# Electric air assist pusher??



## Guest (Nov 11, 2010)

Really! How much thought went into this idea?
Did you test your hypothesis or just open .......... and insert foot.


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## revoman (Nov 11, 2010)

You choose
Obviously you have already thought it through and rejected it.
Why?


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## helluvaengineer96 (Oct 8, 2010)

Conservation of energy in an enclosed system. I'm sure there is a law that can be named, but I've been our of school for a while now.

Whatever energy you get from your fans.... you are spending as added resistance (your motor must work hard to spin those fans hence you are spending more energy).

You will burn more energy than you gain due to system components be inefficient.






revoman said:


> You choose
> Obviously you have already thought it through and rejected it.
> Why?


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## revoman (Nov 11, 2010)

helluvaengineer96 said:


> Conservation of energy in an enclosed system. I'm sure there is a law that can be named, but I've been our of school for a while now.
> 
> Whatever energy you get from your fans.... you are spending as added resistance (your motor must work hard to spin those fans hence you are spending more energy).
> 
> You will burn more energy than you gain due to system components be inefficient.


Maybe I didn't make it clear.

Instead of batteries running wheels on the ground as an assist
push as in a trailer, I would use fans blowing out the back of my 
truck to assist the ICE at highway speeds.

The fans aren't charging anything; I would do that at home from the grid.


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## helluvaengineer96 (Oct 8, 2010)

Oh... My bad I read your post too quickly...

You would want a turbine... but trust me, most efficient use of your power is applying it directly to the ground...




revoman said:


> Maybe I didn't make it clear.
> 
> Instead of batteries running wheels on the ground as an assist
> push as in a trailer, I would use fans blowing out the back of my
> truck to assist the ICE at highway speeds.


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## revoman (Nov 11, 2010)

helluvaengineer96 said:


> Oh... My bad I read your post too quickly...
> 
> You would want a turbine... but trust me, most efficient use of your power is applying it directly to the ground...


Sure, I know it is, but it could be technically complex to do it 
as a pushing mechanism and I am not in the position to make my
truck all electric. I just wondered what the forum's thoughts would be
on doing something simple like this and if there would be appreciable
gains.

I think that there would be and it could be fairly simple and cheap to 
execute for a %25 or better gain in mileage.


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## Jimdear2 (Oct 12, 2008)

helluvaengineer96 said:


> You would want a turbine... but trust me, most efficient use of your power is applying it directly to the ground...


Better bet would be applying you electric power directly to the drive train as mechanical energy. It is considerably more efficient.

Using electric motors to move air to produce thrust/pressure is probably near the bottom of a list of efficient uses of power.

The only possible boost I could see coming from such a system would be if you could evacuate the high pressure area in front of the vehicle while using less power then you would use to just push it out of the way.


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## revoman (Nov 11, 2010)

Jimdear2 said:


> Better bet would be applying you electric power directly to the drive train as mechanical energy. It is considerably more efficient.
> 
> Using electric motors to move air to produce thrust/pressure is probably near the bottom of a list of efficient uses of power.
> 
> The only possible boost I could see coming from such a system would be if you could evacuate the high pressure area in front of the vehicle while using less power then you would use to just push it out of the way.


Sure, I know it is, but it could be technically complex to do it 
as a pushing mechanism and I am not in the position to make my
truck all electric (expensive). I just wondered what the forum's thoughts would be on doing something simple like this and if there would be appreciable
gains.

I think that there would be and it could be fairly simple and cheap to 
execute for a %25 or better gain in mileage.


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## jeremyjs (Sep 22, 2010)

I seriously doubt you'd ever seen any noticeable gains. Even with a lot of battery power and some big blowers.


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## newenergy (Oct 20, 2010)

My gut feeling would be that it would be very inefficient, but airplanes are pretty efficient, right?

I think the idea of evacuating air in front of the car to improve aerodynamics sounds good. Like a wide narrow inlet that sucks air out in front and then propels it out the back.

Seems like the fan/turbine would have to spin very fast though for the drag to be small compared to the thrust. 

from wikipedia on turbines:

"As a general rule, the smaller the engine the higher the rotation rate of the shaft(s) needs to be to maintain top speed. Turbine blade top speed determines the maximum pressure that can be gained,this produces the maximum power possible independent of the size of the engine. Jet engines operate around 10,000 rpm and micro turbines around 100,000 rpm."

