Crossbow triggers

I often hear or read where folks are wanting to improve their crossbow trigger and in particular make the pull smoother and perhaps a bit lighter. And whilst understanding that the loads applied to a crossbow trigger when cocked, can be vastly more than those on a firearm trigger, there are some things that remain constant and are just as applicable to our needs. The following video from Brownell's wonderful website is most informative and provides much insight into how certain parts should operate together.




Pavise

Thank you Pavise for starting this topic.

I was hesitant to start it prior to compiling a list showing the variety of trigger variations as well as the accompanying glossary of terms required for this discussion, but It won't be long now and I will be adding a link very soon.*

The information provided in the videos is great and deals with a very important aspect of fine tuning the trigger pull weight(although there was no sound in the second video in the series, it was still great). Think this will be a great resource for those who are simply wishing to modify their store bought crossbows or fine tuning the trigger pull of the self built ones.

Given most of us are going to actually fabricate our own triggers and all together do our projects straight from the blueprint, this topic can go much further. Many in our hobby overlook a very important factor when building the trigger by basing it on the ones seen on firearms.>>> http://webarcherie.com/forum/index.php/topic/16046-mecanismes-de-declenchement/page__view__findpost__p__397095?s=974a49821a919a39dcab46ae5e6876de

The beautiful thing about crossbows is that we don't need the hammer to make it work..there is no primer to fire-up...so building the trigger around the idea of a "transitional lever" in my opinion is the best thing, as it will in it's mechanical simplicity reduce the pull weight considerably...and then when the trigger is built around the traditional sear design the above videos are still going to be applicable to further fine tuning the pull. What do you think Pavise, are we going in the right direction?

Geezer here, with observations. Even with the simple 'tickler' trigger of the one-axle roller-nut crossbow, there's much that can be done to improve release. Over the years, I have learned to position the pivot-pin the distal end in a straight-horizontal line with the sear. The further aft you put the pivot, the quicker the distal end (bit that goes into the sear) moves, but the leverage will work out to more work. The further forward you put the pivot, the easier the pull on the tickler, but the movement of the distal end will be slower... it's simple leverage. Placement of the sear in the nut effects release. A sear on the precise bottom of the nut (as shown by Payne-Gallwey) along with a very slightly arced distal-end on the tickler, will reduce the effort and smooth release. On the other hand, moving the sear back a quarter inch, so it's a bit behind the bottom-center will substantially reduce the pressure of the nut trying to rise out of it's round socket. That gives you longer lock-life and reduces the tendency of the nut to tear out the back of the socket on release.
With the complex multi-lever releases found on sophisticated Renaissance crossbows, the sear is moved to the back-surface of the nut, so the nut is held into its socket by the cam-action of the last bits of the lever-train. That means the nut-socket, which fits the roller closely at the front, can be quite loose at the back, so there's no strain there. You will note that nut-sockets are commonly heavily reinforced with a big chunk of bone or antler at the front, but the back 'lager' block is normally much thinner, or even absent entirely. All the rear 'lager' block really does in one of these complex locks is provide a low-friction surface. Of course they hang the roller itself on the 'nussfaden' cord, to keep it from oscillating or jumping out on release, but in fact the 'nussfaden' doesn't actually bear any load when the lock is set... it only keeps things running smoothly aftger release.
Like I say, it's complicated. .. Does the above make sense? Geezer

Hi Guys,

Again this forum demonstrates just how good information can be conveniently shared for the common good. Some great observations and tips from Geezer as usual and another fantastic link and more from Ivo.

Mechanism No. 4 in the link provided, is especially attractive inasmuch as it is of an overclaw type, which mitigates string rollover, and one which also minimises the trigger pull because the sear is only holding the spring powered hammer; much the same as in a firearm. What is often overlooked though is the inertia energy remaining in a nut or claw after release takes place. This momentum has to be arrested and the claws remain static and in the ready to cock position. It is amazing how these seemingly small parts will sometimes bounce only to stop halfways at times.

We're definately going in the right direction Ivo and I look forward to seeing the additions to this topic.

Pavise

Pavise wrote:It is amazing how these seemingly small parts will sometimes bounce only to stop halfways at times.

