Tuning What is this oring size - FX Impact MK2 PP on the valve rod

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bigHUN

bigHUN

Member
Jan 16, 2020
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L4G7X4 Canada
I am very much ready (in my mind) to start a heavy porting upgrade but I want to make sure that I have spare parts in my drawers.

I have a full Impact oring kit in NBR90 from oringsandmore, only missing this one on the vale pin end, What is this oring size not listed in the BOM?

20200719_212830.1605326820.jpg


The other thing I am finding interesting, we are closing the 2020 soon and the Impact pdf BOM (revision 20.05) is still creating a mess wherever I go.

Lets take a look for example this valve seal. I just want to make a new peek poppet for a bigger port, really doesn't matter if I could get a pin only or the entire rod kit.

PN 20275 which is as per FX pdf the B28 the valve pin only, but the europeairguns ( Price: 35.75 € ) and bagnallandkirkwood ( £47.93 ) showing the same PN as an entire rod kit.

FX Impact PP valve rod.1605327286.JPG


FX Impact PP valve rod BOM.1605327300.JPG


Also I would need a oringsandmore PN for the green oring inside PP, could that be the same NBR70 or 90 or really must be PUR90?
 
... HNBR (hydrogenated Buna-N). A bit tougher than standard Buna-N if exposed to abrasion...
Click to expand...

Inside deep in the PP end cap there are two orings, the inner is that green and the outer black, in a sandwich configuration. Abrasion is only from the valve rod, but I would agree that longitudinal motion/friction is pretty aggressive, even Ernest put up recently a new youtube video polishing that valve rod (and some other moving parts along the rod) indeed for different purpose. But polishing is late for folks with high shot counts or that would need a new and fresh oring "sandwich" for a new OD. I am on the safer side with very low shot counts but my intentions are parallel.

I guess I go with a simple solution = NBR90.

Still need the oring size for the (PP) valve pin end.
 
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Polyurethane of any kind is an excellent choice where abrasion is relevant. But yes the best ones are the cast ones (Disogrin). I’ve received them that are either clear or nearly opaque white. I don’t know why the difference in color.


FWIW, I don’t make a crusade out of using them unless I know it to be an especially demanding application. The final stage O-ring of a high pressure pump for example, or a spot where an O-ring has already demonstrated an early demise from material loss. Buna-N is actually quite good in the overwhelming majority of cases, and particularly so if a 90 durometer can be used.
 
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Here is another issue , way need to take into consideration. When you see the Valve stem flushing out into the Magazine side and not allowing the mag to seat, like the one below,

Then you need to check the B-28 Valve seat derlin ( black ) above the conical funnel shape seat on the rod. In my FX , its really damaged by 1 mm ( squeezed in ) and that was the reason to have the Rod pushing our of the valve assembly

WhatsApp Image 2021-01-19 at 1.31.02 PM.1611071809.jpeg


Valve stem Derlon issue.1611071914.JPG

 
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