no different, there is what is technically the "law" and then how it is applied in the real world. The real world is that if you go down the street with a 2 or 4 stroke engine wailing away on your push bike, you will get pulled over by the boys in blue and ticketed. Meanwhile, a guy with 5-10 times as much power in a silent electric bike will glide straight past..... The several hundred dollars difference between a motor/generator and a bunch of Lipo, will soon be made up for with court and lawyers fees.

well, for one, 20s lipo is 74v. secondly, 3360 watts of lipo, is about 52 pounds of battery. i was only looking at needing about a third of that, 17.5 pounds. not horrible. thirdly, range is not a question of Ah, it's a question of watts, Ah is only half the equation. i understand what you're meaning though, that, adding batteries, in parallel, adds to your range. i just find it inadequate, it makes someone guess what voltage you're running at, not to mention, it's not always constant. as for gas bike, that's motor vehicle, and would be prohibited on the trails i'm looking at. what part of extensive muffler didn't you catch? i wouldn't go wailin anywhere. i'm looking at lipo, it's the only simple solution, i'm just not ruling out the possibility of hybrid. and the hybrid would have a small compliment of lipo anyway, and 10s of 2Ah 15C would be plenty to actually propel the bike with the ICE off, to prove that it's not powered by the ICE. not that i want to be proving it, hence extensive muffling (not to mention spark arrestor). as for courts, traffic law is immediately scheduled at the time of ticket here, about 3 weeks in the future.

as for real world vs theory, it's certainly worth finding out. lose, go to lipo, win, good chance of not being harassed again. not to mention maybe enlightening people to the possibilities, i think that's a good thing. if people just stick their heads in the sand, there's 0% chance of getting what you want, or of anything changing. me, i like change.

I like the idea, but I think it would be more suitable on an electric car, where plug in charging is limited. Case in point is I C E is most efficient at set load and R P M , even better if design to do so. Plus I C E is happier running continuously and will last longer say 24/7 !! ( the dream set up would be to recoup heat from exhaust with a steam or steerling engine or whatever ?? ) This seems possible with an engine that runs at said load and R P M all the time.

Rough math and bad typing L O L: Lets say the daily commute needs 72000 watt hours,. So a 3000 watt hours Genset would be required, and any plug In's would be more gravy. Not to mention this would clearly solve the battery and cabin heat issues in cold climates L O L !!

Now I just need a big shop ya ya ya!!

Hey thanks for the dream page

Around here, just having the engine on there running, regardless of it powering the wheel directly or not, would get you noticed by people a lot more than a nice silent battery-powered electric system.

In some places, I would bet you a good dinner that it's not going to matter a whit to the legal system whether the gas motor is directly connected to the wheel or not, but will still cause you legal grief if you are stopped (probably the stop would happen because of the noise, even if muffled). I'd guess that the most likely complication is that you would be told that it doesnt' fit *any* vehicle classification that's allowed on the road, and thus can't be used at all, with or without a registration or license or whatever. At worst, it might be classified as whatever vehicle type uses a gas engine the size of your generator engine, and get you the ticket(s) for that violation.


But my own take on it is that unless you need it for extra range, it's probably going to be heavier, more costly, and more physically complex to setup the generator and engine on there, just to indirectly drive the electric motor, than to just use a battery to run it, depending on the range you need.

At 200W and the low speeds dictated by places that limit to that, it doesnt' take much of a battery to go quite a ways.

well, for one, 20s lipo is 74v. secondly, 3360 watts of lipo, is about 52 pounds of battery. i was only looking at needing about a third of that, 17.5 pounds. not horrible. thirdly, range is not a question of Ah, it's a question of watts,

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I am not being confrontational nor having a go, but pretty much everything in that quote is wrong.

20S lipo is 74 nominal, but when fully charged (ie 4.2v per cell) is 84v.

What do you mean by "3360 watts of Lipo"? That doesn't even make sense. I was just giving an example, that on a hub motor with a 40amp controller, you would be getting that as power, which will get you up pretty much any hill with the right motor. Where do you calculate that 20S of Lipo weighs 52 pounds? At 666g of 5ah 5S lipo, you could have a 5ah 20S Lipo battery for 2664g (ie 5.87 pounds). And what do you mean by range is not a question of AH, it's a question of watts?. THat is basically like posing a problem that says "John's bike has a motor that produces 1000W of power, Steve's bike has a battery with 20ah capacity, who will go the furthest?

You'd need to smoke quite a few bongs to answer that question.....

