QB78 Striker throw

QB78 Striker throw

Joined: July 2nd, 2006, 6:50 pm

September 7th, 2010, 12:39 am #1

Does the striker hit the inside plug when you fire one off. I was thinking about shaving off some of the face of the striker to get a longer throw at the stem, with a side benefit of a lighter striker. With the striker sitting against the plug there is a little more room left in the slot before the striker pin bottoms out in the slot.

David

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Joined: November 17th, 2006, 3:51 am

September 7th, 2010, 1:30 am #2

Been working on that. Take he valve out of the gun, put the steel ring back in, and check to see if the striker can butt -up to that ring or not. Once you get too short, the pins hit the end of the slot before the striker hits the steel ring.

Kept cutting this one in stages (often cold blue them before I cut to make it a little eaiser to see the cuts). Already lightned by some other cuts on the body, can lathe the face to a rebated shape. Guess if you want to, could lathe a button nose that would actually enter the steel ring that holds the valve (the old Crosman 180s had a button nosed striker to do just that).

[/IMG]

Same striker farther along with testing. It got lathed flat, which is as far as you can go and not cut into the pins seat. Needed to extend the slots in the frame a touch to get this one to butt-up to the steel ring.

[/IMG]
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Joined: June 7th, 2010, 12:14 am

September 7th, 2010, 1:49 am #3

That is well shy of the stop block (0200)

I have not "tested" striker travel in HPA/PCP conditions.

I could turn up some Alu "strikers" if anyone wants to try an ultralight.
Service life would be short without putting hard points in for the trigger release and valve pin impact point, but .....for the sake of science.
Actually, the valve impact point would be easy to "harden".

Without a Chrony, my own efforts would be without substantiation.

Regards

Calg
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Joined: July 2nd, 2006, 6:50 pm

September 7th, 2010, 2:01 am #4

Been working on that. Take he valve out of the gun, put the steel ring back in, and check to see if the striker can butt -up to that ring or not. Once you get too short, the pins hit the end of the slot before the striker hits the steel ring.

Kept cutting this one in stages (often cold blue them before I cut to make it a little eaiser to see the cuts). Already lightned by some other cuts on the body, can lathe the face to a rebated shape. Guess if you want to, could lathe a button nose that would actually enter the steel ring that holds the valve (the old Crosman 180s had a button nosed striker to do just that).

[/IMG]

Same striker farther along with testing. It got lathed flat, which is as far as you can go and not cut into the pins seat. Needed to extend the slots in the frame a touch to get this one to butt-up to the steel ring.

[/IMG]
I have shaved the face off the striker and left just enough that the pin wont get hammered into the end of the slot. I turned off a little more weight to get down to 48 grams. I used a belt sander to do the valve face. It was all the micro mark could do. Thats the hardest metal I have ever seen and do not want to do another.

Shortening the valve stem will give you some more travel, but where is the trade off between a longer throw and less valve lift.

I still have the question of does the striker actually smack the steel ring on every shot or does the valve stem with all the pressure behind it limit the travel.

And why does that pin have the slot in it. I dont see what it is for.

Sorry for all the questions, I cant help it, finding out what makes things tick and improving them is rewarding and a curse depending on the outcome LOL
David


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Joined: July 2nd, 2006, 6:50 pm

September 7th, 2010, 2:13 am #5

That is well shy of the stop block (0200)

I have not "tested" striker travel in HPA/PCP conditions.

I could turn up some Alu "strikers" if anyone wants to try an ultralight.
Service life would be short without putting hard points in for the trigger release and valve pin impact point, but .....for the sake of science.
Actually, the valve impact point would be easy to "harden".

Without a Chrony, my own efforts would be without substantiation.

Regards

Calg
That was something I couldnt figure out. I have .144 of stem sticking out of the plug, so looks like about .064 left before the striker will smack into the plug. Still, shaving the valve face will give me a little more travel. I am still pondering taking some off of the stem. .144 sounds a little long from what I have been reading doing a search.

David

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Joined: November 17th, 2006, 3:51 am

September 7th, 2010, 2:40 am #6

I have shaved the face off the striker and left just enough that the pin wont get hammered into the end of the slot. I turned off a little more weight to get down to 48 grams. I used a belt sander to do the valve face. It was all the micro mark could do. Thats the hardest metal I have ever seen and do not want to do another.

Shortening the valve stem will give you some more travel, but where is the trade off between a longer throw and less valve lift.

I still have the question of does the striker actually smack the steel ring on every shot or does the valve stem with all the pressure behind it limit the travel.

And why does that pin have the slot in it. I dont see what it is for.

