Tuning FX Impact Mk2/M3 - slower first shot - no reg creep - quasi-scientific analysis

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GMANCO said:
Instead of drilling that conical section out to create a flat seat area and "risking" violating min thickness, could you press fit a soft metal plug into that conical section and then drill a clean hole for the rod to pass through?
Click to expand...
mubhaur on this forum has the answer for this problem....I been using it for a couple months now and have no slow first shot at all anymore.... Even after a couple days off sitting.....
Someone just needs to take his design and have it mass produced and stop trying to fix an old defective part I think.. 🤷

20240815_171414.jpg
 
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Airgunnerscott said:
mubhaur on this forum has the answer for this problem....I been using it for a couple months now and have no slow first shot at all anymore.... Even after a couple days off sitting.....
Someone just needs to take his design and have it mass produced and stop trying to fix an old defective part
Click to expand...

I’d be a buyer for sure!
 
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Airgunnerscott said:
mubhaur on this forum has the answer for this problem....I been using it for a couple months now and have no slow first shot at all anymore.... Even after a couple days off sitting.....
Someone just needs to take his design and have it mass produced and stop trying to fix an old defective part I think.. 🤷

View attachment 589678
Click to expand...
By the grace of God I didn't receive any negative feedback on this part yet.

I just wanted to help out airgunning community. The problem is this that there is very thin profit margin on this part. Such things cannot run the kitchen. I am a professional accountant and airgun modification is just my hobby. My machinist makes these parts on manual laith machine and it takes him more than two days to make one part.

I have shared the details of this part with Huma-Air for mass production without charging them money.

Huma clearly refused as perhaps this is also not a good profit making item for them.

Mubhaur
 
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Superpete said:
I think FX left white o-rins dep there and not contacting the black bushing so the black bushing not pressing on the white oring and not compressing it under its force, who knows what they were thinking, but I like the concept. In order to drill it correct depth we would really need some precise maching to kae that hole just so.
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Pressing the bushing against the o-ring is indeed never the intention, but I assume that if you press it, you want it to be at a fixed distance just behind the o-ring without the 2 mm clearance it currently has.
Unless the bushing really has no other purpose than to more or less hold the o-ring in place when it is not under pressure.
 
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GMANCO said:
Instead of drilling that conical section out to create a flat seat area and "risking" violating min thickness, could you press fit a soft metal plug into that conical section and then drill a clean hole for the rod to pass through?
Click to expand...
I fear this would increase the risk of leaks.

There is room to drill the seat flat.
The question is, how far, and is the part that is modified by FX and currently installed on the M4 and sold as a spare within tolerance?
If so, it would be helpful if FX could confirm this.
This is a simple question asked out of genuine concern, not emotion or a desire to cause fuss.
Hopefully, this concern is unfounded, as I have an M4 on my shortlist and therefore, confirmation would be greatly appreciated.
 
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Yesterday, I installed the new plenum end piece without the plastic bushing, but with the supporting o-ring (5.5x1.5 NBR70) so that the new o-ring (2.9x1.78 PUR90) stays in place during installation.

Today, I checked and saw that everything had remained under pressure whitout a leak, so I decided to test it.
The first shot was 3 fps slower than the last one yesterday.

Yesterday, after reassembling it, I didn't adjust it very precise and there was a 10 fps spread, so I can't even say if it still had an effect after 24 hours.

It now really seems that drilling the conical seat flat was the solution.
Why it took so long or why they had to drill it out so far is something I'll never know.

It's also clear that the bushing only serves to keep the o-ring more or less in place during assembly.
Anyway, fortunately, it works just as well without the bushing and with the supporting o-ring.
 
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Apollo said:
The M3 and first M4 had the same part.
FX is currently modifying this part, and the new or modified part is now being installed on the M4.

It can also be ordered as a spare part. It has the same part number: 10338
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Today I had an interesting conversation with Utah Airguns. The person I spoke with (who said they verified this with one of their airgun techs), said they were not aware of any slower first few shot issues with the M3. They said they are only aware of issues with the M4, and stated the solution was to go back to the M3 type o-rings to solve the problem which is definitely not the solution.

I had contacted them to see if I could purchase one of the new power plenum valvetube ends (P/N 10338) that Apollo has shown had been recently released. Utah Airguns was not aware of any change, and said the ones they had in stock were still the same original M3 design.

