New Linear Flow Valve

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Drenchenator
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Postby Drenchenator » Sat Sep 15, 2007 11:30 am

I posted about this at SSC but since WaterWolf and iSoaker discussed this here I though I might was well post a compilation of posts at SSC.

Drenchenator has been working on a type of pull valve with mixed results. It's not at all like what I described and is a completely new valve design. It needs some bugs worked out definitely, but right now it is functional. I'll leave posting about it to him.

The valve that Ben described is truly a completely new kind of valve. I don't have a good name for it; Until I do, let's call it a "new linear flow valve." It is like a gate valve but also like a ball valve. It probably just is a homemade gate valve though. I wasn't planning on posting it until my CPS homemade was done, but it works and Ben "burst the bubble." This valve show in pictures below is in fact the prototype for an improved valve I plan to build when I get time during Winter Break.

A few people have tried to build homemade pull valves with limited results. Ideally, a valve should provide linear and then laminar flow; a pull valve does not. I built this out of a desire for a "homemade linear flow valve." I also wanted the valve to open easily and close automatically after I failed to do so with my CPS homemade.

Image

The valve works like a ball valve; however, instead of a ball with a hole in it, a cylinder with a hole is used. The cross contains a section of 1/2" PVC to house the cylinder. This video or the animation below show how the valve works.

Image

(the valve disassembled)

Image

The prototype's cylinder is a sanded CPVC pipe filled with foam backer rod and glued in place with epoxy. It still leaks though. In the end, a 5/8" rubber rod will be used in the final version of this valve.

Some questions from the topic at SSC:

Is it easier and does it work as well as a ball valve?


It opens very easily. One single push opens it manually. This valve was designed to be used in a triggered gun, so a pull downwards also opens the valve. To complete my CPS homemade, I have to figure out how to do that using the pull of the trigger.

This valve should ideally work as well as a ball valve, but as I said this prototype leaks out of the non-machined cylinder. The rubber rod will fix that problem.

I don't know how much the rubber rod you will be using costs so can you give some info on that, thanks.


My local Lowes doesn't stock rubber rod. On McMaster a 6" length of 5/8" diameter medium soft rubber rod is a costly $9.13. Nonetheless, it is well worth it if I can finish my CPS gun's trigger system with this valve.

I'm wondering how you'll make sure the rod stays aligned. I feel it could easily twist, which could suddenly induce turbulence in a full-bore valve. Any solutions, besides a groove or square guide rod or something?


It has linear guides that limit the cylinder's motion. It won't twist as long as the steel rod is in. Plus, I made an "alignment hole" to properly align in the first place. I have video of the assembly of the valve that could demonstrate this but it is big (~60 MB). Furthermore, it didn't twist during testing. The spring doesn't provide a rotational force; it can't see how it would twist unless someone actually grabbed it and twisted it.

Image

The guides also limit vertical motion; the cylinder cannot be removed without the removal of the steel rod. I thought the design through.

Do you think though on your valve, if I was to make the hole bigger it would work?

Yes, it should work as long as the hole is not as wide as the pipe (the cylinder would split into two at that point). This valve is a prototype for a later version that I will build using rubber rod and a larger hole as discussed earlier. Since the pipe is 5/8" wide, I would probably try a 7/16" hole at most. The hole in the prototype is 5/16" wide.

I have long wondered whether it would be possible to make something that could open and close near instantly with good linear.

It does open quickly. Another advantage of this valve is that it closes automatically. Though ball valves offer the maximum flow, they do not close automatically like this one. I tried for a long time while building my CPS homemade to make a ball valve close with a spring. No matter how I oriented the spring, it would not close the valve all the valve. I was able to get the trigger system to open the valve all the way, but if the valve can't close all the way the gun is pretty much useless. I still have to figure out a trigger system for this valve though (pullies come to mind).

Again, I don't actually have experience with this, but to make a cleaner "spring-stopper", would be to possible to simply continue the piece of 1" pipe downwards a little farther and put an end-cap on it?

I like your spring stopper idea. I don't know why he didn't do that actually. Sounds way simpler.

