Trigger Q's

[Aimrite]

Aloha Everyone

I don't normally post unless I feel strongly about a topic. In regards to triggers I have made several thousand! Designing and testing started two years prior to that, we have been producing these triggers over the last five years and we have a "zero failure rate"!

We actually produced the testing machine before even making our triggers that way we could test different materials. We use an extremely dense polymer for our housing and our sere and trigger is investment casted. During the design process the sere was the most difficult to get right we must have went back to the drawing board 6-8 times before getting it right. We wanted a sere and shaft configuration that was 90 degree locked into 90 degree angle to prevent any and all inadvertant shaft discharge. Measurements as small as .010" can make all the difference in the world never mind the geometry of making the sere and trigger working together. This is what I feel is beyond the capabilities of the "homesmith", filing on your sere is like playing with fire! Besides this would be my case in point; if you can file your home built sere the material you are using is way too soft! The rockwell hardness of the sere should "well exceed" the hardness of the 17-4 stainless steel shaft you are using. You cannot achieve this by simply copying someones design and having it laser cut. If your sere is softer than the shaft it is holding it will fail with time.

Last note, someone before I in this thread said that a trigger should have be 120% safe. This is very underrated, the average reef gun has approximately 150 lbs of force behind it (2 bands) that would make our trigger have a 800% -1000% safety margin. If you want to talk Tuna guns the average gun has about 400 lbs of force and our trigger would then have a safety margin of 300%. Think about this before making your decision, would you trust the safety of one of your children using your homemade trigger?

I hope this information helps

Rick Bettua
Aimrite Hawaii

 

[Warthaug]

a) the surface is filed to alter it's angle

If the trigger you made works on the same principle as the the one shown above then the problem your having is probably caused by the profile of the trigger face being slightly off.

Thanx for that - that was the problem exactly. The profile of my spoons handle was a little different then yours, so it required a slightly different set to get the angle right. Rather then filing it I just extended the trigger arm slightly - that was enough to change the slope of the release from near-horizontal to slightly downwards. Works perfectly now, under a good range of tentions. Now all I need to do is build a gun. . .

Once again, thanx for your help.

Bryan

 

[milhouse]

I never tested to 1000 pounds, that's true. I put about 400 pounds on it for a long time, than shaked it really hard. I never put more than 2 bands on these, and I don't sell them. I use one of these since 2 years, and it never failed.

Compare it with a sporasub, Omer (regular trigger), or any euro gun, and you'll see that it's way more tough and safer. My gun are euro style,like these.

I have a question. Are Aimrite trigger parts the same than Riffe? On picture, they looks to have the same design.

 

[Fish Tale]

Thanx for that - that was the problem exactly. Works perfectly now, under a good range of tentions. Now all I need to do is build a gun. . .

Bryan

Glad you figured it out!

Before you take your speargun for a swim please make sure you build in a safety of some type. The type I've added to my Butter Knife trigger spearguns is very simple to make and has worked out really well.

Let us know how your gun turns out.

 

[rigdvr]

Compare it with a sporasub, Omer (regular trigger), or any euro gun, and you'll see that it's way more tough and safer. My gun are euro style,like these.

I have a question. Are Aimrite trigger parts the same than Riffe? On picture, they looks to have the same design.

Milhouse, I am not trying to slam you. I appluad people with the ingenuity and ability to do things that are well beyond my own ability. That being said, I think its bad form to assume everyone will have the abilities you have and by offering your advice you might find yourself in a bad position one day if something does go wrong...just a thought.

As for the Riffe and Aimrite triggers...looks are all they share. They did this so people can upgrade the triggers to other guns and the Riffe trigger was the common choice at that time. The sear is totally different. Perhaps Rick can go into the details if he reads this.

 

[Aimrite]

Aloha Millhouse

You want to know if our triggers are the same as a competitors brand? Well only the outside dimensions, we did this so anyone having difficulty with one could just slide ours in. Geometry is a funny thing if your not a graduate of MIT or Georgia Tech and there is a world of difference in the geometry of both of our triggers. You seem to be a "Bluecollar" worker Millhouse like me, when I was 17 I enlisted in the US Navy to be a deep sea diver and have been doing it sence. Maybe it would have not taken so long had I spared a few years going to a good Engineering School as the two named above but I eventually got it right. Good luck in your quest

Rick Bettua
Aimrite Inc

 

[Daryl Wong]

Hi Spearos,

My forte is building and designing spearguns and thought Rick could help you guys out. I'd like to thank Rick for filling in some blanks on the speargun mechanisms for you guys. Another point that should be taken by all is that is fine to want to build your own spearguns and I applaud anyone that does so. I am more than happy to provide any information about making, finishing or customizing a speargun. My partner Rick and I would also like to stress that the mechanism is the heart or engine of the speargun. It is what is always in use and under pressure and stress. That is why we had our hydraulic tester made before our mechanism was even built and would never recommend building your own mechanism with just plain stainless steel material. Because unless it is fabricated and heat treated to a Rockwell hardness harder than 17-4 shafts it WILL fail eventually either by wear, or the geometry making the shaft sliding upward in the housing and having the housing fail. Either result will mean the release of the shaft without warning. Maybe it will work for years and you give it to your son. Then he uses it and it finally wears. If he's lucky no one is hurt, if not......

