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Old 08-14-2022, 07:56 PM   #1
divenfish
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Mythicon Erevos fail to latch shaft

Looking for the trigger mechanism diagram for an older Mythicon Erevos which no longer latches/holds the shaft.

Thank you!
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Old 08-14-2022, 08:47 PM   #2
popgun pete
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Re: Mythicon Erevos fail to latch shaft

All I know about that mechanism is that the trigger operates a control rod that runs back to the rear mounted mechanism that you can adjust to change the trigger position with respect to the handle grip. Triggers that will not relatch are often caused by (a) the line release lever not being fully swung back which fouls the sear lever swinging, (b) the trigger or the locking arm it is joined to by the rod not being able to move as the sear lever has to push them away momentarily as the mechanism resets and (c) parts of the mechanism have been bent or distorted enough to rub on the housing walls or even jam. The latter is unlikely on the thick mechanism levers used these days.as distinct from those thin levers merely stamped out in the past.

The position of the line release lever indicates that the mechanism is of the usual forward type as being a mid-handle gun the mechanism housing does not need to be shallow.
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Last edited by popgun pete; 08-14-2022 at 09:15 PM. Reason: added some photos
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Old 08-15-2022, 11:14 AM   #3
divenfish
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Re: Mythicon Erevos fail to latch shaft

Thank you Pete for your reply.
I will follow your suggestions. If there is nothing obviously wrong, I will remove the mechanism, inspect it and report back.

Cheers!
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Old 08-16-2022, 12:51 AM   #4
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Re: Mythicon Erevos fail to latch shaft

A closer inspection of the trigger mechanism revealed uneven spacing between the housing and the mechanism, front to back. I centered it, however the mechanism can slide side to side on the cross pins as much as 4-5 mm. I'm unsure if the large spacing is by design or it is a flaw.
I disassembled the mechanism and added one nylon washer on each side of the trigger to reduce the gap to the housing in the hopes of keeping the mechanism more centered than previously.
Now the shaft latches, but occasionally I need to slightly pull the trigger in order to engage the shaft.
I tried several diameter euro shafts 6.5, 7 and 8mm.
For some reason the Riffe euro shaft (7mm?) would not engage (to be investigated), whereas the Omer, Picasso and Hunt, latched just fine.
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Old 08-16-2022, 02:57 AM   #5
popgun pete
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Re: Mythicon Erevos fail to latch shaft

I think that the mechanism must have had spacer washers as usually the levers are close flanked by the housing walls or you need spacers which are often nylon washers. Washers can crack and break and fall out once the material ages. In order to find the reason for the Riffe euro shaft not latching easily you need to compare the tails of the various spears. Some spears have a longer end behind the spear tail notch than others which usually does not affect latching, but does affect line release levers that position by leaning on the rear of the spear tail. That will not be a problem in your gun as it is a forward mech, like a Riffe.

Thickness of the tail needs to be checked as euro shafts have flat top tails.
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Old 08-16-2022, 04:55 AM   #6
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Re: Mythicon Erevos fail to latch shaft

If you could take the trigger out completely and take good quality close up pictures then maybe can have a better idea of what is happening. Also ... did this happen all of a sudden or was this non shaft compatibility from the beginning? If this is something that is new I would definetly not want to load the gun even with the shafts that are loading. It could be that something has changed where they shafts are holding just barely and could randomly go off when fully loaded.

As for the gap on what seems to be a trigger sear, it is possible that it is "self centering" and has no nylon spacers ... but for sure in that case some nylon spacers can help. Actually the correct spacers would be Teflon spacers but most likely that is quite expensive and difficult to procur. IMHO if this is self centering this method is not a good idea as it depends on extremely high tolerances which are difficult to achieve at a reasonable cost.

