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Valve Help


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#1 Lighthawk

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Posted 04 September 2011 - 04:21 PM

[IMG]http://i1208.photobucket.com/albums/cc374/lighthawk2/ValveDiagram.jpg[/IMG

(Thanks, roboman)

I'm having trouble with the grommet's seal on the valve I'm making. I epoxied it into place and the seal will hold up to 20 psi. After that, it leaks from the area between the standoff and the ID of the grommet. How can I fix this? I'm out of delrin so I hope to fix this without having to remachine the whole thing. Perhaps the trouble is because I made this on a drill press instead of a lathe, possibly causing a slight misalignment.

Edited by Lighthawk, 05 September 2011 - 08:54 AM.

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#2 roboman

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Posted 04 September 2011 - 05:34 PM

Posted Image

(I hope I put up the image the right way.) (why is this so hard?)

I'm having trouble with the grommet's seal on the valve I'm making. I epoxied it into place and the seal will hold up to 20 psi. After that, it leaks from the area between the standoff and the ID of the grommet. How can I fix this? I'm out of delrin so I hope to fix this without having to remachine the whole thing. Perhaps the trouble is because I made this on a drill press instead of a lathe, possibly causing a slight misalignment.


[IMG]http://i1208.photobucket.com/albums/cc374/lighthawk2/ValveDiagram.jpg[/IMG]
Copy/paste that in place of the broken image code in your post.

It would really help me if the image was bigger - I can't read the text around it.
From what you've said, your problem could stem from the grommet not being tight enough around the pin. You probably need to make the counterbore where the grommet goes slightly smaller, which means that you'll most likely have to re-make the entire thing. A lathe would be quite helpful.
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#3 Lighthawk

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Posted 05 September 2011 - 09:11 AM

It would really help me if the image was bigger - I can't read the text around it.
From what you've said, your problem could stem from the grommet not being tight enough around the pin. You probably need to make the counterbore where the grommet goes slightly smaller, which means that you'll most likely have to re-make the entire thing. A lathe would be quite helpful.
[/quote]

I guess that as long as you can see the picture, I can fill you in on the problem area (the rest doesn't matter.) Basically the main valve ID is 7/16in then it tapers to 1/4in and then it expands to 1/2in to fit in the grommet. It has friction between the firing pin and the grommet already, and the surface area of the ID of the grommet is about an 1/8in deep. I don't have access to a lathe, and I don't really want to have to spend alot of money to get it custom made. I know you do custom work for a relatively cheap price, but it's still an expense I'd like to avoid.
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#4 ricochet

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Posted 05 September 2011 - 10:24 AM

I guess that as long as you can see the picture, I can fill you in on the problem area (the rest doesn't matter.) Basically the main valve ID is 7/16in then it tapers to 1/4in and then it expands to 1/2in to fit in the grommet. It has friction between the firing pin and the grommet already, and the surface area of the ID of the grommet is about an 1/8in deep. I don't have access to a lathe, and I don't really want to have to spend alot of money to get it custom made. I know you do custom work for a relatively cheap price, but it's still an expense I'd like to avoid.


If I understand your explanation correctly, my suggestion would be to eliminate the tapering factor. If you keep the OD the same you can replace the grommet with an oring. Orings are simple, yet one of the best choices for reliable sealing. For example, in my valve I use a 1/2" OD x 1/4" ID oring, which seals perfectly and is low friction. As the OD gets smaller more friction is applied to your grommet. Essentially if you eliminate the tapering, you eliminate a lot of the friction as well.
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#5 roboman

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Posted 05 September 2011 - 11:24 AM

It would really help me if the image was bigger - I can't read the text around it.
From what you've said, your problem could stem from the grommet not being tight enough around the pin. You probably need to make the counterbore where the grommet goes slightly smaller, which means that you'll most likely have to re-make the entire thing. A lathe would be quite helpful.


I guess that as long as you can see the picture, I can fill you in on the problem area (the rest doesn't matter.) Basically the main valve ID is 7/16in then it tapers to 1/4in and then it expands to 1/2in to fit in the grommet. It has friction between the firing pin and the grommet already, and the surface area of the ID of the grommet is about an 1/8in deep. I don't have access to a lathe, and I don't really want to have to spend alot of money to get it custom made. I know you do custom work for a relatively cheap price, but it's still an expense I'd like to avoid.


I see. If I correctly understand what Ricochet is saying, he's suggesting a second set of o-rings on the stem. This a a really good idea, as it is easier to implement, especially if you've used a bolt and standoff as your pin. All you'd need to do is make another o-ring "sandwich," like you did before, and install it on the other end of the rod. This would necessitate the removal of the area that normally holds the grommet in place, but should make the valve much easier to produce, should you ever need to make another.
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