Author Topic: Any Interest in 6mm ? - Build Thread  (Read 7913 times)

rsterne

  • Member 2000+fps Club
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1537
  • Mozey-On-Inn and see what Coalmont has to offer!
    • Mozey-On-Inn
Re: Any Interest in 6mm ? - Build Thread
« Reply #30 on: December 11, 2017, 05:00:28 PM »
Yes, the headstock bore on my lathe is only 3/4", so I can't pass a 1.25" tube though it to single-point thread it.... and the 36" bed of the lathe is not long enough to use a steady rest on the 39" tube and still get to the end to thread it.... That meant I would have had to use a tap, which I don't have.... Pinning the plug like I did is plenty strong enough (3 screws would have done it), and much easier for me to do....

Bob
  • Coalmont, BC

Alan

  • Administrator
  • Hero Member
  • *****
  • Posts: 2022
  • Set the example... Don't be one!
    • Mobile Amateur Radio
Re: Any Interest in 6mm ? - Build Thread
« Reply #31 on: December 12, 2017, 04:35:30 AM »
I won't speak for Bob, but I'd bet it is much stronger!
  • Roswell, New Mexico
Alan

I have an Omega compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your portable tank as a courtesy.

rsterne

  • Member 2000+fps Club
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1537
  • Mozey-On-Inn and see what Coalmont has to offer!
    • Mozey-On-Inn
Re: Any Interest in 6mm ? - Build Thread
« Reply #32 on: December 12, 2017, 08:30:28 AM »
Threads and pinning can both have equal strength.... certainly sufficient to provide greater strength than the tube itself if desired.... Proper design is the key.... My preference is to have the weakest link in the chain the bearing load of the screw-heads in the sockets in the tube.... so that if a failure is imminent, those holes will show distortion before anything catastrophic occurs.... That is something that can't be done with threads, the weakest point is almost always just inboard of the threads, but outboard of the O-ring.... because the most common method of failure with a threaded end plug is pulling the entire assembly from the end of the tube outboard of the O-ring.... where the thread has reduced the wall thickness of the tube....

Bob
  • Coalmont, BC

rsterne

  • Member 2000+fps Club
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1537
  • Mozey-On-Inn and see what Coalmont has to offer!
    • Mozey-On-Inn
Re: Any Interest in 6mm ? - Build Thread
« Reply #33 on: December 12, 2017, 08:09:41 PM »
Today I tackled the job I hate the most, but possibly the most satisfying if it turns out well.... I turned the stub and rear face of the tank block.... The piece I started with was a 1-1/4 x 3-1/2" piece of 6061-T6 rectangular bar stock.... I roughed out the stub material with my power hacksaw (finished with a hand saw) and then cut a piece 2-3/4" long, ending up with an "L" shaped piece of aluminum.... The small part of the "L" is for the round stub that inserts into the front of the tube, so I had to mount it in the lathe to make that round and the correct diameter, and cut the O-ring groove.... In the same operation, you face the rear surface of the block flat square to the stub.... The trick was mounting it in my lathe....

I have a 4-jaw chuck, with reversible jaws, but with them in the normal orientation one jaw was right out past the chuck face, because the block has to be offset so that the round stub is at one end.... I reversed that jaw, which solved that problem, but then the block has to sit on top of the first ledge on the jaw, and I didn't like the idea of trying to shim the block at the other end, there is incredible load when turning this piece, and it must be very rigidly mounted.... or it could jar loose and come flying out of the lathe, or break something (and maybe me).... I came up with the idea of reversing the opposite jaw as well, so that the block would sit on both of them, but NOT reverse the side jaws, so that they had more clamping area.... it worked perfectly, as you can see below.... Top and bottom jaws reversed, side jaws "normal"....



