My Version of the Millenium Pumper

[rsterne]

OK, OK, the lightbulb just went on.... The downturn of the maximum travel curves at maximum preload is the "bstaley" effect showing up.... I was just slow to recognize it.... I was thinking of it backwards.... Once you run enough preload it is possible to drive the hammer into the back of the valve IF the stroke adjuster is fully inside the hammer (maximum throw).... Here is the data replotted for the maximum preload with the 2.00" x 0.045" spring at coil bind....



What is happening is that if the center of the hammer face (the striker part) is recessed as far as it can go, it is limiting the valve lift to 0.100".... That is what is happening at the "Maximum" setting in the above graph.... As you move the striker forward (towards the hammer face) it opens the valve further (eg. at 1 turn).... At 2 or more turns, the hammer is no longer hitting the valve body, so the velocity limits at it's usual "plateau" like I'm used to seeing.... If I continued reducing the recess in the front of the hammer (which also reduces hammer throw) I would again see a velocity loss....

I'm going to have to ponder this for a while....

Bob

[1377x]

looking at your graph
maximum means flush or sticking out of the hammer correct?
each less turn means the further in/more reccessed the striker is??

[rsterne]

On that last graph, "Maximum" means maximum stroke/travel.... ie fully recessed (about 0.20") into the face of the hammer.... The fact that the face is so deeply recessed limits how far the valve can open before the rim of the hammer face hits the back of the valve body.... That in turn, limits the velocity....

Bob

[rsterne]

My version of the Millenium Pumper is finally finished.... It uses a .25 cal Lothar Walther barrel, a Disco main tube, and a Mac1 extended Billet linkage, and weighs 7.25 lbs. without the scope, which is a Leapers 4-16 x 40 AO MilDot.... Here's what it looks like....



The Boyd's Blaster thumbhole stock has a swell in the forearm right where you grip it for pumping, and was a perfect choice.... The pump stroke is long, but significantly easier at 1800 psi than the Carbine was at 1500.... I have pumped the gun by hand to 2000 psi, and I would consider that a safe upper limit.... Over 60 FPE with EunJins should be pretty easy at that pressure....



The pump actually works better than the one in the Carbine did, filling the 28.5 cc valve faster than the Carbine did its 27 cc valve.... It takes 80 pumps to fill to 1800 psi from empty.... The second graph shows the number of pumps to refill after each shot when the gun is set up for three shots of 40 FPE.... This gun actually takes fewer pumps while producing 40 FPE per shot than the Carbine did at 30 FPE per shot....



Filling to 1800 psi gives a choice of three different tunes just by resetting the RVA.... I can get 1 shot at 950 fps (51 FPE), 2 shots at 898 fps (45.4 FPE), or 3 shots at an average of 846 fps (40.4 FPE) within 30 fps (less than a 4% ES).... While the gun can be pumped to 2000 psi, I feel that these three settings give the best balance between power and pumping....



The graph above shows the velocity of the "next" shot in each string.... You can see that the 4th shot when the gun is set up for three shots of 40 FPE is still about 30 FPE.... plenty good enough for a close follow-up or a coup de gras.... I'm extremely pleased with the way this project turned out.... It surpassed all my expectations, and performs better than I could have ever dreamed or hoped for....

Bob

[lloyd-ss]

WOW Bob!  Great design, engineering, and execution!  You've got it all in this one.
Very nice.
Lloyd

[1377x]

looking good!
very nice shooter!

[rsterne]

Somebody asked what the FPE was if I maxed out the settings at 2000 psi.... With 42.4 gr. EunJin Points, it hit 858 fps, which works out to 69.3 FPE.... Mind you, it took half the air in the valve to do that, and MAN was it LOUD !!!

Bob

[Donny]

WOW super nice. I will trade you one of my kids for this rifle 

[Sqrl Klr]

Great project Bob. Is it any harder or easier to use that than a benj hand pump? Wondering if you may have to switch arms every 20 pumps or so.

[Rescue35]

Bob,

You do a great job at not only reaching your functional requirements, but looking good while doing it!

[LAalex]

Awesome rifle Bob.  Have you shot any targets yet ?

Scotty

[rsterne]

Snow everywhere here, so only indoors.... At 7 yards it just makes one pencil sized hole.... In my experience, LW barrels are never a problem....

Bob

[Sinner]

This thread has been incredibly fascinating! Thank you very much for taking the time to share the details of your project. Finished product looks amazing! Hope it performs as well as it looks!

[Kowboi]

I want one! Seriously, I want one!

[venxxxxx]

Very cool thread. Thanks.

[knomraski]

This is, literally, the most amazing display of airgun engineering skill displayed by a single person I've ver seen.

I am in awe.

Thank you.

[rsterne]

Seeing this thread resurface made me smile.... The gun is now residing with a friend who had a heart attack over the winter, and has renewed his waning interest in airguns, much to his wife's chagrin.... The funds recovered (and more) have gone into my .30 cal Disco Double project.... so the gun continues to bring pleasure to both of us.... For sure it's the hardest hitting pumper either of us have ever seen.... and with only 12 pumps for a single 40 FPE shot doesn't wear you out too bad....

Bob

[QVTom]

It's nice to hear your efforts have found a nice home   Guns never seem to loose value, it seems this is true for many AGs as well. 

Tom

[cwlongshot]

VERY NICE and VERY VERY Impressive numbers!!

CW

[PakProtector]

I gotta tune my psychic antenna...I completely missed your thoughts considering parting with it...LOL I would have walked out to pick it up...in winter, in sandals.
cheers,
Douglas