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Old 02-08-2020, 09:40 AM   #16
spearq8
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Re: Rob Allen Tests Stainless Trigger Mechs

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Originally Posted by ninjagazz View Post
Good discussion,

120kilo load seems very excessive, surely a normal RA wouldn't experience there pressures?

I know freedivers and rabitech recently changed to SS triggers. The price of Freedivers is significantly less than that of RAs here in Australia (I reckon the RA distributors here are making good $$).

I was looking at the freedivers rollers (with bearings) earlier, as they can be bought for less than a RA.

No body has answered my question about the effect on the sear tooth? is this not normally a problem.

Diving Gecko I think the early "Salvimar Metal" were the guns with the trigger issues they use a different mech to the hero. I think the rollers were failing under heavy load.

I would appreciate to know of other brands that have had issues.
Actually on the DR trigger the testing is done at 230 KG or 500 lb for 1000 shots with pretty much the same trigger pull at the 500lb load (around 3.5lb pull). It was also tested to 750lb with good results but that type of loading is probably not realistic and is more to see how far things can go. This was the older version using the 3 part cut plates held together by 2 screws for the shaft sear. Now that shaft sear part is made of a solid block of SS and the roller is a much wider 6mm … so theoretical that is more surface area and should be able to handle loads even better.

With the Salvimar … the Metal was rated at 250 KG … I can tell you for a fact that it can't even take 80 KG … so obviously the 250 KG claim is incorrect. The front roller that they used on the metal was 2.5 mm … without getting into too many details I can assure you that this way too little. The Hero has a more robust 3.5 mm front roller and is rated 350 KG. I haven't tested it at high loads so I don't know if that claim is correct.
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Old 02-08-2020, 03:10 PM   #17
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Re: Rob Allen Tests Stainless Trigger Mechs

I remember this thread as being very informative.

http://spearboard.com/showthread.php?t=192490

The essential issues are Friction, Strength, and Geometry. The Problem is scratching/galling of metal/metal surfaces both on the trigger sear/shaft sear interface and on the shaft sear/shaft interface.

These issues are not only found in Speargun mechanism design. Look around and you'll see many examples where the strength and resiliance of metal is required of two moving parts. Metal/Metal friction is generally shied away from in more explored applications such as Engines, Shaft drives, etc. An intermediary surface such as a self lubricating polymer is often used, or the movement of a Metal/Metal join is controlled by gears which allow the movement but in a controlled non slipping way. Tin Man's approach is another.

Regarding the Rob Allen Test, it would be interesting to learn the compostion of the Metal and the method of cutting used. Similarly, are we only looking at half of the issue? I didn't see the Shaft Sear being discussed? Was there no galling, scratching, deformation on the Shaft Sear/Shaft interface which would also influence the perfection of the shot release?

One other consideration. The Plastic Housing. It could be argued that there is a very good reason for using a Moulded Stainless Housing.. who knows how those sears would look if they were truly being held still. Not sure I'd want to see that mech go through cycles at 300Kgs..

Last but not least. Geometry. I know Rob Allen is a god damned legendary speargun engineering genius, but does that geometry look a little severe to anyone else? If you are going to go with a Metal/Metal slide, isn't it better to use a falling angle or even arc rather than the cockbanger option? I mean if you wanted to rub the glans of the sear intentionally upon exit, that would be a good design, but sure looks like you are concentrating a ho bunch of force on the tip of skinny willy there.
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Old 02-08-2020, 04:56 PM   #18
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Re: Rob Allen Tests Stainless Trigger Mechs

A picture is worth a thousand words.

When you are manufacturing guns in the hundreds if not thousands then economics come into it as in quality fit for the purpose. Guns need a long service life, but nothing lasts forever, including the gun owner! The cassette trigger mechanism being a removable element it can be replaced if and when required.
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Old 02-08-2020, 06:08 PM   #19
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Re: Rob Allen Tests Stainless Trigger Mechs

Pete, not everyone understands your force vector drawings perfectly. Myself included. To me, I see a little uplift in the tip of that Shaft sear. Consider it this way. A Slip Tip. A slip tip should not have Parrallel sides as it will be prone to binding. It requires a sloped (falling angle) or Arced (Rounding) to assure release if pressured from the side. I know that the Geometry both in shape of sears, and arc radii can have a uge effect on the Force of Friction. For example if I understand correctly The Coefficient of Friction between two metal Sears will remain constant. It is what it is.. But the Force of Friction is dependent on the Angle as well. ie, it takes a lot less force to slide a block of 304 down a steeply inclined 304 slide than it does to slide the same block of 304 down a less inclined slide. A falling angle. Similarly, it is a lot easier to initiate the process of sliding with a steeper entrance into an arc.