Before putting the block in the chuck, I laid out and drilled a center hole for the stub, using a 60* center drill.... The by using a 60* center in the tail stock, pressing the block against the two reversed chuck jaws, it was pretty simple to get it centered.... I have never turned such a large, offset block before, and the impact with the tool bit is considerable if you take too big a bite.... so I used the slowest feed rate (0.004") and could only remove 0.005" per pass off the flat surface beside the stub.... I had left the material 1/10" oversize, so that took 20 passes at over 3 min. each.... well over an hour just to machine that flat surface.... Then I had to turn the 1-1/4" square stub that was sticking out to a 1.05" circular one, drill the center air passage (1/8") and cut the O-ring groove.... Between the setup and machining, it took all afternoon, and some of the evening.... I must be the world's  ~ s l o w e s t ~  machinist....  ::)

It was pretty nerve-wracking, so I will have a good sleep and tackle the rest of the block tomorrow....

Bob
  • Coalmont, BC

rsterne

  • Member 2000+fps Club
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1537
  • Mozey-On-Inn and see what Coalmont has to offer!
    • Mozey-On-Inn
Re: Any Interest in 6mm ? - Build Thread
« Reply #34 on: December 13, 2017, 10:32:44 PM »
I finished the tank block today.... My 300 bar, 500cc Carbon Fibre tank clears the main tube by just over 1/16" when installed.... Here is the side view, showing the regulator installed....



The notch on the top front is for a barrel band, there are two 6-32 holes drilled and tapped on the front face to attach it.... As you can see, there is a Picatinny rail on the bottom.... The hole there is for the plug for the vertical air passage.... The plug is a low-profile 10-32 SHCS with a # 008 O-ring under the head in the milled 5/16" recess.... There are four 10-32 screws to retain the stub of the tank block in the tube, again drilled at a 45 deg. angle so that the tank block can be removed without removing the barrel.... The stub seals into the tube with a single # 118 O-ring.... The 1/8"-27 NPT tapped hole in the side is for a gauge for the pressure downstream of the regulator.... Below is the rear view....



The method of mounting the regulator is different from common practice.... Instead of using the two (red) O-rings inboard of the threads in a bored hole, the hole in the block is simply drilled deep enough to clear the length of the regulator and tapped 1/2"-14 NPS.... At the top of the hole is a recess milled with a 7/8" end mill to a depth of 0.085" to accept a # 115 O-ring.... This is a snug fit over the regulator, in the groove between the threads and the shoulder on the bonnet, which is 0.900" OD.... When the regulator is tightened into place, that O-ring fits into the groove in the tank block, and seals the regulator outboard of the threads.... This trick, pioneered by Travis, is much easier to machine, and is used on the Flex and Cobra.... Qudos to him and Jim Gaska for coming up with the idea.... The three 5/8" wide grooves milled around the middle of the tank block and the back and sides are only to remove a bit of weight, and pretty it up a bit.... Even so, the block weighs a hefty 8 ozs....  ::)

Bob
  • Coalmont, BC

Christopher

  • Sr. Member
  • ****
  • Posts: 402
Re: Any Interest in 6mm ? - Build Thread
« Reply #35 on: December 14, 2017, 03:10:16 AM »
Looking real nice. When you machine out your o-ring grooves, like for the #118 where your plenum tube will go, do you have a "rule of thumb" as to how wide and how deep you machine the groove in comparison to the o-ring? For example, the nominal thickness of a #118 is 3/32", or .094 (nominally), so how wide and deep do you go to ensure a good seal? Great work!

Thanks,
Chris
  • dead end road KY

Nvreloader

  • Jr. Member
  • **
  • Posts: 78
Re: Any Interest in 6mm ? - Build Thread
« Reply #36 on: December 14, 2017, 08:07:16 AM »
Very nice and interesting machining tricks you used.........  8) I am still following along, and learning from you,
I for one greatly appreciate your info,photo's you pass along. 
Thank you, Bob.

Tia,
Don
  • Western NV
NRA Life member

"We must reject the idea that every time a law's broken, society is guilty rather than the lawbreaker.
It is time to restore the American precept, that each individual is accountable for their actions"
Ronald Reagan

"Speeds fine, but Accuracy is final"

rsterne

  • Member 2000+fps Club
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1537
  • Mozey-On-Inn and see what Coalmont has to offer!
    • Mozey-On-Inn
Re: Any Interest in 6mm ? - Build Thread
« Reply #37 on: December 14, 2017, 08:58:11 AM »
HI Chris....

There are lots of sites that give O-ring gland dimensions, either in formula form, or tables.... For a 100 series (3/32" CS) O-ring, which are actually 0.103" nominal, the tables say 0.081-0.085" gland depth for static seals, which is 0.020" compression.... Dynamic (sliding) seals have a bit less compression (deeper glands).... The recommended groove width is 0.144", but I usually cut mine with a 1/8" tool, as there is still enough volume in the groove for the "squashed" O-ring at that width.... It is important to measure the gland depth from the TUBE ID that the O-ring is going to seal in, NOT the valve OD, which is smaller, often by about 0.010".... For the tube on my 6mm, the tubing ID is 1.062", so at 0.081" gland depth that means the groove ID is (1.062 - 2x0.081) = 1.062 - 0.162 = 0.900".... If the gland depth was 0.085", the groove diameter would be 0.892".... The grooves on an MRod valve are 0.895" on the ones I have here with roughly the same tube ID, maybe a couple of thou smaller....

Deeper grooves are easier to assemble (eg. when sliding the O-ring past the valve screw holes).... but more prone to leaking.... Harder O-rings, eg. 90D instead of 70D seem to be a bit easier to guide past a hole without damage, but on the other hand are harder to get started in the end of the tube without a good taper there.... IMO a 90D O-ring in a 0.085" gland depth "feels" like a 70D O-ring in a 0.081" gland depth when starting it into the tube.... because the 70D compresses easier.... 90D O-rings resist extrusion into the gap between the valve and tube at a higher pressure than a 70D.... although to be truthful I have never seen a problem with extrusion, even with a 70D O-ring into a 0.005" gap at 3,000 psi.... which is too big a gap according to the tables....

Bob
  • Coalmont, BC

sixshootertexan

  • Sr. Member
  • ****
  • Posts: 417
  • Ricky B
Re: Any Interest in 6mm ? - Build Thread
« Reply #38 on: December 14, 2017, 09:59:51 PM »
You can just Google Parker oring handbook and download a pdf of it.

Looks good Bob. Wish I had known about the oring trick before I sent my lower to get anodized. Would have been a nice backup to the other 2 orings. I wanted to put a down stream gauge on mine but just didn't have the room.
CCS 2300, CCS 2400, Custom Built Regulated .25, Custom Built PRod Clone, .308 Bullet shooter, XS46U .177, Custom regulated .177, 850 Hammerli .177

rsterne

  • Member 2000+fps Club
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1537
  • Mozey-On-Inn and see what Coalmont has to offer!
    • Mozey-On-Inn
Re: Any Interest in 6mm ? - Build Thread
« Reply #39 on: December 15, 2017, 09:21:34 AM »
The hardest thing about making female ASA fittings is that 0.696" bored hole inside the threads for the O-rings to seal on.... sometimes I get away with cutting it with an 11/16" end mill, and sometimes it leaks (or is too small).... plus it is difficult to thread to the shoulder it creates (I actually made a bottoming tap to do that previously).... It was a brilliant solution WAR came up with to eliminate that seal and just seal at the outer end of the threads against the bonnet.... They use a 15/16" O-ring but I didn't have that size end mill, but I found that a # 115 O-ring had to be stretched a bit to fit on the regulator bonnet in the groove between the threads and the shoulder, so I went with that.... You just drill a 47/64" hole 0.70" deep and then tap it with a 1/2"-14 NPS tap.... mill a 0.085" deep recess for the O-ring with a 7/8" mill and it's done....  8)

Bob
  • Coalmont, BC

rsterne

  • Member 2000+fps Club
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1537
  • Mozey-On-Inn and see what Coalmont has to offer!
    • Mozey-On-Inn
Re: Any Interest in 6mm ? - Build Thread
« Reply #40 on: December 21, 2017, 04:43:19 PM »
A couple of days ago I got a start on one of the valves.... got it roughed out, made some parts for the inside, and then spent a day finishing off the design.... Today I finished the first valve.... Here is the inside roughed out.... The valve is 5/8" ID with a 5/16" throat and a 1/8" stem....