Rick has a six year old son that we hope will follow in his dad's footsteps and we would hope he never dive's with someone using a home made mechanism, unless it was pre-tested under controlled conditions to ensure that it will not fail under stress.
We have tested other manufacturers mechanisms and have found some to fail under a stress load over a few hours. Granted this is extreme, but why have to worry about that at all?

I know Rick is so concerned with safety that he has even offered a spearo a free mechanism because he said he couldn't afford a mechanism and wanted to make a jury rigged one for his gun. We are not trying to get spearos to only use production mechanisms, we want spearos to use mechanisms that are safe,tested, and proven. Safety is our number one concern. We hope it is yours.

Aloha, Daryl

 

[milhouse]

Thanks guys,

I don't want you to spit on these brands, but about the "cheap" triggers I mentionned earlier, are they tough enough?

The first time I saw a Sporasub trigger (open), I was a bit affraid. I tought to all the time I spent with it loaded...

It was twisted (under pressure) and I think that it help me to be confident about my own ones.

I'll take care and will put my triggers to more pressure, at least to make me more concious of the danger it means. Maybe if I see this break under more pressure, i'll be less confident, and by the way, safer.

Thanks!

(If those "commercial guy's" comments were said by other than you, I don't think I'd take them so seriously!)

 

[Daryl Wong]

Hi Mill house,

We won't put down other manufacturers about their triggers, because as all of those in the business are trying to put out the best product the can produce and believe in what they are marketing. Kind of like cars, some are better than others, some have more attention to detail in them. I know the concern you have about the euro style trigger, but they are all made to perform within certain parameters.
I'll have my Aimrite partner Rick address this since he's our two man companies resident expert on this subject.

To be continiued.

Aloha, Daryl

 

[Fish Tale]

The strength of a speargun trigger is a very interesting subject.

Load testing of a mechanism can reveal design or material defects present in a specific component at the time the component is tested. Structural flaws in materials and weak geometric designs will speed the failure of any mechanism. Doing some reading I've learned that there's a thing specifically called "damage tolerant design theory" and it's as important to speargun trigger design and manufacturing as it is to designing and building just about anything. Understanding how design failures evolve is important for home builders as well as commercial manufacturers.

In an ideal world everyone who uses a speargun would understand how they can fail. In the educational spirit of the world wide web I just did a Google search to find some reading that might help people better understand fatigue failures. Here's a link to some interesting reading about fatigue failures.

LINK: http://www.kuleuven.ac.be/bwk/materials/Teaching/master/wg12/l1400.htm]

As people have mentioned in the posts above, wear or deformation of trigger components is another factor that contributes to trigger mechanism failures.

Anyone who builds their own trigger or uses one that someone else built needs to consider the factors that could contribute to the eventual failure of the mechanism so that they can maintain the components to a standard that reduces the chances of a failure occuring.

Unfortunately there is no such thing as an absolutely safe speargun trigger. Spearguns are designed to damage and kill living things. Assuming Spearguns are or will be harmless without user intent is foolish.

A boulder that tumbles off a mountain is always a threat to anything in its path.

 

[Warthaug]

Glad you figured it out!

Before you take your speargun for a swim please make sure you build in a safety of some type.

Already in the plans. I figure a stainless steel cotter pin which blocks the trigger from moving should do the trick...

Let us know how your gun turns out.

Will do!

Thanx again for your help.

Bryan

 

[ajwaverider]

I talked to a member on this forum about some of these same issues a couple months ago. My words to him was "I'm the type of person that believes that anything these guys can build , I can build to the same or better standards. And I have not failed at anything i've tried so far.He has the same attitude and thats why he has earned my business. He also has a good college background but realises that having a degree does not give him the right to make jugements on another mans abilitys.The place where I work has plenty of college graduates with lots of engineering degrees but the funny thing about it is they never seem to keep there job for more than sixs months or so .I don't hold any spearfisher or speargun builder to a higher regard than any other person but I do respect there ability and have alot of respect for a true craftsman. If
I have time i'm going to take some these triggers and have them tested and i'll let you guys know what I found out .The way all these products should be tested is buy a third party that has nothing to gain or lose from the results. AJ out.

