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Crossbows - Everything about Building, Modding, and Using your Crossbow Gear

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    Post by jaeger22 Tue Jun 17, 2014 3:07 pm

    First topic message reminder :

    OK I am talking about the part here not us X bow builders and shooters! Laughing 
    So I was thinking about why there are relatively few people building their own crossbows. It seems like crossbows are becoming more popular and we see them more and more in both the large and small screen as well as in the woods. So why are there not a ton of DIY builders?
    My theory is that many are stopped by the need for some basic machined parts and the lack of tools or skills to make them. Many have the skills to build the stock, bows and strings are available for purchase at entry level prices. And there are several low tech ways to make bows like the car springs and the multi slat system KenH used so effectively. But try to buy a nut or trigger module.  Sad 
    I think the availability of a low cost high quality set of trigger parts and/or assembly would open the door to a lot of new builders. So I may be a Don Quixote tilting at windmills but I want to take on that problem. But I need the help of you more experienced builders here.
    My son owns a machine shop and I am an engineer and I plan to coerce him into using his fabulous CNC machines to produce some parts for us. I am thinking two levels; The first level is a simple nut and trigger/tickler set. Maybe a set of side plates. These could be a kit or individual parts. The idea is to have standard parts to keep the price low but give the builder maximum flexibility to do his own design and construction. This should work for entry level first timers on up to fairly serious recreations of antique crossbows. So low cost and high quality are needed. That is the domain of CNC machines. Smile 
    The second level is a drop in cartage of a modern type based on my own design with the hammer. (See new member and new trigger design). More on that later.
    So I am thinking 1.5” diameter nut made of black Delrin,  ¼” axel hole and a small hardened tool steel plate for the trigger notch. Here are some pictures of an aluminum prototype I made last night. (I have some 1.5” delrin rod on order)
    I would love to get your thoughts.

    Rough cut on the band saw (from .875" stock).
    Universal standard Crossbow nut - Page 2 P1010821_zpsbc9220fe
    After a quick run on the lathe:
    Universal standard Crossbow nut - Page 2 P1010825_zpsfab5245c

    Here is the tool steel wedge has been pressed in but not cut off and trimmed yet.
    Universal standard Crossbow nut - Page 2 P1010831_zpsdb486c83
    This picture is a bit fuzzy but it shows the trigger notch. It is wide enough to accommodate up to a .375" trigger.
    Universal standard Crossbow nut - Page 2 P1010835_zps4136767e

    Here the machining is basically finished.  It just needs hand file clean up:
    Universal standard Crossbow nut - Page 2 P1010840_zps11875c81
    Please let me know your thoughts.
    Thanks,
    John
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    Post by hullutiedemies Thu Jun 26, 2014 4:48 am

    Notice important detail above that seems to be missing from your prototype:
    nock groove

    These were originally used with nocked arrows.

    I have made this type locks and given up with them. - They work fine and very nicely with normal archery arrows, but string jumps easily over nockless bolt.

    Just something you might want to know before you start marketing these.


    Point 2. Setting the transmission fork in a manner that it swings minimum amount after release helps with lock time - notice the elevated sear on previous page sample.


    Btw, on plus side -
    I tested a bare plywood fork against claw sear of soft iron nail with 150# bow- held well , no sign of wear. The sear surfaces are not under abrading pressure, so they can be made of soft materials like plastic or light metals.
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    Post by rolynd Thu Jun 26, 2014 5:54 am

    Nothing to laugh about, its fully functional and does everything you want it to do, my test rig for the pulley systems  is much more ugly than that but  it just needs to work not shine.  

    I think they did use other fletching than the 3 vaned equidistant spaced we use now. either it was just 2 vanes horizontally or 3 vanes  with two of them horizontal and the third at 90° angle at the top so the bottom of the arrow stayed free from fletching. I only ever saw these trigger housings with a shallow groove to accomodate the arrow shaft, none I have seen have any kind of slot.

    Universal standard Crossbow nut - Page 2 0324D-Crossbow-mecha--nism-_zps29d6b8fc
    Universal standard Crossbow nut - Page 2 Post-50-1112461131_zps1cb85263

    But If its to be used with the "modern" fletching a slot is definitely necessary. Without a slot You could not use storebought arrows or have to flech them your own. 