Seems like such a set up would cost more than putting power to the wheels.


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## DavidDymaxion (Dec 1, 2008)

I was thinking of doing the same idea for my bicycle. I think it would be less efficient than driving the wheels, but it would be really simple to build, would just need a switch (no controller needed), and would be really easy to put on or take off (just strap it to the rear rack). You would learn a lot both faster and cheaper by trying a bike version first.


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## Jimdear2 (Oct 12, 2008)

For a bicycle you might look into one of those powered parasailing backpacks.

Probably be VERY fast (??land speed record??)

What revoman is missing, is that at 60 mph in his vehicle, he would have to spin the fans at the equivalent of 60 mph just to get nothing.


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## Mark C (Jun 25, 2010)

revoman, when all is said and done, I think you'd do better on the http://ecomodder.com/ website. There are many avenues discussed on ecomodder about ways to increase the distance traveled versus the fuel you buy. The cost for doing ranges from $0.00 for adjusting the "nut behind the wheel," to some serious aerodynamic modifications that can cost as much as you want to spend.

Either way you choose to go, reducing the amount of fuel you burn to propel your vehicle of choice is a worthy goal that most here would encourage. Later, when the budget allows, you can buy or build an EV to completely eliminate the oil man.


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## revoman (Nov 11, 2010)

Jimdear2 said:


> For a bicycle you might look into one of those powered parasailing backpacks.
> 
> Probably be VERY fast (??land speed record??)
> 
> What revoman is missing, is that at 60 mph in his vehicle, he would have to spin the fans at the equivalent of 60 mph just to get nothing.


No, I get that. Just trying to make it as easy and cheap as possible.

Also considering a rear frame attached electric pusher, but it will probably
be more expensive and complex.


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## Bottomfeeder (Jun 13, 2008)

I agree with Mark C. There are lots better ways to improve mileage, and almost all of them are on ecomodder. I understand the desire to try some new idea that you have, but rarely is that practice the most economical. Since you'd be trying new things, you'll spend a lot of effort and money toying with the idea trying to find a decent solution. Sometimes you have to swallow your engineering pride and try the well worn solutions first. That being said, keep us updated with your harebrained schemes.


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## Roy Von Rogers (Mar 21, 2009)

http://www.youtube.com/watch?v=UWSr62Xnb2M

Now if you took that motor and coupled it directly to the wheels of an automobile, which do you think is more economical and faster, the car or the boat.

Roy


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## Soundboats (Oct 6, 2010)

To see if this concept is feasible I would suggest you look into the operating parameters of an air boat. These use a big propeller to move a boat. By researching this technology you might find out how much horsepower the props produce and how it might improve your vehicle's performance. 

One issue that comes up with propellers is the speed of the tip. For the type of application you are considering the tip of the propeller cannot be moving faster than the speed of sound. There is a tradeoff between rpm and length of prop. You will get more power with a bigger prop moving at a lower rpm (just like in boats).


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## poprock (Apr 29, 2010)

revoman said:


> I have an idea that is difficult to research online.
> 
> I am thinking of putting electrically driven fans (squirrel cage?)
> in the bed of my pickup to give my ICE a boost on the highway.
> ...


 When I was 10 I tried to lift myself up by my shoelaces.It didn't work either.


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## Guest (Nov 12, 2010)

poprock1 said:


> When I was 10 I tried to lift myself up by my shoelaces.It didn't work either.


What do ya mean? It worked fine for me as long as I only lifted one foot at a time. Arm assist is what you might call it. Works to assist the leg. Like you when I tried both feet at once I'd fall down, go boom


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## Duncan (Dec 8, 2008)

Hi Revoman

You need to do some numbers to see if its a worthwhile idea
Here is my contribution - can be used to look at rocket belts, jump jets, helicopters

Force in Newtons (from a "rocket or jet or anything that works by throwing stuff backwards) = Exhaust velocity (m/sec) x the amount of stuff (kg/sec)

The amount of energy it takes to throw the stuff (Watts) = 1/2 x the amount of stuff (kg/s) x exhaust velocity squared
the old half M V squared from school

Air masses about 1.2 Kg/m3 (at sea level and 15C ....)

