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PostPosted: Sun Dec 28, 2014 10:45 am 
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It must be nice to work in a really well equipped shop, endless racks of tools to hand, and preferably any custom tools already made the last time a particular part was needed. I'm beginning to realise that there are two major problems to being a beginner machinist. The first is not knowing one's arse from one's elbow, and the second is not having had twenty years of collecting and making tools.

Arse-elbow confusion resulted in me ruining the first attempt at the valve yesterday by not leaving enough space between the front o-ring groove and the hole for the frame screw. Threading the frame screw hole was the last thing I did, after about 5 hours work, at which point the o-ring wouldn't hold air any more because the screw hole broke through the side of the groove and allowed the o-ring to distort. *sigh*

So today I'm doing it all over again, and this time making the frame screw hole has been moved up the order of operations. On the tool front, that frame screw hole is a blind hole, and all my taps are either taper or (US) plug and don't even get started. So I had to grind the front off an old tap to make a bottoming tap. A bit awkward to get started but it did the job. The other area where I had problems was creating the inner valve surface for the poppet to seat against. I guess they use some sort of custom shaped bit to do that. My original plan was to use end mills to create a flat surface, but my end mills have shoulders and can't reach far enough into the valve. I ended up grinding some old drills, one to create a flat and then a second with a concave front to create some relief around the face. It took a few goes, but worked in the end. Let's hope it does again today.

Jim


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PostPosted: Sun Dec 28, 2014 5:15 pm 
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Is it safe to assume this is going to be an extended (volume) valve? :mrgreen:

Photo's would be nice.

Regards,

Doc Sharptail

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PostPosted: Sun Dec 28, 2014 6:36 pm 
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Hi Doc, no actually it's a reduced volume valve, just to be contrary :) And I'm happy to say it's working. I had some trouble getting the check valve to seal, but a slight reshaping and facing of the poppet sorted out. I put together a 1377 from the spare parts box and got completely sidetracked shooting targets. There's something rather fun about a bare bones 1377, it's light and simple and at 3 pumps fairly quiet but still accurate.

I'll try and remember to take some photos tomorrow when I next have it apart.

The reasons for making it are a bit convoluted. Partly I want to experiment with trying to make a more efficient pump for my 1377 rifle. It would be nice if I could get mid to high 400s with three pumps and no retained air, and hopefully something in the 300s with two pumps for quiet plinking. The bigger picture is that I'd like to try making my own pumper and this is a small step on that path. The reduced volume is because I've kept the wall as thick as possible so that I can drill a hole for a high pressure port. I've got some pressure gauges, so one of the things I want to do is attach one of those so that I can see what pressures are being generated by the pump. The other thing I want to do is try and build a pressure relief valve. That will allow me to set the max pressure to keep the 1377 below 500 fps while still having a strong enough hammer spring to avoid retained air.

Jim


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PostPosted: Sun Dec 28, 2014 8:09 pm 
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I'll have to refer to my notes, but I'm pretty sure I'm getting 460'ish @ 5 strokes out of my ftp'd 13-77.
I'm not seeing retained air until 12 pumps or so, but I did lighten the valve stem return spring...

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Doc Sharptail

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PostPosted: Sun Dec 28, 2014 9:59 pm 
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I wondered what you were up to... I think it's a great idea. Any reason for not using an existing valve body and filling it with something? I assume you're using a flat top piston and valve?
Have you heard of doing it kinda pcp like? By that I mean pressurizing the valve (maybe a larger valve) with say 15 pumps, then only feeding off of a small amount like a pcp by using a controlled hammer weight/pressure. Then it only needs say 3 pumps to top it off again and repeat. More of a pita I suppose, maybe, but a thought to play with. I was also wondering, since you're making parts, is a single stroke. I'm picturing a larger tube, maybe 50% more area, and more stroke all compressing into a smaller volume. No check valve etc req'd so you could have the longer stroke in the same length gun. Harder to pump that one stroke obviously, but it's something I've wondered about. Making the piston length adjustable you could control the pressure and thus the power and pump effort. I love experimenting with stuff too, so best of luck and post results, and pix :)


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PostPosted: Sun Dec 28, 2014 10:03 pm 
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Beaten to the post...but on that note... :lol:


Might have been easier to stuff the valve?? :)

A few bits of delrin..larger looking piece is a cylinder.

