Author Topic: Wind powered car  (Read 3408 times)

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Offline karpa-alTopic starter

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Wind powered car
« on: May 03, 2011, 03:08:02 PM »
I have project to do about wind powered car , to be specific it's something like this :
On the front i'll place a propeller and on the other end of the axle a gear . the gear will spin a dc motor that will produce 6-9- volt's next with parralel connected capacitors the voltage will charge a battery.
From the battery the voltage will power on (one or two) DC motor that turns the wheels.And the car will always run against the wind, this feature will be enabled with rudder that will steer the front wheels.
Can anybody help me how to start it because i'm not familiar with generator's (i think it can be a dc motor) and gear systems (the steering system is not a problem because i'm going to do it on a toy (dodge viper) that already has a steering system ).
The deadline for the project is in one week so i need your HELP!!!
thanks in advance!!!!!!!!!!

Offline corrado33

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Re: Wind powered car
« Reply #1 on: May 03, 2011, 03:15:54 PM »
I'd expect there to be drivetrain losses, so you're going to lose energy.  It's going to have to charge for a bit, then move, then charge for a bit, then move. 

And you're probably gunna catch some flak for having us do YOUR homework. 

Offline Soeren

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Re: Wind powered car
« Reply #2 on: May 03, 2011, 05:49:22 PM »
I have project to do about wind powered car , to be specific it's something like this :
On the front i'll place a propeller and on the other end of the axle a gear . the gear will spin a dc motor that will produce 6-9- volt's next with parralel connected capacitors the voltage will charge a battery.
From the battery the voltage will power on (one or two) DC motor that turns the wheels.And the car will always run against the wind, [...]

The deadline for the project is in one week so i need your HELP!!!
Sorry, but it takes a wee bit more than a week to make a working over-unity device (something like forever and a day actually).

Study the laws of thermodynamics for a while and then consider the losses you have to overcome...
Propellor to motor loss
Motor internal loss
Charging loss (charging a battery takes more than 150% of the power you can use)
Motor losses once more
Coupling from motor to wheels
Friction between wheels and the surface
Wind resistance


Just mount a sail on the car and turn it 180°.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Aberg098

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Re: Wind powered car
« Reply #3 on: May 04, 2011, 06:46:42 AM »
try googling "sail buggy". There's definately something to those, however, the Wile E. Coyote idea of blowing into your own sail doesn't work...

While I think that your "energy recovery" idea is an interesting learning experience, I don't think you'd be increasing your efficiency very much, likely actually decreasing it... You should try to see if running your propeller makes your toy car go any further or not. This is what Soeren is referring to as thermodynamics, energy put in the system vs energy taken out of the system.

Now addressing your motors and gear question, since you ARE on a tight deadline, Try making everything out of LEGO. They have DC motors that you can hook up wheels to directly and quickly. Failing that, cheap DC motors with wheels glued or attached directly to them. This is simple enough to work and shouldn't take too long to make.

Good luck, keep us apprised of your results  ;)

Offline Billy

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Re: Wind powered car
« Reply #4 on: May 09, 2011, 02:23:40 PM »
Sarcastic comments about the thermo and physics aside, it sounds like a fun project.
I assume the teacher will provide a strong wind source such as a large fan.

Why do all the electrical conversion? Why not just use gearing from the propeller to the drive wheel. A 100:1 ratio for starters may work.

If you're set on using generator/motor combination, I suggest you make sure your drive wheel uses a geared motor with a very high ratio.

The teacher should tell you now what the wind speed will be, allowing you get a feel for how quickly the propeller can spin. This will allow you to determine the maximum voltage it will produce. Then choose a driver motor that runs at less than 20% of that voltage. Current generated by the propeller will cause the propeller to slow, so the no load speed will be MUCH higher than the speed when the circuit is connected. Of course I haven't seen the propeller or anything else you're talking about so I taking stabs at how to make your initial setup.

Remember of course, the teacher is hopefully less interested in the performance of the result than they are in the process of how you approached it. I have to trust that you will credit any ideas taken from this group. Of course, if you decide not to credit, then that's on you.

