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    Epoxy putty material for a roller nut?

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    amir
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    Epoxy putty material for a roller nut?

    Post by amir on Sat Nov 01, 2014 2:13 pm

    i saw many different kinds of epoxy putty : steel, aluminium, wood, etc..

    was wondering if i can pressure cast a roller nut from one of them and how light and strong are they?

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    Re: Epoxy putty material for a roller nut?

    Post by kenh on Sat Nov 01, 2014 5:46 pm

    I would bet that any nut made from epoxy of any kind will not be hard enough to make a nut.

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    Re: Epoxy putty material for a roller nut?

    Post by amir on Sun Nov 02, 2014 1:39 am

    how would you suggest to test its hardness?
    https://www.youtube.com/watch?v=DPIWeRKHBRE

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    Re: Epoxy putty material for a roller nut?

    Post by kenh on Sun Nov 02, 2014 6:28 am

    It's not just a matter of hardness, although that is a factor; I believe strength of something like a roller nut is also of factor of what's called sheer strength.  Check with the manufacturer of the epoxy to find both its cured Hardness and its Sheer Strength and compare those to the antler, steel, Delrin, etc. that we usually use to make roller nuts.

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    Re: Epoxy putty material for a roller nut?

    Post by Geezer on Sun Nov 02, 2014 6:38 am

    Epoxy putty for crossbow nuts?  I used to know a guy who made lightweight crossbows for medieval clubs that used some sort of poured epoxy for roller nuts.  I think he had some trouble getting them really round and right-angle on the edges, but as far as I know, they worked pretty well for draws around 60-70 lb. I certainly wouldn't suggest epoxy for anything over 100 lb... failure in shear seems likely.  Geezer

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    Re: Epoxy putty material for a roller nut?

    Post by amir on Sun Nov 02, 2014 7:13 am

    take a look at the specification of quick steel for example

    looks pretty strong in both strength modules (SHEAR, TENSILE)
    have a look at the second page paragraph 5 where they compare it to ABS plastic


    http://www.superonindia.com/download-pdf/TDS/Z%20711%20(P)%20QUIKSTEEL%20FSL%20EPOXY%20PUTTY.pdf

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    Re: Epoxy putty material for a roller nut?

    Post by Hermit on Sun Nov 02, 2014 7:26 am

    What about wear resistance?,that's about hardness,not the same thing as shear,or even strength,how would the surfaces for the notch hold up?I don't think they would......................
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    Re: Epoxy putty material for a roller nut?

    Post by mac on Sun Nov 02, 2014 4:49 pm

    As long as the tensile, and shear strengths are sufficient, it will not fail catastrophically.  If it wears out too rapidly, it can be replaced.  In the mean time, information will be gained and no one will be injured.

    I would worry about the strength of the material in the place where the lock engages the nut.  Some sort of reinforcement will almost certainly be needed there.

    Mac

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    Re: Epoxy putty material for a roller nut?

    Post by Geezer on Sun Nov 02, 2014 6:13 pm

    medieval bows usually have an iron or steel plug inset in the bottom of the roller-nut for the distal end of the tickler (trigger) to work on.  I drill and tap a passage thru the nut from bottom, slightly behind center to just between the lugs on top, and screw in a section of allthread (threaded rod) 5/16 or 3/8 in allthread will usually suffice. Geezer

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    Re: Epoxy putty material for a roller nut?

    Post by mac on Sun Nov 02, 2014 6:34 pm

    Right.  I'm thinking that if someone were to make up a nut out of epoxy, they could embed that steel reinforcement right from the start.  That allows then to make it whatever shape seems best and not have to worry about how to fit it accurately into the nut.

    Indeed, why stop there?  The lock reinforcement could be part of an more extensive "armature" that included heavy wire pins that fortified the "teeth" of the nut against shear.  Such pins are not uncommon on the antler nuts of the heavier sorts of period crossbows.   If one were casting the nut around such structure, those pins need not even show on the finished surface of the nut.


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    Re: Epoxy putty material for a roller nut?

    Post by Geezer on Sun Nov 02, 2014 6:39 pm

    Yup, that oughta work.
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    Re: Epoxy putty material for a roller nut?

    Post by hullutiedemies on Mon Nov 03, 2014 1:44 am

    Made a 22mm nut with 6mm wide claws out of Standard Milliput(tm) mixed with cotton lint that has been repeatedly shot with 100lb bow. No sign of wear yet.

    amir
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    Re: Epoxy putty material for a roller nut?

    Post by amir on Mon Nov 03, 2014 4:29 am

    Nerd, send in some photos Smile

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    Re: Epoxy putty material for a roller nut?

    Post by Spyro.Magno on Sun Dec 14, 2014 7:33 am

    Yeah Yeah

    Photo please!

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    Re: Epoxy putty material for a roller nut?

    Post by Hermit on Sun Dec 14, 2014 12:46 pm

    Having re-read this thread,it occurs to me that it is very doable.Were I to tackle it,I would cast in a piece of thin brass tube for the trigger pivot,and a piece of hacksaw blade for the sear.I would also mix in powdered metal with the resin prior to adding the hardenerCast iron would be my preference,alumium my second choice.I can hear it now..............."where the hell do I get powdered cast iron."..........answer,you make it yourself.When worked with tools,cast iron swarf comes off as powder,some work with a file on a scrap casting will give you what you need.Regarding scrap castings,many castings are hardened by 'chilling'with gas after they are poured and need to be heated to cherry red  to soften them.Soft cast iron can be filed easily with a coarse file.There is a product called 'liquid steel',but I am not sure of it's make up or suitability,and it is not so far as I know sold in large quantities,so if used may be expensive.I think this method would produce a useable nut,but must admit I haven't tried it,if anyone does,I would be interested to hear it it works for them
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    Re: Epoxy putty material for a roller nut?

    Post by Geezer on Sun Dec 14, 2014 7:15 pm

    I will conceed the point: No doubt one could make workable roller-nuts out of epoxy putty, mixed with whatever... and I suspect one could make them out of fossilized shark coproplites as well as a lot of other stuff.  But WHY? 
    Geezer

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    Re: Epoxy putty material for a roller nut?

    Post by Hermit on Sun Dec 14, 2014 9:26 pm

    Imagine,Geezer,that like me,you live out in the back of beyond,2hrs. away from the nearest small city.You want to make a crossbow nut.You root around in your shop for suitable materials.you can't find anything suitable to make that nut,but you do find a can of resin,and an old casting...................to name but one possible reason................
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    Re: Epoxy putty material for a roller nut?

    Post by Geezer on Sun Dec 14, 2014 9:44 pm

    Yes, Hermit, it does make sense. Unfortunately, the one example I have seen of epoxy roller-nuts was rather underwhelming.  No doubt a careful craftsman could do better, but I think in the long run, you'd have to put your cast epoxy 'roller' on a lathe to get it really round anyhow, in which case, I suspect I could find something that would work out better. But don't mind me, I'm just being picky.
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    Re: Epoxy putty material for a roller nut?

    Post by edstuff on Thu Dec 18, 2014 7:59 am

    You gave me an idea.  I was working on a nut made from (2) washers and a couple small tubes tack welded together.  It works but not real pretty.  If I sandblasted it and then used strong epoxy to fill in the gaps it would look a lot nicer.  And since the steel parts would be holding all the pressure the epoxy would just be filler.

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    Re: Epoxy putty material for a roller nut?

    Post by Hermit on Thu Dec 18, 2014 10:50 am

    If it's just filling you want,auto body filler would work,you may even have some...............
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