Sorry for all the questions, I cant help it, finding out what makes things tick and improving them is rewarding and a curse depending on the outcome LOL
David

yes, those strikers are rock hard for a good depth. Break though the hard layer and he steel is softer. Best way to make a striker, hard for wear on the otuside, less hard for shock resistance inside. Is why the bearing areas (outside full diameter of both ends) and the sear surface are off limits.

On the first one i lightened, annealed the striker, did the lathe work, then rehardened (kaseKnit). For the others, bought commercial T-C lathe bits to make the first cuts, then back to HS steel for the softer steel underneath.

Haven't thought about 12gr. guns. the 12gr. would act as a stop. not letting the valve stem travel any farther than the hole it poked in the 12gr. Standard valve, and it's short stiff return spring, probably limits travel when bulk filled as well.

My conclusion so far is that if you want a little bit more travel, lathing the rear face of the steel ring the valve sits on is the easier way (although that part is rock hard as well). If the valve stem is NOT being pushed all the way to the steel ring (which it won't with a 12gr. gun), then make a shorter valve stem. If you want a somewhat lighter striker, it's easiest to work on the middle diameter of the striker and the back of the front section.

Just testing, playing with PCP. Some other makes of guns are better at self regulation that QB valves Makes sense, as QB valves were designed to work in a pretty narrow pressure range (co2 in human-frindly temperatures). One difference between air valves and QB valves seems to be valve travel. Can make a bulk valve with a longer return spring (so the tension builds up slower and allows more travel), and do some of the above to get the ability for the valve to move more (the possibility of increasing valve dwell). Get it all balanced so that return pressure is the major player in valve travel (rather than running into mechanical stops) and it does seem to allow better self regulation.
Last edited by gubb33ps on September 7th, 2010, 2:49 am, edited 1 time in total.
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Joined: June 7th, 2010, 12:14 am

September 7th, 2010, 2:53 am #7

Hardness of the striker didn't even come into the equation.

If the striker does not contact the stop block, then making the valve stem shorter only lengthens the striker travel (faster?). There must be an intersection in plots of striker travel and valve opening. But where? (charge pressure dependence with HPA, CO2 is constant)

.140" possible valve opening, and .080 actual opening with carts is a HUGE difference, that could only be accompanied with much waste of pressurized gas. That is. double the travel is much more than double the flow volume, and NO WAY will you see double the FPS.
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Joined: July 2nd, 2006, 6:50 pm

September 7th, 2010, 3:01 am #8

I ate up all 3 points on the indexable insert just to do the middle and back end. I wish I had a tool post grinder, its a heck of a lot easier

David

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Joined: June 7th, 2010, 12:14 am

September 7th, 2010, 3:11 am #9

And I always wondered why I would want to grind a tool post ;-) nt
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Joined: November 17th, 2006, 3:51 am

September 7th, 2010, 3:19 am #10

I have shaved the face off the striker and left just enough that the pin wont get hammered into the end of the slot. I turned off a little more weight to get down to 48 grams. I used a belt sander to do the valve face. It was all the micro mark could do. Thats the hardest metal I have ever seen and do not want to do another.

Shortening the valve stem will give you some more travel, but where is the trade off between a longer throw and less valve lift.

I still have the question of does the striker actually smack the steel ring on every shot or does the valve stem with all the pressure behind it limit the travel.

And why does that pin have the slot in it. I dont see what it is for.

Sorry for all the questions, I cant help it, finding out what makes things tick and improving them is rewarding and a curse depending on the outcome LOL
David

If you want a lighter striker, grind it. Have to leave the top 1/4 alone for the pins (and the pins keep the striker from rotating). Have to leave the bottom 1/4 along as that's where the sear contact is. But the sides can all go.

Sumatra varies its power not by changing striker strength, but by a varialbe mechanical stop that limits how much of the valve stem sticks up to be smacked by the striker. Low power, less valve stem sticking up, less dwell.

BAM 50, 51, and Marauders have adjustments that vary the striker travel (Marauder has a crap load of adjustments besides that). Longer travel, harder hit, longer dwell.

Crosman used a mechanical stop on their 12gr. co2 Challenger (along with a really small transfer port, a fatter valve stem seal to decreased gas flow inside the valve, and a light striker/spring). The valve stem has a longer brass shank, which limits the valve travel.

[/IMG]

So if I were to try for the most shots per 12gr. possible (at low-low velocity) would probably combine all of that. Shorter striker travel, strangled off transfer port, fatter valve stem seal, light striker, shorter valve stem, and a built in mechanical stop.
Last edited by gubb33ps on September 7th, 2010, 3:21 am, edited 1 time in total.
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