In retrospect, I should have done that and didn't think about that until now. To tell the truth, I used a "short pipe" for only two reasons: it made drilling the "valve holes" much easier and with the bottom section installed, the cylinder can't go past the open position. I didn't just pick an arbitrary point to end the 1/2" pipe; I picked the point where if the cylinder was in the open position, it's end would be at the end of the pipe. I can drill a hole through both the pipe and cylinder, resulting in a cleaner drilling (they would align better in the future). This method made sure that I could drill the hole correctly.

Instead, I should have just continued the pipe and have then used a short but accurate length of dowel to push the cylinder to the correct position so that I drill the hole in the right spot. The guides would make sure that the cylinder doesn't go past the open position then.

Thanks WaterWolf, I don't know why I didn't think of this before. It will be implemented into my final design.
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Postby isoaker » Sat Sep 22, 2007 9:16 am

Doh! I didn't notice this thread since WaterWolf's Silver Bullet thread had gotten my attention. At any rate, this is a pretty slick homemade valve. I'm not sure it's a totally new design (it reminds me of those draw string spring-loaded things that you push the button to allow it to slide, but obviously a water-tight version). However, it's likely the first or perhaps a first in terms of applying such a valve system to a homemade water blaster. This valve design looks fairly promising if watertight seals can be kept while allowing smooth motion during opening and closing of the valve opening.

I'm sort of curious how well this thing behaves if the hole through the cylinder were shaped and used pretty much as the nozzle of the water blaster. I also wonder whether one could find parts to create a sliding rectangular block as opposed to a cylinder as this would eliminate the need for the rotational guide and only require a vertical-motion limiter (not to mention it might be easier to drill in larger holes into a rectangular block without compromising side-wall strength too much).

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Postby HBWW » Sat Sep 22, 2007 12:27 pm

If you can get the seal to work well, the valve might even work for WBL's, as long as it opens fairly fast. Either way, it seems like the valve would give a good trigger feel similar to the old Soakers' pull valves, a type of feel and durability unmatched by WW and Max-D ball valves.

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Postby Drenchenator » Sat Sep 22, 2007 3:08 pm

I'm sort of curious how well this thing behaves if the hole through the cylinder were shaped and used pretty much as the nozzle of the water blaster.

That's quite a novel idea. I suppose it would work. Builders could then use a tees instead of a crosses. However, I designed this valve to be internal. I am sure that I am the only person who has built a water blaster with internals like standard Super Soakers. This valve was made to fit inside of a gun. It could work like that but the idea would remove one of the advantages of homemades: multiple nozzles.

I also wonder whether one could find parts to create a sliding rectangular block as opposed to a cylinder as this would eliminate the need for the rotational guide and only require a vertical-motion limiter (not to mention it might be easier to drill in larger holes into a rectangular block without compromising side-wall strength too much).

That is a great idea, but frankly since PVC is cylindrical it just is not feasible. Ideally, I would definitely use a rectangular block instead of a cylinder for the reasons you listed. It would simplify the thing as a whole. Nonetheless, I was working with pipe with circular cross-sections and designed the valve with that in mind.

If you can get the seal to work well, the valve might even work for WBL's, as long as it opens fairly fast.

It would be better than a ball valve but worse than a solenoid in a launcher. Personally, I wouldn't use it in a launcher because I designed for soakers. But it should work well enough in launchers.
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Postby WaterWolf » Tue Sep 25, 2007 7:26 am

It would be better than a ball valve but worse than a solenoid in a launcher. Personally, I wouldn't use it in a launcher because I designed for soakers. But it should work well enough in launchers.


Recently, I started doing some tests to compare a pneumatically operated solenoid valve VS a ball-valve.
Even with the few test runs I've done so far, it was obvious that the solenoid valve was much less efficient. Shots went only about half the distance the ball-valve ones did.
My guess is that the air has to make four turns inside the valve before it is released out the barrel, resulting in less linear flow. Also, that it has lower flow volume, since the air has to squeeze itself past the piston and plastic.

It may be that the solenoid works better on larger launchers, or requires a longer barrel. The WBL I'm testing it on is a slightly scaled down one.
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Postby Drenchenator » Tue Sep 25, 2007 2:37 pm

It may be that the solenoid works better on larger launchers, or requires a longer barrel. The WBL I'm testing it on is a slightly scaled down one.

