Crazy Frenchman : The Movie !

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cauchoiskev
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Crazy Frenchman : The Movie !

Post by cauchoiskev »

DIY sphere regassing using a washing machine motor, and, erm, air....






I like this guy !

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Post by admiral51 »

now thats what i call proper recycling :lol: :lol:

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Post by ellevie »

F O R M I D A B L E ! ! !
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Post by Way2go »

Ingenious but I wonder if he dries the air before it enters the sphere? :D 8)
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Post by Jaba »

Quel mec !

Once again he shows an eccentric and innovative solution to BX maintenance. It must have taken him DAYS to create his compressor and pressure tester.
He must know that air is mostly nitrogen anyway so what does a bit of oxygen and water matter at 50 bar.
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DavidRutherford
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Post by DavidRutherford »

Fascinating.

I just wish my French was better so that I could understand what he's saying. I can get little bits of it, but not much really. The most ingenious bit of the system he's got there is how he pressurises the sphere, and then puts the bolt back in under pressure.

Time to experiment methinks!
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Post by Brian »

I also could not understand the dialogue, but indeed a very interesting system.

Tightening the bolt after presurising was not obvious, pity the camera was not mounted on a tripod, it may have shown clearer how it was done.

I always put the intake tube to the compressor into a freezer, that reduces the water content in the air.

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Post by BX Bandit »

If nothing else I feel dizzy! Very interesting. I wonder if the missus would notice if I nicked the motor out the washing machine.....
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Post by CitroXim »

Clever but shockingly dangerous :shock: Full marks for ingenuity but zero for common sense :P

That compressor is very good to be able to pump a sphere up to getting on for 600psi (40 bar) but more to the point, there is no way it will be rated to operate at this sort of pressure and is a potential shrapnel grenade.

The copper piping is not up to the pressure either. Personally, I'd not go within 500 feet of it.

How he is still alive and in one piece is just as remarkable as his invention :lol:

There is a really good reason why spheres are filled with very pure nitrogen and why it is a bad idea to use "contaminated" air but it currently escapes me. I'll keep digging..
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Post by MULLEY »

Is it to do with heat = gas expansion, nitrogen doesnt expand much as opposed to air. His car could have 5 grenades ready to explode if it gets too hot????

Or am i totally wrong :oops:

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Post by Way2go »

citrojim wrote:That compressor is very good to be able to pump a sphere up to getting on for 600psi (40 bar) but more to the point, there is no way it will be rated to operate at this sort of pressure and is a potential shrapnel grenade.
40 bar is one of the lower pressures for the spheres (some being 55 bar) , and there will be a factor of safety in the sphere design too so although the rig is Heath Robinson once completed the spheres cannot be considered “grenades”. As regards the compressor then as that will be the other side of a non-return valve there is only a very small volume of compressed gas present internally at any one time so massive explosive decompression is unlikely. Generally though, with the quality of pipes and exposed motors and belts it wouldn’t get health and safety approval.
citrojim wrote:There is a really good reason why spheres are filled with very pure nitrogen and why it is a bad idea to use "contaminated" air but it currently escapes me. I'll keep digging.
Often Argon is used for many fillings like light bulbs etc because it is an inert gas but is much less plentiful in air than the major constituent which is Nitrogen. Consequently Nitrogen being considerably cheaper is used whenever there is no chemical reaction to it expected.
The Nitrogen used in the spheres is dry and if a membrane in the sphere ruptures then it is unlikely to contaminate the LHM.
If air is compressed for use, apart from anything else it will have a “wetness” which will most likely rust the sphere around the membrane causing early failure. Also the “wet” air venting to atmosphere through the LHM will certainly contaminate it.
MULLEY wrote:Is it to do with heat = gas expansion, nitrogen doesnt expand much as opposed to air. His car could have 5 grenades ready to explode if it gets too hot????

Or am i totally wrong :oops:
Are you serious? I don’t think so. This conjures up an image of the BX being used in Iraq and Afghanistan as an IED.
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Post by CitroXim »

I didn't mean the spheres being grenades, I was refrerring to the compressor itself. I have a homebrew twin-cylinnder compressor driven by a 3/4HP motor in my garage and the motor works hard to pump the receiver up to 100psi. He must have been using a really good compressor to get over 600psi, even when using a non-return valve. I'm frankly surprised the smallish motor and flimsy belt could transmit sufficient power get anywhere near 600psi, whatever the compressor.

I maintan that 600psi will be well beyond the design pressure of the compressor and taking the pressure up that high is frankly dangerous. I agree it is a very small volume of air but still...