Image

Al


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PostPosted: Mon Dec 29, 2014 4:48 am 
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By 5 minutes apparently... Have you considered cropping and resizing photos so they fit better?
I use this guy which is free, good, and fast: http://photofiltre-studio.com/pf7-en.htm
I get the portable one on the bottom, then I delete all the folders and files except the exe and the English translation PLG file.
For posting pix here I crop out all the unneeded stuff and size it to 4" wide. Just a thought...
So do tell how that insert changed the way it behaves, and your thoughts on it.


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PostPosted: Mon Dec 29, 2014 7:01 am 
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Chevota wrote:
I wondered what you were up to... I think it's a great idea. Any reason for not using an existing valve body and filling it with something? I assume you're using a flat top piston and valve?


Ah, embarrassing admission time. I started off modifying an existing valve but didn't think it through carefully enough when I drilled the hole for the relief valve. I dropped in too close to the check valve face and trashed that one, so I started a new front from scratch.

Chevota wrote:
Have you heard of doing it kinda pcp like? By that I mean pressurizing the valve (maybe a larger valve) with say 15 pumps, then only feeding off of a small amount like a pcp by using a controlled hammer weight/pressure. Then it only needs say 3 pumps to top it off again and repeat.


Yes indeed. Some of the ideas I'm playing with are based off an exchange of emails with Bob about this time last year. I was thinking of trying to make a very simple version of Bob's millennial pumper by taking a 1377 and stretching it a little to increase the compressed volume. Subsequent versions could use a longer pump stroke and a larger diameter tube. It seemed like a nice progression at the time, but I'm not so sure now that I want three multi-pumpers :) What I might do is just use the current test gun as a rig to play with some different ideas. Once I've added a port on the high pressure side, originally intended for the relief valve, I could also play with adding additional volume, potentially all the way up to a second tube running parallel to the original one. Lord knows how long it would take to pump up with the tiny 1377 pump though.

Chevota wrote:
I was also wondering, since you're making parts, is a single stroke. I'm picturing a larger tube, maybe 50% more area, and more stroke all compressing into a smaller volume. No check valve etc req'd so you could have the longer stroke in the same length gun. Harder to pump that one stroke obviously, but it's something I've wondered about. Making the piston length adjustable you could control the pressure and thus the power and pump effort.


Heh, yes the contrast between the Daisy 953 single stroke to 500 fps and the original Canadian detuned 1377 "pump your guts out for 430" was enough to make me wonder why I was bothering with multi-pump at all. The Daisy is great but flimsy, so I am tempted to build a single stroke on a nice solid piece of steel tube. The thing that really has me excited at the moment is the idea of a nice regulated pcp setup. So I might bypass a lot of other ideas for now and try and head directly towards that.

Gippeto wrote:
Might have been easier to stuff the valve?? :)

Yes, you're probably right. But I'm also quite leary of the threads for the relief valve letting go, so having a thicker wall to drill into is nice from that perspective. The ideal would be to build a relief valve internally, but it's pretty cramped and even allowing for a new valve rear end that was 1/4" longer with an offset valve stem I didn't think I could fit it in there. Having it outside will make it a lot easier to experiment until I have a better idea of what sort of spring I need.

Jim


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PostPosted: Mon Dec 29, 2014 8:10 am 
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Mr ota...did not realize there was a problem with picture size. Views fine on my computer...or is it a file size issue that you're having?

Stuffed valve takes fewer pumps to get to pressure...power was below acceptable levels for my use.(hunting) Crosman does this in the same manner (cylinder) on the valves used in their 2300 IIRC could be mistaken but I don't think so. Remember seeing it somewhere on a factory valve at any rate.

Everhopeful...have a valve with the relief valve from an old 760 somewhere...yours if you want it...and if I can find it :lol: ...will possibly save you making the relief valve. pm with address if you want it.

