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    Reinforcing a Wooden Nut

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    Xamllew
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    Reinforcing a Wooden Nut

    Post by Xamllew on Sun Jul 26, 2015 6:47 pm

    Hello folks, I'm currently working on my first xbow and I'm pretty limited on materials to make a nut out of, so I decided on 3 laminates of .5" oak with the grains running in different directions, first layer runs vertical, middle horizontal, and third vertical same as first. I'm pretty happy with the results but I still feel like a split could occur with anything over a 100lb draw weight. I already have plans to reinforce the surface where the tickler will sit with a small metal plate, but I'm more worried about the fingers that hold the string.

    My only plan right now is either to coat the entire nut in epoxy or superglue to give it an added level of hardness, or perhaps fire hardening it would be another option although I can see a lot of problems with this too (not sure how the glue will react to the temperature).

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    Re: Reinforcing a Wooden Nut

    Post by c sitas on Mon Jul 27, 2015 2:49 pm

    How about laminating two pieces metal on each of the outer sides. I would run three or four  screws through the sides. Sink them flush, then pull apart and glue with industrial epoxy. Tighten the screws before the glue sets up .Would end up like a rock.Your metal plate could be incorporated into the whole thing. I'm a welder and I could weld the plate to the sides with a perfect fit.Make two wooden plugs and use one for making this assembly. This metal could also be make in one piece with some careful work
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    Xamllew
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    Re: Reinforcing a Wooden Nut

    Post by Xamllew on Mon Jul 27, 2015 4:18 pm

    c sitas wrote:How about laminating two pieces metal on each of the outer sides. I would run three or four  screws through the sides. Sink them flush, then pull apart and glue with industrial epoxy. Tighten the screws before the glue sets up .Would end up like a rock.Your metal plate could be incorporated into the whole thing. I'm a welder and I could weld the plate to the sides with a perfect fit.Make two wooden plugs and use one for making this assembly. This metal could also be make in one piece with some careful work

    That sounds like it'd do the trick. It could be done with sheet metal thin enough for me to cut, but I haven't got the tools needed for cutting anything too thick into the profile of the nut. How thick do you think the plates would need to be?

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    Re: Reinforcing a Wooden Nut

    Post by c sitas on Mon Jul 27, 2015 7:45 pm

    Some 1/16" stuff would work great. My thoughts,and just a suggestion, would be to bend the whole thing from one piece. You could make practice piece's out of some valley tin or aluminum. Do that to get your width of the roller. Once you have how wide good,it would be a simple matter to cut the sides out . Picture this, you'll have an axle right? Then I would put one bolt just below the floor of the fingers, and the other one some where ahead of the sear .Use taper headed screws. You could carefully tape threads for the screws and use "red" locktight  to put it together.

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    Re: Reinforcing a Wooden Nut

    Post by rolynd on Tue Jul 28, 2015 11:15 am

    Well, what kind of materials other than wood can you get? Just coating it with epoxy on the outside will not make it take more load.

    Delrin(/POM as its called here) is relatively easy to work even with hand tools and has been used for roller nuts in previous builds. small scrap pieces are always on ebay here and cost a pittance.

    If you cant get that and have to use wood a sheet metal reinforcement as suggested would be certainly a good idea. I would hesitate to trust a merely wooden nut with larger draw weights.

    If you can get steel round stock of sufficient diameter (old axles , large bolts, etc from the scrapyard for example)  cutting off a bit with a hacksaw and shaping with files is entirely doable - requires a bit of elbow grease though, you wont be finished in 5min... But much better than having the fingers break at an inopportune moment...

    I have even seen one made from several stacked and interconected metal washers if the central hole is not too big.

    as said a simple wooden roller nut is only for low draw weight...wood is good for the tiller.
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    Xamllew
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    Re: Reinforcing a Wooden Nut

    Post by Xamllew on Tue Jul 28, 2015 10:17 pm

    rolynd wrote:Well, what kind of materials other than wood can you get? Just coating it with epoxy on the outside will not make it take more load.

    Delrin(/POM as its called here) is relatively easy to work even with hand tools and has been used for roller nuts in previous builds. small scrap pieces are always on ebay here and cost a pittance.

    If you cant get that and have to use wood a sheet metal reinforcement as suggested would be certainly a good idea. I would hesitate to trust a merely wooden nut with larger draw weights.

    If you can get steel round stock of sufficient diameter (old axles , large bolts, etc from the scrapyard for example)  cutting off a bit with a hacksaw and shaping with files is entirely doable - requires a bit of elbow grease though, you wont be finished in 5min... But much better than having the fingers break at an inopportune moment...

    I have even seen one made from several stacked and interconected metal washers if the central hole is not too big.

    as said a simple wooden roller nut is only for low draw weight...wood is good for the tiller.

    The only other material I have at my disposal is aluminum round stock but that's solid metal, I could sooner order a pre-made delrin nut and have it at my doorstep than to try to file and hack away at that stuff with the tools I have. I do like the metal washer idea, although there's still a lot of elbow grease in doing that as well.

    I'm going to give the plating idea Sitas mentioned a try since I've got some ready to use. I'm aiming to have it hold at around 150 lb draw. I've used oak for similar weight bearing functions before and I kinda trust it to hold up pretty well however testing will be performed alone in the woods so a failure shouldn't be much of a concern for safety.

    I appreciate the ideas.

    c sitas
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    Re: Reinforcing a Wooden Nut

    Post by c sitas on Wed Jul 29, 2015 11:46 am

    Just between you and I, you won't have to worry about a failure. At least from the  nut ,I had to stop and think how to word. Don't want to offend anyone .If you go this route, after you have the nut finished,then make every effort to file or sand a good square face on the metal on the nut. Just has to be where the sear will ride.Also want the bottom nice and square. This will help the sear break nice and clean. Take polishing cloth and really smooth the area of the top fingers. Don't want to nick a string.Don't try to harden anything.

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    Re: Reinforcing a Wooden Nut

    Post by c sitas on Thu Jul 30, 2015 12:10 am

    You know; The only reason I'm working here with a wooden nut is that's what you mentioned . I firmly believe it can be done safely. Is it the quickest and best , maybe not .  I use delrin but , you have to have the machinery to work with it . I use a plate where my sear rides. I'd trust them  period. I don't see my self ever needing more than say 2 or 2.5  hundred  pds. pull . I anchor my plates with red loctite and two 8/32 set screws, one each side. I use a three trip trigger. It works smooth. Ya there is some extra travel but I could eliminate that with a set trigger just like Todd did. I don't see it as a problem.Using your brain here is what this is all about. That is what really makes this forum so fantastic. If your all wet, someone  will pipe up and respectfully tell  you. I love that , as I'm a go for broker and make worker type.
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    Re: Reinforcing a Wooden Nut

    Post by OrienM on Fri Aug 14, 2015 12:38 pm

    I made a wooden nut, and it worked out OK. My advice would be to use more, thinner wood laminates (thin enough that each finger has several lams in it) and to rotate the grain direction of some of the laminates 90 degrees, plywood-style, for more strength.

    Also, Red Oak is probably not the best wood choice...something harder and more consistent in texture would be better. I'd suggest hard maple, or maybe an exotic hardwood...I used ziricote in mine, a Mexican hardwood fairly similar to ebony.

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