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Beau Brown

New Member
Hello all!

I'm new to the forum, and while I'll introduce myself elsewhere, I do have a question that needs answering.

I'm constructing a compressed air engine. This works the same as a single-piston reciprocating steam engine would, except it runs on air. The mechanics of the engine, however, aren't important.

The engine would be powered by a small electric leaf blower. I found a fair-priced leaf blower online, which is the Toro Power Sweep 51585. It weighs less than two pounds, produces 160 mph winds on full speed and operates on 7-amps.

This will provide air to the engine (I'll worry about throttles and such later). On the drive shaft of the engine is a larger gear, which is connected to a smaller gear... I'm thinking of a 5 to 1 gear ratio. The smaller gear will be connected to a DC motor or more likely an alternator. As I'm sure all of you know, this will produce electricity when spun. From there (I may begin to sound repetitive), wires are hooked up to both terminals, with a blocking diode on the positive wire. This will lead to a 12 Volt 7AH Battery.

Another set of wires will be connected to the terminals, and the other wires will lead to one of those devices (the name would be much appreciated) where there are two terminals for both positive and negative wires, but at the other end of this device is an outlet for a standard plug, which in this case would be the plug of the aforementioned leaf blower.

Basically, I'm trying to construct a device where the battery powers the leaf blower, which powers the engine, and have the engine gradually re-charge or supply energy to the same battery (while this wouldn't be an infinite cycle, I'm guessing that it would give the battery a longer life).

Are there any improvements needed to run this device at the specifications given (and if I need different parts, please do tell me)? And I'm missing anything, any information would be very helpful. Also, any information on the installation of a blocking diode would also be helpful.

Thank you,
-Beau Brown
 

Sceadwian

Banned
Beau.... Please immediately burn the plans for this project. I don't mean to offend but what you're talking about building would not work (violates the first law of thermodynamics) All your entire setup would do is waste all the energy lost in friction and poor conversion.
 

tcmtech

Banned
Most Helpful Member
ONE: A piston type air engine requires higher pressure and lower volume. A leaf blower is high volume low pressure. YOU would need a turbine type air engine to get it to run off a leaf blower.

TWO: Air driven anything is low in total efficiency. An air powered die grinder takes a 5 hp comercial capacity air compressor to run it. But an electric die grinder has the same power and performance with only about 1/2 hp. 10:1 total energy loss with air driven when factoring air pumping system and air motor losses.

THREE: Typical electric motors are around 80%-90% efficient. Same with most alternators or generators so 100 watts of electric motor gives you say 85 watts mechanical energy which in turn drives a generator that gives you back about 85% of 85%. OR about 72 watts.

So far you are at 100/10=10. 10*.72 = 7.2 watts returned for every 100 put in.

FOUR: Your leaf blower runs ar 120 volts so you will need to step up your voltage from the 12 vlot battery withan inverter. Most of them are in that 80%-90% efficiency range too. SO 7.2 *.85 = 6.1 watts

FIVE: your 12volt 7AH battery holds about 84 watts of energy. At 120 volts and 7 amps the blower motor draws 840 watts. factor in the 85% inverter efficiency and you are now drawing 988 watts off that battery. Theoreticaly it will go dead in 5 minutes. But with the theoretical 6.1 % return on your losses it will go dead in 5 minutes and 24 seconds.

Just short out the battery and watch it burn. you will be time and money ahead!


If your really looking for perpetual motion, thats simple. Just use a perpetual energy source! Nature put them all around us! Think about it!

I will bet my lifes worth that you will not out live the sun, wind or the flowing water in streams and rivers!
And once your dead will it matter to you how much longer they will keep going?
 
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audioguru

Well-Known Member
Most Helpful Member
Connect the shaft of an electric motor to the shaft of a generator. Connect their wires together then give the shafts a spin.
Does it keep spinning forever without doing any work?
Or does it stop almost instantly due to losses?
 

Sceadwian

Banned
They'll generally run faster not connected to anything because of the losses. It is however an interesting way of decoupling AC power =)
 

Beau Brown

New Member
Hello all,

Thank you for your advice. Bear in mind that I'm not looking for overunity, perpetual motion or incredible efficiency. All that I wanted to have made is an engine which ran on air, and would at the same time gradually restore some energy to the battery, which I thought would give it a longer battery life.

I'm very new to electronics (only a few days), so I'm not surprised that my logic wasn't that great.

So basically, I suppose I'll have to go back to the original plan; an air engine with some sort of blowing device, connected to a battery or something.

What would you all suggest for a blower which produces a higher pressure and lower volume?

Thank you,
-BB
 

Sceadwian

Banned
It will not give it a longer life it will in fact drain it faster.
An air compressor will obviously produce high pressure at a lower volume, as TCM was saying though air engine's are incredibly inefficient. They're just used because it's available. There are a few air engine projects going on for automobiles recently, but the required air pressure makes the energy released in an accident a pale comparison to a 'fire' from modern auto's. The blow up with some ferocity. Especially from over heating.
 
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Beau Brown

New Member
Well, I'm honestly not in the market for efficiency. I'm mainly doing this for the sake of doing a mechanical project.

Thank you for the suggestion of the air compressor; I'll definitely look into that. The only reason why I thought that a leaf blower would help is because I saw somebody power his with a vacuum cleaner on a blowing setting, but I suppose that they're two different things.

Thank you!
 

Sceadwian

Banned
Keep in mind Beau if this is for the sake of a mechanical project there is no point to it, as it will not actually serve any function. It's just a complicated version of attaching a belt between two wheels. If you're going to make something for the sake of just doing something mechanical make it at least have a function, otherwise you're better off twiddling your thumbs.
 

arunb

Member
compressed air vehicles do exist, but they use a tank of highly compressed air as a source of energy, this air is pumped into an engine, thus causing motion, I saw a tv programme on Discovery that showed a car running on this principle, the car had a small petrol powered compressor that pumped air back into the tank.

See Compressed air car - Wikipedia, the free encyclopedia

thanks
aa
 
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Sceadwian

Banned
4500psi. I would hate to see that in a crash. Not as bad as hydrogen for explosion but the power available in 10 cubic feet of 4500psi air tank is incredible.
 
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