Tuesday, 12 November 2013

SMK B45-3 Revisit, yet again.






Pleased with the results so far.


Well here we are on a lovely Sunday morning and again i'm stripping the valve
, If i've done it once , Ive done it a thousand times, literally.

Breakfast of champions.

 Again it's the seal on air inlet valve, as the body of the valve is machined into the compression tube i can't see much detail of the surface the seal rests upon.

Why i put the scope back on every time i test a new inlet valve seal i do not know.


Two screws and the stock is of, again. We have been here before many times before so i'll sort of skip through this bit.

Handy needle nose pliers for removing the collar screw, Again !


Every thing out, AGAIN! Notice the original seal washer and the O ring above which now replaces it, i now place it out side the valve so the sear doesn't hit too hard on returning after firing.

 I know it has a sharp circular outer edge that cuts into the seals i've been putting in, today i took a mold of that part of the valve body internals with some modelling clay. Now i can see what angle the edge is and how high the collar is, so i can either make a PTFE or Delrin seal or fill the space outside the collar with a washer to go on the outside so only a tiny part sticks up and doesn't cut into the seals.

Mold taken in Fimo and baked, now i can see what i'm dealing with in detail.

This air rifle was sold with instructions and an exploded diagram along with spare seals, so you could replace the seal when it broke.


Advert for the Custom model, still got that ugly pump handle though.


Parts diagram that comes with gun, that should tell you something really.


Instuctions on how to use and strip the bugger. That should have alarm bells ringing by now.

I suppose if you pumped too much air pressure in the valve that would take it over the legal limit and it would cut the seal, that's one way to keep the rifle within legal power. 

Someone else's nice example of the Custom B45-3, last 4 pictures where photo's off the computer screen so thanks and sorry to who ever put the up.
Also the route the air travels through and around the firing pin housing would keep the power down, if it ran direct to the transfer port there would be more pressure behind the pellet.

I have glued some rubber to the air flow channel of the firing pin housing, in the hope of needing less pumps and using the air in the valve more effectively.

 This i think is the reason that no matter if you pump it 6 or 15 times the power doesn't increase, it makes a sort of sense and that is what happens.

Pump arm locks away firmly.

Another thing that is bugging me is the loose fit of the pump arm at the sight base, there is a lot of side to side play when the arm is extended.

But is a bit wobbly when extended.

  I've tried washers in the past which reduce it a little, but have not yet found the right thickness to place either side to reduce it evenly. So i reckon i will make some shims up out of the metal off a drinks can, this way i can add layers till there is as little play as possible. It sure has paid off buying some good strong French coffee for a change, it certainly gets them tired old brain cells kicking in the mornings.

Air rifles i am currently tinkering with, along with tools and spares box, there is a most useful chronoscope in the little white box.

Looking in Halfords the other day i noticed they had some Bio grease for bikes, this i thought might be good for lubricating the piston linkage in the compression tube. So if any gets in the valve it doesn't soften the seals up, which is exactly what petrolium based greases do. Its an idea i will have to research, any way it's back to tinkering.

TTFN

Wing Commander Sir Nigel Tetlington-Smythe.

More caffine and nicotine please, as it takes the same amount of time to strip and reassemble this gun as it does to make and drink a cup of coffee. 

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