The short of the Long. Pete, do those geometries seem just a little bit off to you? Ie. could they be improved? In few words?

One other thought. Once the Geometries are Just right. Does it make sense that a wider Sear interface is less likely to gall? For example 1/4" or greater vs. 1/8" or 3/16" sear thickness.
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Old 02-08-2020, 06:44 PM   #20
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Re: Rob Allen Tests Stainless Trigger Mechs

I think the geometry is about right, the mechanism cam locks because the force directed upwards from the sear lever tail is directed at the trigger pivot pin, or a tiny amount forwards of it as the lime green circle shows. (A triangle with its hypotenuse as the circle diameter always has its apex on the circumference of the circle).

Being a eurogun with a ramped tooth a vector of the spear pull force tries to blow the roof off the sear box, an action which is opposed by the walls of the cassette and the sear lever pivot pin axle. Many euroguns rely on the spear tail which has a flat on top being clamped firmly on the ceiling of the sear box roof by the action of the ramped tooth.

The gearing is shown by the relative lengths of the red lines radiating from the sear lever pivot pin axis, so although the mechanism does not have big levers the gearing is good enough for the loads that the gun has been designed to take.

On some plastic trigger guns users with strong fingers could in a moment of carelessness yank so hard on the trigger with the safety still engaged that they could bust the lower tip of the trigger off. That is why fore-aft this trigger has been fattened up.

Arc matching makes sure the trigger swing does not push the sear lever backwards (see attachment).

The wider the contact areas then for a given force the contact pressure goes down. As you pull the trigger on arc matched mechanisms the contact area shrinks as the overlap decreases. A good reason to pull triggers quickly and not have them sit just as they "go over the falls". The reason being a high loading will damage the straight edges, hence sensitivity adjustments are not a good idea in spearguns where the power of the gun is opposed by the trigger mechanism, unlike firearms where you only have the power of the trigger mechanism springs which is comparatively low.
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Old 02-08-2020, 07:17 PM   #21
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Re: Rob Allen Tests Stainless Trigger Mechs

Big wide and thick levers keep the contact forces down in the Kitto M3 and M5 "Main Battle Tank" trigger mechanisms as they are not curve matched, the three levers, four if you count the necessary swinging remote trigger, are to handle elephant gun shooting power and are so heavy your gun needs to be a log.
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Old 02-08-2020, 07:41 PM   #22
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Re: Rob Allen Tests Stainless Trigger Mechs

The Picture you have above looks different than the picture in the video. It's that very tip of the Phallus to which I am referring. There is a slight Downturn in your picture? and a slight Upturn in the Sear in the Video? It's that slight upturn which could be adjusted? Additionally, if it were you Pete, who was drawing the sears, would you not have rounded the edge a little more on both sears? I guess where I'm going with this is that there are subtleties to design here which may be aggravating the problem. More force ramped up onto a smaller cross section may be adding to problem?
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Old 02-08-2020, 08:09 PM   #23
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Re: Rob Allen Tests Stainless Trigger Mechs

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Originally Posted by Behslayer View Post
The Picture you have above looks different than the picture in the video. It's that very tip of the Phallus to which I am referring. There is a slight Downturn in your picture? and a slight Upturn in the Sear in the Video? It's that slight upturn which could be adjusted?
That damage is the "over the falls" loading as the sliding surfaces are just about to part company when the trigger retention step lets go of the sear lever tail. The levers are not sitting quite square to each other as the damage is not fully across the straight transverse edge which is being rounded off by the high contact pressure. When you first pull on the trigger the contact surfaces are overlapping on the smooth curve matched sections and the trigger pull will not be too affected until the chewed up surfaces engage. If you open most trigger mechanisms up then you will see some damage, but not enough to make the trigger pull too hard. Also the levers can rock slightly on their pivot pin laterally and the pin spacing is not absolutely fixed as the force can try to stretch and twist the plastic sear box if you put too much load on it.

Not for nothing are thick stainless steel side plates forming the sear box on those Kitto mechanisms with a quarter inch diameter sear lever pivot pin (of course you need to be slightly crazy to use one). The plastic spacers are replaced with stainless steel ones for heavy duty use.