Thanks for the explanation about the nitrogen. It also has bigger molecules and thus diffusion leakage across the membrane is less.

I gues he gets the bolt done up again by keeping the outer of the pressurisation attachment tight against the sphere and rotating the bolt through a (very good) pressure seal at the base, hence why the bolt head was held tight with set-screws in a cup.

As I say, very clever and ingenious and fair play to him for a tremendous effort but I still maintain, incredibly dangerous :twisted:
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Post by DavidRutherford »

I don't think the pressures are the problem really. Think about the fact that the suspension pipes on a Hydro Cit can be running at up to 3000psi, and even cupronikel pipes work just fine. Copper water piping isn't ideal, but it will take something like 80bar before it fails.

The compressor seems to work just fine as although it can generate high pressures, it probably has a flow rate of about 0.05 CFM. Noted by the ratio of pulleys between the motor and the pump.

My biggest worry would be the sphere becoming dislodged as the plug bolt is being inserted, and shooting round the workshop like a missile. That strikes me as somewhat dangerous!
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Post by Way2go »

citrojim wrote:Thanks for the explanation about the nitrogen. It also has bigger molecules and thus diffusion leakage across the membrane is less.
Nitrogen is an element (Atomic Radius: 71 pm) but yes, the molecule N2 is larger than O2 (as oxygen's atomic radius is 66 pm) so this could also be a benefit.

Maybe the following article in relation to Car Tyres, Nitrogen versus Air will help:
Most tires are filled with compressed air, which when dry consists of about 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases by volume. Water vapor (humidity) can make up as much as 5 percent of the volume of air under worst-case conditions. Filling your tires with nitrogen mainly does two things: it eliminates moisture, and it replaces skinny oxygen molecules with fat nitrogen molecules, reducing the rate at which compressed gas diffuses through porous tire walls. That means, theoretically at least, that a tire filled with nitrogen retains optimal pressure longer, leading to more uniform tire wear and better gas mileage. The commonly quoted figure is that tires inflated to 32 psi get 3 percent better mileage than at 24 psi.

Does nitrogen make any practical difference? You couldn't prove it by me. I found no scientific tests showing that nitrogen-filled tires stayed inflated longer than average under normal conditions. A car-buff buddy was sure it worked but conceded he had only anecdotal evidence that it did.

As for moisture, changes in humidity affect tire performance two ways. First, the density of humid air fluctuates more with temperature than that of dry air, so removing humidity can keep your tire pressure more consistent, especially when the temperature climbs over 100 degrees Fahrenheit. That may be a legitimate concern in Formula One racing, but it's not much of an issue if you're just tooling around town.

Humidity can also be a factor in wheel maintenance — since pure nitrogen doesn't have moisture in it, supposedly your wheels won't rust as quickly, which could lead to improved wheel performance and air sealing. The question is, how big a problem is wheel rust these days? According to a few tire and wheel shops we contacted, not very. Seriously rusted wheels are uncommon in typical steel-wheeled cars, and many high-performance cars have alloy wheels that don't rust at all. One exception is work vehicles such as dump trucks, which are exposed to a much harsher environment.

Another claim I've seen is that since nitrogen is slightly lighter than air, you'll save weight and get better performance. However, we're talking about a weight difference of less than 4 percent of the gas in the tire — in other words, a difference of less than an ounce for most vehicles. A possibly more realistic benefit is that nitrogen is largely inert chemically at low (i.e., normal) temperatures, so it won't attack the rubber in your tires like oxygen does. Oxygen attack is something both the National Highway Traffic Safety Administration and Ford Research have studied, and can be a problem for tires used for a long time or in rough conditions.

More important, nitrogen doesn't support combustion, which is one reason aircraft and the space shuttle use nitrogen in their tires. The wisdom of this precaution was brought home by the crash of Mexicana Airlines flight 940 on March 31, 1986. Shortly after the Boeing 727 took off from Mexico City en route to Puerto Vallarta, an overheated landing-gear brake caused a tire improperly filled with air instead of nitrogen to overheat as well and explode, rupturing fuel and hydraulic lines. The ensuing fire and crash killed 167 passengers and crew. However, unless your driving habits are of the X-treme variety, the chances of your tires catching fire anytime soon are slim.

Overall, filling up with nitrogen won't hurt and may provide some minimal benefit. Is it worth it? If you go to some place like Costco that does it for free with new tires, sure, why not? Elsewhere, though, I've seen prices quoted as high as $10 per tire, which is way more than I'd pay. Rather than shell out for nitrogen, you'd be better off just checking and adjusting your tire pressure regularly, something the NHTSA says less than 60 percent of U.S. motorists actually do.
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