Author Topic: A New Method for Increasing the Efficiency of a PCP - the SSG (Read 373408 times))

rsterne · « **Reply #200 on:** January 07, 2016, 12:39:56 PM »

I use a rounded end on my guide rod to allow it to find it's own angle with the hammer, regardless of the shape of the bottom of the hole in the hammer.... It is important not to have too close a fit between the guide rod and the gap adjusting nut which keeps it straight in the tube.... I had one with a 3/16" rod (0.188") running in a 0.191" hole and it had drag and I had to drill it out to 0.194".... the gun picked up 150 fps once the drag on the rod was eliminated....

Bob

oldpro · « **Reply #201 on:** January 07, 2016, 02:10:48 PM »

Exactly right Bob. Half of why it works so well is limiting drag on the hammer walls and spring adjuster. Use smaller spring to bore than stock to elimate any contact possible.

Motorhead · « **Reply #202 on:** January 07, 2016, 02:31:04 PM »

Quote from: oldpro on January 07, 2016, 02:10:48 PM

Exactly right Bob. Half of why it works so well is limiting drag on the hammer walls and spring adjuster. Use smaller spring to bore than stock to elimate any contact possible.

Lol ... or a Nylon hammer ... or lined spring bore than really has so little drag

Guess I'm blind to issues you guys are seeing running steel hammers within steel tubes with steel springs on steel guides. DRAGGY NO DOUBT !!

oldpro · « **Reply #203 on:** January 07, 2016, 02:40:07 PM »

Even with a Nylon hammer I still wouldnt want any part of the spring or guide touching the sidewall if it can simply be designed around, no need to introduce any friction at all if it can easily be avoided.

Tomg · « **Reply #204 on:** January 07, 2016, 02:43:22 PM »

Mine had "tight" clearance when I started, but realized quickly there were to much friction in various places. So I reamed out the hammer, turned the head of the guide round-ish and enlarged the hole in the rear cap so the guide could freefloat the way it wants.

oldpro · « **Reply #205 on:** January 07, 2016, 02:47:03 PM »

Tomg thats exactly how im doing it now and is giving me the best results so far.

Bullfrog · « **Reply #206 on:** January 07, 2016, 05:58:34 PM »

So does the SSG require an insert to keep the rod centered, say in an Mrod which already has an open end cap? Ya'll are losing me a little bit when talking about letting the rod free fly.

Gerard · « **Reply #207 on:** January 07, 2016, 06:27:59 PM »

Whether or not one uses a low-friction insert, some slop should probably be built into the fit owing to the somewhat wiggly fit of the striker/hammer and its tendency to start off at a slight angle. The sear holding it at one edge forces the spring to cant the back end the opposite way. I found that with too snug a fit on the guide rod it would jam for a moment, sometimes even causing delayed firing by a second or more. This was a smooth fit, easy to slide by hand, but under cocked angular strain was jamming. A couple or a few thousandths ought to be plenty.

rsterne · « **Reply #208 on:** January 07, 2016, 07:28:30 PM »

I don't want any interference anywhere.... My hammer ID on the new Monocoque is 1/2" with a 3/8" spring.... Drilled hole (tapered end) with a rounded end on the guide that self-centers.... and NO contact between the guide and hammer once it stops.... I am less concerned with a close fit between the guide and the adjusting bolt is slides through, I would like the hole to keep the guide centered in the hammer.... but not to the point of being draggy.... It does, after all, have 5-15 lbs. of force pulling it forward during firing.... pulling, not pushing, so very unlikely to bind, providing there is a few thou clearance.... I don't see anything wrong with a bit of lube on the spring/guide either.... I used a couple drops of oil with 10% Moly in it....

Bob

PakProtector · « **Reply #209 on:** January 07, 2016, 07:35:37 PM »

I am making the stationary nut/stop from Bronze. AL for the rod...either moly grease or 2C45 Krytox should do the job keeping it slippery. Or maybe slide in a PEEK bushing...

cheers,
Douglas

Rallyshark · « **Reply #210 on:** January 07, 2016, 09:00:05 PM »

Quote from: rsterne on January 04, 2016, 11:09:08 PM

I didn't say I was going to convert EVERY PCP I have.... *LOL*.... Yes, the AT-44 could be quite a challenge, and since it already has an anti-bounce device, may not be worth it....

