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    Suggestions, Corrections ot Input appreciated

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    Tinker
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    Suggestions, Corrections ot Input appreciated

    Post by Tinker on Sun Aug 01, 2010 9:31 am




    Can you veterans of the Arbalist give me your opinions on this idea before I start whittling and screw things up?

    The sketch is to scale. 1 1/2" x 1" nut. Set from side into a machined 1" wide nylon block. The block is inlet from the top and is held in by a blind screw from the bottom (front) and the single axle/cross pin that the tickler pivots on. Tickler is 3/8" square and flattened slightly as it sweeps to the rear. I am thinking that if the nut to block fit is close clearance that the depth that the nut is set into the block it should be retained and will not require a pivot axle. The low nylon to nylon friction should be sufficiently low for a 90-95# prodd.

    Workable or am I nutz scratch
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    Good plan!

    Post by Geezer on Sun Aug 01, 2010 12:00 pm

    Tinker: Your plan is good. The only suggestion I have is this: Payne-Gallwey specifies a 1.5 inch diameter nut with the center 3/16 below the top of the socket. That is awfully shallow. You want the nut sunk just about 2/3 of it's diameter, with 1/3 sticking out of the socket. If you sink the nut by as much as 3/4 you may not be able to remove the nut from the top of the socket. If it's sunk as little as 3/5 of it's diameter, you will end up stressing the edges of the socket excessively. As Mama bear said, 2/3 is Jusssst Riiiight! If the nut fits the socket correctly, you won't need any sort of axle or pin to hold it in place, but some sort of little floating pin or 'nussfaden' cord will keep it from falling out or oscillating on release with unnecessary wear on the nut and socket.
    anyhow, your plan is quite workable. I say 'do it'. Geezer
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    Re: Suggestions, Corrections ot Input appreciated

    Post by Tinker on Sun Aug 01, 2010 1:55 pm

    Thanks GEEZER for the input. My intent was to seize the nut by setting it deeper in the block. (Two pieces of nylon; Nut and the Block as an assembly) To remove the assembly would require removing the (blind) screw from the bottom; removing the tickler axle and sliding the whole assembly out form the top, Then the nut could be slid out of the side of the assembly block. So, it should be physically impossible for the nut to come out even without an axle or retainer binding through it's center. The question now is, "do I have enough for the bowstring 'catch' to function properly?"

    I have a prodd, string and nut ordered from Alchem Inc. that was supposed to be in stock and in the mail soon. When I get the parts I will have a better idea of the string serving diameter.

    If'n you still think it's a viable idea I will give it a shot cheers

    PS: I got a LOT out of your "Iolo's First Book on Crossbows".... GREAT Job!
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    Tinker's mortised lock

    Post by Geezer on Mon Aug 02, 2010 9:02 am

    Tinker: This sort of seperately installed or 'mortised' lock is quite common on medieval bows. Usually their rollers are only about 2/3 buried in the socket, so they can be 'keyed' out if the nussfaden-cord (axle) is cut, but if you can make the whole lock assembly removable, I don't see why you can't bury the whole thing deeper... in which case, just dispense with the axle through the roller-nut. If you don't need an axle, why add the extra complexity and friction?
    Of course medieval bowyers had to rely on natural fibers, like linen and hemp, which necessitated thicker bowstrings, so their roller-nuts required larger lugs. If you're gonna use modern stuff, like Dacron or Fastflite, you should be able to get away with much thinner strings... particularly if you look into double-ended strings, as illustrated by Harmuth in "Die Armbrust" Yes, I know Payne-Gallwey offers an alternate way to make reinforced ends, but if the 'auxilary loops' aren't stressed the same as the rest of the skein, I think his method may result in strings that are heavier, but no stronger.
    Anyhow, you can always go for a slightly larger diameter roller-nut if you want taller lugs to handle the string. So go for it. Geezer
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    Re: Suggestions, Corrections ot Input appreciated

    Post by Tinker on Mon Aug 02, 2010 3:20 pm

    "OKEY-DOKEY" sander

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    Re: Suggestions, Corrections ot Input appreciated

    Post by Regerald on Tue Aug 03, 2010 1:45 pm

    Looking good. I suggest one little improvement:
    I would add one additional screw, to secure whole assembly in a stock. In a picture I explained why I think it's necessary.

    It will work also without this screw, but after few hundreds of shots wooden walls will give up and mount will loose..
    Screw can also be covered by a bolt-keeper plate, so it won't even be visible..
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    Re: Suggestions, Corrections ot Input appreciated

    Post by Tinker on Tue Aug 03, 2010 5:38 pm

    Regerald; Thanks for the input. Point well taken. I can see a tendency to torque UP at the rear.