In the gun testing rig the trigger mechanism is pointing straight up so that any chunks of metal ripped out fall into the trigger retention step and can accumulate, that never happens in spearfishing use.
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Old 02-09-2020, 03:47 AM   #24
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Re: Rob Allen Tests Stainless Trigger Mechs

Hi Jon and Pete,


As mentioned, interesting thread.


First off, regarding this test machine we built, it was built to test 2 or 3 gun handle components per manufactured batch of 1500. It was not built to show wear on stainless steel triggers. We built this testing rig because we needed to be sure our products going out were as safe as we could make them and, have a way to show this. These tests are run for many hours, 1000’s of cycles at 120kg (264lb) tension. We then break test (destruction test) these to make sure the spear hold ability is still way above that what is needed.


The max load on our biggest gun is around 110kg (242lb) so, we set it above that just to make sure the components can handle the increased power. The stainless trigger was run at the same power to show like for like.



Simulating normal use, not that easy. We could have set the machine sideways and all submerged but, it was much easier to run it vertically with just the working parts of the gun underwater in a separate tank under everything. It is fresh water, not salt, I don't think that would make a huge difference.



That big jolt you see Jon, is the sudden release of 120kgs of tension. It was much worse when we first built the machine and we had to stiffen it up. It is good to have this jolt as it would also jolt in you hand when shot. I agree the movement is not exactly the same as that of a gun in hand but, is as close as we can get it.



The fact there is a big jolt in the water, I would think it would dislodge any fretted partials easily as there is a lot of space for them to move out the way inside the cassette. The particles I found were not stuck to the parts but loose in the cassette.



I can easily run this test again with water pumped at pressure through the housing at the sear/trigger engagement point. I doubt there will be any difference. I will have no problem admitting this if I’m wrong.



Regarding the way we cut our sears, these are wire cut, more accurate than water or laser cut. I have no idea how the stainless trigger was cut, not our part but is an after-market product sold to “upgrade” our handle. We have seen many sintered sears brake, this is why we still make from solid plate.



Regarding the plastic cassette/housing Jon, these are made with 60% glass fibre in toughened nylon. After 17000 cycles at 120kg the pins are still tight in the cassette. Even after break testing where we often need 400kg of force to pull the shaft out, the pins are still tight fitting in the cassette and perfectly straight. There is also no damage to the inner roof of the cassette. The only damage is to the top of the sear. The trailing edge of the spear cuts a notch out. You can see this in a previous handle destruction test video.



Jon, there is an arch on our trigger and there was one on the s/s trigger tested. It is hard to see in a picture. You are right, there has to be an arc. On some of our first triggers there was not and, the trigger pull was easy at first but did get tighter. This was only noticeable on powered up guns.



Many thanks Pete for you input.
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Old 02-09-2020, 04:35 AM   #25
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Re: Rob Allen Tests Stainless Trigger Mechs

Thanks very much for your comments Rob. My water flow suggestion was just a means to simulate any debris falling out from the open bottom of the cassette as guns are usually upright and horizontal when they are shot or are pointing on an angle downwards for any fish that are below, although on occasion I have shot fish from nearly upside down as they ran past underneath me or the surge tipped me over and then I usually missed. That is when you appreciate having a closed muzzle and line slide socket on your gun.

I have never shot a gun pointing vertically upwards as what goes up must come down, but as you say your test rig is chiefly for cycling your gun for overall durability and quality control testing, not emulating a diver on the hunt.
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Old 02-09-2020, 02:55 PM   #26
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Re: Rob Allen Tests Stainless Trigger Mechs

Hi Rob, thanks for the explanation.

In this test the Trigger Pull triples within 200 shots. I have seen this happen with Stainless Trigger Mechs where the trigger becomes increasingly hard to pull over time to the point where it throws off the shot or prevents the shot. Frustrating terribly the user. Sometimes this happened after only a few shots. These were all on Rail Guns with 2 bands. Even after buffing out the galling the issue would return. The mechs needed to be replaced. It wasn't just one. It was all of them.. and we all heard about it.

And yet.. We have been using American made Stainless Reverse Trigger Mechs for a decade. Without running into noticeable increases in Trigger Squeeze related to trigger sear galling while using them with Higher loads than just two bands. Is there some minor scratching or galling? Yes. Do I understand the benefits of Stainless Roller Mech Sears or using a Polymer Trigger Sear/Stainless Shaft Sear? Yes. Look at TinMans test data of his Roller Mech. But.. that is not what we are talking about here. You ran a test of 200 shots with the force of 2 bands. The mech became unuseable. Anyone would notice and complain about a trigger pull going from 1.8 to 6.9. We all would certainly would hear a lot about it..