Very true, I've also been taught that the claw should stop after it has traveled it's path and remain in that position until once again cocked. The opposite goes for the other parts as we want them to cock
automatically once the crossbow is cocked.

Geezer wrote:Like I say, it's complicated.

Soon we might need to start posting pictures in order to keep track of this.

---

Before I created this forum I was a member of this one other crossbow forum... not the French one that Kali introduced to me(where that link came from), but a Russian crossbow forum. The latest of the triggers displayed there have been simply amazing in demonstrating the use of the "transitional lever"(if my terminology is correct) that I mentioned earlier.

Credit for presenting this trigger goes to Сергей(Phoenix) >>>Build details



and this trigger was fabricated by Zmeelink >>> the actual crossbow is still in the works.



I'd say more, but I'm still looking through the gunsmithing books to find the terminology I need.

By the way, for those who would like to help in putting together a dictionary of terms PM me for more info.  
All help is appreciated.

I would like to build a crossbow with a sophisticated trigger in the future, but for now I am going to put together a more primitive design. Something along the lines of a southeast Asian style. Having said that, how do they release the string from the notch in the stock/tiller. It does not appear they use the medieval push up peg system. I have looked at various pics but is not completelty clear. maybe someone know better how their trigger works.

Todd

Geezer here: Uhhh, guys, I'm familiar with the simple southeast Asian trigger. It's a very chancy thing... a notch with a funny little lever at the front, that lets you change the incline and alout the string to slip out. I cannot recommend it for security. If you want to do a simple notch-lock, look at one of the push-pin models, either with a lever on top or underneath. Geezer

Thanks Geezer, having described how it works it makes sense on what I am seeing. I will not try it for the reasons you stated. I do have my own idea for a variation of it though. Will post pics when finished.

Todd

I know of only one Chinese crossbow trigger. Is this the one we are talking about? >>>Link

Our French friend did an excellent job on presenting how it functions.

Thats not the one I am thinking of. Geezer understands. The one I am talking about isn't Chinese but is more Vietamese or Tiawanese style. I am trying one simular to number 9 in that link above.

Todd

#9 follows the same principal as the one I'm working on ... only it is a bit simpler(no transitional piece, no automatic safety).


....from what I "imagine" this one might indeed be a bit "chancy" as Geezer said... without a transitional piece it might just roll back into release unless of coarse this action is blocked with a special pin or even an over all interior shape of the housing.

What do you think about this design from Robin Allen's site?



There is absolutely no chance of roll-back.

Geezer here: Yup, the S.E. Asian locks I have seen are more like no. 9 mentioned above, but substantially cheesier. Not for strong bows and not for the faint-hearted.

Hi Ivo,
That trigger from Robins site is a very good design. Good enough to be standard issue for Excalibur and Tenpoint crossbows. I think tenpoint call that design "power touch".
I was lucky enough to score a couple of Excalibur locks and have used them on some heavy weight crossbows. Even at a high draw weight (+300#) they are still crisp, have a short and easy pull and a couple of hundred shots later, have shown minimal signs of wear on their sear sufaces .
I researched the specs on these locks before I used them in a high weight crossbow and decided 300# is still well within their margin of safety, although, for obvious reasons, I cannot reccomend that other people do the same.

Very good thread guys, Some excellent information here.

Regards
James

I've recently had to move so I had to take a shovel to my shop in order to dig my way through it...guess what I found.>>> Kasenit

And because this trigger is really dependent on good hard steel for the sear - Kasenit might just allow me to use it on my next
crossbow.

There was an interesting topic on Russian forum about these triggers where a guy was tuning them a bit...I'll be back with some interesting pictures/info as soon as I find that topic.

I'm back

There was a topic on the Russian weapons forum Guns.ru where a guy by the nickname "sopel" had just bought a crossbow to play with while deciding on what crossbow to buy and then waiting on his Excalibur to arrive...well he couldn't sit that long so he started messing with that little crossbow without even making a single shot ... >>>Link ...

The trigger mech that was used in that crossbow is very interesting in that it's made entirely of sheet metal and that the housing is a piece of square(well maybe a bit more rectangular) steel profile/pipe like structure.

