More Airsporter help please

[Airsporter1st]

Thank you all again for taking the time to suggest solutions to my problem.
I have reassembled the trigger as it came to me when I got the gun. I’ve uploaded more pictures that better show the trigger components as assembled by me.
It seems to function as a trigger ok but not latch due to insufficient travel of the piston in to the trigger block, sorry if I’m repeating myself in this matter but I can’t see how it would have worked even before I got it.
More pictures.

http://i513.photobucket.com/albums/t...psnixh5cjt.jpg

http://i513.photobucket.com/albums/t...psmcdqprgo.jpg

regards
phil

The trigger certainly looks right now, anyway.

No idea what is wrong now, but there must be a reason! Can you take a similar picture to the first one, but with the piston rod fully inside the trigger block to its maximum depth?

[tomlinn]

How much did you polish the underside of the piston where the cocking lever sits? I had this problem where around 1mm had worn away. This then caused it to not latch fully when cocking as the lever could not push the piston back far enough before it hit a barrier. If the gun was doing this already it might explain why they removed threads to try and make up the difference. However I fixed it by welding a couple of mm back on to the underside of the piston. It was surprising how that slight worn down area caused the issue. You can test this by placing something in to create a gap and testing the movement without the spring in to see if it latches.

[philcbr]

Hi all

as requested more pictures added.
While polishing the piston I did not do the end of the rod that inserts in to the trigger block, it does not have any noticable wear marrks on the end.

http://i513.photobucket.com/albums/t...pswuqbdecn.jpg

http://i513.photobucket.com/albums/t...psu09r4vzm.jpg

I will assemble the gun tomorrow minus the spring and try suggestions from the group.

Regards

Phil.

[tomlinn]

Not the rod I meant the groove in the piston itself, mine had worn away so not allowing the rod to push the piston the whole distance it needed to travel.

[Airsporter1st]

Hi all

as requested more pictures added.
While polishing the piston I did not do the end of the rod that inserts in to the trigger block, it does not have any noticable wear marrks on the end.

http://i513.photobucket.com/albums/t...pswuqbdecn.jpg

http://i513.photobucket.com/albums/t...psu09r4vzm.jpg

I will assemble the gun tomorrow minus the spring and try suggestions from the group.

Regards

Phil.

In one of your photos, you are showing the trigger cocked and the sear engagement part of the piston rod well behind the main sear, so that part of the geometry is correct. Therefore, when the spring is in it is either becoming coil bound, or the end of the piston rod is not long enough to bear on the back end of the main sear in order to cock the trigger, or the cocking lever/slot is mis-matched, such that the piston is not being pushed back far enough.

[crowbar]

I have a flat top piston (mk4) which measures from to skirt to the bent face one and three quarter inch .

I have a cone top piston (mk2) which measures from the skirt to the bent face one and twenty three
thirty seconds of an inch .

So of the two pistons I have on the desk I am sitting at the distance of the cone top is one thirty second
shorter than the flat top piston .

The measurements were taken using a vernier caliper so reasonable accuracy .

Both these pistons are standard with no polishing .

Cheers Crowbar

[crowbar]

I seem to remember somebody having a similar problem that the piston would not latch .
When the action was split the trigger block unscrew from the steel comp tube end plug leaving said
plug still screwed into the comp tube and having to be removed individually .

The trigger block is joined to the end block by a hollow bolt which the piston rod passes through,
this hollow bolt has a large round head and friction splines on the face of the head.

These friction splines mate with the friction splines on the comp back block to lock them together .

When the trigger block screws off the back block it is because the comp block has seized in
the comp tube and the force needed to free it causes the locking splines to ride over each other altering
the setting and the trigger won't latch.

Cheers Crowbar

[Benelli B76]

Hi all

as requested more pictures added.
While polishing the piston I did not do the end of the rod that inserts in to the trigger block, it does not have any noticable wear marrks on the end.

http://i513.photobucket.com/albums/t...pswuqbdecn.jpg

http://i513.photobucket.com/albums/t...psu09r4vzm.jpg

I will assemble the gun tomorrow minus the spring and try suggestions from the group.

Regards

Phil.

Phil re query on bucket pic, I have one that measures 56mm on the dimension you ask. It is 44mm to the actual latching point.

Baz

[frogboy]

Although I can't add anything of use to this thread, it is fascinating and I am waiting in anticipation to hear the eventual correct diagnosis and hopefully happy ending

These threads are like soap operas for airgun nuts

Good luck, can hardly wait for the next instalment

[crowbar]

The hollow bolt head is hexagon not round as stated .

Cheers Crowbar

[philcbr]

Hi all

Thanks for the responses, the plot thickens.
Crowbar and Baz have kindly supplied measurements of the distance between the piston skirt and the latching rod end, mine appears to be different.
Baz measured 56mm form skirt to end of the rod mine is 51,3 and 44mm from skirt to latching point, mine is 40.50mm.
This could explain why some threads have been removed from the part that screws in to the cylinder, allowing the latching rod to travel further in to the trigger block.
I have noticed the latching rod is a separate part to the piston body, this being brazed to secure it in place. Could this have been modified to make it shorter in an attempt increase power? When I removed the piston from the gun originally I noticed it had a “blob” of braze on the outside of the piston surface. My thought originally was that someone had tried to increase the weight of the piston by doing so, attempting to increase power again?
I’m adding more pictures for reference. I made a video of the cocking action but photobucket will not load it, it’s not very large only 10mbit but I’ve given up wasting time on it.

http://i513.photobucket.com/albums/t...psqvuudcxn.jpg

http://i513.photobucket.com/albums/t...psl7t6nugs.jpg

http://i513.photobucket.com/albums/t...ps4yuf3sip.jpg
Regards
Phil