Also try contacting the manufacturer of the gun as they might have a better insight of what is going on. Shaft compatibility has nothing to do with the diameter of the shaft you use but rather it has to do with the back tang cut design used by shaft manufacturer. A Pathos 6.5mm tang and an 8mm tang will be identical. Some shafts have a shorter flat area in the back and so the transition to the full shaft diameter can cause the shaft flat area to run out of space and thus not allow the shaft back to engage as it hits the top of the mech box. This can easily be fixed with a small file where you open up a few millimiters on top of the mech box in a C shape or simply just file the area of the shaft that is preventing the shaft from entering fully.

I have shot that gun and I like the design (except for the trigger) and it should be a good shooter and gun design is very good. Personally I would remove the trigger and install an Ermessub Double Roller Trigger Long. If trigger is installed correctly it will transform your gun. Don't do it unless of course you have good DIY skills or know someone that can do it for you.
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Old 08-16-2022, 11:55 AM   #7
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Re: Mythicon Erevos fail to latch shaft

Thank you, Pete and Majd, for your inputs.
I will compare the Riffe shaft tang cut to the shafts that work.
The shaft latching is not a new problem, to me. I bought the gun used years ago, so I have very little knowledge of its history. I used this gun seldom, as a back-up gun
I remember once while diving, I struggled loading the spear. Centering the mechanism within the housing, with the tip of my dive knife seemed to help.
The "new" problem was apparently the new Riffe shaft, which was handy when i started fiddling with the gun.
I will contact the manufacturer in regards to the trigger housing gap.

Thanks again!
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Old 08-16-2022, 04:33 PM   #8
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Re: Mythicon Erevos fail to latch shaft

A while back I drew up in 3D exact dimensions of about 20 different shaft tangs to help Mario from Ermessub make sure there would be no compatibility issues with any shafts (including American Cut tangs). I would place the 3D shafts into a fully functional 3D simulation and simulate the action on the computer. The Riffe american shaft was problematic as the tang was very short and slope of the tang would prevent the shaft from entering fully and engaging. So I changed the top of the mech box and cut a C shape and that made the trigger compatible with every shaft I could find. If I remember correctly the change was very minute ... maybe only about .5mm ... but amazingly that was caught in simulation and avoided any compatibility issues. Although in that case the requirement was much more difficult (compatibility with American cut shafts as well as euro cut shafts) I do remember that the Riffe shafts had an extremely short tang. This could possibly be the problem and the fix is really easy ... just a small file to the slope of the tang and file until the shaft fits properly. Of course you could also file the top of the mech box to allow the same but I wouldn't want to touch the mech box unless you really know what you are doing.

Here are some dimensions I found that I had drawn up a while back. Unfortunately I can't find the full 20 shaft set. You can see how the Riffe tang is very short (17.6 mm) and it is possible the Riffe shaft you have is the same.
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Old 08-16-2022, 05:35 PM   #9
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Re: Mythicon Erevos fail to latch shaft

Thank you again, Majd, for the information.
The tang on my Riffe Euro shaft it's quite long (50+mm), as compared to the tangs on Riffe's American shafts, and even longer tha, the Picasso shaft, that fits fine. Attached is a pix of the Riffe Euro side by side with a Picasso shaft. It could be that the butt on the Riffe shaft needs to be rounded or shortened a bit. I will investigate further where the problem is. I have plenty shafts that fit for now.

Since you mentioned Mario's mechanism, so it happened that I just installed one in my Abellan, and so far I'm pleased with it. I broke the trigger lever (white plastic piece) while installing a home made trigger guard on my Denton,
and since my inquiries to Harry and Gabri were unanswered, I contacted Erves/Mario, who shipped a Future mechanism which fit with a bit of tweaking.
I have not tried it with an American mechanism, but the Hunt euro shaft fits perfectly.