I have images of a similar model taken from a bull-pupp styled crossbow where the trigger hook is set forward a certain distance...Personally I really like this trigger despite the way it was manufactured...not perfect and can be rather tight it, but these downfalls can be slightly cushioned with a few careful alterations and of coarse - polishing.

I really need to do a better diagram that shows the principal on which the automatic safety operates in this trigger, but till then this is what I got.

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If you go through the pages of the topic I linked to in the beginning of the post>>> this guy is on a roll and got his Excal...wooohooo...straight off starting to mess with it by first polishing the sears.



>>> All niiiicccce and smoooooth in operation of release...Yaaayyy ...only one other thing popped up

After polishing he realized that the safety doesn't function as intended. He blames the company a bit, but I think otherwise for this reason, heh...he even explains it himself >>> It was the appearance of that tiny bit of space due to polishing that caused the shift in the system that in the end caused safety to fail it's function...as the author describes > safety now causes a the crossbow to discharge as soon as the safety is taken off. ... I highly doubt that "factory made" crossbows are designed in a way that really makes them open for user modification



Anyway...he solved this problem by making a small addition from sheet metal that filled the gap and brought things back into balance.



Whatever the case was, he is a pretty lucky guy in that hew was able to bring the trigger back into operation..Thanks to him now you have this good piece of info...especially those who are thinking of going on a grinding/polishing frenzy just as this fella did.

---

Now there was one thing that I didn't notice, but my fellow crossbowman igora did...

Not sure if this was due to the modifications done to this trigger...whether it was the shift in the system after polishing of the sears or due to the scratches from sanding, but there appeared a tiny and barely visible "crack" right near the axel.



another reason why I like the version presented on Robins site over the one Excals use >>> It's just beefier in my opinion.



Now I'm going to go sleep with my hands in the bucket of ice.

Ivo,

With the utmost respect to readers.

"A little bit of knowledge can be very dangerous". I don't know who first said that, but too many folks think that all they have to do to "improve" a trigger, is simply polish the sear and bent engagement points. Wrong, wrong, wrong!!!!!!

You apparently endorse "Robin's" trigger and some might see this as "it" being more resistant to the maladies of messing about with. Not at all my friends, and if you look at the engagement points you will see that they are almost identical to those of the example in the subject story. (Before they were altered.) However it is my opinion that any "safety" block be so designed and installed as to bear directly on the bent where it drops away from the sear, and not at some more distant part where stress and possible bending of parts might negatively effect its purpose. Robin doesn't believe in "safeties" inasmuch as folks are inclined to trust them instead of always keeping the weapon pointed in safe direction and not load it until ready to shoot. In fact the word "safety" is extremely misleading and such devices must never be fully relied upon to prevent unintended release.

We crossbow builders must never forget the oft enormous loads being held back by those two tiny areas of metal and it is VITAL that the angle of engagement be maintained and NOT altered during the act of polishing etc. In fact it is better if the sear face has a slight positive interface with the bent-lip and thus tends to force more engagement rather than less and thus excite disengagement when reduced (polished) friction plays a lesser part in the design of operation. The hand-grip and index finger relationships are very important too and the proper distances for these are contributors to the "feel" of the trigger pull which can be "heavy" simply because the finger is not in the optimum position when these muscles are applied to the trigger lever.

Please not let's treat our crossbow triggers too lightly. (Pun intended.)

Pavise

No No No Good Sir!..but Yes Yes Yes at the same time!

Perhaps I really overdid it with sarcasm in my above post, but I do not i na any way advise anyone to do what this guy did. I forgot to say at the end >>> MAKE YOUR OWN TRIGGERS > YOU WILL LEARN MORE!!!.

Sear engagement angles is what our topic here began with and once again we comeback to it saying the complete opposite > while being right at the same time.

When in firearms the same set of laws applies, it is really irrelevant when crossbow action is in the spotlight. There is no firearm that I know of where a sear has to maintain hundreds of pounds. Should this much poundage be applied to the sear angled greater than 90 degrees (modified Excal trigger from above post) obviously things will slip and slide(especially if sears are polished and lubricated )...as you said "proper angles" MUST BE MAINTAINED! And I agree...In trigger from Robin's site these angles are clearly visible.

You also mentioned...

