Impact power plenum hammer springs.

Jump to latest Follow Reply
AirSupply

AirSupply

Member
Jan 12, 2017
1,419
284
Victoria, Australia
The Impact Power Plenums managed to get to Australia just before c19 really slowed everything down. 
Installing my kit I was unsure as to whether to use the original HS or the new shorter one supplied with the kit. . I had seen a few post from people not happy with the power they achieved with the new spring so I decided to go with my old longer spring. 
With the old spring I had plenty of power (.22cal 26g slugs @ 970fps/ 125b)but also consistent pretension on the power wheel. Even on minimum with the adjuster screw backed out I couldn’t get any free play on the slider. It wasn’t tight but as soon as you started turning the power wheel it got tight after 1 or 2 clicks.

There are a couple of issues with it set up this way. 1 you lose your free floating hammer and 2 you have excessive wear on your power wheel. You don’t want to turn it with back pressure against it. They do wear out even under normal conditions. I’m on my second. 
So what to do.

I was looking very closely at the new and old springs side by side and they are slightly different. The new spring has slightly more coils per inch. The more coils a spring has the softer it is. I know to a lot of people this doesn’t make sense but it a fact. Also a shorter spring is stiffer than a long spring all things equal again a fact. So my guess is fx where tying to match the spring rate of the old longer spring with a shorter spring and that’s why it has slightly more coils.
So what Ive done to get a higher spring rate and regain the use of my power wheel is cut the original spring to the shorter length. 
Here they are side by side. In the second photo I have lined up the coils as accurately as possible. As you go down the spring you can see the coils start to stagger because the old spring has less coils per inch. (Stiffer)
1587644081_11754337795ea186b1c203f6.08055255.jpeg
1587644082_5341483475ea186b2560c30.04462617.jpeg

I’ve just got the gun back together. It’s late here in Oz so I’ll test it tomorrow. Adjustment of the power wheel are now as they where with the old set up. 
I couldn’t see a down side in trying this as even with a higher spring rate I can still adjust it down with my power wheel and I’m only going to be shooting slugs or RD monsters. 

So Im hoping can get 970fps with my 26g slugs at 125bar as before but have normal adjustment on the power wheel. 
Oh and Realisation 🙄You can no longer dry fire the gun to empty the plenum with the valve adjuster off.......😬



 
Some other interesting “Spring “ facts. I shorter spring will be more consistent in its output energy when compressed and released. This is interesting and important for the hammer spring also the new return spring. 
The new shorter return spring has definitely tightened up shot to shot consistency.over the old very long spring. We have lost the valve stop (rubber ball) but why couldn’t I still have a valve adjuster inside the return spring?
 
Upvote 0
If you use the 57mm hammer spring you Will have a small free play on MIN so the only difference i Can see is the it is the same as the new one but you Can adjust those 3mm more with the 57mm.

if you have the hammer set in MID range both springs are on tension so it should not make a Hole difference?

i am shooting the 25,6 gr jsb KOs at 1010fps on 110 bars

ES about 8fps

I am loving this setup, but it Can not shot 18gr pellets though.


 
Upvote 0
I have the PP spring installed again, the PP spring is actually stiffer than the old spring (Mine has got the same amount of coils, same wire diameter but is slightly shorter than the old one.) 

I've measured the stiffness of both springs, and the old spring needs 3415g for 10mm compression, the PP spring needs 3560g for 10mm compression. Measured compression with my digital readout on the milling machine. 

Advantage of the PP spring is the bigger adjustment range between min and max. because of the higher spring rate like Michael already said. 

Cheers, Gijs

1587670752_17677424295ea1eee080b182.48588091.jpg
1587670753_5475926545ea1eee14d5930.41196932.jpg



 
Upvote 0
There will be quiet a difference when cocking the gun, between the PP spring, and the original spring. If you adjust the power wheel with slack on the adjustment screw on setting "min", the longer spring will be compressed more, when cocking the gun. When using the short spring, you can move the cocking lever further, before the spring starts to compress. I found the long spring being to "powerful" for normal pellet use, as it will hit hammer to hard on even the "min" setting on wheel. 
 
Upvote 0
Hi Gijs 

That’s interesting. I had a spare old 57mm spring so was happy to cut that. When I cut it to exactly the same length as the new spring it had 1 less coil than the new spring so they where close. 
It would be interesting to see that same test comparing the new short spring and a cut old spring of identical length. 
I can’t wait to get it over the chronograph 😊

Great to see you active on the forum. Love your posts. 👍 Michael
 
Upvote 0
Hi tor47. I don’t see it that way. The cocking mechanism moves back the same distance for both springs. If you move the adjuster back for the longer spring to remove pre tension cocking the gun will give the same distance of compression. If you start with some pre tension yes you will create more spring rate.

If 2 springs are identical apart from 1 being shorter and then you compress them the same distance the shorter spring will require ‘more’ cocking effort and have more power when released. It isn’t going to be much difference as it’s only 4mm but in theory the shorter spring is stiffer.
Michael

 
Upvote 0
If you are shooting lets say 960fps with the 54mm spring on power 4 and you are shooting the same 960fps with the 57mm spring but on power 2 then it is the same thing, only difference is that with the small spring you Can shot lighter pellets and with the 57mm you Can shoot heavyer pellets.

i use the 57mm for slugs and i don’t shoot pellets so i use the extra power with the 57mm spring to tune the reg Down for more shot count.



i am shooting 25,6gr slugs at 1010fps with reg pressure at 110bar
 
Upvote 0
Hi tor47. I don’t see it that way. The cocking mechanism moves back the same distance for both springs. If you move the adjuster back for the longer spring to remove pre tension cocking the gun will give the same distance of compression. If you start with some pre tension yes you will create more spring rate.

If 2 springs are identical apart from 1 being shorter and then you compress them the same distance the shorter spring will require ‘more’ cocking effort and have more power when released. It isn’t going to be much difference as it’s only 4mm but in theory the shorter spring is stiffer.
Michael
Click to expand...

If adjustement screw on wheel does not engage at all, then we are at the minimum compression. When I tuned my impact to shoot 33 grain heavys at low 800fps, on 90 bar, the " min" gave to much speed for my tune, when using the long spring. I use a 700mm barrel. I could turn in valve adjuster, to get where I needed, but I prefer having the option to lower hammer force also. The long spring probably works better when shooting slugs, with high reg pressure.
 
Upvote 0
Got to shoot the gun over the chronograph today. With reg just under 125b the 26g shot at 985fps on Max with the shortened spring. So the shorter spring has produced more power than the long spring with other settings the same. 
Im happier having the full use of the power wheel.
It’s a great gun and obviously works with different springs/settings. 

 
Upvote 0
Got to shoot the gun over the chronograph today. With reg just under 125b the 26g shot at 985fps on Max with the shortened spring. So the shorter spring has produced more power than the long spring with other settings the same. 
Im happier having the full use of the power wheel.
It’s a great gun and obviously works with different springs/settings. 
Click to expand...

When you say “shortened spring”, you mean the old longer spring cut at the same length as the new spring. The shortened spring produce more power than the old spring at the same adjustments? That is very informative. Thank you.
 
Upvote 0
I have the new factory PP impact 700 .22 pellet liner when trying the original PP shorter spring shooting 27.5 slug maximum fps was 1000 on 155 bar reg and its not increasing if I increased the regulator pressure so I think the maximum regulator pressure that the PP spring can open in between 150-155 

then installed the old longer spring same setting only the spring chang gives me 1030 so 30 fps increase in speed but as mentioned above there is no play in the power wheel.
 
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu