(Login Dnadnnoid) Crosman Forum Member from IP address 184.108.40.206
because the hammer still bounces, just not against the stem
i cut off about 4.5 coils from a 1377 valve spring and glued it to a washer/rivet thingy. using double sided tape i stuck it to the outside of the valve. the theory was to absorb most of the hammers energy before it even touched the stem and it seems to work. now it just taps the stem and my valve retains quite a bit of air.
i get two decent shots. the first one being the most powerful and the second shot loses about 200-230 fps. then i have to actually dry fire it TWICE to get the remaining air out. now i just need to get a lighter hammer and figure out a way to make a spring adjuster for it
let me hear what you guys think. I know some of you are very well educated in the physics of this type of stuff. i think it could be improved a bit
oh btw i switched hammer springs too. i used a 2240 spring
This message has been edited by Dnadnnoid from IP address 220.127.116.11 on May 12, 2013 10:32 AM This message has been edited by Dnadnnoid from IP address 18.104.22.168 on Jun 11, 2012 10:31 AM This message has been edited by Dnadnnoid from IP address 22.214.171.124 on Jun 11, 2012 10:28 AM
Well, the thing is: Springs don't dissipate energy. They store it and then give it back.
June 11 2012, 10:39 AM
I'm sure you're right that your spring buffer accepts a lot of the hammer's energy and prevents it from making it to the valve stem. But then it gives that energy back to the hammer in the form of a more violent bounce.
So my question would be, what prevents that added bounce energy from rebounding from the hammer spring, then driving the hammer back to compress the buffer spring and hitting the stem again?
I just did. To sum up: My experience is that springy buffers are
June 11 2012, 11:22 AM
...essentially exactly the same in effect as reducing the energy of the hammer strike by any other means - e.g., by reducing the rate or preload of the hammer spring.
To get useful hammer debouncing, I found that you always need to provide somewhere for the energy of the hammer's rebound to be dissipated permanently - not just temporarily stored. Springs can't do that.
(Login curt44319) Crosman Forum Member 126.96.36.199
Re: Moving heat from where it is not wanted is a wonderful thing
June 13 2012, 1:53 PM
I've used with some degree of effectiveness ( and other problems ) a bit of 1/8 ID soft vinyl tubing slipped over the valve stem, and left slightly longer than the valve stem.
This does several things.
It does convert striker energy into heat, as the plastic deforms. ( on both initial and rebound strikes )
It prevents all of the striker energy from getting to the valve in the first place, hence requires a stronger hammer spring to break even. ( length is quite critical )
Being slightly long, although it doesn't suppress bounce as well as Steve's do-hicky, it does prevent the hammer from reaching the valve on re-re-bound.
It may aid in sealing the hole that the valve stem comes through, though I suspect that's about 90% wishful thinking on my part.
I'm pretty sure it works, because the no pressure dry fire boin-oin-oin-oing is replaced by
a much better ( methinks ) thwap-bump.
In any case, Steve is very right. The rebound energy must go somewhere.
Steve's devices convert a small amount to friction heat, with the balance going into recoil momentum of the entire gun. It's all dissipated.
My little tube trick mostly converts it into heat, and rebound bounce that's merely low enough in energy to not reach the valve stem for the second strike. It's all dissipated, but a greater proportion is dissipated in spring bounce and vibrations as a damped wave that's merely prevented from reaching the valve.
Steve's works with lower powered springs.
The tube trick mandates a spring much stronger than otherwise required, in order to achieve the first strike at all.
The tube trick works with the plastic breach.
Cal (Login CalG) Crosman Forum Member 188.8.131.52
That seems to have worked for me!
June 11 2012, 6:31 PM
The new 392 sports a light weight striker. less than 40 grams, and a preload adjuster that allows zero preload prior to cocking.
Along with a teflon "friction collar" that fits around the striker (my own design HDD ;0!) The report on firing is much subdued and a simple Pfft where previously the sound lacked crispness.
I do need to pass some shots over the chronometer however.
A side note, this configuration Holds POI for the first shot on ten pump strokes (Oversized valve volume) and still requires FIVE shots to empty the valve.
Like I said, I need to get it over the chronometer.
edits, as some of the text regarding striker and spring seemed not to make the jump to hyperspace.
This message has been edited by CalG from IP address 184.108.40.206 on Jun 11, 2012 7:18 PM This message has been edited by CalG from IP address 220.127.116.11 on Jun 11, 2012 7:14 PM This message has been edited by CalG from IP address 18.104.22.168 on Jun 11, 2012 7:10 PM
This message has been edited by CalG from IP address 22.214.171.124 on Jun 12, 2012 9:42 AM This message has been edited by CalG from IP address 126.96.36.199 on Jun 11, 2012 7:44 PM This message has been edited by CalG from IP address 188.8.131.52 on Jun 11, 2012 7:20 PM