Something may be wrong. From what I know some sprinkler valves don't work pneumatically because they have a guide rod (read more here). Some solenoids just don't release air as fast as others too. Nonetheless, since they are used quite prevalently in spud gunning for cheap, fast opening valves, they are better valves for launchers than ball valves.
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Re: New Linear Flow Valve

Postby Croc » Sat Mar 01, 2008 10:15 am

Sorry to revive this topic, but

Would this system be easy to spring load?
ie. Pull the trigger in a spiral shape that will open the valve, and the a spring auto returns it.

Would that be too difficult, or would it not work at all? I am considering using this trigger system in my CPHzooka, and need to know

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Re: New Linear Flow Valve

Postby Drenchenator » Sat Mar 01, 2008 1:43 pm

As shown in the pictures and the video, the valve is already spring loaded; you just have to use a properly sealing cylinder and a pulley system to open the valve. I ran out of time last summer to finish it, so I didn't do that.

In this system would not be too difficult to buy provided that you have access to the tools and a good selection of materials. The right size cylinder is the key to the valve; mine took forever to make and still leaked. You can just buy 5/8" rubber rod off of McMaster though, which should work perfectly and cut the construction time immensely.
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Re: New Linear Flow Valve

Postby Tim » Mon Nov 28, 2016 5:44 pm

Image
Last edited by Tim on Sat Feb 11, 2017 12:09 am, edited 1 time in total.

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Re: New Linear Flow Valve

Postby Drenchenator » Tue Nov 29, 2016 10:03 pm

Wow, cool animation! Certainly better than my ancient MacDraw gif! Is that a design of yours Tim, or is that a pre-made part? I remember looking for a pre-made part like this valve design at the time, but didn't find anything worthwhile. This certainly fits the bill, though, and should perform much better.
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Re: New Linear Flow Valve

Postby Tim » Wed Nov 30, 2016 5:58 pm

Hi Drench,

Yes; that is my design.

A few months ago, I said I'd be building a CPH in January (I should have said I’d start in January). As you may recall, the ball valve actuation mechanism I proposed was questionable, and to have any chance of working, I was planning on a 3/4” valve with a 5/8” port. This port size is not horrible (as evidenced by POPCAP), but I got greedy the more I thought about it. The 3/4” gate valve in the animation has a 13/16” (0.8125”) port. “Full Port” valves have a slightly smaller diameter than this, but I want to drill an opening in the gate as close as I can to the ID of 3/4” Schedule 40 pipe, which is 0.824”.

I posted the gate valve animation here because clearly this thread was my inspiration. Initially, I started designing a piston valve like you proposed, but with a 3D-printed body. I switched to a gate valve for a couple reasons. First, the piston valve version would have been even more expensive to 3D print because the body has to have extra length to accommodate the alignment slots. Second, the end-to-end length of my piston valve concept was longer than I preferred because a large-diameter piston is needed to accommodate a 13/16” port.

I will receive all of the parts for this valve for Christmas. I anticipate some trial and error upon assembly. I designed a tight clearance between the valve body and the gate because I don’t know how much material will be removed by Shapeways’ polishing process after the print (I want it polished for a nice look). Also, I don’t know where in the ±0.010" width tolerance the Delrin gate will be (I am not overly worried about the thickness because that has a +0.005" tolerance). As for the seals, I probably went overboard with the compression (interference between seals & gate), but I am trying to compensate for the lack of smoothness in the 3D print. Below is a screenshot showing the seals...

Image

VR,

Tim

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Re: New Linear Flow Valve

Postby Drenchenator » Thu Dec 01, 2016 12:41 am

Tim, your design looks quite good. It seems to fix all of the problems that I encountered that led me to abandon this kind of valve before. Here are few things that I especially like:

1) The seals are minimal but also redundant. I originally intended to use a rubber cylinder in the final design, but that would require a lot of force to open that wall. A planar design, like yours, avoids this completely.

2) A planar design also allows for the seals to be replaced easy. When the seals get shot in my design, you have to completely remake the piston, not a good idea.

