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Old 11-01-2012, 01:00 PM   #16
KungPaoDog
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Originally Posted by PhiSig1071 View Post
Scuba Tanks are DOT regulated, which would make them easier to use, but yes, they're heavy. Scale up a large carbon fiber tank from a paint ball gun and the weight would be MUCH lower, but, much more prone to damage and not DOT regulated (as far as I know) which would make them harder to use. An 88ci CF tank at 4500 psi weighs about 12lbs. If CF tanks ever make it to scuba I'll be in heaven.
Actually, the Carbon Fiber over-wrap tanks are pretty tough, all things considered. Not that I'd want to have a dirt bike crash full force right on the tank, but I wouldn't want that to happen to a steel tank, either.
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Old 11-01-2012, 01:01 PM   #17
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You've got to handle compressed air tanks with due care; if you bust off the nozzle in a fall, it becomes a missile. Seems a sketchy idea on a dirtbike.
That's when the pressure exiting the new hole (from the missing valve) only has to push the 10 or so pounds that the tank weighs.

Attach that tank securely to a 200 pound plus dirt bike and I don't think the pressure exiting the hole in the tank is going to be shooting the crashed dirt bike around like a missile...

Could be wrong, just guessing. 200 pound dirt bike is 20 times the weight of the cylinder that the exiting pressure has to try and muscle around!
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Old 11-01-2012, 01:29 PM   #18
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Originally Posted by Ben Carufel View Post
That's when the pressure exiting the new hole (from the missing valve) only has to push the 10 or so pounds that the tank weighs.

Attach that tank securely to a 200 pound plus dirt bike and I don't think the pressure exiting the hole in the tank is going to be shooting the crashed dirt bike around like a missile...

Could be wrong, just guessing. 200 pound dirt bike is 20 times the weight of the cylinder that the exiting pressure has to try and muscle around!
Depends on how securely the tank is mounted. It would be kinda cool if they were removable so you could swap them out.
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Old 11-01-2012, 01:56 PM   #19
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I'm always skeptical about things like this. These guys should know exactly how much torque and power this thing produces, but they won't say the numbers. Why?

It just makes me think the whole thing is a fraud.
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Old 11-01-2012, 02:05 PM   #20
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If CF tanks ever make it to scuba I'll be in heaven.
Not a diver- but wouldn't that just mean you'd have to wear more weights?
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Old 11-01-2012, 04:18 PM   #21
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Originally Posted by PhiSig1071 View Post
Depends on how securely the tank is mounted. It would be kinda cool if they were removable so you could swap them out.
Yeah, I was thinking if the bottom (blunt) end of the tank was pushed against a plate welded to the backbone of the bike, that'd probably (maybe?) be enough to absorb the stress of a tank pissing away thousands of PSI in a few tenths of a second.

So, the tanks could be easily swapped, and the "cradle" for the tank would hold it such that if shit hit the fan, the tank wouldn't go loose from the bike.
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Old 11-01-2012, 04:25 PM   #22
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Old 11-01-2012, 04:41 PM   #23
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Woohoo! That's awesome.
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Old 11-01-2012, 04:46 PM   #24
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Here's one with actual SCUBA tanks! 4351PSI (300BAR) in these tanks. The composite/aluminum combo tank is the craziest, IMO.

http://www.youtube.com/watch?feature...v=tyINNUaXa8Q#!
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Old 11-01-2012, 04:55 PM   #25
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Not a diver- but wouldn't that just mean you'd have to wear more weights?
Depends. And that might not be that big of an issue. The ubiquitous AL80 is negatively buoyant full, but ends up positively buoyant when low on air. If the CF tanks were consistent in their buoyancy characteristics they would be better to dive with. Also, CF tanks tend to be smaller, which is nice underwater, more streamlined, less bulky, etc. I have seen some retardedly high pressure CF tanks too, like 10k psi, that could expand your range a LOT. Right now I dive steel, I think they're HP92's if I remember correctly, and I like them, mostly because I don't have to wear any weight. But, the weight is all on your back and that is kind of tough sometimes, it has a tendency to flip you over.
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Old 11-01-2012, 11:20 PM   #26
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Not necessarily. If it is set up to feed air to the motor via a two-stage system, then there would be a first stage valve that reduces the pressure from the tank to the feeder line to a maximum value, then a second stage valve that reduces the pressure again to the feed into the engine.

Assuming for the sake of argument that the engine runs with a 10:1 compression ratio, then at sea level, the second stage regulator valve would need to deliver about 140 PSI to the engine. Until the tank pressure dropped to below 140 PSI, the feed would be at a constant pressure, due to the regulator valves stepping down the pressure, much like an electrical transformer.

Edit: now that I think about it, because this engine is not using IC to generate pressure, the sea level thing does not apply. You would merely need to regulate the air pressure down to whatever the engine is designed to handle.
It'll be a LOT more than 140psi. An engine, remember, burns fuel. You squeeze the air/fuel mixture to 140psi or so, THEN you set fire to it, and THAT gives you the pressure rise that powers the vehicle. That gives you a pressure in the power stroke of 1000 to 1500 psi. SO yes, if you regulate it to that, you'll get constant power until the cylinder gets to that level -- the last third to quarter of the tank will give you lower performance.