    I think even a flat section, maybe slightly angled would accomodate the uper short arm of the fork. Sadly I have found no photos of the interior of this special kind of claw. The only ones I have are from those with a round bar, it seems the frontal bar is -at least with some of them - not the only point where the claw halves connect as I assumed previously.

    Universal standard Crossbow nut - Page 2 Post-50-1106384636_zpsb6155b49
    Universal standard Crossbow nut - Page 2 Post-17-1110028060_zps6b18fdb6
    Universal standard Crossbow nut - Page 2 Post-17-1110028190_zpsd001f357
    Universal standard Crossbow nut - Page 2 Post-50-1110977895_zps2ac9fc2c


    The longer I study these photos the more I start to wonder at how these were actually produced.

    We know that these were mass-produced in great quantities. Generally its believed these were cast as a single piece. The chinese were proficient masters of bronze casting and both sandcasting and lost wax were known to them.
    In mass production sandcasting would be much faster than making a wax model , investing the mould and burning it out before casting. One could make dozends of sand molds in the time it costs to make  a lost wax casting. Maybe they did this like in jewellery today in casting multiple waxes on a sprued "tree" at once, thus speeding up the process. It still would take more time than knocking out a few sand molds. The larger the sprued tree in a lost wax mould the longer the burnout, several hours  up to half a day, for really large molds even several days are needed.

    A simple sand mould could be finished in mere minutes and is ready to cast immediately. 

    There are often some grinding marks to see on the parts  so they must have been cleaned up  after casting and fit to tolerances.


    If I look at the claw parts  - these do lend themselves not very much to sandcasting. A master pattern could not be easily removed from the mould, so the only way to cast these as single pieces would be lost wax method.

    When you look closely at the last photo you see a small misalignment of the round connector bar in the front. This got me wondering if the claw could have been made from  two parts and brazed together afterwards. Brazing was known at the time. It would be easy to make the claw "halves" in a sand mold and then braze them together afterwards.

    But it could as easily be just a fault in the wax master... so  its still rather inconclusive and lets me wondering at how these were actually made. Maybe it was a combination of sandcasting and lost wax for different parts. Assuming they were not dumb they would have opted for the fastest yet most economic  method producing a ervicable endresult.

    We know from recent archaeological investigations on the earlier triggers from the tomb of the first emperor that they had a elaborate production chain with strident quality controll of all the parts. It was found after careful measuring of the parts that these triggers were made by different small production groups and made in small batches with only minimal variation within the group but cleary different in small variation from batchs made by other production goups.

    Article here:http://www.ucl.ac.uk/terracotta-army/blog/posts/2014-03-06 





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    Post by kenh Thu Jun 26, 2014 6:37 am

    I've never seen anywhere, in ATARN or elsewhere (Stephen Selby's definitive Chinese Archery),  evidence that the Ming crossbows used nocked arrows rather than flat butted bolts.  In fact I've seen photos of Ming period Chinese bolts that were not nocked at the end.  rather, I should say they had nocks that were solid horn and flat, without a notch for the string.

    Rolynd is right about the fletching -- it was either 2 fletch or 3 fletch at right angles not 120 deg.  By the way.  There is a really good discussion and much better drawings of that Chinese Triple-Prod siege crossbow over on ATARN:

    http://198.170.107.188/phpBB2/viewtopic.php?t=2447


    Last edited by kenh on Sat Jun 28, 2014 5:04 am; edited 1 time in total (Reason for editing : added link to ATARN discussion)
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    Post by jaeger22 Sat Jun 28, 2014 6:09 am

    nerd flintstone wrote:Notice important detail above that seems to be missing from your prototype:
    nock groove
    Pardon my ignorance but what is a nock grove? Is that just an extension of the main center grove to allow room for the nock to extend past the claw? I might see if I can include that as well as it doesn't seem like it would hurt anything.
    Rolynd, thanks so much for the additional pictures! I am going to start on that design as soon as I can but have had little time and I wanted to get the Delrin nut going. Here is what that looks like now.
    Universal standard Crossbow nut - Page 2 P1010903_zps72406233

    Set screw to hold in striker plate:
    Universal standard Crossbow nut - Page 2 P1010901_zpsbd1601f0

    top view:
    Universal standard Crossbow nut - Page 2 P1010900_zpsadfcb3ae
    I machined in a .025 raised area on each side to reduce friction.
    Thoughts?

