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Why US spearguns use a square cut sear tooth and Europeans used angled teeth.

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popgun pete

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Jul 30, 2008
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It all dates back to early speargun history, as in Europe the spring gun was first out of the blocks and set the trend for all the weapons that followed. As the shaft was pushed by a long coil spring sitting directly behind the spear the first attempt used a single-piece trigger with a trigger pivot pin below the barrel tube and as that was very unreliable the decision was then made to use a pull down sear lever in the gun. Because they wanted to avoid pushing the spear backwards when pulling the trigger they angled the retaining tooth. If you use a long enough sear lever arm then it swings on a flatter arc, but there was only so much length available in the gun’s usually alloy grip handle, thus the tooth had to be angled, but never by enough to completely eliminate the problem.

Side slotted barrel band guns got rid of the long propulsion spring, but they kept that same trigger mechanism for both them and the next weapons revolution the French band powered Arbaletes, even though it no longer had a coil spring pushing over the top of it as had been the case with the compression spring gun. Le Prieur used something similar in his “declic” trigger.

Because in the USA they never started with the spring gun they used a single-piece trigger and they only work well with a square cut tooth. Some early US spearguns used the wishbone directly on the shaft tail and thus had no sear box roof, but that type of gun did not last long as securing the spear tail with a sear box roof was a much better idea. However such guns must use a square cut shaft tail or the shaft can pop off the tooth at the wrong moment

Of course Europeans also used single-piece triggers, but they were not as easy to pull with larger band loads as the two piece pull down sear lever trigger guns were and their spears were not as universal compared with the French Arbalete shafts. In the USA most guns used shafts with square cut tails until improved euroguns arrived in recent decades as formerly the guns were considered too weak being principally designed for reef work and smaller fish.
Kramarenko spring gun 1937.jpg

Wilen's spring gun handle.jpg

SwimasterSpearfisherman_and_ProdanovichSingle.jpg

trigger declic.jpg

Freshman2.jpg

Wally Potts Scubapro trigger mechanism.jpg
 
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Note that while they look vaguely similar the Beuchat is a single-piece trigger while the Cavalero Champion gun is a two-piece pull down sear lever trigger. The Champion gun was more widely copied than the Beuchat gun was because of that better trigger. Beuchat then made a two-piece trigger gun that used a star wheel sear lever which also required using an angled tooth for its spear tail notch.
Beuchat Peche Sport spear R.jpg

Beuchat shaft tail R.jpg

Rossi star sear.jpg
 
When plastic grip handles replaced cast alloy gun handles the star sear lever also made it into those guns. The leverage advantage of a star wheel trigger is zero, no better than a single-piece trigger, but it had more teeth to spread any tooth wear over.
Beuchat star sear lever.jpg

Caraibe healthways line wrap R.jpg
 
There were a few spearfishermen in the USA who decided to follow the pull down sear lever used by the Europeans, the most notable being the Sampson gun. Another was the 1955 gun invented by Thorburn whose idea was to shoot directly from the reel with the shooting line and reel line being one and the same. His gun is interesting as it is integrated into a single tube body with bulkheads sealing some sections off as buoyancy elements, but you can see pulling the trigger will move the spear slightly backwards against the band pull. That and shooting from a reel is not a good idea as the reel spinning will add a lot of drag to the shot.
Sampson internals detail.jpg

Thorburn gun.jpg
 
The advantage of the square cut sear tooth and matching spear tail notch is the load bearing area is much greater if the opposing faces press flatly against each other, but in practice they may not if the sear lever is tilted too far forward with the mechanism latched. Although we do not have the capacity to tune this a lot will depend on how accurately the levers were made and how horizontal the mechanism or its cassette sit inside the gun, or if the rear grip handle tilts on the gun barrel. Those keen enough could file the faces and hope most of their spear tail notches were cut square to the shaft axis.
 
In Australia very early spearguns were variations on the hinge gun which uses a friction trigger, much like the tilting washer on a modern caulking gun. This means the gun has no spear tail notch and can be cocked for the shot at any insertion length, many such guns were spear tail drivers using a mid-handle with next to no gun stock and a tail cap pusher on the spear.

These guns were replaced with single-piece trigger weapons like everywhere else, and that meant square tail cut spears, same as the USA.
undersee Hornet 6.jpg

Undersee Bantam.jpg

Undersee Comet 1.jpg
 
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The next evolution was the two-piece cam lock trigger which had the advantage of using existing square cut tail spears, the most famous being the Undersee trigger mechanism invented by Denny Wells. Another was that used in the Lyle Davis gun, this being a formative period for all modern band spearguns. The sear lever now rotated separately in a sear box with a roof and floor so that the spear tail was wiped off the rolling sear lever tooth and the spear was allowed to fly from the gun.
Undersee Trigger 001.jpg

Lyle Davis mech cocked.jpg

Lyle Davis mech fired.jpg

Lyle Davis complete.jpg
 
Australian Wally Gibbins with assistance from John Lawson crafted a reverse trigger mechanism that used the principles enabled in the Denny Wells trigger mechanism, but had a completely closed sear box, not just a partial floor.