 

[Aimrite]

Euro vs American triggers

Aloha everyone, first off this is not a post on how or why one trigger is better than the other but rather to enlighten folks on the difference.

European triggers are built lightwieght in design, mainly due to the gun originating in the Med and primarily used to hunt smaller reef fish. The pro's if you will of the design is quiet and easy trigger pull, they accomplish this by capturing the shaft between the sear and trigger housing roof. Basically like pinching you thumb and index finger together. The cons would be, the trigger can only handle so much pressure (ie 1-2 bands) or better yet normally less than 225 lbs of force.

American triggers are normally built heavier because wieght is not a factor. The shaft is held by the sear at a 90 degree angle vice being pinched, the roof usually is not a factor at all. Pro's of this method is a much higher holding power as well a safety factor. Con's would be the trigger pull is a little more difficult to achieve.

Testing, of all the triggers we have made we "test to failure" about 5 %. Because we are dealing with the same type of test repeatedly the failure can be tracked as low as 1250 lbs to well over 1500 lbs. But that is just one type of test, we then loaded a trigger to 600 lbs of force for 24 hours! Now that will put some stress on something. But I think of all the testing we have done the most brutal was loading a trigger 500 times at a pressure of 600 lbs and pulling the trigger! This is where you can actually see the two metals start to gall or meld together from the shaft and sear.

I hope this information helps. BTW this summer my son Nicholas is going to get spearfishing 101 from Daryl and myself hopefully we can teach him a thing or two. Daryl made my son the smallest carbon fiber hybrid gun ever and Nicholas cant wait to use it! We will keep you posted

Rick Bettua
Aimrite Inc

 

[GilbertG.]

Mr. Bettua,

Can you please tell us what type of stainless you are using for your sear??

 

[Aimrite]

Aloha

Are sear and trigger are investment casted, it is quite a process. There are several materials used and some "very expensive tooling". What is most important though is finding the same material for all parts so corrosion won't be a factor. Next would be those parts should have a Rockwell hardness of about 1:5 to 1:0 compared to the 17-4 shaft so in other words the normal heat treated shaft is about 38-42 on the Rockwell chart your sear should be at least 60

That is about as much as I can tell you I hope this helps, good luck

Rick Bettua

 

[miles]

Hiya

Warthaug, small little story for you. One of my dive buddies loves tinkering with his guns. He decided to build a small 55" woodie powered by 3 16mm rubbers. It wasn't a question of money, just that he LOVES building his own guns. On the very first trip out the gun worked fine. Halfway through the day, i was next to him when he missed a fish and was busy reloading. After loading the third band, the gun discharged, hitting him on the chest!!! I had to drop my gun and help him back to the boat. The doctor put him off for 6 months!!! Broken ribs. The doctor said he was lucky as he broken rib could've easily punctured his lung.

Aimrite and Daryl Wong are known to be one of THE BEST gun manufacturers out there. LISTEN to their advice!!!! There's absolutely no point in trying to re-invent the wheel!!

Have fun with your project, and post some pic's!!!

Regards
miles

 

[Fish Tale]

So what is investment casting?

Here's a link to a web page that talks about investment casting: http://www.wtec.org/loyola/rp/10_01.htm
and another.
http://www.vulcangroup.com/invest.htm

The first article points out the advantages of this type of part manufacturing:

Investment casting is usually required for fabricating complex shapes where other manufacturing processes are too costly and time-consuming. Another advantage of rapid prototyping casting is the low cost of producing castings in small lot sizes.

It's a cost effective way of producing intricate parts on a low volume basis.


Cast parts require heat treatment to reduce any weaknesses that are frozen into the steel during the cooling process. (that's the simple explanation)

Here's a web page that talks a bit about that. http://www.azom.com/details.asp?ArticleID=1141

Drop forging probably has the best potential to create the strongest longest lasting triggers. Making small parts that way would probably be tricky though.

 

[ajwaverider]

Fish Tale, Thats some good information.I stumbled across a thread in another forum where they were making silver rings with the same process.They would cast wax copies of the ring then
put like a 100 or so on a tree,then coat the whole thing with ceramic.Very nice finished products.

 

[ajwaverider]

Here's the link to the to the thread I was talking about .I belong to this forum also .Lots of good info there. [ame="http://www.cnczone.com/forums/showthread.php?t=4666"]Investment Casting - CNCzone.com-The Largest Machinist Community on the net![/ame]

 

[GilbertG.]

Mr. Bettua,

I kind of expected that answer. I respect your wanting to keep your trade secrets. But are you implying by your advice that your sears are hardened to HRC 60?

Gilbert