Tuning Reassembling an Impact straight

[Khornet]

Today I had to replace my valve rod assembly after the issue rod developed a bent tip when my C1 got loose. I noticed that it seems possible to misalign the front and rear halves of the gun, that is forward of the plenum vs plenum rearward, and that it's the top plate which lines the two halves up. In my initial efforts I found that one or two top plate screws did not engage freely until I fiddled around with the relation of the two halves. I ended up leaving the plate loose with all screws engaged but not tight, seating the barrel assembly and tightening the grub screw, then tightening the top plate screws. Since the barrel is gripped in channels in both halves, I would think it's possible to reassemble in such a way that you cause pressure or flex on the barrel assembly, which can't be helpful. Is there a trick, or a jig, to make sure this is done right?

 

[broekzwans]

I’ve created a video about it on my Instagram page some weeks ago: Link

 

[cahil_2]

You have to insert the barrel to hold everything straight while you put the top plate on. 

 

[Khornet]

Broekzwans, sorry, can't open the video but thanks. Also noticed that the Saber Tactical bag rider exerts force between front and rear halves of the rifle. Cahill, that's exactly what I wound up doing, thanks.

 

[jeffman]

This is the way we do it to keep everything aligned 

https://www.youtube.com/watch?v=SBL-tpKRrug&t=1s

skip to 24.25, it is a sub 12 version so some bits are different but the order is the same

 

[biohazardman]

Although that is the way I usually do it I had a bit of trouble doing it that way, with my Impact, after replacing the rear block for some unknown reason.

https://www.airgunnation.com/topic/gen1-impact-top-plate-guiding-plate-flexing-when-air-tank-is-installed/?referrer=1

 

[Khornet]

Thanks to all hands. There's always something to learn with this rifle.

 

[broekzwans]

@khornet that's weird, normally you should be able to open the videos without an account -> just tried, indeed unable to open the story without an account .



To make it easier I've decided to put it on Youtube

https://www.youtube.com/watch?v=ymYWi-_nUfA&t=12s

 

[Khornet]

Thank you, Broekzwans. That worked.

 

[bigHUN]

I have to be honest I did not watch the videos above but from a mechanical engineering point of view I can give an advise and I am taking my time to do it this way. No hurry, you want to make it right.

When you start assembling the Impact - from bits and pieces - just place all the screws and no one tighten with the allenkey yet.

(assume the barrel is in place as well) grab with one hand the top plate and plenum and with the other hand start torquing the screws.

Never torque fully one screw then the other then the other!

Always torque - just a littlebit, let say 10 minutes - all at ones starting from end and progressing to the other opposite end.

Never letting the hand grip of holding it together. Torque all at ones, then start from beginning again, torque all at ones, then start from beginning again, torque all at ones...incrementally. With a gentle torque on allenkey (with one or two fingers) you will finally realize which screw/thread is more or less moving, try to make that equally engaging.

Now you had it over for let say 2-3 times and all the screws holding it the Impact together and firm, you can let down your hand grip, and check if the barrel is sliding in-and-out freely. It shall....

A very last step, I final torque the M3's to 2.5 Nm, M4's to 3.0 Nm, M5 to 3.5 Nm.