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 Posted: Sat Dec 06, 2008 12:01 pm |
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| cjs |
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| Joined: 02 Jan 2008 |
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Great work!
Sorry for jacking the thread, but I was just trying to kill time until we got to see your photos.
Thanks.
-Chris
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F2003-ga |
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Last edited by cjs on Fri Feb 11, 2011 5:48 pm; edited 1 time in total |
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| Posted: Sun Dec 07, 2008 10:38 pm |
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| ustilago |
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| Joined: 07 Dec 2008 |
| Posts: 24 |
| Location: Coldhell, AB |
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Heh, I started out with a dremel, a drill press and way too much free time. . . Now I'm about $10 000 in debt but, I certainly have fun at work (being self employed is nice that way :D).
This is one of the earlier Dual Powered hammers that I made. It's kind of ugly. It weighed in at ~45g (stock 2240/50/60 hammers are ~60g).
Lately, I have cut the weight down to ~35g and I tend to polish the living snot out of everything :D
heh, I found my old pic of the hammer in vAgRaNt's 2240 :D
I have also done the DPH in a non-rear cocking version.
On an otherwise bone stock 2240 from the pawn shop that hammer managed to more than double the number of useable shots from a single 12g cartridge :D
I like that flat curve from #1 to #80 :D Moreso, when the "competition" claims 30-40% more shots per cartridge with a $20 band-aid solution. How does 100+% more shots with no loss of velocity sound?
How's that for an introduction? Anyway, I gotta go make some more chips so I can ship this order in the AM. . . ttfn |
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| Posted: Mon Dec 08, 2008 2:03 am |
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| vAgRaNt |
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| Joined: 24 Oct 2008 |
| Posts: 35 |
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| cjs wrote: |
Sorry for jacking the thread, but I was just trying to kill time until we got to see your photos.
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No apologies required - you were havin' fun, and so was I. Glad you liked the pic's; like I said though, I remember
it being more interesting when I was building it. . . . .
| CrustyB wrote: |
| How's that for an introduction? |
Welcome aboard Swarfboy! What the heck took you so long, I thought you were a member everywhere already? 
Damn, they got great smilies over here. . . .  |
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| Posted: Mon Dec 08, 2008 11:24 am |
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| Slavia |
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| Joined: 31 Mar 2008 |
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| Location: Waseca, Minnesota, USA |
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Ustilago - welcome to the forum; you make a grand entrance. The graph is wonderful.
Now a question about subjective stuff: How does the 2240 sound after the mod? Is it louder or softer? Is there any audible clue as to how the valve is behaving now? |
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 ¡Listo! ¡Apunte! ¡Fuego! |
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| Posted: Mon Dec 08, 2008 12:57 pm |
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| ustilago |
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| Joined: 07 Dec 2008 |
| Posts: 24 |
| Location: Coldhell, AB |
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| Slavia wrote: |
Ustilago - welcome to the forum; you make a grand entrance. The graph is wonderful.
Now a question about subjective stuff: How does the 2240 sound after the mod? Is it louder or softer? Is there any audible clue as to how the valve is behaving now? |
Definitely quieter.
On the low power setting, velocity is tuned with the Rear Velocity Adjuster (RVA). The valve is on the the verge of valve lock and the hammer has just enough force to open the valve once. Instead of the distinctive CRACKKKK! you get a muted and very clipped pop.
I don't need no steenkeen LDC or otherwise illegal (locally anyway) hardware on the end of the barrel to be discrete :D
Not quiet enough that I can shoot while grumpy is sleeping but it definitely brings the volume down several notches :D |
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| Posted: Mon Dec 08, 2008 11:00 pm |
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| Slavia |
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| Quote: |
| velocity is tuned with the Rear Velocity Adjuster (RVA). |
What is your procedure for calibrating the hammer? |
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| Posted: Tue Dec 09, 2008 12:40 am |
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| vAgRaNt |
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| Joined: 24 Oct 2008 |
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| Quote: |
| What is your procedure for calibrating the hammer? |
I'm not the "maker", but I own two of these devices, so I feel qualified to comment. . . .
First you have to decide what you want - Do you want a specific "High" speed, or a specific "Low" speed,
cause the other speed is pretty much gonna fall where it may, based on the state of tune of your valve,
TP dimension, etc, etc. Not at all dis-similar to the MarkI with the dual cocking hammer, and front spring
tension adjuster. . . . . .
The RVA is the threaded brass insert in the rear end cap - this portion of the device allows you to fine tune
the hammer spring preload on either of the hammer settings, to achieve the desired velocity with whichever
pellet you choose to use.
For the initial setup, if you have some very particular velocity/energy requirements, there may be
a need to use a modified hammer spring (longer, shorter, higher or lower rate, etc). A really nice
feature of the DPH with integeral RVA, is that the hammer spring can be changed out without disassemb-
ling the rear half of the gun. Simply undo the knurled brass cocking knob, unwind the RVA collar, drop out
the old spring and install the new, reassemble the brass bits, and you're back on your way.
The RVA on my DPH'd .177 CO2 gun will allow for about 60-80fps of range on the low setting. The "high"
setting adds about another ~125fps to the dialed in "low" hammer number. Bare in mind, my CO2 gun
is setup to be a real propellant sipper, and I have some other factors in play in the valve to limit ultimate top
end velocity, in persuit of high shot count per cart values. I promised earlier I'd do a separate post on that
gun as well, I'll see if I can't get some pics up next weekend.
Does that "kinda" answer your question, or were you more interested in how Usti came up with the reduced
target weight of the lightened hammer assembly?
