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| POS |
 Posted: 10/31/2006 17:54 PM Post subject: How far should a piston atleast move backwards? |
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Major
Joined: 14 Sep 2006
Posts: 395
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The title says it all. How far should a piston move back in a barrel sealing piston valve ?
If I think logicaly, I would say at least half of the ID of the barrel. Can anyone confirm this ? |
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| jrrdw |
| Posted: 10/31/2006 20:00 PM Post subject: |
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Donating Moderator
Joined: 16 Nov 2005
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| This is a good question, i think there are to many verieables (sp) to generalize it, you know - air pressure/side clerances/over all size/ect... |
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| squeaks |
| Posted: 10/31/2006 20:02 PM Post subject: |
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Captain
Joined: 01 Oct 2006
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| I'd say as far as you possibly could allow the piston would be the best. Wait, never mind that, because if it moves farther then it adds space for the air to go, so I guess you wouldn't want it to go too far. |
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| djt |
| Posted: 10/31/2006 20:19 PM Post subject: |
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Major
Joined: 11 Mar 2006
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| i would say a little more than the diameter of your barrel. like if you have a 1 1/2 barrel then make it move back 1 1/2. sounds logical to me anyways |
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| SquishY |
| Posted: 10/31/2006 20:22 PM Post subject: |
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Master Sergeant
Joined: 07 Feb 2006
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| Math says that it should move atleast 1/4 of the sealing face, so for a 2" sealing face it should go back .5" for max flow. Suppose a little more wouldn't hurt. |
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| markfh11q |
| Posted: 10/31/2006 22:39 PM Post subject: |
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| SquishY's got it. 1/4 of the barrel diameter is all you need for maximum flow. Any more is just wasting energy. |
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| drac |
| Posted: 10/31/2006 22:49 PM Post subject: |
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Metalhead Moderator
Joined: 24 Apr 2005
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| No, it's 1/4 of the barrel's cross sectional area if i recall correctly. |
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| Brian the brain |
| Posted: 11/01/2006 0:34 AM Post subject: |
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Brigadier General
Joined: 05 Dec 2005
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Yes that's right.More will hurt performance, and so will less..
You could make it open a little more to account for the neoprene flap blocking flow a little as it bends with the airflow, as we did with Chappy.. |
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| SquishY |
| Posted: 11/01/2006 13:56 PM Post subject: |
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| I'm not sure how far mine will open but I will try to compensate for it by playing with tthe piston length before sticking it together. I how ever can not take credit for the original math but I have since applied it, Gort and I were talking and that came up so yeah. |
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| POS |
| Posted: 11/04/2006 13:28 PM Post subject: |
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Major
Joined: 14 Sep 2006
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Thanks for the answers. I let mine move half of the inner diameter of the barrel. That should be good.
In the MB2 I made, the piston moves back 4 cm, the barrel is 28 mm. The piston got dammaged all the time, cause it smashed against the stopper. Got a steel stopper now, the piston itself has a steel bolt in it.
So, with this new information, my fourth gun, also the first PVC gun, will be a lot bether. |
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| SquishY |
| Posted: 11/04/2006 16:25 PM Post subject: |
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Master Sergeant
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| As we've posted, to much movement can hinder the performance, go by what the math says and you will have a much better valve. |
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| sgort87 |
| Posted: 11/04/2006 17:36 PM Post subject: |
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The Gort
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| squeaks |
| Posted: 11/04/2006 18:02 PM Post subject: |
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Captain
Joined: 01 Oct 2006
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| Wait, one quick second here. Is it different for chamber sealing vs. barrel sealing valves or is it the same? |
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| boilingleadbath |
| Posted: 11/05/2006 14:38 PM Post subject: |
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| It might change it some... but it shouldn't hurt preformance (or saftey) noticably to allow it to move back twice as far as calculated, so you might as well let it. Anyways, it makes sure it moves back far enough to allow full flow. |
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| POS |
| Posted: 11/05/2006 15:51 PM Post subject: |
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Major
Joined: 14 Sep 2006
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| SquishY wrote: | | As we've posted, to much movement can hinder the performance, go by what the math says and you will have a much better valve. |
And what does math tells us ?
I think it is logical the piston moves about 1/2 of the diameter of the barrel. If math tells otherwise, how come ? How do you calculate it ? |
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