So if your fans have an area of 1m2 at 60 mph (26 m/sec) - 26 x 1.2 kg/sec is coming in (31kg/sec)

If you blow it out at 56 m/sec (126mph) you will get (56-26) x 31 = 930N of force
it will take ((56 x 56) - (26 x 26)) 0.5 x 31 = 38Kw

If you drive the ground it will take 930N x 26M/sec = 24Kw

All of this assumes perfect 100% efficiency!

As the fans get smaller - the relationship gets worse - the power required goes up at the square of the velocity - the thrust goes up in proportion to the velocity

Look up the most energetic rocket fuels known and calculate how long a rocket belt can hover!

Which is why the Kiwi one has fans - and why it needs over 200 Hp!


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## Guest (Nov 12, 2010)

Why is it that you all are doing this work for someone who needs to do this himself? He needs to do his own homework.


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## Duncan (Dec 8, 2008)

Hi gottdi,

A lot of these simple calculations are very new to some people - five minutes explaining how things work can help them to help themselves in the future

Your recent elections show that a lot of Americans have real difficulty with numbers!


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## Guest (Nov 12, 2010)

Well, yes that is a no brainer about the numbers thing. But that just enforces my stand that they need to do their own work if they are truly serious. It's fine to present the formulas because it is even harder for them to know which one to use or even where to find them but they can do it. I did and struggled through the math but I get it now and can do any thing with a formula in hand. Don't coddle, make them do the work. Be there to help. If you do the work they never learn. They expect others to do the work for them. It is one serious thing in our society. It really sucks. 

Pete


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## dimitri (May 16, 2008)

newenergy said:


> but airplanes are pretty efficient, right?


This is quite arguable point in this context. Why do you think jets climb to 30,000 feet? Just for a cool view? No, because air is thin, so its easier to punch thru it. On the ground level jet's efficiency would be horrible.

This whole idea is silly just simply because of weight added by the trailer itself, loaded with batteries, which will make any potential thrust generated by the fan negligible compared to extra energy needed to push the trailer itself.

I think out of all silly ideas this forum has seen, this must be in top 5 

No offense to the original poster.

Take a look at fanboats, same concept http://en.wikipedia.org/wiki/Airboat

they use lots of horsepower to glide on water. Translate such horsepower to electric and you will see that no amount of batteries will make it a feasible solution, ever. Plus I don't think DOT will allow you to drive this thing on a public road


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## revoman (Nov 11, 2010)

dimitri said:


> This is quite arguable point in this context. Why do you think jets climb to 30,000 feet? Just for a cool view? No, because air is thin, so its easier to punch thru it. On the ground level jet's efficiency would be horrible.
> 
> This whole idea is silly just simply because of weight added by the trailer itself, loaded with batteries, which will make any potential thrust generated by the fan negligible compared to extra energy needed to push the trailer itself.
> 
> ...


No offense taken, although I will say I did not expect to see the feedback I have seen on this forum. Some has been a little nasty and I do not understand why. I would think users here would be much more open to sharing information with a little more class.

BTW, no trailer would be involved. The calculations provide in this string make the feasibility obvious.


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## revoman (Nov 11, 2010)

Duncan said:


> Hi Revoman
> 
> You need to do some numbers to see if its a worthwhile idea
> Here is my contribution - can be used to look at rocket belts, jump jets, helicopters
> ...


Much appreciated, Duncan.


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## dimitri (May 16, 2008)

revoman said:


> No offense taken, although I will say I did not expect to see the feedback I have seen on this forum. Some has been a little nasty and I do not understand why. I would think users here would be much more open to sharing information with a little more class.
> 
> BTW, no trailer would be involved. The calculations provide in this string make the feasibility obvious.


I think most people interested in electric drive understand that system efficiency is the key. Even most advanced battery's poor energy density compared to gasoline requires us to take efficiency very seriously, we can't afford to waste energy on pushing air, its just too wasteful, might as well stick to gasoline.

This is why all wild ideas are rejected around here, because they all waste energy. The shortest mechanical path from the motor to the wheel is the key to high efficiency, everything else is a failure.

Look at all vehicles using fan drives, they do it because they have no other choice, but in the car you have a better choice, wheels, to apply power.


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## Coley (Jul 26, 2007)

So many buttons to push and so little time.................


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