December 3, 2007 at 4:05 am #923
I have a small update for my Talon/Condor/whatever it ends up as build…
my bushing turned down and ready to be shrink fit…
Here it is after a painfully steep learning curve with shrink fitting. The third time was the charm…
The set screws are my insurance policy in case my first ever attempt at shrink fitting turns out marginal. I’ll likely hide then under the rail and trigger group block.
And the bits so far together.
I’m going to tackle the guts of my valve this week and hopefully get the openings and slots cut into the tube.
More updates as I progress.
MBDecember 3, 2007 at 1:42 pm #28557
How much interference did you use?
In other words, how much larger was the OD of the brass, verses the ID of the aluminum?
What grade brass did you use?
What grade aluminum did you use?
Roy S.December 3, 2007 at 11:07 pm #28606
I went with .005″ interference between the parts. A bit of searching online seemed to indicate that .002 to .004 was typical for interference fits for bearings and such, so I went with the high end thinking that aluminum would expand more than steel and permit the extra .001″. I’m planning on anchoring the rail and trigger block through the tube and into the bushing for extra security. I kept the valve body screwed into the bushing when I froze it to give it some extra thermal mass. That seemed to make all the difference when it came time for assembly. without the mass of the valve body the brass would grow too much between the time I pulled it out of the freezer and tried to set it in place.
The Aluminum is 6061-T6511, the brass is, uh…yellowy/gold? Honestly I don’t know what grade brass it is, just an off cut from metal supermarket. I would presume it is 360 ASTM B16, I think that is all they sell in rounds.
I got some bits and pieces to play with fabricating the valve internals, I’l going to give it a go tonight I hope!
MBDecember 6, 2007 at 4:32 am #28735
Another little update…
Ok, so my valve works 😀
I just managed to fab up the stem seal and gave it a low pressure test. Apart from a minor leak past the valve seat until pressure builds enough to seal it, it seems to work. Time will tell if it passes enough gas to do the job, things are looking mighty tight in there…
I still have to tap in two more ports for the burst disk and the tank gauge. I figured I’d stick the gauge on just out of curiosity for how much pressure drop I experience and to relate that to how the valve manages to self regulate over a wide temp/pressure range(if it does at all).
The top hat is next. I screwed up and figured on a max stroke of 1/4″ but forgot to leave extra stem unthreaded for the top hat set screw to bear down on. I guess I might grind some flats around the threaded section for the set screw to seat on or just hope that if I’m gentle with the allen key I don’t mess up the threads too badly.
I could likely turn the seal diameter down to get more volume and flow but I’m not sure how much meat is necessary to prevent the valve seat from shearing off the thin edge of the seal and sending the stem out the valve 😯
P.S. This is for a CO2 powered version, not sure if I mentioned that in the origional post…December 6, 2007 at 4:40 am #28736
Does you Foster male fitting have built in check valve?
Like what you are doing, nice work.
Roy S.December 6, 2007 at 4:41 am #28737walkonkingParticipant
Looks great. Good ideaDecember 6, 2007 at 7:33 pm #28767quote :
Yup, it’s the simple shouldered pin with an O-ring check valve method. I hadn’t thought about the check valve pin contacting the valve return spring during filling, I’m thinking I’ll give it a try and if it pushed the spring off the seat of the stem I’ll have to forgo the fitting and make up a fill adapter.
As you might guess I’m making this up as I go along.
With a little luck I’ll have the valve done shortly and I can get on to the actual gun i.e. “the cool part”
MBDecember 12, 2007 at 3:38 am #29148
Baby steps…baby steps…
MBDecember 13, 2007 at 3:27 am #29234
Another micro update…
Well I managed to cut in the loading/cocking port on my body tube. My drill press was none too happy with it’s responsibility’s as a milling machine and chose to show its displeasure by cutting erratically and sloppily. Fortunately I stopped my cuts short of my desired outline on all but one side. The bushing side cut did slightly cut into the brass bushing but only by .001″ so only my pride was hurt.
I had to do a fair amount of cleanup with small files to get everything reasonably neat. Unfortunately I won’t have that crisp “precision milled” look to much of my body tube but it should still function. I’m a little worried about how the radius’s for the top and bottom rails will turn out if I try and mill them with my drill press. I know thats going to be pushing the limit of what my drill press can handle. I may have to try an alternative approach or see if I can find somewhere that could prep my rail blanks with the appropriate radius cuts so I can just shape them and inlet them as needed.
So… one more step done, countless more still to do…
MBDecember 13, 2007 at 3:44 am #29237shadohParticipant
That looks damn nice for drill press work. I know guys with mills who would struggle with that. I hate guys with all the nice toys and they dont know how to use them.December 13, 2007 at 9:27 am #29263buba-bParticipant
Looking good MB , drill press is far from ideal but half the fun is working around the limitations of your home tooling 😀 youre just have to take very light cuts 😯 good luckDecember 13, 2007 at 11:31 am #29268
Great to see what one can do, with what they have.
Roy S.December 13, 2007 at 2:33 pm #29273yParticipantquote Shadoh:
Hey hey hey.. back it down…. Wait.. you didnt mention me by name, nevermind 😆February 19, 2008 at 5:14 am #34325
After much delay and procrastination I have a bit more work done on my build…
RakatiTakityTickaty Bang goes the drill press, yet it keeps on chipping away at what I throw at it…
MBFebruary 24, 2008 at 3:39 am #34779brushy-billParticipant
As a journeyman toolmaker, I have to tell you that is some fine looking work you have done there. 😯 It sounds like you are doing it the “hard way” But you sure cannot tell by its appearance. cant wait to see the finished project. and see some shooting results.
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