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    Post by kenh Sat Jun 28, 2014 12:17 pm

    Lookin' good on that Delrin nut!
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    Post by jeep Sat Jun 28, 2014 3:21 pm

    jaeger22
    Your Chinese trigger look very promising. I am a fan of this mechanism since many years. I used those fore modern crossbow with very good result whatever could be the draw weight . I used aluminium for some of them or steel ,I don't have lath or grinding machine and no welding capacity's  so I used, saw,file and rivets to put them together. The first picture is a small fancy crossbow I build years ago(near a real Chinese nuts),you can see the mechanism in details in the following pictures.  
    Universal standard Crossbow nut - Page 2 Chinoi10
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    Post by jeep Sat Jun 28, 2014 3:23 pm

    ;this one is steel near a real oneUniversal standard Crossbow nut - Page 2 Chinoi11
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    Post by jeep Sat Jun 28, 2014 3:25 pm

    With Trigger housing (folded steel band)
    Universal standard Crossbow nut - Page 2 Chinoi12
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    Post by jeep Sat Jun 28, 2014 3:41 pm

    Other but alloy, for the first versions of the early two shot crossbow. You can see I double the upper "ear" and make it shorter. like this it can be used like a sight. for me Chinese  can match modern trigger. It is easy to build very cheap reasonably safe (safe can be added) and don't need spring.
    Universal standard Crossbow nut - Page 2 Et_02110
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    Post by jeep Sat Jun 28, 2014 3:45 pm

    Early version Finished
    Universal standard Crossbow nut - Page 2 Et_02410
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    Post by jeep Sat Jun 28, 2014 3:57 pm

    The one for my han crossbow
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    Post by jeep Sat Jun 28, 2014 3:58 pm

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    Post by jeep Sat Jun 28, 2014 4:00 pm

    With the crossbow.
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    Post by jaeger22 Mon Jun 30, 2014 5:19 am

    Thanks Jeep! Very nice work. If you had machine tools you would be dangerous! LOL Laughing 
    I like the way you made the case by bending flat bar around. Cleaver!
    Here are the first two parts of my next experiment. For this version I am using brass for the claw and case and steel for the fork and trigger. The claw was machined as a single piece. It is a bit of a pain to machine this way but it is very solid.
    First test fit of the claw and fork:
    Universal standard Crossbow nut - Page 2 P1010905_zps4bc352d6

    This is just a close up of the fit:
    Universal standard Crossbow nut - Page 2 P1010906_zps4cab375d
    Here are the parts separated for a better view:
    Universal standard Crossbow nut - Page 2 P1010907_zps84f36f65
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    Post by kenh Mon Jun 30, 2014 5:31 am

    Lookin' good there, jaeger.    I just noticed you're up in Orlando, while I've over in Fort Myers, FL.  Small world, eh?
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    Post by jaeger22 Tue Jul 01, 2014 4:45 pm

    Ken, yes small world. We should get together and shoot sometime.

    Well I had a bit of a set back. The main claw part failed. I cut a bit too much off the bottom sides in an attempt to lighten it. Then I when to lock it into the mil vice and it crushed and broke. Sad
    I spent most of the day machining a new one.
    But then that is why we build prototypes! LOL Laughing 
    That one part is a real pain to machine.
    Here is a picture of the failed one and the new one next to it:
    Universal standard Crossbow nut - Page 2 P1010910_zpsca82eb2f
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    Post by rolynd Tue Jul 01, 2014 8:46 pm

