Steering, Suspension, & Brakes

tips, technology, tools and techniques related to non-driveline mechanical components

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roverman
Art Gertz
Winchester, CA.
(3150 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Airbags n' More
Posted by: roverman
Date: October 29, 2011 01:11PM

I wonder, instead of an air compressor and tank, perhaps a "small" CO2 bottle/regulator ? Being in the bottle as a liquid, it makes quite a volume of gas, at the pressures we will need. This system could possibly double funtion as a fire extinguisher ? Upward, roverman.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6070 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Airbags n' More
Posted by: BlownMGB-V8
Date: October 29, 2011 05:57PM

That would work but it adds quite a bit of weight for the tank. Also I think it's overly optimistic to think the gas will liquify at those pressures.

JB


roverman
Art Gertz
Winchester, CA.
(3150 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Airbags n' More
Posted by: roverman
Date: November 04, 2011 04:32PM

5 lb aluminum co2 tank weighs 12.5 lbs full, approx 650 psi. Jim, dia. of bags on the MGB ? I've found 4" dia. rated at 1,500 lbs/axle and 4 3/4" dia. @ 2,400 lbs/axle. Healey should be close in weight to MGB. Thanks, roverman.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6070 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Airbags n' More
Posted by: BlownMGB-V8
Date: November 06, 2011 12:04PM

Art, I have tried two sizes of air bags. Don't recall the exact specifications at the moment but the larger one is as big as will fit the MG and runs well at 80 psi. The smaller one requires around 120 psi running pressure which means the system needs to be able to put out 150 at least. That's too high to pump the system up at a gas station if the pump goes out, or in your case if your cylinder runs low. However if you want to experiment with your bottle system I have a pair of the smaller air bags that I will sell you at a good price.

Nitrogen is more commonly used for inflation and such, as it is cheap and relatively inert. Typical bottle pressures are around 2000 psi. You can also get 2000psi bottled air at any dive shop and aluminum bottles are available in a variety of sizes. Almost nothing in the atmosphere liquifies at these pressures and ambient temperatures, although by cooling the gasses you can liquify it. Some such as hydrocarbons and fluorocarbons excepted. Anyway, at these pressures and standard ambient temperatures the contents of the bottle are in a supercritical state, sort of neither gas nor liquid, so volume calculations will be different. I don't know the details but you can find them. Still, I'm sure you have used gas bottles for welding and such and should have a feel for how long they will last. We used a nitrogen bottle at the race track to power air tools and inflate tires and it took a couple of them to last through a 24 hour endurance race but it depends on usage. If you have zero leakage your recharge interval can be fairly long but that's easier said than done. I've spent hundreds of dollars just finding fittings and connectors with an acceptably low leakage rate. This is a very difficult application for standard fittings to conquer and custom fittings are prohibitively expensive to produce for such a small market, so finding components that fit with close enough tolerances to not leak even a little at these pressures while constantly moving about in a less than clean environment takes a trial and error approach, and with the wide range of fittings and manufacturers (there are literally dozens upon dozens of makers of each type of fitting) it doesn't take long for costs to add up.

I've come up with a package that works well, and Steve has verified that. If you want to duplicate my efforts you are welcome to go ahead and do so but it would be easier to just buy the fittings and components from me. I wouldn't be able to provide you with a bottle and regulator, but the rest wouldn't be too hard I don't think.

JB


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