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    Re: Suggestions, Corrections ot Input appreciated

    Post by Ivo on Wed Aug 04, 2010 2:01 am

    Perhaps not he most elegant of the choices, but if I'm not mistaken it is how the block was held in place on the original crossbows.

    Two pins holding the block in place...



    Regerald's idea is much easier on the eye though.




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    Re: Suggestions, Corrections ot Input appreciated

    Post by Tinker on Wed Aug 04, 2010 8:56 am

    Ivo wrote:Perhaps not he most elegant of the choices, but if I'm not mistaken it is how the block was held in place on the original crossbows.

    Two pins holding the block in place...



    Regerald's idea is much easier on the eye though.

    My idea was to use the tickler thru-pin as the rear anchor. However, making it captive and not binding the tickler would be a challenge. Making the tickler pivot pin the width of the block only and eliminating the forward screw would only add one more hole in the stock than I envisioned. No real need to make those two you suggest captive as they are not '"working" as the tickler pivot would be. I would suppose screws were unheard of in early crossbows where pins would have been commonplace. Your suggestion may be the best 'mousetrap', Ivo.

    Tinker


    Last edited by Tinker on Thu Aug 05, 2010 8:54 am; edited 1 time in total (Reason for editing : 'weenie'typing fingers...)
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    Re: Suggestions, Corrections ot Input appreciated

    Post by basileus on Thu Aug 05, 2010 12:49 am

    Geezer wrote:
    Of course medieval bowyers had to rely on natural fibers, like linen and hemp, which necessitated thicker bowstrings, so their roller-nuts required larger lugs. If you're gonna use modern stuff, like Dacron or Fastflite, you should be able to get away with much thinner strings... particularly if you look into double-ended strings, as illustrated by Harmuth in "Die Armbrust" Yes, I know Payne-Gallwey offers an alternate way to make reinforced ends, but if the 'auxilary loops' aren't stressed the same as the rest of the skein, I think his method may result in strings that are heavier, but no stronger.

    Payne-Gallway's loop reinforcement method definitely works - I've made many bowstrings that way. Also, as Payne-Gallway states, some medieval crossbows used the reinforcement loops he describes (on page 111). I've documented the entire bowstring making process here (see "Reinforced endless loop strings"). I hope that helps someone avoid the practical mistakes I made initially.

    In a nutshell, the reinforcement loops won't become slack if you make them properly. And they do reinforce the loops - without them the bowstring will almost always break at the loops. With them it will break at the center. That said, making a reinforced (Payne-Gallway) -style takes a lot more (3-4x) time than a simple endless loop string. Also, there's really no point in reinforcing the loops for most synthetic fibers: the loops are only a little weaker than the main skein (not half). You can try the Tim Baker (2000: 219) test to verify this:

    • measure the breaking weight of a cord
    • fold the same kind of cord over a round (metal) bar
    • measure the breaking strength of the cords (combined)
    The folded cord will take nearly double the weight to break. I've heard (not tested myself) that the breaking strength of some plant fibers (e.g. linen) is reduced noticeably if they have to bend around sharp angles and thus would benefit from reinforced loops. Personally, I only reinforce the loops for linen strings.

    References:

    Baker, Tim [1992] 2000b. Strings. Traditional bowyers bible, volume two. Ed. Jimm Hamm. 187-258.
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    Re: Suggestions, Corrections ot Input appreciated

    Post by basileus on Thu Aug 05, 2010 12:52 am

    Oh, forgot the original topic Smile... take a look here for info about how to align the nut and trigger properly to make the release smooth and comfortable.
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    Re: Suggestions, Corrections ot Input appreciated

    Post by Ivo on Thu Aug 05, 2010 3:18 am

    I would suppose screws were unheard of in early crossbows where pins
    would have been commonplace. Your suggestion may be the best
    'moousetrap', Ivo.

    Hey it's no biggie...

    This retention with two pins/screws is just one of the variations I yanked from Ralph Payne-Gallwya's book, page 92-100 >>>Link




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    Re: Suggestions, Corrections ot Input appreciated

    Post by Tinker on Thu Aug 05, 2010 8:52 am

    You guys are GREAT! (Ever been hugged by a gorilla?) cheers
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    Re: Suggestions, Corrections ot Input appreciated

    Post by Tinker on Wed Aug 11, 2010 6:15 pm

    Well, here is the gizmo. It will be anchored with two cross pins like IVO suggested. It will be tight-inlet to support everything. Cut line on the black block will be about where the line is on the nut. Waiting till after it is inlet to whack the block off as nylon/delron does not work by hand that well.





