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diy speargun trigger mechanism help

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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F

fishfood

New Member
Jun 14, 2010
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hi all, first post

I am planning on building a spear gun and i do not want to have to buy a trigger mechanism. I have access to a full machine shop so fabricating is not an issue. The problem I have is a cannot find designs for one. I need something that is simple and affective. I am thinking of something like a Alexander trigger. I have searched on this forum and the internet and have not found much on building your own trigger mechanism. the most productive was this forum but there was no designs with the post. Any help will be greatly appreciated
 
Reactions: Mr. X
It has always been a sensitive issue but because there are now such fantastic commercially available units for very reasonable cost, I cant think of anyone building there own units anymore.
We have several highly skilled experts on the forum who might be more helpful, Tin man & Don Paul both spring to mind but I am pretty sure both these legends now buy their units.
 
Reactions: Don Paul
I'm not in Don Paul's league, and I do in fact buy all of my trigger mechs rather than attempting to build them. I'll throw out a few "watch outs" though.

You didn't say how large a gun you are contemplating. Some smaller guns use 316 stainless for both the trigger and the sear, but be aware the 316 can gall and stick to itself under load. So mechanisms for heavier guns almost always use 17-4 stainless for one or both pieces. 17-4 doesn't attain its full strength until it undergoes a heat treating process at around 950°F to 1150°F, depending on the final characteristics desired.

The exact geometry of the trigger to sear interface is critical. If the angles are off just a hair, the trigger can either fire unexpectedly, or be unacceptably heavy to pull.

I have never seen dimensioned plans posted for any of the commercially available mechs, and I know that some of those guys have been burned by supplying that information.

I do know of one guy who regularly builds his own mechs. Visit his site at Spearfishing, Rene Potvin, peche en apnee and maybe contact him.
 
Reactions: Mr. X, Don Paul and foxfish
We have several highly skilled experts on the forum who might be more helpful, Tin man & Don Paul both spring to mind but I am pretty sure both these legends now buy their units. Quote; foxfish.

The only reason I built my own 17/4 mechanisms is; thirty years ago there were very few choices on the market for the hi power I was attempting to engineer into the guns I built. My first mechanism was merely a clone of the popular UnderSee two part unit. I had issues with the stock unit deforming the sear pivot rivet and discharging the spear when four 5/8's bands were used. I simply drilled out the rivets from a sheet metal UnderSee mech, flatted out the thin sear housing and traced onto thicker 1/16'' 17/4 ph SS sheet painted with Dykem machinist dye. The same process was applied to the trigger and sear (copied) onto 17/4 plate 1/16 thicker then the stock brass/bronze parts. I then lightly deburred and polished all parts and sent out to certified heat treatment. I machined over sized pivot pins from maraging steel. Three of the Undersee clones I fabricated still live in guns a use on a high duty cycle with no glitches what
so ever.

The sear box in my gun Double Trouble gun was milled from 1/2'' 17/4 plate and
uses Ti trigger linkage and other bits.

When I build my next personal gun I will be calling Josh @ Neptronics as I
need not reinvent the wheel. I also like the reverse trigger euro systems
out there for a reef type gun.

All the best, Don
 
Last edited:
'm not in Don Paul's league, Quote: TinMan.

Your are way too modest and in fact your are out of my league in terms of
new product output and design.

I'm just a old skindiver that can fab his own ideas and bits for personal use.
Cheers, Don
 
Hey.. . . I guess I'm a bit slow getting into the discussion here but I have drawn up plans for a few different style triggers - if you are interested I could share those with you. They are currently drawn in Auto-cad. Let me know if you are interested and we can share some Ideas.
 
I thank you all for replying
theonetruerat I would be interested in talking with you PM me
I am planning on build A moderate power spear gun I have yet to determan spacific specifacations there are so many options
and thankyou seafox for the contacts
 
There have been numerous trigger mechanism designs for spearguns, but few that actually work reliably in the marine environment. Consequently many competing brands are variations on a common theme as evolution has got rid of the rest that either failed to lock reliably, or wore out too quickly, or jammed with just a few grains of sand in them. You really need to extensively bench and then field test new trigger mechanism designs or some bad consequences may ensue when they are least expected! Question is whether this is worth it for maybe only one or two guns. I suggest that you copy something like an Undersee mechanism first as radical designs tend to lock and release OK "on paper", but fail miserably in the field! Dimensioned trigger mechanism design drawings are not published as proprietary knowledge is not going to be given away over the Net, especially when months of work may be involved in getting everything just right. Even the major manufacturers have come up with a few duds over the years, they need to be clean as a whistle to work properly.
 
Reactions: Don Paul
yeah dude please share the autocad things
 
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