Trigger Problems on a Wooden Speargun

[ubik]

Hey Deeperblue Community

Four years ago i ordered my first wooden Speargun. A Spetton Cubera 2 90cm.
It worked well until last year, i sometimes had the spear released without using the Trigger.
Last year i removed the Trigger looked at it and it looked good, so i just cleaned it and put it back in. This worked for a while, but now if i put on the second rubber the shaft releases and kicks my solarplexus.
I dont know if the trigger releases, or the shaft goes over the trigger?

Today i again removed the trigger and disassambled it. From my point of view it looks good, i dont know why it releases the shaft. I attached some pictures of the trigger, but for me it looks good. Maybe theres is to much play above the shaft?

Any help is apprechiated. I can take other pictures if needed.

Thx in advance

jan

 

[popgun pete]

It is possible the spear tail is jumping the tooth on the sear lever as the tooth is barely tall enough. If you mount the levers on the outside of the sear box by using longer pins substituting for the actual pins you can see what is happening. An example of this method is shown here where you can get an idea of how big the spear tail or tooth need to be to provide a strong grip on the shaft. Under load parts can deflect slightly, so you need good overlap of the interlocking parts.

Something like this approximation.

Also any wear in the sear box roof can allow the spear tail to escape if the nip is enlarged. Ditto if there is wear on the tail, so the shaft needs examining as well.

 

[ubik]

Hey Pete
Thanks for your answer.
I will try that.
But i think too, that there is a problem whith the space on the top of the sear box.
I will look there. So it only can be the shaft notch, oder the top of the sear box.

I saw that on some of my shafts the U is longer than on others. I could try another shaft aswell.

If i replace the trigger fo a better one, as im not sure i i get one of these again, for what i should look out?
I saw some at ermes sub, which look the same, but im not sure.

Thanks

 

[musubi]

That's scary that the gun just fires like that!
Seems like the shaft is barely locked in and just slips with enough force. While it could be the shaft notch, my guess is the issue is with the mechanism sear. Maybe something worn or defective? Is your plan to fix the current mech or try an replace it? I'm surprised that the mech gave problems only 3 years in. Have you tried contacting the manufacturer? The easiest might be seeking a direct replacement mechanism. The Ermes sub mechanisms are top quality and great if you're able to fit one of their mechs in your gun.

 

[popgun pete]

The trigger is based on the Riffe/Undersee design that is almost bulletproof, however one difference is the sear box housing is much wider than the lever thickness. I see in your photo that there are nylon washers to centre the levers in the housing, but you should check that the washers that centre the trigger are still in place. If the levers can independently wander from side to side in the housing then it is possible that they are slipping out of engagement. If not that then the nip between the top of the tooth and the sear box ceiling is too large for the shaft you are using or the shaft tail has worn.

One thing about this trigger mechanism is the pivot pins are relatively close together, but that is to make the housing not too deep when the trigger latches as the sear lever tail swings downwards. I am not a fan of swapping trigger mechanisms in guns with alternative parts as rarely are they drop in replacements, but that said some manufacturers make replacements specifically for some guns.

Stamping the front mounting ears from the housing walls has meant that the sear lever pivot pin is pushed back from the leading edge of the sear box, another reason for the pivot pin spacing being what it is.

 

[ubik]

Thank you again for your answers and for your nice drawings a pete. So its much easier for me to understand what you are talking about.
I did what you said and looked at the shaft end, which looks a bit worn and even bent. The round egde doesnt look that sharp anymore.
On the picture you see the one above is brand new and the edge looks "sharper".

And yes there are 4 washers in place, quite tight.

I also dismantled the trigger and put it together outside. For me it looks like the space is tight enough above the shaft.
The top of the sear box is ok.

So i think i will just chnage the shaft and tighten the screws of the triggermech really well. The thing is i cant try it out here in austria.
I might find someone who is crazy enough to let me test it in the pool.

I will write back, when tested.

 

[popgun pete]

This diagram shows how the shaft tail to sear box ceiling (which is the underside of the sear box roof) clearance will affect the grip on the shaft tail as the shaft tail notch rides up on the sear tooth. To decrease the gap if the underside of the roof has worn away one can put a dent or crease in the sear box roof, but really it is better to change the sear box.

 

[ubik]

The gap between the sear box ceiling and the top of the new shaft doesnt look too big. As i also tighten the screws really tight, so the distance from the sear box ceiling in relation to the shaft is smaller. So i think its two reasons. The worn shaft end and the screws of the sear box not completely tight.
The searbox ceiling doesnt look worn.

Thanks again

Jan

 

[ubik]

I just came back from spearfishing in Croatia. What i changed to get the gun working reliable again. Ich changed the shaft to a new one, tightend the screws of the housing, to keep the spear down and changed the rubber length vom 2x54cm to 2x60cm. Wich is a lot better in terms of needed power to load, accuracy and the energy on the shaft notch. So thank you all for the help, to get my gun working!