Tuning More internal hammer pre tension?

[MEC17670]

Hey Folks,

How can I increase the hammer striking force when my power wheel is on 24 already?

My Crown mk2 is sending 24.54 grain at a very flat line at 905 fps power wheel at 23 , reg 110 . Quiet, definitely in harmony. Nail driver.

However, I would like to shoot 26 gr. slugs at 940 ish. If I increase my reg pressure, I'm not sure there's enough hammer to allow that pressure to be transfer, the hammer force won't be enough to allow the valve stay open long enough to be balanced. 24 on the wheel won't do it! 

Any suggestions?

Thanks Mike

 

[BackStop]

I have no experience here, but you might try placing washers at the back of the hammer spring or you may need a stronger spring altogether. Certainly there are aftermarket offerings for Fx guns being that they are all the rage these days.

 

[Long_Gun_Dallas]

 

https://www.youtube.com/watch?v=uvTZ4cmYDO4

Seen here is the screw used to adjust preload. Mine is set to about 6.7mm

 

[Motorhead]

Raise the Reg pressure ....

 

[MEC17670]

Great video, thank you.

 

[MEC17670]

Raise the Reg pressure ....

Thats my problem, if I raise the reg pressure, the hammer doesn't strike it hard or long enough to raise the velocity. 

Tried raising the reg pressure and the velocity dropped even with the power wheel set on max.

Equation not balanced.

 

[MEC17670]

I wondering if the valve is getting struck with a lighter hammer pressure, would that make the valve remain open longer until the pressure dissipates, have I have been looking at this backwards?

Heres a screen shot with the reg at 110 hammer at 23, transfer port at high

 

[corny]

If you have maxed out your HS and can’t open the valve. Then your above the power level of the gun. You either need to add more hammer weight or spring. 


im not familiar with the crown, but I’ve work on other fx products. Did you max out Hammer screw ? Or just the power wheel. 
Correct me if I’m wrong but on all fx products that I’ve ever worked on. The power wheel covers a range, but the hammer screw sets where that range is.

 

[Ghostranger169]

MEC17670,

Something is amiss. Max fps for a Crown MK2 should come with the pretension screw almost all the way tightened, HS on 23, TP on High, with reg pressure at around 155 to 165.

You didn't mention how long you barrel is. With a 700mm barrel(even with the older round hole TP), it will sling a JSB KO slug or MRD pellet at over 980 fps. With shorter barrels you will still achieve max fps(albeit a lower speed compared to using a longer barrel) with this setup, but will be wasting air.

https://www.airgunnation.com/topic/tuning-help-for-fx-dreamline-and-crown-airguns/#post-1147415

 

[MEC17670]

Hey Guys,

600 mm barrel in .25 and 500mm in.22.

Internal pre-tension still has more room to be tighten. Not sure how much but will measure where its set today, then adjust and see what happens. Approximately, how far out will the internal screw be extended out without it becoming unsafe due to lack of thread contact?

Do I adjust with the HS so it starts the hammer moving at 23 or 24? Move reg pressure to 155?

I love where it's shooting now, very sweet! Once I go up in velocity, I will be able to get back to present pellet tune by adjusting pw down and regulator back down to 110, am I correct?

I have ordered a Huma after market hammer spring if needed. 

With you Guys help, I believe I'm getting my head around this tuning process. 

Thanks for all of the input.

Mike

 

[Ghostranger169]

Mike,

This is a (near)Max fps tune-

Increase hammer spring pre-tension screw to within 1/4 turn away from max(shouldn't have any clearance issues, even completely maxxed out, the pretension screw should still clear the HS wheel). Replace power wheel and turn it to max. Fill with air, load magazine, and fire over chronograph watching fps. With a regulator pressure at 110 bar increase regulator 1/4 turn at a time and fire over chronograph. Fps should get higher. Repeat process until fps goes down. Then DECREASE reg pressure 1/4 turn(dry fire 3 or 4 times to allow the reg to "settle" whenever you DECREASE reg pressure). This point is (almost) the max reg pressure that your hammerspring can open fully.

Fire several more shots over chronograph to verify consistent fps.

At this point, smaller turns on the regulator (increasing or decreasing) may "fine tune" your max power if needed.

Shoot on different power wheel/transfer port settings to determine most accurate setting for your prefered ammo. And I would recommend indexing the liner in the upward direction if you haven't already. 

This results in a tune that will give you the ability to use all most barrels/calibers/ammos and help reduce variance in extreme spreads over your shot string.

Good luck,

Phil

 

[MEC17670]

Great procedure spelled out for me, thank you.