Cheers!!
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Old 08-16-2022, 06:11 PM   #10
popgun pete
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Re: Mythicon Erevos fail to latch shaft

I figured that you might have bought the gun second-hand and it is very likely the spacing washers have fallen out after deteriorating. The forward latching trigger mechanisms are very reliable but were designed to be centred with the swinging levers held by the housing side walls with little clearance to the levers. Euroguns traditionally have rectangular sear box mouths as they originated with cast alloy clamshell handle guns and bosses in the clamshell halves took care of lever centralising duties. When you make folded metal sear box cassettes the levers needed plastic washers or spacers to stop the levers moving from side to side and losing engagement in the wider housing. The reason for rectangular sear box mouths on euroguns was originally the stop lugs for the shaft line side flanked the spear tail and this went right into the sear box.

If you replace the plastic washers then you should have no trouble.

Note that many reverse trigger mechanisms built for euroguns utilize wound torsion springs that sit on the trigger pivot pin to bias the trigger in order to centre that lever in the housing. However the sear lever pivot pin still needs washers for this job and it is a good idea to check them from time to time if made of nylon as they allow the full width of the two levers to engage.

Last edited by popgun pete; 08-16-2022 at 06:21 PM. Reason: extra comment
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Old 08-16-2022, 06:38 PM   #11
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Re: Mythicon Erevos fail to latch shaft

A reverse trigger mechanism not made for euroguns is the Australian Sea Hornet and its American counterpart the Biller. Unlike most reverse trigger mechanisms these are cam lockers that use close wall housings to centre the levers with the sear box tunnel being a tube sitting on top of the side walls of the housing. Another example is the Ultimate speargun which used cast clamshells for its housings which were machined to final shape and as a consequence they were heavy guns.

Note that the long sear box roof of the Sea Hornet prevented the spear tail jumping off the sear lever tooth and held it in line as it exited the housing. Most reverse trigger mechanisms don't have a long roof due to the housing being cut back on the top.
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Last edited by popgun pete; 08-16-2022 at 06:49 PM. Reason: added a photo
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Old 08-16-2022, 11:13 PM   #12
popgun pete
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Re: Mythicon Erevos fail to latch shaft

The Riffe eurogun uses a forward mech similar externally to its standard square shaft tail mech, whereas most euroguns now use reverse mechs, but not all of them. The rear of the spear tail and the distance forwards to the spear tail notch cut out underneath the shaft have to fit in the gap between the backing projection and sear tooth on the sear lever as when the tail of the spear hits the backing projection it rolls the sear lever up and the tooth then lifts into the spear tail notch. There is usually a bit of a gap allowed as when mechanisms latch the spear often pulls forwards slightly when it loads up on the tooth. If the tail extending behind the spear tail notch is too long then the tooth comes up slightly behind the spear tail notch and then it will not allow a latch, but I have rarely seen this happen. Spear tail notches are usually elongated for this reason especially on US square tail shafts.

Some guns with a dipping sear tooth action on a moving sear lever pivot pin using elongated slots don’t have a backing projection on the sear lever and can use long spear tails, but slam the shaft in too hard and you can bust the rear wall that terminates the sear box tunnel. I have seen a few of those!
.
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Last edited by popgun pete; 08-16-2022 at 11:35 PM. Reason: added a photo
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Old 08-17-2022, 12:25 AM   #13
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Re: Mythicon Erevos fail to latch shaft

Thank you Pete for the information. It sure make sense to me in regards to the spacers.
I emailed Mythicon USA, see what they come back with.
Cheers!
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Old 08-17-2022, 11:49 AM   #14
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Re: Mythicon Erevos fail to latch shaft

This trigger Mechanism needs to be replaced. Even though the gun is over 10 years old and he bought it used we still honor the warranty. The trigger mechanism will be replaced free of charge. I have contacted the owner of the gun who emailed me this thread.
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Old 08-17-2022, 11:57 AM   #15
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Re: Mythicon Erevos fail to latch shaft

Quote:
Originally Posted by MythiconUSA View Post
This trigger Mechanism needs to be replaced. Even though the gun is over 10 years old and he bought it used we still honor the warranty. The trigger mechanism will be replaced free of charge. I have contacted the owner of the gun who emailed me this thread.
Classy move!
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