The spring retainer end cap is a vented wheel that fits into a recess in the front of the valve and is retained by an circlip.... The area for the wheel is 3/4" ID.... I made the 3/8" thick and machined out the inside, leaving a 1/8" vented web.... That was my solution to the difficulty of holding a 1/8" thick part for machining....



Here is a front view of the completed valve.... The two long 6-32 screws are the front mounting bolts for the receiver.... They penetrate the valve BEHIND the valve seat, straddling the throat, which allows me to use larger screws than an MRod valve and yet have a larger ID....



The O-ring is located behind the recess for the wheel, where the valve wall is full thickness.... The gauge is tapped directly into the left side of the valve, behind the O-ring, so no need to drag it across a large hole in the tube.... Here is the back view, showing the huge 0.257" port, which is on a 30 deg. angle towards the 5/16" throat for improved flow....



The four valve mounting bolts are 10-32 x 1/4" SHCSs set down with the heads in shear.... They are in staggered pairs, the top and bottom pair in a similar location to an MRod valve, but the ones on the sides are 1/4" further forward.... I had to do that to make sure there was enough tube material for proper strength on the RH screw, which sits ahead of the cocking slot for the hammer.... The slot ends exactly at the back edge of the valve body....

The reason for no photos of the inside is that this valve is my own home-made version of the ART/SS valve.... Since I was privy to the development of it, I was able to design and make my own version.... but out of respect for Travis, I am not divulging the details until he gets his patent in place.... My sincere thanks to Lloyd and Travis for their help while I was making the very intricate guts for these valves.... I made several versions before I managed to get any parts that were even usable, they are, to say the least, challenging.... and well worth their price, IMO....

Bob
« Last Edit: December 21, 2017, 04:54:31 PM by rsterne »
  • Coalmont, BC

Christopher

  • Sr. Member
  • ****
  • Posts: 402
Re: Any Interest in 6mm ? - Build Thread
« Reply #41 on: December 21, 2017, 04:53:41 PM »
WWOOOWW Bob! Awesome machining skills.  I figured you were up to something intricate since you hadn't updated the build in a few days. Looks like it all came together nicely.  I like the fourth screw, integrated gauge and the beefier breech screws, not to mention that it's a balanced valve as well.... 8)

Great job,
Chris
  • dead end road KY

oldpro

  • Hero Member
  • *****
  • Posts: 1228
Re: Any Interest in 6mm ? - Build Thread
« Reply #42 on: December 21, 2017, 06:23:15 PM »
Man o man that is a bit of work! The hours of time and R&D will pay off in the end I’m sure: This will be fun to watch.
  • Mount Shasta Ca.

rsterne

  • Member 2000+fps Club
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1537
  • Mozey-On-Inn and see what Coalmont has to offer!
    • Mozey-On-Inn
Re: Any Interest in 6mm ? - Build Thread
« Reply #43 on: December 21, 2017, 06:36:16 PM »
My first ART/SS valve.... it better work, I've bet the farm (these two guns) that it will....   :o .... It would be almost impossible to get enough hammer strike for a conventional valve of these dimensions at the operating pressures I intend, within the space I have for the hammer.... unless I can find a Gorilla to cock it.... ::)

Bob
  • Coalmont, BC

oldpro

  • Hero Member
  • *****
  • Posts: 1228
Re: Any Interest in 6mm ? - Build Thread
« Reply #44 on: December 21, 2017, 06:57:41 PM »
My first ART/SS valve.... it better work, I've bet the farm (these two guns) that it will....   :o .... It would be almost impossible to get enough hammer strike for a conventional valve of these dimensions at the operating pressures I intend, within the space I have for the hammer.... unless I can find a Gorilla to cock it.... ::)

Bob

 I have a feeling you will be just fine ;)
  • Mount Shasta Ca.