How much horsepower?

[Reffoxel]

Anyone have any information on how much hp it takes to spin the alternator?
I'm researching a project that uses a motorcycle as a powerplant. However the motorcycle alternator/stator does not produce enough power to run the accessories I want/need to have. So was researching the feasibility of having the motorcycle alternator/stator just run an electric motor, and have the electric motor run an automotive alternator. So need to know how much hp it takes to run the automotive alternator, so that I know what sized electric motor I'd need, to determine if the motorcycle alternator/stator can meet the demand. If there's any EE's out there that might be able to give me any advice I'd appreciate it. I'm going to find out tomorrow what my bikes alternator/stator puts out. I think it's like 22 amps but I don't know if it's 6 or 12 volts.

 

[smo0f]

Okay here is what you do. First, measure the diameter of the crank shaft or the drive pulley, and alternator pulley. Then divide the crank shaft puelly diam by the alt. pulley diam. The result is your engine to alternator rpm ratio. A regular/normal ratio is about 2.5 to 1. so say your crank shaft pulley is 7 inches and your alternator pulley is 2.75 inches, you divide 7 by 2.75 and you get 2.54 : 1, engine rpm to alternator rpm. so if the engine in this case was 2000 rpm, then your alternator is goin at 5080 rpm. so if you're relating to a car, the avg idle speed is 800 rpm. So at idle, most alternators are spinning at 2000rpm. hope this helps.

 

[Reffoxel]

guess I misstated myself. I guess what I meant was how much torque does it take to spin the alternator. But thanks that'll help down the road too.

 

[smo0f]

torque in ft/lbs?

 

[Reffoxel]

I guess or oz/in or nm

 

[smo0f]

( torque * 2 * pi * rpms) / minute

is your forumla for torque. pi being 3.142

 

[smo0f]

update?

 

[Puckpimp71]

hmmm I was worried that I wasn't going to learn anything new today. +rep for you.

+rep's not working for me...??? I owe you one.

 

[smo0f]

hah, dont worry, rep doesnt work for anyone

 

[Reffoxel]

can't give an update. still trying to figure out how much force it takes to spin the alternator. I don't think formula's are going to help me. I don't know how difficult it is to spin the alternator.

 

[smo0f]

you're not really good at explaining things so it'll be a lot harder for you to get a question. find out exactly what you are trying to look for first, then ask questions

 

[protegeric]

eeeeee.... sounds kinda prissy. HAHA! I said prissy! WOO @ everyone...

you're not really good at explaining things so it'll be a lot harder for you to get a question. find out exactly what you are trying to look for first, then ask questions

 

[Reffoxel]

Ok let me phrase it this way, How much hp does an alternator rob from the engine. Does that give you a better idea of what I'm looking for?

 

[protegeric]

I know what you`re askin` but I don`t know how the hell you`re gonna figure it out! Anyway, why not just say it`s gonna take 3 HP and just make an overestimated guess? You ask hard questions... Make my brain hurt.

can't give an update. still trying to figure out how much force it takes to spin the alternator. I don't think formula's are going to help me. I don't know how difficult it is to spin the alternator.

 

[protegeric]

I have an idea though. Call a reputable alternator manufacturer or email them and ask??? There`s gotta be one out there that claims they have the most efficient or somehtin`.

Ok let me phrase it this way, How much hp does an alternator rob from the engine. Does that give you a better idea of what I'm looking for?

 

[smo0f]

why dont you dyno the bike with and without an alternator.....omg, that's like, an idea.

 

[protegeric]

Yeah, but is that easy enuff to do? Ahh... I don`t even really know. I would call a manufacturer or make an overestimated guess... I`ll ask my dad too.

why dont you dyno the bike with and without an alternator.....omg, that's like, an idea.

 

[65racecoupe]

1 or 2 hp maybe

 

[flat_black]

So was researching the feasibility of having the motorcycle alternator/stator just run an electric motor, and have the electric motor run an automotive alternator.

Well, in this case, you would lose power... In order to develop more power, you would have to have a higher amperage alternator, not try and produce more power by using an electric motor to turn a larger alternator, because when it comes down to it, you'll just be wasting electrical current. The alternator will burn out if you have it drawing at max constantly... You could overdrive the alternator, by having a larger crank pulley, or a smaller alternator pulley, but that may or may not work out well for you.

It's a simple concept that you're not going to invent a perpetual energy source. =) Hence why developing more energy by using more energy to run a motor to create MORE energy isn't going to work.

Out of curiosity, can you give us more details on the project on which you're working? Some folks here could try and give you some ideas if you can tell us that.

 

[Reffoxel]

Not trying to create a perpetual energy source. My problem is this. I'm researching building an enclosed 3 wheeler (2f1b) whose powerplant/driveline is a motorcycle. The alternator for the motorcycle is not belt driven, it's geardriven off the crank or idle shaft in the tranny(depending on manufacturer) and doesn't produce the voltage and amps to power some of the accessories I feel are needed for this project. They don't make larger amperage alternators for the bike I have. So was thinking to use the alternator on the bike to drive just an electric motor which could then drive a higher capacity automotive alternator. So gas engine runs small alternator, small alternator powers electric motor which powers larger alternator giving me the power to run bike electronics, ignition and the accessories like 12 volt a/c system, radio, backup motor, etc. btw this is not what refered to as perpetual energy source. Perpetual energy source is after an initial input of energy the device is self sustaining, what I'm talking about requires constant energy input from the gas engine, I'm just trying to ramp up the amount of electrical energy so I can run more stuff.


But debate on this, I believe is basically going to be mute. Rather than spend lots of money trying to make what I have work, I'm probably going to sell the bike I have and use the money to buy a used goldwing which, it is possible to attach a pully system to run a/c compressor and automotive alternator, plus the 90 and newer models had built in electic reverse (atleast that's what the honda guys said at the cycleshop).

So thanks guys for your help. But figure not much point in reinventing the wheel when there is already something out there that'll do the job. Just didn't want to go through the hassle of selling my bike and buying different one.

Well, in this case, you would lose power... In order to develop more power, you would have to have a higher amperage alternator, not try and produce more power by using an electric motor to turn a larger alternator, because when it comes down to it, you'll just be wasting electrical current. The alternator will burn out if you have it drawing at max constantly... You could overdrive the alternator, by having a larger crank pulley, or a smaller alternator pulley, but that may or may not work out well for you.

It's a simple concept that you're not going to invent a perpetual energy source. =) Hence why developing more energy by using more energy to run a motor to create MORE energy isn't going to work.

Out of curiosity, can you give us more details on the project on which you're working? Some folks here could try and give you some ideas if you can tell us that.