hmmm I was considering Delrin for the bolt and bolt guide but now I might reserve it to the guide or not use it at all. Thanks, that info might save me some headaches down the road!
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I'm using Delrin for the guide in one of mine (working prototype), and it seems to work nicely. It simply holds the o-ring that makes the seal though, and doesn't make a sliding seal with an o-ring. Even if it got scratched to high hell, as long as it doesn't scratch in the o-ring groove (which would be incredibly difficult to do) it shouldn't suffer the same fate.Comment
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same here only seals on the bolt guide are o-rings which are captured in grooves. The price difference sure is worth it as long as it doesnt create problems.Comment
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Didnt have much time to work on it tonight, but I did figure out a way to shave 1/10" off the bolt and re-route the internal air routes so only one port in the side is needed now. The new air route should also have better flow for filling the dump chamber. Unfortunately the change screwed up a bunch of other crap including the entire 3 way pin I had just drew up. Just, just have to re-dimension a few things sometime.
y0da900 do you have any experience with threading Delrin? I was considering making the back end cap(also the bolt guide) out of Delrin, but it will see some decent forces(~200lbs of pressure) on ~2/10" of threads with a 1.1" diameter. I'm not too worried about it as I'm thinking fine threads should be able to handle it, but maybe you have a experience with it that might be helpful?
I also considered not threading the exterior of the bolt guide and simply making a plate which would be screwed onto the lower portion of the body and possibly also the bolt guide itself. This way no threading is required in the back of the body, so wall thickness wouldnt have to be thickened(with threads there would be a "hump" at the back edge of the marker that I never bothered to add) anyway I'm just rambling on once again so I'll stfu, not that anyones reading this anyway.
no pics tonight as the only external thing to change was a hole disappeared.Comment
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With threading it - yes. Threading it in a situation it would have to hold a force of that magnitude - no. If your design is at all what I'm thinking, I would go with an aluminum backcap separate from the bolt guide, and make a threaded hole for a removable bolt guide in the backcap. This would allow you to experiment with different bolt guide designs to see what works better with minimal cost and work, and alleviate the potential of Delrin having to hold much force. Something like this would be incredibly handy in a gun like a Dangerous Powers G3.Comment
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hmmm I like your idea on the threaded backcap made out of aluminum....would allow easy and cheap experimentation with the gas release point a few other things....and it would greatly reduce the amount of aluminum required since the main portion of the bolt guide is then made up of Delrin.
Since you mentioned it, I checked out the working animations of the DP G3...DP did exactly what I thought of when I saw the DP Threshold animation awhile back. I never really understood why they made the Threshold so long to being with
anyway the bolt guide is similar so the separate bolt guide/endcap will work perfectly.
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well did a little more work on it, modeled the guide/backcap which turned out nicely.
I redid the body a little bit, but I forgot to fix the asa and very back corener of the body before taking a screenshot(asa was thrown together to see how it would look)
While I was at it I changes a few aspects of the bolt to decrease the amt of gas which is required to move the bolt.
anyone have any good places to pick up o-rings or any recommendations?
another question for anyone that might know: how bad is "bolt bounce" in these spool markers? I mean when the bolt resets back, there is always more force pushing the bolt back, but has anyone every studied it to see if the bolt oscillates(sp?) when the bolt resets? If there is a significant amt it could possibly cause some major problems.Last edited by Hilltop Customs; 09-03-2008, 05:38 PM.Comment
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O-rings are nice and cheap at mcmaster-carr as well. If you haven't found it already, I highly recommend going through this book. It is sort of the bible of o-ring application and design.Comment
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thanks you once again y0da, that book is what I've been searching for....have some reading to do
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It's a great reference. I do almost all of my work in AutoCAD, just because I'm used to it. To save time, I created a file that I drop into any and all new projects that has o-rings and their appropriate glands (both rod and bore) done as solid models from size 001 to 020 based on the recommended dynamic seal design dimensions from that manual. Makes designing rods and bores much faster.Comment
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wow thats a great idea....I just started listing them up in excel file, but I think I'll do something similar once I get switched over to Pro E.