Al


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PostPosted: Mon Dec 29, 2014 11:44 am 
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Al, that's very kind of you, pm sent.

As promised, some photos. It looks much like any other flat-top valve:
Attachment:
IMG_8105.JPG
IMG_8105.JPG [ 91.49 KiB | Viewed 860 times ]

I used a smaller than usual diameter for the inlet (3/64) so as to reduce the volume of gas on the outside of the check valve
Attachment:
IMG_8104.JPG
IMG_8104.JPG [ 109.54 KiB | Viewed 860 times ]

Cutting the 1/2-20 threads was difficult, using the largest die I have. Some day I need to add thread-cutting ability to my lathe! Fortunately I have a die holder attachement that goes on the tail stock of the lathe so at least I can keep everything lined up. I had to use the 4-jaw to get enough grip on the work piece to prevent it rotating.
Attachment:
IMG_8106.JPG
IMG_8106.JPG [ 102.24 KiB | Viewed 860 times ]


...


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PostPosted: Mon Dec 29, 2014 11:52 am 
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...
This is the drill I ground with a concave tip to create some relief around the inlet
Attachment:
IMG_8115.JPG
IMG_8115.JPG [ 91.9 KiB | Viewed 858 times ]

It's hard to get a decent photo of the inside of the valve, but you can sort of make out the shiny area around the inlet which is the polished seating surface. The next circle out is the 1/4" diameter of the modified drill, and I had to reduce the poppet slightly to fit inside that diameter to get it to seat well. The bore is the smallest diameter that I could get the poppet and spring to fit easily. I left my notes downstairs, but if I remember correctly it ended up at 23/64.
Attachment:
IMG_8116.JPG
IMG_8116.JPG [ 107.14 KiB | Viewed 858 times ]

I made a quick and easy replacement for the piston cup so that I could try things out. I have an adjustable FTP in the 1377 rifle, so I'm not sure if I will get around to making another one for this test gun
Attachment:
IMG_8116.JPG
IMG_8116.JPG [ 107.14 KiB | Viewed 858 times ]


[Hmm, preview doesn't make any sense compared to the input text, not sure how this will work out. Badly it seems. Imagine that the 2nd copy of the inside is actually the piston!]
...


Attachments:
IMG_8122.JPG
IMG_8122.JPG [ 57.57 KiB | Viewed 858 times ]
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PostPosted: Mon Dec 29, 2014 11:59 am 
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Here's some shots from today's effort at drilling a port to tap into the high pressure air.
I use the lathe for precision drilling as my drill press has a lot of slop in the bearings.
Attachment:
IMG_8117.JPG
IMG_8117.JPG [ 137.36 KiB | Viewed 854 times ]

The nice thing about using the lathe for drilling is that you can use it to hold the tap with everything already lined up. The tap is turned by hand of course.
Attachment:
IMG_8118.JPG
IMG_8118.JPG [ 137.95 KiB | Viewed 854 times ]

Then I used an end mill to provide a flat for an o-ring to seal against
Attachment:
IMG_8121.JPG
IMG_8121.JPG [ 134.87 KiB | Viewed 854 times ]


Jim


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PostPosted: Mon Dec 29, 2014 12:04 pm 
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EverHopeful wrote:
...
Attachment:
IMG_8116.JPG


...


Nice work there Everhopeful.
Do you know the width of your seating surface ring that will reside against the poppet?

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Whitewolf


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PostPosted: Mon Dec 29, 2014 2:07 pm 
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Image


Nice work. I don't have the patience that setting that particular piston for length requires...
My time may come yet.

Regards,

Doc Sharptail

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"Ain't no half-way"
-S.R.V.


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PostPosted: Mon Dec 29, 2014 2:29 pm 
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Whitewolf wrote:
Do you know the width of your seating surface ring that will reside against the poppet?


No, I cut a rather arbitrary dome around the inlet with that abused drill and then ground it flat with a small dremel bit. so the actual dimension is a bit of a mystery down in there. I guess I can measure the indent on the poppet when I next have it out.


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