Beeman QB Chief .22 broke down

[OTmachine]

Should the .275 to .390 diameter transition probably be a flat surface instead of a chamfer due to it being the seat for the spring? Good job!  Nice looking Poppet!
And Thanks to Ribbonstone for providing the dimensions.

[hotspot]

Hello,

I was wrong about the poppet in my Chief was fine. Please check the pic attached. At least one crack is found and there is another one smaller.

John, you said you made a poppet with delrin. I don't have machine tool or a lathe. Not sure if possible to make it myself. If not, the gun will be worth nothing but being discarded.
Thanks.

I can make you one off Ribbonstone's dimensions.

If you could make one for me with these dimensions I would be happy to pay you.

[Ribbonstone]

TOM: thanks for stepping up….all my good tooling was lost when lightening hit the shop shed.   

Never really figured out why the original valve stem needed to be that long.

Aligning all the guts oustide the tube, did find that the valve itself does NOT butt up against the internal steel ring (the front breech screw threads in from the top, stock screw from the bottom)...so the 3 valve retention screws are “it” for retention.

Why they machined that ‘step” at on the valve is anyone’s guess, it doesn’t seem to serve any purpose.

Slot in the tube for the striker’s cocking pin is shorter than on QB’s….but there seems to way more valve valve dwell than needed before the striker pin ran out of slot.

So running it outside the tube.  If the striker pin was driven all the way to the end of the cocking slot, would depress the valve stem by about .2”. 

You won’t really want the striker pin to crash into the end of it’s slot, but that’s still a whole lot more valve dwell than you’d ever need.

Shorter stem would likely work...I’d not want the striker to run into metal during compression, which would really exacerbate bounce.

[nervoustrigger]

Regarding the stem travel, yeah it's not much.  Having an overly long stem is a detriment because it limits the hammer's travel which means you need more hammer spring tension to achieve the necessary lift and dwell.  It not only increases cocking effort but also the force acting on the sear which translates back to the trigger pull weight.
 
As Bob has detailed elsewhere, the maximum possible flow is attained when the poppet has been knocked free of the valve seat by about 25% of the throat's diameter.  So for example a valve having a 1/4" diameter throat, it's flowing as much as it can flow when the poppet is lifted by just 1/16", but like Robert said you want to allow for more than that so the hammer doesn't run the risk of smacking the back of the valve* and rebounding, which would make the valve dwell drop precipitously and cause a loss of velocity.  I haven't explored the limits of just how miserly we can be but I've never had a problem when having a stem projection of 50% of the throat diameter.  So for the hypothetical 1/4" throat in this example, I would leave the stem projecting by 1/8".  If making a poppet from scratch, leave it a bit long and then cut or file it down to give the desired projection.
 
This approach has always worked well for me with models with a typical steel hammer.  I like to leave a little more projection when using a lightweight (plastic) hammer, that way if I need a little more lift to get the necessary dwell, there's room for it.  I'll use more like 75% of the throat's diameter in that scenario.  Again, maybe I could get by with a little less but that has worked well for a number of builds.
 
If one were to get motivated to explore the absolute minimum, bear in mind that even a steel hammer will often indent a few thousandths after impacting a hardened valve stem a few hundred times.  All things being equal, more for a lightweight hammer.  Also, a stem that has been press-fitted into a poppet may settle a bit after being impacted a number of times so be sure to account for these changes that will reduce the available lift slightly.
 
* or the cocking pin reaching the end of its slot, as seems to be the limiting factor for the Chief per Robert’s analysis

[Ribbonstone]

Don't hold me to exact numbers...guys who live in the mythical world of the 10,000ths are going to argue with me.

Basically I lined up the screw holes for the valve without the poppet return spring (taped it down)...screw holes for the internal steel ring (taped it down)...and the striker at the point where the cocking pin would run into the end of the cocking slot.

IT LOOKS like the tube slot is the same length as the breech cocking slot...would be  under-eyeball-noticed  difference.

Measured the valve travel (no return spring) from first contact to where the striker’s cocking pin hit the end of it’s slot.  NOT that I ever thing it does (or I’d have noticed the metal to metal slam...or it would have left a mark on the end of the slot/cocking pin),

Came up with .2” of possible valve stem travel….not that it actually happens ... the  ball-park/make-shift numbers are not engraved in stone.

[nervoustrigger]

I apologize if I gave the impression of second-guessing the measurements or the method.  The only reason I mentioned the cocking pin in the footnote was because I wanted to give the more general case in the body of the message…the scenario where the hammer overdrives the valve stem and rebounds off the back of the valve.  In hindsight, I probably should have done it the other way seeing as how the thread is about the Chief in specific.
 
The TL;DR for my previous reply is leave enough stem travel to get the job done, which isn’t much.  Leaving a lot is a waste.  Make sure you understand what limits the travel so you can either account for it if necessary or anticipate what will happen if something bottoms out (a good example being the B50 valve spring potentially going to coil bind, driving the stem through the poppet and shattering it).

[hotspot]

Well here is the first attempt, anyone with first hand knowledge of the poppet have any input on the dimensions?  If people think it'll work I'll send it over, I'd just want to be reimbursed shipping.

These are the measurements of my poppet. If you could make one for me using these dimensions I would be happy to pay you.

[CableStop]

Well here is the first attempt, anyone with first hand knowledge of the poppet have any input on the dimensions?  If people think it'll work I'll send it over, I'd just want to be reimbursed shipping.

These are the measurements of my poppet. If you could make one for me using these dimensions I would be happy to pay you.