    Thats unfortunate, but things like that happen. The new one looks quite sturdy though. 
    I dont know how much time and effort it takes to machine the claw part, maybe you should give the  soldering option another thought?  Hard soldering will take quite some strain before faliure and with a little experience its done quickly with minimal need for cleanup. A short pickling to get rid of the scale + flux residue would be all it takes.
    But you obviously know what your doing. From the responses in this thread it seems there is quite some interest in this project, so your efforts are very much appreciated! Keep up the good work!
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    Post by chaz Wed Jul 02, 2014 12:33 am

    Nice work jeep and jaeger22 enjoyed the thread

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    Post by kenh Wed Jul 02, 2014 5:04 am

    I'm wondering if brass is just that much more brittle than bronze, and if that contributed to the fracture of the claw.
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    Post by jaeger22 Wed Jul 02, 2014 5:20 am

    Thanks Guys! Yes I am keeping the soldering option mind. It would definitely be a faster method in my shop.  But if my son can work out a CNC process that does not involve to much operator labor, the one piece would be nice. I am not sure which would faster for a small production run.
    The aluminum and steel one with the 1/4"bolt is still working fine. I did add locktight to the threads. But the brass one has a much nicer feel. The movement feels slick compared to the aluminum. I hope to get the new brass one mounted in the test bed today and try it out. Smile
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    Post by kenh Thu Jul 03, 2014 4:55 am

    When you get this action worked out and ready to sell, I know a number of folks, outside of the Arbalist Guild, who would be interested in buying them as well.
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    Post by jaeger22 Sat Jul 05, 2014 4:57 am

    I finished up both the brass Chinese lock and the Delrin nut drop in trigger assembly and got to shoot them so I thought I would share the results so far. Here are the three:
    Universal standard Crossbow nut - Page 2 P1010923_zps3006480a
    I had to re-drill the through holes for the brass Chinese so I could not go back to the aluminum one but I did make the drop in nut assembly the same size box as the brass so I can go back and forth in the same cheesy test stock and compare. It was interesting and the results were not exactly what I expected.
    First the brass Chinese. This is the solid one piece claw. It is a pain to machine by hand but seems very strong and it is noticeably slicker than the aluminum one. The trigger pull is actually very light and crisp.  It was TOO light at first. It got lighter as the parts smoothed each other out until it reached the point that it would not hold. I locked back the bow string and about 4 seconds later it just let go all by itself and dry fired. Shocked 
    Not at all good on a pine stock! LOL
    Universal standard Crossbow nut - Page 2 P1010912_zpsbc4772c0

    But not a major issue, a little glue over night and it was back in business. And I cut the notch in the trigger deeper and it was better but still light. It might be OK, even good for the experienced folks here but I would not be comfortable giving it to a new person. I may be able to play with the trigger notch and make it stiffer but the notch is very deep now.
    I learned that there are few drawbacks to this lock style. First it makes a hell of a loud CLACK when fired because of the metal on metal impact that stops the rotation. It sounds about like some one hit it with a large hammer. Not a deal breaker but a bit annoying. I didn't notice it on the aluminum version, I assume because it is lighter and aluminum deadens the sound. But brass, not so much. . .
     
    Second issue is that because the fork is in the front of the lock and near the top, I can not cut a deep notch for the fletch to clear. I tried it on the aluminum version but it did no good because of the fork. You can what I mean here:
    This results in difficulty
    Universal standard Crossbow nut - Page 2 P1010930_zps3edab74c
    This results in difficulty using most of my existing arrows. You can see the issue here:

    Universal standard Crossbow nut - Page 2 P1010926_zpsf5e6387f

    To get around it, you could 180/90 degree fletch like this:
    Universal standard Crossbow nut - Page 2 P1010933_zpsa088156c

    That is what I did as I happened to have an old bolt of this style in my junk box. Or you could use just two fletch. . .
    You could move the fletch forward but that would place them a bit too far from the rear where they would do the most good for my taste. Still I expect it would work.
    And the third issue is that I don't see an easy way to add a hold down spring and of course no way if you use the 180/90 degree fletch.
    I would love to hear feed back from those of you that have actually used this lock and how you solved or get around these issues.
    So next is the roller nut.

