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| Thread ID: 103343 | 2009-09-19 06:59:00 | Vacuum question | prefect (6291) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 811884 | 2009-09-19 10:47:00 | It does not have a seal on a piston like an air or hydraulic cylinder. The cylinder looks like a flying saucer ( but smaller) and has a diaphragm across the middle of the cylinder with a butty spring behind it But you could be one to something because I have seen combined vaccum/ pressure test gauges |
prefect (6291) | ||
| 811885 | 2009-09-19 10:48:00 | Strike a blow for freedom and new openings - suck it and see. | R2x1 (4628) | ||
| 811886 | 2009-09-19 10:58:00 | It does not have a seal on a piston like an air or hydraulic cylinder. The cylinder looks like a flying saucer ( but smaller) and has a diaphragm across the middle of the cylinder with a butty spring behind it But you could be one to something because I have seen combined vaccum/ pressure test gauges I know the ones you mean, you see them under truck/trailers near the wheels. The movement of the piston & linkages is what opens the bus door (Truck brakes). If the vacuum diaphragm will stand 30 psi of vacuum, I wonder if it would work with 30 psi pressure.The in/out pipework would need changing tho? PJ |
Poppa John (284) | ||
| 811887 | 2009-09-19 11:00:00 | Strike a blow for freedom and new openings - suck it and see. Hey...watch it...this IS a family forum!!! PJ:eek::) |
Poppa John (284) | ||
| 811888 | 2009-09-19 11:02:00 | What you are talking about on trucks trailers and buses are brake airpots some (backs) are sprung on and need air to release them. They are very dangerous and so powerful I have seen them used as homemade riveting machines like to rivet on brake linings. People have gone on to heaven/hell after trying to take them apart and the spring has hit them. I f you hooked one to a door and something got trapped in they would crushed to death ( and killed) |
prefect (6291) | ||
| 811889 | 2009-09-19 11:07:00 | What you are talking about on trucks trailers and buses are brake airpots some (backs) are sprung on and need air to release them. They are very dangerous and so powerful I have seen them used as homemade riveting machines like to rivet on brake linings. People have gone on to heaven/hell after trying to take them apart and the spring has hit them. I f you hooked one to a door and something got trapped in they would crushed to death ( and killed) Ahh, Ok. But my thought still stands re the diaphragm. PJ . PJ |
Poppa John (284) | ||
| 811890 | 2009-09-19 21:07:00 | I was only an electrician but this is my thinking . I believe that the maximum vacuum is minus 30 lbs per sq inch . Is that right? So if the air pressure is no more than that, there should be no damage . However . . . the seals in the cylinder will be the wrong way round, won't they? The air will blow past the seal . The seal is designed for suction pressure not air pressure . PJ Sorry - wrong . A close to perfect vacuum would be 29 . 999 inches of mercury which has NO relationship to pounds of pressure or ATI . The only relative value with which we can logically work is on Earth where our atmosphere is limited to the weight of the air above your head . The fact that ambient vacuum achievable on Earth is a few decimal points away from a perfect vacuum, and although it CAN be created in a laboratory - we cannot use that value as a real number with which to work . What we typically see if a value of 14 . 7 lb/square inch, and that's only at sea level . Vacuum is rated or measured by the columnar lift in inches of either water or the standard: Mercury - drawn up into a tube above normal fluid level . With that in mind, we can almost extrapolate that a pressure of about 15 lbs/sq inch is close to an Earth-based (and very good) vacuum of 14 . 7 lbs/square inch or 29 . 9 in/Hg . Again though, 29 . 99 inches of vacuum is hard to achieve and most engines and/or motor vehicle vacuum pumps only get to around 15 inches of Mercury as an operating value . |
SurferJoe46 (51) | ||
| 811891 | 2009-09-19 21:29:00 | It quite possible to get 29 inches of mercury on a petrol engine intake manifold on deacceleration | prefect (6291) | ||
| 811892 | 2009-09-20 03:47:00 | It quite possible to get 29 inches of mercury on a petrol engine intake manifold on deacceleration MAYBE at sea level on a damp day and with a very good engine and throttle plate closure, no exhaust restrictions and fresh rings on the pistons. The cam has to not be too radical and there should be a fully charged power brake reservoir as well as any other vacuum devices fully charged or inoperative. Then - just MAYBE. But a running engine has a lot less than that for intake manifold vacuum values. |
SurferJoe46 (51) | ||
| 811893 | 2009-09-20 05:03:00 | An ok engine should be running at 21 inches of mercury at idle with no flicker of the gauge and up to 29 inches on over run. | prefect (6291) | ||
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