Sure, I'll see what I can do.  This is for a different gun I take it?

[CableStop]

TOM: thanks for stepping up….all my good tooling was lost when lightening hit the shop shed.   

I'd be pretty devastated if I lost my workshop, really sorry to hear that happened.

[Ribbonstone]

Could have been worse...thunderstorm and a garden hose put out the fire....evidently the 50 feet of boot-leg wiring didn't trip the circuit soon enough.  MAde an interresting dead grass strip running from the shed to the house.

Have not been lucky with lightening....40 year ago,  was 50 feet away from a stike on campus (UNO...might have been LSUNO back then) that basically cooked ta guy.

Had a previous house  (maybe 30 years ago) hit with no obvious damage.  Just an odd loud "SNAP" and the circuit breakers tripped.  For years never knew what that "snap" was....until I moved/replaced the gas stove.   Then I found  where a rivet on the back of the stove had been melted and blown though the wall. 

20 years ago, me and a hunting buddy felt the hairs on our arms stand up/smelled a kind of ozone smell, dropped to the mud and a tree exploded (steam) 15 feet away.

 10 years ago, the shed when "boom".


I'm going to stay out of the rain.

[CableStop]

Should the .275 to .390 diameter transition probably be a flat surface instead of a chamfer due to it being the seat for the spring? Good job!  Nice looking Poppet!
And Thanks to Ribbonstone for providing the dimensions.

Genuinely curious since I don't have tons of experience making poppets, will the tapered spring seat deform the spring?  I can flatten it to a 90 degree if that'd be better.

[Ribbonstone]

Personally (which makes no never mind as I'm not making it)...have kept away from sharp 90degree corners where the spring connects to the poppet.  Know that right angles tend to focus stress, so generally radius that corner a bit.

[OTmachine]

Should the .275 to .390 diameter transition probably be a flat surface instead of a chamfer due to it being the seat for the spring? Good job!  Nice looking Poppet!
And Thanks to Ribbonstone for providing the dimensions.

Genuinely curious since I don't have tons of experience making poppets, will the tapered spring seat deform the spring?  I can flatten it to a 90 degree if that'd be better.

Have not made a poppet as of yet.  Have the skills, tools, materials, and some mechanical ability.  Just would rather have a solid load bearing surface, (flat, 90 degree), for best performance. And yes, always a corner radius to reduce stress risers.  Working too much to have time for my hobbies.

[hotspot]

Well here is the first attempt, anyone with first hand knowledge of the poppet have any input on the dimensions?  If people think it'll work I'll send it over, I'd just want to be reimbursed shipping.

These are the measurements of my poppet. If you could make one for me using these dimensions I would be happy to pay you.

Sure, I'll see what I can do.  This is for a different gun I take it?

This is for the Beeman Chief.

[CableStop]

Well here is the first attempt, anyone with first hand knowledge of the poppet have any input on the dimensions?  If people think it'll work I'll send it over, I'd just want to be reimbursed shipping.

These are the measurements of my poppet. If you could make one for me using these dimensions I would be happy to pay you.

Sure, I'll see what I can do.  This is for a different gun I take it?

This is for the Beeman Chief.

Any idea if the difference in size is a chief 1 vs 2 thing?  I'm not trying to question you, I just want to make sure whatever I make fits.

[wll2506]

Any idea if the difference in size is a chief 1 vs 2 thing?  I'm not trying to question you, I just want to make sure whatever I make fits.

I'm  interested in this also as I have a Chief II Plus !!!

wll

[hotspot]

Well here is the first attempt, anyone with first hand knowledge of the poppet have any input on the dimensions?  If people think it'll work I'll send it over, I'd just want to be reimbursed shipping.

These are the measurements of my poppet. If you could make one for me using these dimensions I would be happy to pay you.

Sure, I'll see what I can do.  This is for a different gun I take it?

This is for the Beeman Chief.

Any idea if the difference in size is a chief 1 vs 2 thing?  I'm not trying to question you, I just want to make sure whatever I make fits.

My rifle is the Chief, not the Chief 2.

[Ribbonstone]

NOT wishing you bad luck….sooner or later you will have to take the Chief II (plus) apart….could be years from now.

Not having one to pull apart, I’ve no idea what changes they may have made to get it to function as a 3K repeater….just guesses.

Suspect the Commander….the barrel band and rear sight look very “SPA”ish….even though it’s a 3K repeater, it might have a different heritage than the Chief/Chief Ii/Chief II Plus.

There will likely be changes from the Chief to the Chief II.

Just from the pictures...definitely a different receiver...and a different LENGTH receiver.

The bolt throw on the Chief isn’t long enough for a mag. fed repeater…. So I ASSUME that there has to be some changes in the striker/cocking system in order to get the bolt to move farther to the rear….which would also change the striker stroke.

Possibly all sorts of changes I’ve not thought of….or it could be same-same in many aspects.

I’d NOT take it apart just to find out…..buy the time you might NEED to take it apart, would be soon enough.

[z_johnq]

Hey Tom,

I think it is worth trying. Let me have your address so I can send you a check. My address is:
in case you need to call. Not sure if you use Paypal. If you do, I can do Paypal too.

Thanks.
John

[BigBird]

Hey Tom,

I think it is worth trying. Let me have your address so I can send you a check. My address is: .
 in case you need to call. Not sure if you use Paypal. If you do, I can do Paypal too.

Thanks.
John

You may want to PM as the whole internet sees your contact info.  Now youll get phone calls from people selling you extended warranties or the social security people who really arent from our government.