Apollo: For clarification are you installing the new design power plenum on an M3 Impact (sorry if you already stated that somewhere earlier)? And where were you able to obtain this new part, or do you have a newer M4 that had this new design part already? I see you are located in Belgium, so it appears this info and part hasn't made it to the USA yet.
 
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If it wasn't a problem, they solved it anyway with their modified part :)

At least at the 100 bar at which I tested it.
It is possible that at a higher plenum pressure of up to 160 bar, more pressure will be put on the o-ring, causing it to stick again but most likley not.

Recent M4s were equipped with this modified part, so I assume that most recent M4s have the modified plenum end piece, as well as the updated valve stem.
The first M4s did not have these new parts.

The modified part is now also supplied as a spare part. If it is not yet available in the US, I assume it will follow soon.

Hopefully, they will continue to supply it without pressing the bushing into it, as this can also be done with the supporting o-ring, making it easier if the o-ring ever needs to be replaced.
 
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For those interested, the newly drilled out part seems still strong enough at 0.6 mm.

The safety factor is 2100/1317.5=1.59.
So it seems the thin disk is okay for the pressure of 250 bar but not if the failure of the pressure valve is sudden and creates an impact which could be 3 times more.
engineering.stackexchange.com

Strength calculation for pressurized cylinder top

I have a question regarding the strength calculation of a pressurized cylinder top. It concerns a cylindrical part that is subjected to a pressure of up to 160 bar. In the center there is a shaft t...
engineering.stackexchange.com engineering.stackexchange.com
 
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re inventing the wheel, the new plenum is fine once installed in the gun strength wise its clamped in, it also takes the same o ring as the DRS Leopard and Panthera
the guys over at accu shot orings had these made roughly 4-6 weeks ago .
like they say unless its a custom made oring 95% come with silicone rubber in them which cause the valve rod to drag until it gets warm
once warm the silicone becomes slippery shoots great,,, set it down for 10 min it starts all over again, been there tried all these fixes
and water / moisture due to no oil base lubricant the silicone grease washes away in time and breaks down more water quicker it happens.
even bought 2 plenums one was from mubhar the other from accu shot very similar in design i preferred the thumb screw over the nut
also both have a 2mm hole which quickens the refresh rate also mubhars plenum is 0.80 longer due to the nut so c1 adjustment is needed.
they both work the same i sold both and drilled my plenum from 1mm to 2mm installed there new o rings keep dry air the guns have been great.
the new valve rod with the peek bushing is a plus, also nicer design on the small o ring end. now i see why this thread is so old holy moly...
 
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PcpMachinist said:
even bought 2 plenums one was from mubhar the other from accu shot very similar in design i preferred the thumb screw over the nut
also both have a 2mm hole which quickens the refresh rate also mubhars plenum is 0.80 longer due to the nut so c1 adjustment is needed.
Click to expand...

If this was the case, the top plane wont fit anymore since the plenumneck is longer as you stated.

With the new valve rod from FX I only have 5mm with the c1 installed, my old valverod had 6mm with Mubhaur his part, there was no difference even if the part “may” be longer
 
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Ries said:
If this was the case, the top plane wont fit anymore since the plenumneck is longer as you stated.

With the new valve rod from FX I only have 5mm with the c1 installed, my old valverod had 6mm with Mubhaur his part, there was no difference even if the part “may” be longer
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it still fits with no issue of the top plate it just screws in another thread and a half no biggie.
a few of us bought them and noticed the refresh was quicker , under further inspection using a pin gauge
we found both plenums used a 2mm hole between the 2 9x 1.5 o rings vs 1mm stock fx plenum.
between the 5 of us 4 still use the aftermarket plenums but use the accu-shot valve rod oring ( only one to date that works)
whatever they use in that o ring is very slippery unlike the pur 90 there o ring is almost translucent the Pur90 is an off white.
i have to laugh when i was reading this entire article wont buy from a copy cat i say kudos to whoever can machine such a part
as a machinist i can tell you its hours of work with no mistakes, then have them hydro tested.
we have found 2 things contribute to the slow shot /cold shot issue ,plenum o rings and the regulator once balanced its fine, getting there can be a bugger.
i also say kudos to the 2 guys who did all the R&D on those o rings as well because without those the 1st 6-10 shots would be all over the place
and very inconsistent until warmed up.
the new fx plenum that uses the smaller o ring like drs/leopard i swapped mine back to the duel plenum o ring design much better
3-4 fps spread on 20 shots vs 7-10 i think that small oring was a step backwards.
all in all good article with lots of opinions ideas and fixes.....
 
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