 

Offline karpa-alTopic starter

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Re: Wind powered car
« Reply #5 on: May 09, 2011, 03:05:00 PM »
There will be  notation that you guys were helping me  ;) .And i must do it with a generator because this project is a subtopic of "electro-energetic devices". And thanks a lot for your advices.
the chassis for this vehicle is from this car I'm using  6V 300mA dc motor for the rear wheel's but i must find a proper generator to supply the dc motor

Offline Billy

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Re: Wind powered car
« Reply #6 on: May 09, 2011, 06:53:25 PM »
I'm using  6V 300mA dc motor for the rear wheel's but i must find a proper generator to supply the dc motor

Have you considered designing from the propeller end first with the drive motor and gearing chosen last? The wind speed and propeller will determine how much power you can get from the wind. That wind will produce a certain amount of force on the car, of which the drive motor must be able to overcome.  The amount of power from the propeller will be modest, and a heavy amount of gearing is likely required to get the car to move forward at all.  If you start with the stock motor/gear combo that came with the car, you may find yourself with a power train that can't overcome the force of the wind.

And to all the doubters, sail boats can sail into the wind, I see no reason this car can't.

Offline knossos

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Re: Wind powered car
« Reply #7 on: May 09, 2011, 07:53:13 PM »
Technically, boats don't sail into the wind, they sail close hauled or tack into the wind.
"Never regret thy fall,
O Icarus of the fearless flight
For the greatest tragedy of them all
Is never to feel the burning light."
 
— Oscar Wilde

Offline karpa-alTopic starter

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Re: Wind powered car
« Reply #8 on: May 10, 2011, 12:02:55 PM »
no no in this car was no motor or something it's more like an ornament.I've made some modifications to the first design, there will be no battery so if there is wind the car will move ,the propeler and the motor will move for 360 degrees to catch more wind and i must change the steering system the be independent. but still i must find proper generator if you have any ideas would greatly help me. the propeller will be the same as at cpu cooler
thanks in advance !

p.c. can anybody tell me how to calculate if this is a real car and with 150 kg of weight and there is a wind with 5m/s velocity with what speed will move ?
« Last Edit: May 10, 2011, 12:05:03 PM by karpa-al »

Offline Soeren

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Re: Wind powered car
« Reply #9 on: May 10, 2011, 09:31:52 PM »
Hi,

Sarcastic comments about the thermo and physics aside, it sounds like a fun project.

Too bad ignoring the laws of physic don't make them go away.


I assume the teacher will provide a strong wind source such as a large fan.

No matter how strong a wind, a propellor will produce less power than it brakes.


Why do all the electrical conversion? Why not just use gearing from the propeller to the drive wheel. A 100:1 ratio for starters may work.

No it won't and I already stated why.


Remember of course, the teacher is hopefully less interested in the performance of the result than they are in the process of how you approached it.

To put it squarely, his teacher is either an ignorant fool or a closet sadist.


The wind speed and propeller will determine how much power you can get from the wind.

But as mentioned, it will be less than its braking effect.


If you start with the stock motor/gear combo that came with the car, you may find yourself with a power train that can't overcome the force of the wind.

Don't know whether to laugh or cry  :o


And to all the doubters, sail boats can sail into the wind, I see no reason this car can't.

You not seeing it doesn't really change the laws of physics and no, sailboats cannot sail against the wind, they can do what directly translated from Danish means "crossing against the wind" a sort of criss-cross or zig-zag movement where you're always at an angle to the wind - more at http://www.physlink.com/education/askexperts/ae438.cfm if you care for some insight.

Besides, I'm not doubting anything at all. I simply know that a propellor will see the wind resistance at the area of the circle the prop tips describe and that will be more than the output to the shaft, then there's the wind resistance of the car itself (generating no power at all, just braking further), then there's efficiency losses each time you transfer/mesh and there's wheel friction.
To be able to just hold a given position against the wind would require an efficiency of 100%, but at least the wheel friction works in both directions.


Youthful optimism is good, but you need to pair it with a bit of knowledge to make it work for you - as always... Google will do wonders for those that wanna learn, instead of just guess.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Soeren

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Re: Wind powered car
« Reply #10 on: May 10, 2011, 10:04:12 PM »
Hi,

[...] the propeller will be the same as at cpu cooler
Oh oh, even less efficiency that a proper propellor.
Your only hope of going against the wind is to brake the car somehow and use the wind power to charge a capacitor for a while and then move a (very) short bit ahead and repeat.


p.c. can anybody tell me how to calculate if this is a real car and with 150 kg of weight and there is a wind with 5m/s velocity with what speed will move ?
A real car is much heavier, but if anything, it will go backwards.
But you cannot calculate anything without knowing all the factors - will the propellor still be a CPU fan or...?

5m/s is not very windy by the way - it's the speed where a Vertical Axis Wind Turbine (VAWT) is just beginning to produce a little output.

If I were you, I'd have a serious sit down with the teacher, where you ask if he knows the penalty for trying to break the laws of physics  ;D

But if you insist on calculating, the things you need to consider are:
Positives...
- The power output from the propellor

Negatives...
- Air resistance of car
- The braking effect at the given wind speed on a cicular plate the size of the propellor.
- Efficiency of propellor
- Efficiency of generator
- Efficiency of each time you transfer the power from one axle to another or mesh a set of gears
- Friction of wheels against the pavement
- Friction in bearings
- Efficiency of motor
(All efficiencies will be less than 100%)

You could spend a lot of time Googling for formulas, but you don't need to - the fact that the total efficiency is less than 100% means that it won't move forward, no matter its size, design or the speed of the wind (I assume that it's clear to you that with zero wind, it won't move and more wind equals more braking -  at some point it will go backwards)
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Billy

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Re: Wind powered car
« Reply #11 on: May 11, 2011, 02:04:52 PM »

Sarcastic comments about the thermo and physics aside, it sounds like a fun project.

Too bad ignoring the laws of physic don't make them go away.


Reading your other posts on this board it's clear you know a good deal about electronics, but on this post you rushed to judgement and electronics do not equal physics.  I had assumed the comments about unity were in jest, or from a misunderstanding that there wouldn't be a wind source provided. But perhaps it's caused by a lack of understanding.

The propeller will take power from the wind. That power can be used to move anything, including the propeller, against any level of friction or force.

Since I think you're concerned about conservation of energy, think of it this way:

The wind has two effects on the propeller.
 - One is drag that will push the car in reverse.
 - One causes the propeller to spin and has little net effect on the car.

The distance part of the spinning propeller is key, it has a large distance per time as it goes around-and-around and this is where the power needed to move the car comes from.

So we should all agree the spinning propeller provides a source of power.

Given that Power > 0
Power = Energy / time -- power from propeller provides limited amount of energy per second
Energy = Force * distance -- that energy can be used to move the car a distance against the wind

Power = (Force * distance) / time

We can assume Force is fixed in this case by drag on the car.

Power = Force * (distance/time)
Power = Force * velocity -- transferring the propeller power to the wheels allows to push against a force with a velocity

Velocity = power / force  -- velocity can be determined with simple algebra

Power is greater than zero -- we already determined the propeller provides at lease some power
Force is fixed -- it doesn't matter how high the force is

Velocity is greater than zero - the car is moving against the wind. NOTE: yes I know that moving into the wind will increase the force and a proper treatment will require differential equations, but the treatment here is enough to explain the point.

I have a degree in physics so don't need to google this, but on your prompting I did google it and found this:

Wind powered vehicle

Offline karpa-alTopic starter

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Re: Wind powered car
« Reply #12 on: May 11, 2011, 02:49:07 PM »
Thank's for all your effort i really appreciate it, not to be wrongly understood  i did some changes , the car will move in straight line but the propeller  and generator will be high just like on the video and they will move 360 degrees with help of a rudder , and it will be always guided to catch more wind but the car will move regardless of the direction of the wind.
I will resolve all my problems but can anybody tell me where can i find dc motor that will produce 6V and approximately 300 mA . I've founded but the guy in the shop told me that i will gain 6V but not 300mA he said to me that there will be only 100-150 mA , so i thought that i can use the propeller with gear that will be with ratio 10:1 or 1 turn on the propeller=10 turns on DC motors and with a pair of diodes will prevent the currents to go from one engine to another, so i will have 6V and approximately 300 mA.A powerfull compressor will produce the wind so when i'll present the project i'll make sure that the wind will only hit the propeller and i did some calculations and i think that the propeller will spin with 200 turn's in minute so the motors will turn with 2000 and i think that that is enough.