And yet.. 10's of thousands of Sturdy Built, Reverse and Standard, Stainless Mechs are out there for decades without having sear degradation to the point illustrated in your 2 band 200 shot test.

You say the issue is the material. I'm not sure here if you are saying that you have no idea what stainless or what method of cutting was used in the sears in your test? Were the sears in this video cut with Wire? Didn't look like it. Was it 304 or 316 or 17-4ph or alloy? You say it's an aftermarket part supplied by another. Is it laser cut 304 from Chinese Steel? that could explain the crumbly test even with Geometry that might work with better quality Steel.

I did think the Geometry looked strange, but only focussed on it because you had such a poor result on a 2 band test. It reminded me of something I've seen taking apart frustrated friend's Rail Guns. Pointy Thin Sears.. When I think of Sear interfaces I think of the slides at the playgrounds. (maybe because I'm there a lot with the kids) There are straight slides and ones which ramp up in the beginning. In the end they have the same grade, but ofcourse those entrance arcs allow the kids to get moving a lot faster. Those are the ones where they fly into the dirt at the bottom.. maybe you'll understand what I'm trying to say here. I mocked up a quick drawing to illustrate.

I guess the question is. If you took a Neptonics Tuna Mech for example and ran it through 200 shots at 240#.. do you think the trigger pull would triple and the mech would become unuseable? Is the issue "Stainless Trigger Mechs" I don't think so..

Just as a point of information I'll add something. To my suggestion of using MIM sears allowing the formulating of specific alloys, you said that you had seen many sintered sears break and as such use plate. Press Sinter Powder moulding and MIM are two very different processes with very different results. You may want to look into it. MIM offers a much more superior product in all measures of strength as well as having the uge advantage of allowing for much more complex shapes and a higher polish surface. Might be a good match for some of your parts.
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Old 02-09-2020, 05:10 PM   #27
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Re: Rob Allen Tests Stainless Trigger Mechs

Rob said the stainless steel trigger piece is an aftermarket item produced by someone else to retrofit to his guns. This probably came about when some plastic triggers of this type were being busted and some entrepreneur thought a metal version may have been better and offered it for sale to gun owners. The plastic ones busted because with the ambidextrous safety still “on” the weakest point in the trigger is that retention step or notch.

The new plastic trigger is thicker longitudinally and the safety switch has been re-positioned to work where there is more swing movement to differentiate between “on” and “off”, plus the safety slide cannot walk around and accidentally turn itself “on” as before its biasing spring was also the trigger return spring and was more vertically oriented, now the spring sits at an angle.
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Old 02-09-2020, 06:40 PM   #28
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Re: Rob Allen Tests Stainless Trigger Mechs

Pete, for my own understanding of mechs and sears. Does my rough sketch make sense as lowering the Friction force on the part?
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Old 02-09-2020, 07:43 PM   #29
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Re: Rob Allen Tests Stainless Trigger Mechs

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Pete, for my own understanding of mechs and sears. Does my rough sketch make sense as lowering the Friction force on the part?
I think the lower sketch should look like this, after I slightly adjusted it. It is possible that the retention step in the aftermarket stainless steel trigger does not match the sear lever tail exactly, but on such small dimensions it is not all that critical as the step here is very short, as long as the sear lever is not pushed backwards against the band pull. The problem, if there is one, is that if you want to push this mechanism to high loadings then the sear lever tail is too short and that is because the pivot pins are set too close together. However once you have set your handle dimensions and trigger position there is not much that can be changed and given the very large number of Rob Allen guns in service there is no real need to if they work OK, plus remember that these guns have had a few revisions to iron the bugs out. The best change was dropping the dipping sear tooth which only works OK in very clean guns where the sear lever can slide around on its elongated slot, the mechanism relatching in a different sequence to which it releases.

I might add that Jack Prodanovich told me and my associate John Warren about the importance of curve matching. That curve matching on contact tracks is what lowers the friction. Jack had all his mechanism design notes in a red cover book which John got to see with Jack commenting on what the various important design criteria were, but I don't know who has that red book today.
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Old 02-09-2020, 08:13 PM   #30
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Re: Rob Allen Tests Stainless Trigger Mechs

The brown sear lever would work OK, but as the levers swing apart you would only have a line contact running across the width of the levers as gaps opened up in front and behind. Actually most mechanisms work like that as lever contacts are not that perfect and some relied on parts lapping in when they were made of bronze or chrome-plated brass, the plating being very thin or "flash chrome" to make the gun look good in the store. Then it gradually wore off or fell off.
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