More Airsporter help please

[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

[ggggr]

Just take the piston out of the cylinder and push the rod back into the trigger block and see if it latches every time/ that the trigger is working ok.
Then put the piston back in the cylinder but leave out the mainspring/ guide and cocking linkage. Now slide the piston back using a screwdriver/ rod or dowel (it may need a little force to actually latch ----as normally you have leverage) and see if it latches. If it doesn't then that would suggest that the rod or piston skirt are wrong, but in the pics you show of the rod in the trigger already they appear to be ok.
If the gun latches, then fit the cocking linkage and repeat and take it from there. The slot in the piston does not appear to be worn or the lug on the end of the cocking rod. I an wondering (although I've never heard of it on an Airsporter) the cocking arm is slightly bent?

It is a pity there is not someone close by with a piston or another trigger block to try.

[philcbr]

More pictures added showing piston position when the trigger latches.
Do you guys think the issue is with the length of the piston rod as the piston should not have to go that far in to the cylinder threaded section surely ? The piston could not travel that far if a section had not been removed from the threaded part of the trigger block.

http://i513.photobucket.com/albums/t...ps3wqfyczw.jpg
http://i513.photobucket.com/albums/t...psbly1axsg.jpg
http://i513.photobucket.com/albums/t...psjf3xqwjp.jpg
http://i513.photobucket.com/albums/t...pspicfzaue.jpg

Phil