An idea for a homemade

[waterzooka]

It's been a while since I posted, but I thought I would jump in on the check valve discussion.

I have some plans for homemade check valves that I will post tomorrow. (It's on my other computer) It is very simple and uses standard PVC fittings and parts from McMaster Carr. The only part I'm still trying to find is the spring. Total cost should be less than $2.

It's made from a 3/4" coupler with 3/4" x 1/2" reducers stuffed in each end. In the middle is an O-ring, a ball and a spring. I will post the part #s and a sketch.

Ben or Silent Guy - You may want to move the sketch and instructions to a different post, but I will leave that up to you. This homemade check valve would be useful in several different designs.

[Silence]

I think I know where you're headed with that. If I'm guessing correctly, it's a brilliant idea; and if I'm not guessing correctly, it's probably even more brilliant.

I'm guessing you're just putting the O-ring on the ball, and putting the ball and spring inside the coupler, with grooves in the coupler wall. If that's the case, it sounds like a very good design.

However, assuming you're going with what I'm thinking of, you'll have to make sure the grooves won't thin the wall too much. But I think you're going with a different design or have a workaround.

Either way, sounds very creative and very DIY! I'm looking forward to seeing how you'll use a ball in the setup.

[waterzooka]

I was incorrect in my previous post, the coupler is 1 1/4" (not 3/4"), however the overall size is smaller than an off-the-shelf PVC check valve. McMaster Carr has the balls and O-Rings, but in order to reap the savings benefits you will need to by a few ball and rings. I have purchased my share of 1/2" check valves at Lowes and in the long run I still think building your own is the way to go.

I'm still working on a source for the spring and I'm thinking a conical spring would be best. I have outsourced custom springs before for other projects and they are dirt cheap (10-25 cents if you buy a couple hundred) so I will update this post with my findings.

Either way, I thought this would be a cool idea to try. I should be building a few when the weather warms up.

The pics and the McMaster Carr part #s are below:
9338K12 (1.125" Polypropylene Ball - $14.36 per Pack of 50)
9452K206 (-318 Buna-N O-Ring - $5.92 per Pack of 50)

[Silence]

Very neat. Actually, I was just planning to make a homemade check valve myself, because I bought parts for Nerf homemade on impulse yesterday and forgot the single check valve.

Only one check valve is needed because the pump is going to be like that of the Schwinn Air Driver 700. It will basically work like in the 2nd picture at http://sci-toys.com/scitoys/scitoys/aero/vacuum/, which was linked to in the first link. But that's besides the point.

I for some reason thought I wouldn't need a check valve at all...but I do need one. So I might make one by hand after all, and it doesn't seem as hard as I had thought, as other parts of the Nerf homemade would be even harder.

The check valve I was thinking of would be based off the pump design. Basically, I was going to put 1/2" Schedule 80 PVC in between two couplers and get a soft rubber stopper with an OD of 9/16". Pretty much an O-ring, but without a hole in the middle and without the rod.

The groove would be in the side of the Sch. 80 PVC, on one end only. A plastic washer on either side would hold the rubber stopper in place. The groove would continue into a groove in the plastic washer, so when the rubber stopper is on that end, the air can pass through the groove and around. The Sch. 80 PVC would ensure decent strength, even with a groove inside.

However, I seem to like your design more . Of course, I'd need to adapt it to fit 1/2" PVC, but that can't be too hard...very nice design though. I guess the use of a ball means that the sizes don't have to be too precise.

[waterzooka]

I haven't check the internal dimensions for a 1/2" x 1 1/4" Coupler (Reducing Bushing), but I suspect it will work just the same. I choose this design for simplicity, there is no machining (cutting grooves, etc) needed on any of the parts.

[Silence]

True. But how does the O-ring stick to that side of the chamber? Using glue?

Also, how do you get the tubing to be narrower in the mouths--the blue part? What fitting is it? Looks like a clean design though.

EDIT: After a bit more experimentation, I noticed that the inner rim of couplers isn't very well made. The rim is often nonexistent on one side of the bore, but very large on the other side. Just something to watch out for.

[waterzooka]

The O-Ring fits tight within the walls so no glue is needed and it touches in two places so the seal should be airtight. The pressure will force the ball into the O-Ring which will expand the O-Ring into the walls.