Thanks!!!

Offline Billy

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Re: Wind powered car
« Reply #13 on: May 11, 2011, 05:20:58 PM »
the guy in the shop told me that i will gain 6V but not 300mA he said to me that there will be only 100-150 mA , so i thought that i can use the propeller with gear that will be with ratio 10:1 or 1 turn on the propeller

If the motor is rated 300mA, it will still run at 150mA if the load is not too stiff. Try it and see what happens.

Offline Soeren

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Re: Wind powered car
« Reply #14 on: May 12, 2011, 08:07:17 AM »
Hi,

Reading your other posts on this board it's clear you know a good deal about electronics, but on this post you rushed to judgement and electronics do not equal physics.  I had assumed the comments about unity were in jest, or from a misunderstanding that there wouldn't be a wind source provided. But perhaps it's caused by a lack of understanding.

It seems that about 4 or 5 years ago, some "wind institute" (or what it's called) challenged engineering students to compete in making wind cars and my local uni has been participating.
Before that time, I don't think anyone believed it to be possible, but...


The propeller will take power from the wind. That power can be used to move anything, including the propeller, against any level of friction or force.

Since I think you're concerned about conservation of energy, think of it this way:

The wind has two effects on the propeller.
 - One is drag that will push the car in reverse.
 - One causes the propeller to spin and has little net effect on the car.

The distance part of the spinning propeller is key, it has a large distance per time as it goes around-and-around and this is where the power needed to move the car comes from.

So we should all agree the spinning propeller provides a source of power.

Given that Power > 0
Power = Energy / time -- power from propeller provides limited amount of energy per second
Energy = Force * distance -- that energy can be used to move the car a distance against the wind

Power = (Force * distance) / time

We can assume Force is fixed in this case by drag on the car.

Power = Force * (distance/time)
Power = Force * velocity -- transferring the propeller power to the wheels allows to push against a force with a velocity

Velocity = power / force  -- velocity can be determined with simple algebra

Power is greater than zero -- we already determined the propeller provides at lease some power
Force is fixed -- it doesn't matter how high the force is

Velocity is greater than zero - the car is moving against the wind. NOTE: yes I know that moving into the wind will increase the force and a proper treatment will require differential equations, but the treatment here is enough to explain the point.

This explanation is lacking badly I think.You leave out the fact that drag is so much more than a little bit of drag on the vehicle and that there is inertia to overcome.
From what you wrote, a child can push a full size tank.

The wind driven racers is a far cry from what karpa-al wants to construct.
In these non-smoking days it's probably not PC to call their hulls cigar shaped, so let's just say that they resembles a womans "personal relaxation device" for aerodynamic reasons. Each bit involved is carefully designed and materials selected for low weight and to minimize aerodynamic drag. the blades of the propellors are made very narrow (again to reduce drag) and with lift to enable them to go faster than the wind speed. Another crucial thing is, that the power from the propellor is coupled to the wheels as directly as possible (i.e. only one meshing loss) and the wheels are made with the least possible amount of rolling resistance.
And there is a a team of students (almost having their engineering degrees) and their professors, working in groups on each aspect of the cars separately.
These ultra light weight "racers" are push started to overcome inertia and the speeds resulting from the enormous amount of work and expensive materials, is bordering on "extremely embarrassing" with people walking (or even crawling) faster in low winds (if they run at all) and in strong winds, still much slower than a very casual bicycle ride.


Given karpa-al's setup (toy car/inefficient CPU cooling fan) the drag, the rolling resistance and the conversion losses being huge compared, I still believe that he'll have no success in this.

Do you honestly believe he can succeed?


I firmly believe that students should get tasks that enable them the experience of success, as this is the motivator for further interest. So, encouraging with a "try it, it might work" is counter productive IMO and his teacher really ought to give him the full facts (and help him along), but so many teachers these days apparently expects their students to get the help they need from places like this - Tar & Feathers is too good a treatment for such uncommitted teachers.