EDIT: On reflection - I presume when you say "watts" you mean "watt hours", but the whole point I was making in my post, was that 20S @ 40 amps will deliver enough power to get you anywhere, and then I was making the personal (Subjective to my situation) point that 20ah has always been fine range wise for me (of course, you might have a 100km commute for all I know), if we agree on what power is needed (ie, how many watts) (and in our case we were discussing 20S@40amps), then the AH of the battery is the relevant question for range.

i presume you mean bong HITS. ok, put the bong down, and step away from the brownies, lol.

yes, 74v is nominal, not surface charge. how long are you AT 4.2? maybe the first 5-10% of the ride? do you compute your pack wattage capacity by 4.2? no. you multiply Ah by nominal v. just don't presume that everyone is running 20s, is all i'm saying. why do think people use Wh/mi? instead of Ah/mi. jesus, i feel like i'm trying to convince someone to use imperial over metric or something.

yes, watt hours, i've never heard anyone here use watt minutes, or watt seconds, so i thought that would be pretty safe to assume, when referring to pack capacity (but i suppose if you take C into account, it could matter, with respect to output capacity, instead of total capacity). and it doesn't really matter if you use 15Ah @ 48v, or 20Ah @ 36v, you're still using 720 watts, you're not going further, just because you have a bigger Ah rating, if you have the same Wh's. my point, is that amperage AND voltage (which gives you watts), are BOTH relevant. and "pretty much any hill" IS subjective (i have some 20% grades here), and, not taking into account weight (as in, a bit of gear) or road surface (some of it access roads). and one of my trips is more like 35 miles (60 km) roundtrip, and pretty consistent 5% grade on the way there (no gear, real road).

as for weight, why do you all of a sudden change to 5Ah? 40Ah, by your calc, would be, 47 pounds. 47,52, maybe just the difference between something like turnigy and zippy, or 15C and 30C.

"20S @ 40 amps will deliver enough power to get you anywhere". i presume you meant 40 Ah. as for john and steve, it's more like john has a 1000 watts, and steve has 20Ah, who goes further. since you don't know how many volts steve has, we can't figure out how far he'll go. but i CAN figure, if say, 20 mph requires 400 watts (subjectively), john will go 50 miles.

sorry if i AM a little confrontational, it's just my nature, but i'm working on it, lol

@ptd, I hold an AAS in automation robotics. The only thing used in industry more efficient than hydraulics, that I am aware of, would be the AC transformer. Yes, regen braking via electrons is very inefficient relative to charging a hydraulic accumulator.

Personally, I don't see why capacitors aren't used to store electrons rather than the batt. Don't they have a higher cycle rate, and hold more volts? Caps can also be used to store AC power, kinda like a battery stores DC, but alot less.

mat h physics said:

@ptd, I hold an AAS in automation robotics. The only thing used in industry more efficient than hydraulics, that I am aware of, would be the AC transformer. Yes, regen braking via electrons is very inefficient relative to charging a hydraulic accumulator.

Personally, I don't see why capacitors aren't used to store electrons rather than the batt. Don't they have a higher cycle rate, and hold more volts? Caps can also be used to store AC power, kinda like a battery stores DC, but alot less.

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is that like an almost associate of science? i got one of those, lol. ok, looked it up. applied. so, you had a better idea of what you wanted to do instead of just ge, and wanted a quick start in the game. same here. all the calc, started phys and chem. good start, but you should put it to use at a 4 yr institution. that's where all the real education happens.

as for hydraulic, i was saying it IS efficient. my point was that chain is like 96%-98%, not too much room for improvement, and the chain is simpler, lighter, and cheaper. i DID like hydraulics on the old rokon though, kickass torque iirc.

i too like the thought of ultracaps, but not for permanent power storage, their power to weight ratio is horrid. i thought that with deceleration, you'd want to cut power to the electric motor, but the ICE would produce till shutoff. where does the power go. you could stick it in the battery, but it might be at higher than approved charge ratings, damaging the battery. so, ultracap, takes it quick, and feeds it to the battery at the right rate, or back to the electric motor for sudden acceleration, or back to the generator, to start the ICE again. crazy ass controller is what it's looking like.

ps, i've always heard that transformers were bad at efficiency. have there been some new developments somewhere?

I think to get optimal efficiency we ought to (instead of solar) plant seeds with oil burning fuel hogs that cost hundreds of thousands of dollars, then fertilize said seeds with same equipment using fertilizer made from oil burning factories and shipped via oil burning vehicles to the farm, then wait for the sun/rain to grow, then harvest using oil burning fuel hogs (see above), then ship finished product (corn) via oil burning vehicles to oil burning ethanol plants, then process said corn with oil burning processes to get ethanol, then ship said ethanol to various fuel stations via oil burning fuel hogs, then drive our oil burning fuel hogs to said stations, then putting the fuel to the pavement. That is the most efficient way. Or you could just minimize inefficiencies by not stacking inefficient systems. Sorry, I got a little carried away.

ptd,
you need to rationalise your thinking a bit.
Your "hybrid" bike will at the least ride you into several interesting discussions with traffic cops and park rangers etc. Most likely you will spend considerable time effort and money arguing your view in court,..... and VERY likely losing .
An ICE motorized bike is a ICE powered bike in the eyes of the Aussie law, no matter how its connected to the wheels.
A muffler will not "silence" that motor, most of the residual sound is emitted from the cylinder and crankcase walls , since the manufacturers have pretty much optimized the exhaust mufflers for domestic use.
Dont assume every one is thinking the same as you when describing batteries..
... a 20s, 40A battery is very different to a 20s, 40Ahr battery. and capacity is best stated a WHrs,..not Watts or Ahrs.
You are not the first ( by a large degree) to consider a hybrid / range extender Ebike, but you should consider the possible reasons why so few have been actually built ?