Also, how do you get the tubing to be narrower in the mouths--the blue part?

These are Reducing Bushings. They are standard PVC fittings. Lowes has a better selection than Home Depot.

And no need to worry about the inner rim on the Coupler. The Coupler just holds the two Reducing Bushings.

Note:
I updated the drawings I posted with a conical spring and the proper names for the PVC fittings.

[Silence]

Oh, okay...then the design's even better! I've used 1/2" to 3/4" reducing bushings, but those don't have two different IDs because they're so short anyway. But I would imagine you'd see it on a larger reducing bushing. Unfortunately, it won't work on a smaller scale without some sanding...

The poor-quality rim on the coupler affects my design more than it affects yours. But maybe it would work with a washer in place...

I'll try to set up something to be used in 1/2" PVC. It will probably be along the lines of your neat design, but with some differences because the bushing reducer can't be used. Good luck with building yours!

EDIT: Alright, I think I've got something. It's basically your design in 1/2". It involves two couplings, with a piece of PVC in between. Between the PVC and the rim of either coupler is a washer, with a 3/8" ID and a 13/16" OD. One of the washers is part number 93412A423, so it's basically just a rubber washer for better sealing. The ball is part number 1854T54, which is 1/2" in diameter and Buna-N. I've yet to choose the spring, but it can be a very weak spring.

Alternatively, I could just use plastic washers and part number 96385K61 for the ball--it's 5/8" in diameter for a real seal. This method would use a groove in one end of the PVC and in one of the plastic washers.

I like both methods, and they're cheap if you make 10 or so of these. However, your design uses O-rings, which are cheaper still, by a factor of 10.

[CROC]

Originally Posted by waterzooka

The pics and the McMaster Carr part #s are below:
9338K12 (1.125" Polypropylene Ball - $14.36 per Pack of 50)
9452K206 (-318 Buna-N O-Ring - $5.92 per Pack of 50)

This looks as if it involves boring out the space for the O ring to sit in, which involves a lathe
Otherwise, the plans look good. Would it fit 3/4" CPVC though, or would it have to be modified for the different sizes?

[Silence]

I'm under the impression that reducing bushings of that size already have that space bored out. That's why it won't work with smaller sizes, but the layout I suggested should work instead.

Do you want CPVC for the ID difference? If you just need the ID, Schedule 80 PVC should work depending on your tolerance for a slightly different size. Anyway, I'm sure this setup could be done with similar parts but for the corresponding CPVC fittings.

I might have mentioned this already, but I can fit Waterzooka's design for 1/2" PVC using 1/2"-3/4" reducing bushings.

[CROC]

I was thinking of having it connect to the whole 3/4" CPVC, so that I can attatch it without need of 1/2" PVC. I might be able to make a 3/4" check valve, if i have the right materials available to me at my local stores. I live fairly close to a plumbing outlet store, so I will compare prices on items when I am there.

[Silence]

I was only referring to 1/2" PVC for my weapon-in-progress, sorry about the confusion.

The clever design Waterzooka layed out is essentially for 3/4" PVC. It just uses a larger PVC coupling in the middle.

I really don't know the measurements for CPVC, although I suspect its OD is smaller than the corresponding PVC OD. You might have to check McMaster-Carr on that.

I presume if they make fittings to convert CPVC to PVC, then you can incorporate one of those into this design. I don't think CPVC is pressure rated though, so I would only use it on the inlet side of the inlet check valve, if you need one. That's the only place without high pressure.

[CROC]

Once again...its me with another one of my topic resurrections...

I was just doing some shopping and I got the right hand side of my diagram in pieces (minus a check valve). I am waiting to see what kind of check valves I get before I buy any more for this gun
~CROC

[CROC]

Next week I am going to a plumbing store to get check valves and adapters, since I am extremely busy with a science project that is due on Monday. I will post when I get them, and will try to use my bros digital camera to make a step by step instruction page.
~CROC

[CROC]

In a CPH, does the pump width change how hard it is to pump, or will it become rock hard quickly?

I am considering using a foot-long pipe on my CPH, which I haven't really done much on (Search the following text to find my homemade: Idea for a homemade)

I'm maintaining the style, and the pumping mechanism, which goes over the reservoir. I will have a brass ball valve in the front of the gun, to fill with.