That is a "whole other kettle of fish". . . . . . . .
I'm still trying to goad him into building a Delryn QB hammer with a hardened steel insert for valve
pin contact, somewhere in the 25-30gram range. . . . . I have a theory that a suitably tuned
gun with that hammer, could get more than 200x 500fps shots in .177, from a pair of
12gm carts. Not everyones cup-o-tea, but from my perspective, a near perfect basement gun.
Which reminds me, I still need a .177 barrel and bolt for that darn QB. . . . . |
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| Posted: Tue Dec 09, 2008 1:24 am |
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| Slavia |
| Moderator |
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| Joined: 31 Mar 2008 |
| Posts: 4382 |
| Location: Waseca, Minnesota, USA |
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| Quote: |
| Does that "kinda" answer your question |
Given that the goal is economy without significantly sacrificing performance, my sense is that you have reduced the hammer's inertia by reducing travel, mass, and spring pre-load. This brings the gun near the point where the hammer doesn't reliably dump the valve body's contents, but not quite. The adjustable part is to stay on the consistent side of "not quite."
Do you make the adjustment by sound, or with a chronograph, or perhaps by examining grouping? My question related more to the procedure for finding that "sweet spot." Or is the adjustment so forgiving that you just pick a velocity and tune for it?
And as for "kettles of fish," yes, I would be interested in how the hammer's final mass was determined.
I have a 2240 that wants to know.....
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¡Listo! ¡Apunte! ¡Fuego! |
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| Posted: Tue Dec 09, 2008 5:23 am |
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| ustilago |
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| Joined: 07 Dec 2008 |
| Posts: 24 |
| Location: Coldhell, AB |
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Tell ya what Mr. Vague Rant, you track down a barrel, I'll turn it and mill it for the QB and do the bolt. I have a box o' 78 at the moment, waiting for when I have enough free time to start prototyping probed bolts and Delrin or teflon cup seals. I might even take a crack at a delrin/hardened steel striker if you throw enough $$$ and compliments my way :D.
I have a bit of a backlog to clear first (and 4 months worth of neglected paperwork  ).
For tuning the hammer, vAgRaNt has pretty much nailed it. Generally, I will put a cart or two through a bone stock 2240, over my chronograph. Then I swap out the hammer/link pin/rear cap and swap in the DPH. The first couple of shots are used to dial in the Rear Velocity Adjuster on the low power setting to the same power level as the stock hammer setup was giving me (determined by the average velocity from the first shot until the CO2 is depleted and velocity starts to plummet). Then I blow through a couple of cartridges and record velocities without touching the RVA.
I use the same pellets (Crosman wadcutters, 14.3gr) for all shot strings.
The "kill" setting is basically useless with the stock 7.5" barrel, no matter where the RVA is set, you still get MAX POWER!
Switching to a 24" barrel is a different story altogether. Silly national laws restrict my reportable velocities to 499.999999 fps 
| Slavia wrote: |
| Quote: |
| Does that "kinda" answer your question |
Given that the goal is economy without significantly sacrificing performance, my sense is that you have reduced the hammer's inertia by reducing travel, mass, and spring pre-load. This brings the gun near the point where the hammer doesn't reliably dump the valve body's contents, but not quite. The adjustable part is to stay on the consistent side of "not quite."
Do you make the adjustment by sound, or with a chronograph, or perhaps by examining grouping? My question related more to the procedure for finding that "sweet spot." Or is the adjustment so forgiving that you just pick a velocity and tune for it?
And as for "kettles of fish," yes, I would be interested in how the hammer's final mass was determined.
I have a 2240 that wants to know.....
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The decreased hammer mass and travel result in the valve operating in the "self regulating range". Hammer spring preload is used to dial in the desired velocity.
Adjustments are made by observing the velocities reported by my aging Chronotech chronograph (my 5' chrono range does not lend itself well to observations of groupings, I can shoot one ragged hole with my 760 at that range  ).
And finally, the hammer mass is determined by my little digital pocket scale.
Enjoy! |
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| Posted: Tue Dec 09, 2008 5:45 am |
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| broommaster2000 |
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| Joined: 10 Mar 2007 |
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| Location: City of Groningen, Groningen, The Netherlands |
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If you can get .50 balls to go 499.99999999 Fps...  |
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| Posted: Tue Dec 09, 2008 9:37 am |
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| Slavia |
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| Joined: 31 Mar 2008 |
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| Thanks, guys. We'll see what filthy lucre Christmas might bring to pay for the lathe work. And as long as I have a screwdriver in hand, it might be time to get the steel breech that Broommaster was bugging me about. The idea of economy without sacrificing performance is appealing. |
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¡Listo! ¡Apunte! ¡Fuego! |
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| Posted: Tue Dec 09, 2008 9:59 am |
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| broommaster2000 |
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To be honest, it should be quite possiible to turn one of those pumpers into a spring powerd gun.
And yes, Slavia, you'd better put some weight on your Crosman.
Demonic voice: And then you will bring it to me. |
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| Posted: Tue Dec 09, 2008 11:30 am |
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| Slavia |
| Moderator |
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| Joined: 31 Mar 2008 |
| Posts: 4382 |
| Location: Waseca, Minnesota, USA |
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| Quote: |
| Demonic voice: And then you will bring it to me. |
(Spoken with zombie stare): Yeths, mathster. |
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_________________
¡Listo! ¡Apunte! ¡Fuego! |
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| Posted: Tue Dec 09, 2008 3:36 pm |
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| broommaster2000 |
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| I wonder how this looks if you are a just a regular user. |
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