Tuning What size Belleville washer for Impact 2

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Drumsnguns

Member
Jun 14, 2016
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North Carolina, United States
I have an Impact 2, .25 cal. 
The regulator has been acting strange. 
long story short I ordered a new piston and washer set. In fact I ordered two washer sets as the first set would not allow the reg to go beyond 50 Bar. Same for the second set. 
so went back to the first set. Confused? Me too

Last night I got all sets out and measured w calipers

SET1 (in gun), 11 (washers total):

7 washers @ 0.48 mm

4 washers @ 0.57

SET 2: 11 (washers total):

8 washers @ 0.48 mm

3 washers @0.57 mm

SET 3 (14 washer total):

14 washers @ 0.41 mm



Any idea as to the right size and right order?

Thanks




 
Just spoke w Newman at FX he said that washer tolerances vary which would explain using the two sizes in order to achieve the correct specification. 
He said to group like sizes together, put the 0.57’s on first then finish w the thinner ones. When I took mine out to measure they were all mixed up and mismatched. 
I’ll get them sorted and installed correctly and test for a couple of days and see if things hold constant. 


Wanted to pass this along so you guys know that there could be two sizes so take care when tearing the reg down. 
 
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I was having reg problems where it would creep up 5 bar but after a dry fire it would drop 15 bar but only come up 5 bar. It is set at 150 bar, after a few days it goes to maybe 155, I fire it, it drops to 140 bar then only comes up to 144-145 bar. I reset it to 150 and the next time it does it again. I can’t keep opening the adjuster, I’ll run out of threads and will eventually have a high pressure “incident!” So I’ll try it the way FX suggested. If that doesn’t work they suggested me sending the gun in to them. Sent an RA. 
That’s a last ditch option for me. Don’t want to have to send it out. 
Ive gotten pretty good working on my Impacts and other Airguns but this one has me a bit puzzled. 


BTW, Kudos to FX tech support!
 
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Yeah that's a strange one. It's not obvious to me what would make the setpoint fall and require repeated adjustments to bring it back up. Sounds at first like a classic self-adjustment problem where a screw turns on its own but the nature of the forces here should instead make the setpoint increase over time. You might get some settling of the Belleville stack when it's new but not to the extent you're describing.

The only other thing that comes to mind is if this is a reg with a plastic piston, the first Belleville might be cutting into the shoulder as it compresses and relaxes. As it digs in, the stack requires less and less pressure to move the piston to the valve seat, reducing the setpoint. If so, adding a flat washer there would take care of it.
 
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My RP is a Sekhmet Digital. Supposedly accurate to 1% or something like that. 


last night I got another piston and it looked visually perfect. I used a bit of 3M 1200 grit blue paper in the piston shaft to smooth things out. 
went back to the Belleville’s and took 0.57 washers and installed first in the piston. Then the odd number of 0.48 washers installed with the last cupped out towards the bottom of the reg housing. Lightly lubed w super lube beforehand. 
assembled and pressurized. Let sit over night

It crept up from 150 to 154. A dry shot dropped it down to 149. So I consider this a fix. 
I would say it matters keeping like washers grouped together from what I see here. 


To answer the second question, when I tuned the first time ES was something like 7 and SD was 2. 
When I returned, the ES had gone way up into the double digits. Can’t recall here but like in the 30’s. 
I’ll shot over the chronograph tonight to see what the new velocity/ ES/SD is. 

 
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