3) Using two springs also adds an additional layer of redundancy to close the valve.

4) The amount of travel needed should also be minimal and very acceptable. The amount of travel in my ball-valve based designs is just too high and one goal in designing this valve was to make it easier to open (lower force and less travel).

In all, I am really looking forward to seeing you build this valve and your next gun! I think it's a fine design that a clear leap forward from previous designs. Good job! I'm glad that you took the solid core of this idea, stripped it of the bad, and made it your own. I wanted to make this work and was sad that I couldn't, so I'm glad that you picked it up and (apparently) solved it.
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Re: New Linear Flow Valve

Postby Tim » Thu Dec 01, 2016 6:02 pm

Thank you for the encouragement, Drench. Below are some further clarifications in response to your comments.

“1) The seals are minimal but also redundant.”

Actually, only one of the four seals is redundant. Both of the larger seals are needed to prevent leakage through the top and bottom of the valve. In particular, water will bypass the smaller o-rings when the valve is in transition between open and closed (when the hole in the gate straddles the smaller o-rings. The larger seals ensure that all of this bypass-water passes through the nozzle.

Only one of the two smaller o-rings is required (doesn’t matter which one). This o-ring is needed when the valve is in the closed position. Otherwise, water would travel along the surface of the gate, through the hole, along the other side of the gate, and through the nozzle. I will indeed install the second small o-ring for redundancy in the closed position (this is when a tight seal is most critical).

"2) A planar design also allows for the seals to be replaced easy.”

The valve body is all one piece, which will make seal replacement more difficult than with a two-piece body. I steered away from a two-piece body because I was worried about torqueing the bolts unevenly. 3D-printed Nylon is more compressible than cast Nylon, and slight inconsistencies in the gate slot could lead to leakage. I don’t need the additional variable at this point.

To install the o-rings, I will press them in with the ruler from a combination square. I’ll pass the ruler through the slot and push down on both sides of the ruler. To remove o-rings, I’ll pull them out with a dental pick. This will puncture the o-rings, but I figure I’ll only be removing them when they are worn out anyways.

“3) Using two springs also adds an additional layer of redundancy to close the valve.”

There are actually four springs, two on each side (you can see three of them in the animation). This arrangement allowed me to keep the body as short as possible while still applying a balanced spring load on the gate. Essentially, I’m using four “weak” springs instead of one “strong” spring.

“4) The amount of travel needed should also be minimal and very acceptable.”

In my model, the travel is 27.76855 mm. Long-pull bicycle brake levers have a cable travel of about 15 mm. The Travel Agent can increase this travel by a factor of 1.9 to 28.5 mm. I realize this is cutting it close, but I could use McMaster Carr part # 3790K11, which has a published travel of 0.69” (17.526 mm). The Travel Agent could extend this to a safer 33.2994 mm. The Travel Agent also provides the 90-degree turn that would be required to use this valve on a blaster.

***UPDATE***: I misread some information regarding the cable travel length of long-pull bicycle brake levers. The 15 mm travel is for a 20-degree pull. The travel length for a full squeeze of these levers is typically 30 mm to 32 mm. So, I might not need the Travel Agent, but I'll keep it in the design because I could use it to shorten the required trigger-pull or simply use it as a pulley to keep friction lower than it would be with a brake cable noodle.

VR,

Tim
Last edited by Tim on Thu Mar 09, 2017 9:28 pm, edited 2 times in total.

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Re: New Linear Flow Valve

Postby Drenchenator » Fri Dec 02, 2016 11:01 am

Thanks for the additional clarification. Yeah, the stoke/travel of the trigger system always is always an issue, it seems. It's never really short enough. The McMaster part and Travel Agent seem like a good plan.
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Re: New Linear Flow Valve

Postby Tim » Tue Jan 17, 2017 5:10 pm

Hey Drench,

I finally got around to assembling the valve. Although it may not be apparent in the video, this was quite a hack job. I had worse clearance issues than I anticipated, even with the thickness of the gate. To make the clearance adjustable, I had to cut the valve body in half and bolt the halves together with low-profile aluminum binding posts. I do like the two-piece design; I just hadn't thought to use binding posts until I was forced to come up with a solution that would not interfere with the springs.

The hole in the gate is perfectly placed because I put the top stop plate on the gate and used the valve body as a guide for my 13/16” transfer punch. I 3D printed a jig to properly locate the clips for the bottom spring pins. I also used this jig to mark the proper gate length. However, I need a better miter box or something else to make a squarer cut in the gate material. The holes for the stop plate and bottom adjuster bolt are not well centered. I have already modified my jig design to help me locate these holes next time.

I have also modified my gate valve body design to remove $8 of plastic from the 3D print. I still have several functional design changes to make, and I feel I can safely shave even more plastic off. I will add holes for the binding posts so I don't have to drill them. I also need to make some adjustments to the o-ring grooves and the bottom spring pins' "home" position.

When I first tested the valve with a garden hose, it spurted a quick shot of water out the bottom every time the valve was in the process of closing. I'm guessing this was due to water hammer. So, I removed the smaller ID o-ring from the outlet valve-half, and this problem went away. Unfortunately, this led to more leaking in the fully closed position because there was more o-ring "memory" force from the valve-half with two o-rings (the gate was noticeably not centered). To make the o-ring compression more even on both sides, I put two partial sections of o-ring in the smaller groove of the outlet valve-half. This reduced the leaking to a slow drip.

Of course, I am not happy with a slow drip, but this is the beginning, not the end of this design. I think using a softer o-ring material will help. For this MK1 Gate Valve, I used o-rings with a medium durometer of 70A. After I redesign the body, I'll use soft o-rings with a 50A durometer. I may also have better luck replacing each of these fat o-rings with two thinner o-rings for a double seal. I realize I could attempt X-Profile (or even Double X-Profile) o-rings, but then I'd have to use rectangular o-ring grooves instead of trapezoidal ones, which would allow the o-rings to slide around and distort when the valve opens and closes.

I will not be able to work on this project again until I get back home at the end of March. Drench, can I send you the "MK1" Gate Valve in the video below? If so, please PM me an address. I'd like to have your feedback from a hands-on evaluation before I get back to this in the Spring. If you don't have time and/or feel it would be better for someone else to evaluate, please let me know.

Image

VR,

Tim

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Re: New Linear Flow Valve

Postby Drenchenator » Wed Jan 18, 2017 10:50 pm

Hi Tim,

I'm glad you're making progress on this design! It's unfortunate that there is still a slow leak after all that work, but that's part of the design (and re-design) process.

I appreciate you offering me the chance to evaluate the valve, but I don't have any means to test it here at UCLA, unfortunately. All my equipment is back in MD and I'm in CA for the time being.

I do think changing out the O-rings is the right think to do. From my reading of what's going on, the design itself seems to open and close well, but the seal is imperfect. The only aspect of the design that needs work, then, is the seals. It might take some process of elimination, but I think trying out different O-ring materials and designs is that way to go. I don't really have much guidance over what else to try, but it might also help to try to isolate the location of the leak and to see if you can adjust the design to prevent any leaks in the area (if the leaky area is constant).

Well done! I look forward to you picking this project back up again in a few months.
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Re: New Linear Flow Valve

Postby Tim » Thu Jan 19, 2017 5:28 pm

Drench - That's cool; I understand. I just felt you deserved the first right of refusal because of your work in this area.

UPDATE: Below is the most up-to-date version of the valve body half. Although it lacks the binding post holes and other improvements, it shows the plastic I intend to leave out to make the 3D print more economical.

Image

VR,

Tim

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Re: New Linear Flow Valve

Postby Tim » Sat Mar 25, 2017 4:36 pm

I'm finally back home. I updated my model today, making the following changes.

  • Removed Inlet On/Off Seal groove.
  • Made area within Inlet Body Seal equal to the area of the Outlet Body Seal minus the area within the Outlet On/Off Seal in an effort to achieve a “zero-pressure” seal.
  • Made o-ring grooves deeper per AS-568C standards.
  • Made the NPT threads a looser fit to allow bottoming out while still maintaining a good seal.
  • Added Holes for Binding Posts to attach valve halves.
  • Added clearance for width of gate.
  • Designed reduced-friction guides for sides of gate.
  • Further value-engineered the valve halves for 3D printing.
These valve halves and an updated jig for cutting & drilling the corresponding gate are on order...