    Universal standard Crossbow nut - Page 2 P1010924_zps9fef773e
    Please ignore the two extra holes. The stupid guy doing the machining got the part in the mil vice backwards the first time and the lazy SOB didn't want to start all over. LOL Laughing
    Here is what it looks like mounted in the test rig:
    Universal standard Crossbow nut - Page 2 P1010920_zps6ae0f2fe

    The holes in the stock are for the Chinese lock and not used on this one. The pins are flush with the case are captured and held in place by the wood on the sides. The screw in the back is temporary. I have not decided how I want to tie it down yet but the tight inletting takes all the load. I do have a trigger spring in this one but realized that like the Chinese lock, no spring is really needed if the trigger is made "fat". Gravity will push it forward when the bow is being cocked. But I do like the spring because it is more positive.

    Shooting this one is different than the Chinese as expected. The trigger pull is a bit stiff but is very crisp. This is with a 95 LB bow so it could be more of an issue with a heaver bow. I am sure some tuning could get it lighter but for something to sell that is aimed in large part at the new builder, I want it on the stiff side. I would not want it too light for sure. It does make some noise also but nothing like the Chinese. The nut will spin about a second or two after the shot if the trigger is held back, causing a slight buzz due to the imbalance. But to me it is not at all objectionable. The most annoying thing about this lock is that I have to rotate the nut to the pre-cock position by hand every time. I often forget until I have the string pulled back and have to let down and start over. Rolling Eyes  Just a learning process and it is no different than the Xbow I made years ago.
    All in all this one is much nicer to shoot and has no issues with cutting a slot for the fletch so all my old arrows worked.
    So I was expecting to like the Chinese lock a lot better and it is a very interesting and cool looking lock but in actually shooting, I enjoyed the roller nut style a lot more. It should also be cheaper to produce. The same basic lock can use the long tickler style trigger for traditional style bows. So I will start on this one first.
    As a side note, these locks both work and are fun to shoot but very crude compared to my other design, the hammer lock.
    Universal standard Crossbow nut - Page 2 P1010847_zps987eb0f7
    My son is working on getting this in to production now but it will take some time.

    On a scale of 1 to 10 I would rate them like this.
    Hammer lock - 10
    Roller lock - 7
    Chinese Lock -5
    But this is a personal preference thing and as always YMMV.

    Please let me know your thought.
    Thanks,
    John

    P.S. I am leaving a week from today on a coast to coast and back motorcycle trip and will not be able to play with these toys for 6 to 8 weeks. Sad  But I will be online.
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    Post by hullutiedemies Sun Jul 06, 2014 2:30 am

    jaeger22 wrote:

     
    And the third issue is that I don't see an easy way to add a hold down spring and of course no way if you use the 180/90 degree fletch.
    I would love to hear feed back from those of you that have actually used this lock and how you solved or get around these issues.

    Ancient Chinese did not use bolt clips. Bolt clip is a late medieval European invention.
    That is one good reason to use nocked arrows with these.
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    Post by jaeger22 Sun Jul 06, 2014 4:43 am

    Nerd, yes understand that the ancient ones did not have a clip. In fact I didn't even know that the  Europeans had them. But I have seen them added to the roller nut type so know it can be done. I was just pointing out that there is no easy way to do it with the Chinese style that I can see. 
    Good point about the nocked arrows. But I am not clear on what would need to change to accommodate the nock. Deeper groove? Sideways groove in the claw to hold the string higher? What did you mean by nock groove?
    The good news is that I took the locks and drawings to my son and he said it would be no problem to make either or both types in the CNC machines. And the quality will be MUCH better. Once the machines are programmed, the parts can be made from any metal. I left them with him and I hope by the time I get back he will be ready to crank out parts.
    This is going to be fun! We may need some of you experienced hands here to test a few samples. Very Happy
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    Post by hullutiedemies Sun Jul 06, 2014 7:39 am

    jaeger22 wrote: What did you mean by nock groove?

    That extended bolt groove you allready have here behind the claw ,
    Universal standard Crossbow nut - Page 2 P1010926_zpsf5e6387f
    space under and behind the string allowing a nocked arrow to be loaded on the the string.

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