Bob

Bob,

I have my AT-44 apart right now, and just realized there is about 3/16" travel from where the hammer rests on the valve to the hammer stop screw. That means the hammer is moving the valve pin about 3/16" before hitting the hammer stop screw, right? If that is the case, then I would think there is definitely a good possibility of bounce happening? With the pre-load the hammer is just leaning on the valve pin unless cocked, so that tells me the valve would be giving the hammer a good whack when it closes. I'm not sure on what the best approach would be on this, but it would seem there is room for improvement with some sort of SSG type device. What do you think?

oldpro · « **Reply #211 on:** January 07, 2016, 09:37:42 PM »

A little more work done today between jobs. http://i.imgur.com/uxOLtZch.jpg http://i.imgur.com/4DzU43Ah.jpg http://i.imgur.com/V5ZEyczh.jpg

rsterne · « **Reply #212 on:** January 07, 2016, 10:07:46 PM »

So you are saying, Donny, that the AT-44 hammer can rebound 3/16" before hitting the Wishbone?.... Yes, that is enough to store enough energy in the spring to get air-wasting bounce, IMO.... Likely that is the reason the Hatsan is no better for efficiency than a PCP without the anti-bounce device and a similar tune.... In addition, with preload against the hammer when on the valve stem (and increasing while travelling that 3/16") the wishbone may just be causing the hammer to reverse sooner, and then it is still driven by the spring back to the valve.... I'll have to wait until I can pull mine apart to comment, but I hope to come up with an SSG to work in mine....

Travis, I see the lock screw for the adjusting barrel.... How do you turn that barrel, just by using the Nyloc preload adjuster?.... I know I just wind mine down with my fingers until I feel it touch, check the velocity, and if it's too low I add preload and try again.... Once it's a fraction more than I want, then I leave the preload alone and increase the gap to drop the velocity to what I need.... I have a hex on the end of my bolt, so even with the lock screw tight on the plastic plug that acts as a brake, if I need to adjust it I can use a wrench.... You won't have that option, I don't think, you will have to back off the lock screw each time....

Bob

oldpro · « **Reply #213 on:** January 07, 2016, 10:25:15 PM »

I can adjust the barrel by hand just by turning the lock nut with my fingers after loosning the set screw next ill put a groove on end of rod above nut to insert a flat blade screwdriver so one can adjust preload nut. Very simple really.

match · « **Reply #214 on:** January 07, 2016, 10:50:34 PM »

So when a hammer has a throw length adjuster like in the MRod - what do you do? cut it short?

Rallyshark · « **Reply #215 on:** January 07, 2016, 10:57:09 PM »

Quote from: rsterne on January 07, 2016, 10:07:46 PM

So you are saying, Donny, that the AT-44 hammer can rebound 3/16" before hitting the Wishbone?.... Yes, that is enough to store enough energy in the spring to get air-wasting bounce, IMO.... Likely that is the reason the Hatsan is no better for efficiency than a PCP without the anti-bounce device and a similar tune.... In addition, with preload against the hammer when on the valve stem (and increasing while travelling that 3/16") the wishbone may just be causing the hammer to reverse sooner, and then it is still driven by the spring back to the valve.... I'll have to wait until I can pull mine apart to comment, but I hope to come up with an SSG to work in mine....

I completely overlooked the wishbone! I need to go back and look at that. I don't know that it makes a difference with my observations though? Your point about it may very well be the case too, allowing the hammer to rebound faster. Either way, I can see the chance for bounce, especially given the high amount of preload when shooting at 50+fpe. I know that poor little stop screw is getting flattened and bent on my gun, and I can see it getting replaced in the future.

Now, if there was a way to turn that wishbone into some sort of a simple ratchet/catch that would only engage after valve strike, that would do the trick, with no changes in the spring required. Hmmm... You just gave me another thing to think about

match · « **Reply #216 on:** January 07, 2016, 11:05:37 PM »

Quote from: oldpro on January 07, 2016, 10:25:15 PM

I can adjust the barrel by hand just by turning the lock nut with my fingers after loosning the set screw next ill put a groove on end of rod above nut to insert a flat blade screwdriver so one can adjust preload nut. Very simple really.

So you are depending on a "no slip" condition between the center guide, spring, and barrel to adjust the barrel?

Can you be sure of this at all times?

Will you provide an indicator (a milled mark) on the barrel edge to gauge the changes (by the clock)?

oldpro · « **Reply #217 on:** January 08, 2016, 12:19:06 AM »

A milled mark or marks would be easy to do and yes it moves easily because the carrier for the rod and spring is under tension by the spring and adjusting nut and acts like a single unit at rest. Its really simple in design and I like that.

rsterne · « **Reply #218 on:** January 08, 2016, 01:13:43 AM »

If you are using a plastic plug for the brake, you may find it conforms to the threads and you may not be able to turn the barrel by hand.... just something to watch for....

Bob

match · « **Reply #219 on:** January 08, 2016, 01:15:14 AM »

If it always moves as a unit then there is no need for a mark - the position of the nut will do fine.

Just checking the "no slip" condition.

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A New Method for Increasing the Efficiency of a PCP - the SSG

Author Topic: A New Method for Increasing the Efficiency of a PCP - the SSG (Read 373408 times))