I have a degree in physics so don't need to google this, but on your prompting I did google it and found this:
[Snip URL]

Do you really think that it resembles what karpa-al is going towards?

According to what you wrote, even a tiny fan should be able to move a loaded truck and while that would be nice, I think that we can agree that it is a wee bit optimistic claiming that, so you gotta be able to see that there's errors and omissions sprinkled into your post.

(For some reason, this tread reminds me of all the optimists that wanna charge a battery from an inverter fed from the battery - while it supplies power to a load as well. They usually gets aggressive beyond reason while you point out that it cannot be done).


If you have a degree in physics (which can be so many things) and still ignores the laws of nature, what kind of message do you think it sends?

Well, you ought to know a bit of statistics I suppose so...
In each graduating class, a few will be at or near the average.
Around half would be above average.
Around half will be below average.

It's the latter group that troubles me, as they're the ones that makes the most errors that may influence other peoples health or even life. Which group were you in?


Please don't keep ignoring the laws of physics, it's not all that reassuring.


Alternative energy can be a good thing, but some are just too tedious...

Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Razor Concepts

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Re: Wind powered car
« Reply #15 on: May 12, 2011, 10:23:53 AM »

Well, you ought to know a bit of statistics I suppose so...
In each graduating class, a few will be at or near the average.
Around half would be above average.
Around half will be below average.

It's the latter group that troubles me, as they're the ones that makes the most errors that may influence other peoples health or even life. Which group were you in?

I'm pretty sure on average, more people are above average than are below average. I mean, it's crazy to consider that half the people are below and the other half are above.


Offline Billy

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Re: Wind powered car
« Reply #16 on: May 12, 2011, 10:27:38 AM »
Sorry, but it takes a wee bit more than a week to make a working over-unity device (something like forever and a day actually).


Here are examples of children and adult projects that show you're wrong on this.
Windcar (Version 3) , Closeup Pass

Windmill Driven Boat

Rotonaut upwind run #13

Windmill Driven Cart windmill driven car

Windmill car



Well, you ought to know a bit of statistics I suppose so...
In each graduating class, a few will be at or near the average.
Around half would be above average.
Around half will be below average.

It's the latter group that troubles me, as they're the ones that makes the most errors that may influence other peoples health or even life. Which group were you in?


There is no shame in not knowing something.
Little shame in mistakenly believing something that is incorrect.
Lot's of shame in being shown you are wrong and resorting to personal attacks instead of learning from the conversation.

You're in the 3rd category on this. You know a lot about electronics, but don't know how to admit you're wrong.


Do you honestly believe he can succeed?


I hope he does and posts a video back here. I am confident though that even if he does succeed, you will resort to insults and saying it's not possible. For a guy that speaks of learning, you have a remarkably hard time of it.  Respond to this post however you wish. I will not respond to it though, so you'll the final word as it seems you must.

Offline Aberg098

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Re: Wind powered car
« Reply #17 on: May 12, 2011, 01:05:12 PM »
Adding fuel to the fire:
http://jalopnik.com/5556198/wind+powered-car-proves-internet-naysayers-wrong

For those wanting "full-scale" proof.

Offline arrrrgon

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Re: Wind powered car
« Reply #18 on: May 12, 2011, 03:23:00 PM »
You'll need a flux capacitor to make this work.


Offline karpa-alTopic starter

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Re: Wind powered car
« Reply #19 on: May 16, 2011, 03:20:32 PM »
ok after all, can anybody tell me from where can i find dc motor (or two to gain 300mA) that i'll use it to make 6V  maybe some radio set or video recorder or something. i plan to use gear set that will be 1:10 rpm or 1 turn on the propeller=10 turn's on the motor
thanks in forward!!

Offline Razor Concepts

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Re: Wind powered car
« Reply #20 on: May 16, 2011, 07:12:38 PM »
1. Where do you live?

2. Can you purchase online?

Offline karpa-alTopic starter

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Re: Wind powered car
« Reply #21 on: May 17, 2011, 12:27:15 PM »
I live in Macedonia , and yes i can purchase online

 


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