The importance of the sear box roof and floor is the former stops the spear tail jumping the sear lever tooth and the latter wipes the shaft tail off the descending sear lever tooth as it rolls forwards. The significance of this floor will be revealed later.
Sea Hornet parts John Lawson A.jpg

Sea Hornet cutaway.jpg
 
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In Europe not to be outdone speargun makers decided to also use a two-piece cam lock trigger mechanism and a variation on it where the sear lever tooth was pushed aside for the gun to be latched. The latter was a novel idea, but not foolproof. These guns all retained the angled sear tooth and the wide rectangular mouth sear box. The wide mouth let the tail end shaft stops slide in and the flat sear box roof allowed the spear tail to ride up on the angled sear lever tooth. Without a sear box roof these spears can jump the tooth. The upward pressure loading can also wear the roof out, but will take a long time to do so. The flat top tail ends on the spears prevented the shaft rolling in the sear box.
sear tooth backing projection spacing.jpg

Sporasub introduced the first dipping sear tooth gun, you can always pick this type of trigger mechanism by the lack of a backing projection on the sear lever, there being only the sear tooth. To limit how far the spear tail can be pushed into the gun there is usually a stop at the back of the sear box. Shaft ramming into the sear box can bust this stop off!
Sporasub patent.jpg

Polynesia handle.jpg

Also known as the "Surete Rouge" handle due to the ambidextrous red sliding safety button on the top rear of the handle, others have copied it with mixed results.
Beuchat Mundial trigger mechanism.jpg

Another dipping sear tooth gun, here the sear lever pivot pin moves in downward curved slots not shown on the diagram. Works OK provided you keep the gun clean, it needs its springs working properly to aid the mechanism reset, otherwise problems!
 
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At some time the Europeans realised that the shaft tail stop lugs should no longer enter the sear box, but instead be relocated to in front of the shaft wishbone notches, that way the shaft would avoid being snapped off with a big fish fighting the shooting line levering on the wishbone notches. This was soon the practice everywhere on all shaft types. Tradition left the rectangular sear box mouth in place, the gap either side of the shaft tail could now allow a line loop tied to the extreme shaft tail. Snapping shaft tails off soon eliminated this practice, unless the prey was small.
 
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The Sea Hornet and its Biller counterpart had been the only reverse trigger mechanisms in widespread use when many manufacturers decided to also use this arrangement, but to flatten it they nearly always changed it from cam lock to frame lock. That meant the cocked to shoot gun could not revolve the sear lever because they jammed the front edge of the trigger against a cross bar in the housing frame. This works OK, but then they made a big mistake. To improve speargun mechanism gearing they moved the main pivot pins further apart and that allowed a very long sear lever. However they abandoned the sear box floor that allows the spear tail to be wiped off the shaft tail. You can guess what happens next, the shaft tail does not always pop cleanly off the sear tooth and can cause the spear to jump out of the gun. Accuracy of shooting can now go out the window.

One manufacturer used the reverse trigger mechanism as it was originally intended in the Ultimate speargun, ultimate by name rather than excellence. The guns weigh a ton! Scuba spearfishing only and often no shooting line on most of the guns. Shoot it, follow it, then bag it. Or winch it to the surface until its guts inflate.
Ultimate Double trigger mechanisms R.jpg

until
 
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While spear rolling in the sear box is not a problem if you use hard wire wishbones, the square cut spear tail manufacturers employed a number of anti-roll features on their shafts. The Voit/JBL guns use flats either side of the spear tail, Riffe and others use a flat on top of the shaft tail and Biller/Sea Hornet and Ocean Rhino use a short vertical slot in the extreme spear tail. When you see these features you can nearly always identify a shaft through using this “fingerprint”.
 
Folded metal sear boxes used in timber stock guns often have a short run of the shaft to the spear guide track built into the gun body, so the shaft tail can still be wiped off the descending sear lever tooth. However if the shaft has a long run to a shaft guide track, or none at all, then the shaft tail can pop off the tooth. On the Sea Hornet and Biller guns the shaft tail rides in a long tunnel compared with other guns, so there is both a roof and a floor even if the gun has no shaft guide track. The shaft tail slot sits on either side of the sear lever backing projection with the gun cocked to shoot. Ocean Rhino guns even though they now use a standard trigger mechanism have long sear box tunnels and a guide track, the best of all worlds.
Ocean Rhino LHS.JPG

AB Biller spear tail R.jpg

Biller revised mech 1999 patent.jpg

Ocean Rhino handle comparison RX and Wind Song SIGNATURE L.E.R2.jpg
 
We can see the sear box tunnel goes back a long way with this 1940’s Hurricane speargun from France. This gun originally has a tubular frame shoulder stock, like a carbine or rifle.
Hurricane lever rollergun trigger R.jpg

Hurricane Corsair Rifle.jpg
 
Reverse trigger mechanisms that are frame lock can be improved by placing a floor in the sear box just forward of the spear tail latching position, this could even be a couple of transverse pins that go under the shaft as long as they cannot hook the shaft tail notch. Or as the rectangular sear box mouth is no longer necessary they could just close the gap on both sides and cup the shaft tail.
Looking at a forward trigger mechanism like the JBL M series trigger designed by Bill Kitto and Mori you can see that the shaft will be travelling on a guide track almost as soon as it leaves the sear box mouth. Also the pressed metal housing cups the spear tail except for the gap where the levers sit, so as the sear tooth descends the shaft tail will be wiped free of the tooth without any snagging.
JBL M7 trigger R.jpg

By way of contrast if a reverse trigger mechanism with no sear box tunnel has the spear tail stick with the high contact pressure onto the tooth then it can go down with the tooth, the deflection will be very small, but can translate to big changes down range.
bleutec raptor mech_02.jpg
634.png

Now the above trigger mechanism looks like it has a floor, but it is the top of the sear lever which falls away with the mechanism's release. I am not saying the above mechanism is faulty, I just use it being emblematic of a long sear lever, reverse trigger mechanism. Nearly all the folded sheet metal trigger mechanisms housings are made this way.

Similarly the roof of the sear box should be extended forward, right now many of them are too short. These changes would then create that long missing tunnel that aids shaft separation from the sear tooth and stability of the shaft exit.
 
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Just as a guide to nomenclature I use this sketch that I created for the Double Roller triggers.
Ermes Sub DR schematic action.jpg
 
To my knowledge the only star wheel sear lever that had survived into recent times are the Balco Sub “Thunder” and “Arrow” spearguns, the former has a cocking stock, and the latter does not. This gun’s trigger mechanism is actually a frame lock by courtesy of the little bump on the front of the trigger, just above where you pull on it with your finger.
Balco Sub Thunder handle.JPG
Balco Sub Thunder mech detail.jpg

Balco-Sub.jpg
 
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I enjoyed this. With modern Cnc machinery and tighter tolerances we're now seeing hybrid mechanisms that incorporate tolerances to fit both euro and American spec shafts. Though I am staunchly against reverse mechanisms due to the absolute certainty of sear rise to release the sear off of the trigger I opted for an "American" design with a roller pin as seen on riffe, Alexander mechs, etc. American shafts by design are more dependable as they apply the entirety of the band forces onto the sear tooth. Whereas rounded euro notch jams between the tooth and the roof the mech, which is more prone to misfiring debatably.
 
As a Sea Hornet, Undersee and Riffe user it was years before I tried a eurogun and that was only to evaluate it. That was principally because I used cocking stock guns. However the eurogun had more develpment going into it as plastics appeared more in spearguns. The early eurogun I saw the most of was the Polynesia handle Cavalero guns and at one time I had thought of buying a Cavalero Canon, so putting one of those together has been a late project for me. The main requirement was that they delivered a consistent shot, had good handling in the water and had no flimsy parts and I could easily replace anything that needed replacing, hopefully never. To shoot further I reached for the next gun size, I never played around with band sizes, however as most divers will know at times you find yourself with the wrong gun. Even if you have two with you, the small gun always being short, and for its compact power, a pneumatic.

The eurogun is a prisoner of past decisions that stem from its ancestry which is rooted in Kramarenko and Wilen's spring gun from 1937 and the "declic" trigger used by Commandant Le Prieur in his scene setting band gun which was quickly replaced by the Arbalete. Thus the underwater rifle gave way to the crossbow, albeit one without a bow using rubber bands, like a slingshot.
 
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American guns that were the quintessential weapons for generations of spearfishermen: The Voit-Swimaster Magnum, its baby brother the Sawed-Off Magnum and Scubapro''s then big hitter the 648. Today guns use much more powerful bands, these tube guns are all deceptively light, but shoot heavy spears. Hauling a towrope behind it the momentum of the shaft at the target skewered many victims, provided that they were still there when the shaft arrived. Hunters totally familiar with the capabilities of their weapons and knowing the habits of their prey accounted for many fish over the decades.
American guns long R.jpg


You can see the join in the Travel Magnum and the indexing screw in the centre which locates on a half circle cutout in the matching barrel section. A machine screw on either side holds the gun together.. Takes about 5 minutes to assemble the gun after taking the sections out of its travel case. I bought this gun in the early nineties after it had been sent out for a Dive and Travel show as a sample. A new suburban dive shop later had it and other trophy objects on display to spruce up the shop. I asked the store owner was it for sale and he said it was 450 bucks retail, but as no one was interested in it then I could have it for 300 bucks. It was somewhat overshadowed in there by the other big guns on display with far better trigger mechanisms. But I knew exactly what it was as soon as I saw it, in fact I was very surprised to see it there.
 
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