I wish I didnt have to read a case study for tomorrow....much rather learn about the dynamics of o-rings than the ethics of some engineer who made bad decisions.
on another note, I had an epiphany today about a different design....I think it even takes it out of the class of a spool marker since the bolt will be actuated by an internal ram and not be a ram itself(original design used a step bolt design similar to the HollowPoint by Deadlywind, but with some very significant changes) anyway I wasnt quiet happy with it and as I mentioned in another post bolt bounce had me worried as it would pose a serious issue with the design. This new design completely solves all the issues, and has the added benefit of a much smaller bolt design, more efficient use of space, less o-rings and less o-ring contact area for the remaining o-rings(so less o-ring friction)
anyway thanks again for the help y0da
ps I re-drew the grip frame as a single trigger, IMO it looks dead sexy....I'll have to post it up tomorrow.Comment
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The classification varies depending on who you ask. Whether or not you think the gas release mechanism or the cycling action is the more important feature. I tend to classify things that seal axially spools, use face seals a poppet, and hybrid variations of whatever I think fits best. Others think that a poppet requires a valve stem and some form of impact. There are spool valves that have very similar gas release profiles to a poppet valve (near instantaneous separation of the seal like a Hollowpoint opposed to gradual opening like a Shocker, both spools). Poppet (or pressure controlled poppet as they have been coined) systems that have very similar cycling motion to spool valves (Mini and MQ come to mind).
It really seems up to the designer.Comment
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y0da, your just filled with great info! I'm going with a near quick separation like the Hollowpoint, because it allows for an extremely quick re-seal and in turn a quick recharge of the dump chamber. I always thought that the whole spool design referred to the different diameters required to use pressure to move the bolt, in other words I linked the movement of the bolt to the spool design. I see what your saying about sealing axially, as most of the time a seal on the bolt will relate to some type of forward force if pressure is behind the bolt.....come to think of it even in my new design the bolt is still forced forward by pressure and only returned by the ram, so by either definition it would still fall under spool.
Ok so Ive read a quiet a bit in that manual, found the failures of dynamic o-rings really interesting, I also found the chart of dynamic o-rings sizing. One thing I want to make sure of is...a female gland would be on the inside diameter of a surface while a male gland is one which is on the "piston" or exterior diameter of a surface correct?
Now my next problem is to find a rod with minimal cross sectional area, which can support a compression of ~9lbs without deforming....max unsupported length of rod will be around 1.33". The load should be completely axial to the rod. From my calculations a 1/16" diameter rod would be absolutely perfect cross section for the dimensions I have right now, but I'm going to have to slightly re size radius's for o rings anyway.
just for fun heres a shot of the old bolt design....the real one would have had many ports around the circumference. If someone can post how it works they will receive +1 Internets.
(for clarification the bolt is completely hollow and has a stepped inner diameter similar to the exterior)
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I would imagine that what your take on the male and female ring glands is correct, but most of the charts in that manual don't use that terminology, but it makes sense.
My guess on the bolt - it operates very similarly to how a cross between a Hollowpoint and SLG would work, except that the bolt return air is not the chamber pressurizing air, but is still provided through the hole perpendicular to the main axis. As the bolt is pushed back, the middle o-ring crosses a port in the body allowing air to flow through the port in the bolt into the chamber. Upon venting the air in front, the bolt is pushed forward due to a bias in surface area and the pressure in the dump chamber, and the middle o-ring isolates the supply port in the body from the port in the bolt allowing the chamber to operate at a fixed volume with no inflowing air during the shot. Somewhere in the forward movement, a step in the bore crosses a valve ring similar to that in both of the aforementioned designs allowing the chamber to vent.
Close?Comment
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+1 internet for y0da900
that is basically perfect....to create the bias in surface area, there needed to be an internal o-ring on the back of the bolt so the cross sectional area of the bolt would only have pressure pushing it back. This is why bolt bounce would be such an issue, if that rear seal would leak or the bolt would bounce off the seal; the gun would fire even with full pressure pushing the bolt back.
Not bad for only seeing the bolt.
edit: judging from your description I'm guessing the SLG uses something like the side porting.....I'm going to have to look for some diagrams of it.Comment
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