In fact it is better if the sear face has a slight positive interface
with the bent-lip and thus tends to force more engagement rather than
less

I also agree as I've been taught that this in some cases(especially with a polished and graphite lubricated action) will allow a half pressed trigger to ride back into full latch retention...perhaps a very precise operation, but this is what I would go with instead of doing the opposite.

The hand-grip and index finger relationships are very important too and
the proper distances for these are contributors to the "feel" of the
trigger pull which can be "heavy" simply because the finger is not in
the optimum position when these muscles are applied to the trigger lever.

Now this is a wicked topic Pavise...untill now I have not met a single person who would throw this into an explanation...I really hope we can continue a bit on this. All this time I had a feeling and didn't tell anyone untill testing it myself(which I want to do, but my build has halted) >>> My theory is:

A certain stock anatomy trick, whether carved in the stock from beginning or artificially created with addition of pillow like grip anatomy located tight under the trigger finger...in theory I believed that this would change the angle in which the finger engages the trigger hook....ever hear of anything like this?

PS: I really need to make some diagrams, but I'm stuck away from home typing on my cellphone ...so I'll be adding them a tad bit later this week.

Hey guys,


It's been a while since this topic's gotten some love.

So here is a bit of eye candy for you crossbow junkies.

Arbalet.info > Trigger Mechanisms 1

Arbalet.info > Trigger Mechanisms 2

...and of course a very informative topic by Mr. SAM which not only has medieval trigger mechanisms of all flavors, but also crossbow blueprints he so generously drew out and posted for the public.

Arbalet.info > Crossbows XV - XVII century

The pages are in Russian, so it isn't a directly usable resource...you can go ahead and struggle with the translation of these pages(keeping in mind that it's full of Russian idiomatic expressions and badly mistyped/misspelled words) or you can grab a picture and link to the page to discuss it here.

I'm Russian and read those topics, so it will be fun to revisit it with you guys and if you are interested in anything I will be glad to translate it for you.

Ivo

PS: There have been worries of getting viruses from these pages and the
pages they link to and I will talk more about it in this topic >>>Surfing Internet Securely

Hi Ivo, I was just looking at those pages last night! Here is something that can help our readers. Down load Google chrome, it is free and can automatically translates whole pages to English. Translation not perfect of course, but is still very readable.
Todd

5+ Todd

Got a small addition for you all.

Seen this cool little build on another weapons forum where a guy built a mini crossbow...what really caught my eye is the trigger mech. Take a look and let me know what you think...



in my opinion, while it's lacking some healthy engineering - it's still one of the coolest self built triggers I've seen.

Ivo

That is a nice but simple compound lever trigger system and a nice little bow to boot!!

Todd the archer wrote:I would like to build a crossbow with a sophisticated trigger in the future, but for now I am going to put together a more primitive design. Something along the lines of a southeast Asian style. Having said that, how do they release the string from the notch in the stock/tiller. It does not appear they use the medieval push up peg system. I have looked at various pics but is not completelty clear. maybe someone know better how their trigger works.

Todd

Robert

jopsa wrote:

https://2img.net/r/ihimizer/img142/5834/str214215um7.jpg
https://2img.net/r/ihimizer/img142/5163/str216217sy4.jpg
https://2img.net/r/ihimizer/img297/4046/str218219ux5.jpg

Robert

There is this cool show "Weapon Masters" with a creepy and hyperactive "Chad" guy (ignore him )... this episode that vid I yanked from somewhere a while ago shows the internals of that little Chu ko nu crossbow and talks a bit about their history.


By the way, that Chinese guy is Yang Fuxi. A very serious figure in the bow making world.

cmgower wrote:That is a nice but simple compound lever trigger system and a nice little bow to boot!!

I think this thing has potential! I'm looking at a way to put an auto engage safety on it and perhaps make it function like a dog-leg release system (found in archery releases and Twinbow crossbows) to get a quick release with short trigger travel.

This is a Chines copy of the HW Record trigger group for air rifles it's immensely strong, true two stage and can be adjusted safely to a very light let off. It's designed to hold the massive force of a compressed air rifle spring.

Nice thing is you can buy them!!! (Buy a Real HW one though )

May need minor mods but it should work and enhance any bow .


ATB Ora