Image

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Re: New Linear Flow Valve

Postby Drenchenator » Sun Mar 26, 2017 10:26 am

Hi Tim! It looks like you've come up with a good next iteration. I look forward to the results from your testing.

Does this design use different O-rings?
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Re: New Linear Flow Valve

Postby Tim » Sun Jul 30, 2017 10:07 pm

Hi Drench,

Yes; the o-rings are a bit different. In the last trial, I used o-rings with a Shore A durometer of 70 (think car tire). The o-rings I have on order now have a Shore A durometer of 50 (almost as soft as a pencil eraser). Based on what I’ve read, softer o-rings work better in some low pressure applications (even 100 PSI is low pressure compared to typical hydraulic applications).

The previous o-rings were metric and had a 5mm cross-section, but I could not find these with a 50 durometer. The new ones are -300 Series AS-568C o-rings with a nominal cross-section of 3/16” (0.210” actual). So, these new o-rings are a hair thicker.

I think the best improvement towards a leak-free design will stem from balancing the pressure on both sides of the gate in the closed position. As I described in the previous post: Inlet Body Seal Area = Outlet Body Seal Area - Outlet On/Off Seal Area. There is no Inlet On/Off Seal this time.

In my first trial, I removed the Outlet On/Off Seal instead of the Inlet On/Off Seal, but I’m now thinking this was a bad idea because I had pressure on the inlet side of the gate and NO pressure on the outlet side of the gate. Having pressure on one side acts to push the gate away from the seal. You can’t get pressure on the outlet side of the gate if you have an inner on/off seal at the inlet.

Similar to my nozzle & laminator work prior to publishing POPCAP, I’m abandoning the scientific method wherein one controlled variable should be tested at a time. I consciously apply a “kitchen sink” approach because free time comes at a premium. Nonetheless, I have a few more tricks up my sleeve if this trial does not go as planned.

UPDATE:

I performed testing with the revised valve months ago on April 15th. Testing did not go as planned (If it had, I’m thinking I would have provided an update sooner).

Image

Image
I believe I have achieved even WATER force on both sides of the gate, but I should have been aiming for even TOTAL force on both sides of the gate. As you can see by the o-ring grooves in the image above, the two outlet seals have more “Length-of-O-ring” than the one inlet seal. Therefore, there is more o-ring “rebound force” applied on the outlet side of the gate than on the inlet side. For this reason, the gate is not centered, and the inlet seal has broader contact (it is more compressed) with the gate than the outlet seals. In fact, the weeping of water from the valve appears to be coming from the outlet side of the gate (In my first trial, it was leaking from the inlet side because I had equal o-ring force, but water force only at the inlet). To remedy this, I could attempt the following:

  • Add four Teflon bolts (one in each corner of the inlet valve-half) to use as jacking bolts against the gate, which would keep the gate centered and thus the o-ring compression equal.
  • Add the above-mentioned jacking bolts, but increase the area sealed by the inlet seal. This would result in more water force on the inlet side than the outlet side to combat the outlet o-ring force; so, less force would be applied to the jacking bolts (reduced friction). At higher pressures, this might lead to more total force at the inlet, so adding holes to the outlet side for jacking bolts would be a good idea.
  • Instead of the above, I could try to add grooves to the inlet side for “dummy sections” of cut o-ring to match the outlet’s total Length-of-O-ring. This may create more friction than the jacking bolts.
Regardless of what I do to achieve a leak-free seal, the friction will increase. The spring-force required to open and close the valve reliably with a slow weep is already significant. Nonetheless, I am hopeful that a bicycle brake lever will have the leverage necessary to actuate the valve with relative ease. If needed, I could upgrade the gate to Teflon. However, it makes no sense to invest in a lever or a Teflon gate until I have a leak-free design.

VR,

Tim
Last edited by Tim on Sun Aug 20, 2017 5:34 pm, edited 1 time in total.


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