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Old 11-02-2012, 03:50 AM   #27
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Originally Posted by gravityisnotmyfriend View Post
I hate when people make claims like this. It's not powered by air. Most likely it's powered by a fossil fuel - just like everything else.


Compressed air is just energy storage. Terribly inefficiency energy storage at that. I don't know who filled his scuba tank, but I'm guessing they did it with a compressor that either runs on gasoline or deisel or it plugs into the wall where it gets electricity from a coal powered station.

it's not without it's advantages though. Compressed air fills much quicker than you can charge a battery. So that's something. I don't know if there's any weight savings as i suspect a tank capable of holding 4000 psi is going to weigh as much as a comparable lithium battery.
Just like cars and motorcycles are not powered by oil brought up from the depths of the Earth.



Rather that oil must be refined, distilled, heated, broken down, made into a blend that can be combusted in a modern vehicle engine.


Money, machinery, workers, energy - - - - combine to produce YOUR vehicle fuel

Tsk - tsk - tsk!

Education in modern folk is trailing far behind folk of sixty years ago!

Air was decades ago used in locomotives running underground, as a power source, because of safety factors.
Fireless locomotive


Porter Locomotive No. 3290 of 1923.


Compressed air locomotive Alberta, Canada, formerly used in coal mining

Compressed-air vehicle


A compressed-air vehicle (CAV) is powered by an air-engine, using compressed air, which is stored in a tank. Instead of mixing fuel with air and burning it in the engine to drive pistons with hot expanding gases, compressed-air vehicles use the expansion of compressed air to drive their pistons. One manufacturer claims to have designed an engine that is 90 percent efficient.



Victor Tatin aeroplane 1879


Angelo Di Pietro (inventor)

Quote:
The Di Pietro Motor, developed by the Australian company EngineAir, is a rotary engine powered by compressed air. It is smaller than any internal combustion engine although the size may differ between models.
Unlike other rotary engines, the Di Pietro motor uses a simple cylindrical rotary piston (shaft driver) which rolls, with next to no friction, inside the cylindrical stator. Only 1 psi (≈ 6,8 kPa) of pressure is needed to overcome the friction.
The space between stator and rotor is divided in 6 expansion chambers by pivoting dividers. These dividers follow the motion of the shaft driver as it rolls around the stator wall. The cylindrical shaft driver, forced by the air pressure on its outer wall, moves eccentrically, thereby driving the motor shaft by means of two rolling elements mounted on bearings on the shaft. The rolling motion of the shaft driver inside the stator is cushioned by a thin air film. Timing and duration of the air inlet and exhaust is governed by a slotted timer which is mounted on the output shaft and rotates with the same speed as the motor.
. . . . . . . . . . . . . . . . . . . . . . . . .
Motor speed and torque are controlled by throttling the amount or pressure of air into the motor. The Di Pietro motor gives instant torque at zero RPM and can be precisely controlled to give soft start and acceleration control.
The Di Pietro Motor can be used in boats, cars, burden carriers and other vehicles.
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Old 11-02-2012, 05:39 AM   #28
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Originally Posted by PhilB View Post
It'll be a LOT more than 140psi. An engine, remember, burns fuel. You squeeze the air/fuel mixture to 140psi or so, THEN you set fire to it, and THAT gives you the pressure rise that powers the vehicle. That gives you a pressure in the power stroke of 1000 to 1500 psi. SO yes, if you regulate it to that, you'll get constant power until the cylinder gets to that level -- the last third to quarter of the tank will give you lower performance.

PhilB
Good point, Phil.

However, let's also consider that just adapting a regular otto cycle engine for this would be very inefficient. It would be better to use a specially-designed engine, much like a steam locomotive uses multiple valves and pistons to capture the energy of the steam as it gets reduced with each piston stroke. Some of those engines are much more efficient at extracting the energy in the available pressure differential than a conventional otto cycle engine.

Edit: I just read the post above about the Di Pietro motor. Sounds nice.
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Old 11-02-2012, 11:48 AM   #29
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Not a diver- but wouldn't that just mean you'd have to wear more weights?
Another consideration, buoyancy is a result of density, if an object weighs more then the amount of water it displaces then it sinks. An equivalent CF tank would be smaller then a AL tank, therefore, even though it's lighter, it displaces less water, and would take less weight to sink.
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Old 11-02-2012, 12:38 PM   #30
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Originally Posted by PhiSig1071 View Post
Another consideration, buoyancy is a result of density, if an object weighs more then the amount of water it displaces then it sinks. An equivalent CF tank would be smaller then a AL tank, therefore, even though it's lighter, it displaces less water, and would take less weight to sink.
You need to rethink that concept.

The drop in the net weight of a C/F tank versus the same capacity aluminium one will be far less than the reduction in bulk is, so the net buoyancy will be greater, not less.

It's the same mass of air in both tanks...

Speaking of SCUBA tanks, back in the 60's I watched one at the KMCAS dive shack hit the deck the wrong way, just after being filled... it was a short-impulse JATO, and skipped a few times before it finally was grabbed by the water.

The valve took a while to find...
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