    The brass cross pin in the nut does not go through the stock. It's purpose is to lock the threaded sear screw as it has to be removable to take the nut in and out. It extends outside the nut perimeter and serves also as a rotational stop. The fit of the nut in the block should keep it captive.

    If it works, it will be the "Tinker Breech Block" king

    If'n it doesn't, I will call it "Practice" jocolor

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    Re: Suggestions, Corrections ot Input appreciated

    Post by Ivo on Wed Aug 11, 2010 10:50 pm

    I pictured it this way when brainstorming...Threaded sear pin is coated
    with loctite and once in place a small set screw is screwed in to
    further lock the sear pin...

    BUT...I like how everything is coming along and designed to be working together in this one, the brass pin idea is pretty cool considering it will keep all the weight at the center - reducing the lock-time, as opposed to my idea.

    Good Luck and hope it all goes smooth.

    PS. The pin holding the trigger lever is a bit small/thin...or is it just the lighting in the first photo?




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    Rotational stop?

    Post by Geezer on Thu Aug 12, 2010 8:52 am

    "It extends outside the nut perimeter and serves also as a rotational stop." Tinker: Does this mean you're letting the threaded sear-plug extend outside the bottom of the roller-nut, so you can use it to stop nut-rotation?
    If so, remember that the nut will have a good deal of energy when it hits the stop. If it's not very strongly made, you may: 1. Jam the nut in its socket, 2. damage the threaded sear-insert, 3. break the stop.
    How do I know? I tried it. You will at least slowly hammer away the threaded sear-insert and the stop. This doesn't mean you can't do it that way, but you oughta check regularly for excessive wear in the first few weeks/months of testing. Everything wears out, but some things wear out faster than others.
    I once considered making a spring-loaded stop, to absorb the shock better, but decided it would be too expensive for my customers and wasn't very medieval anyway. Since I was making medieval-style bows, I abandoned the idea. Still a spring loaded stop for a roller-nut has possibilities, and though it's not really period practice, one could hide it easily enough.
    Otherwise, the lock looks pretty good. Geezer
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    Re: Suggestions, Corrections ot Input appreciated

    Post by Tinker on Thu Aug 12, 2010 9:44 am

    GEEZER; Yes. What you relate definitely has merit and apparently you have 'proofed' the idea. I considered exactly what you have related as a probable side-effect to doing this. This is a 100# prod. The inertia of the sear pin coming to an abrupt stop has batter things. My thought was the fact that block nylon is absorbing the sear face impact; that just may allow it to function without shear. Or, maybe the bugger will shear cat-out-of-the-box?! Juggle I'm hoping the rotational inertia will dissipate 'peacefully' and damage will be long time. Or, maybe I will have a new wall decoration for the den!

    Your expertise is valued, Tinker
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    Re: Suggestions, Corrections ot Input appreciated

    Post by Tinker on Sun Aug 15, 2010 4:51 pm

    Here is the block assembly inlet into the tiller:





    The two holes through the tiller are for .125" brass pins to lock the assembly into place. So far, so good cheers

    Tinker

    IVO; Thought I answered your question but guess not. "PS. The pin holding the trigger lever is a bit small/thin...or is it just the lighting in the first photo?"
    It is .125" steel drill rod; should be strong enough. If not it can be replaced with a larger diameter one.


    Last edited by Tinker on Sun Aug 15, 2010 7:47 pm; edited 1 time in total (Reason for editing : Response to IVO)
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    Re: Suggestions, Corrections ot Input appreciated

    Post by Ivo on Sun Aug 15, 2010 11:31 pm

    That's really cool Tinker,

    Excellent photography too, I also have some maple work laying around, but I just can't capture the wave in the grain as you did...deffinitely doing something wrong with the lighting/shot angle.
    Are you ordering the prod for this one? or will you take a leap of faith and cut one out yourself? ...either way - Good Luck!

    As for the axle pin, I guess I missed the material choice when it was mentioned...in my case it would have been a case-hardened finishing nail ...sorry for doubting you, I've been cheap lately while saving up for a car!!!




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    Re: Suggestions, Corrections ot Input appreciated

    Post by Tinker on Mon Aug 16, 2010 10:02 am

    That piece of rock maple (Acer saccharum) was left over from the last Kentucky longrifle. I paid for the hit-you-in-the-face fiddleback grain. The trim piece has been collecting dust in the shop and I was elated to be able to make something else with it. The flow around the block/nut area was just how it happened to wind up. The piece dictated its size and lay. In a word, no talent or wisdom involved.

    I have one of ALCHEMS #2316 prods in hand now at 100# rating. It comes with a plastic shrink tube on its center 5.5 inches. I suspect that this is done as a liability issue and even tho they recommend leaving it, I am considering removing it so the prod can be inlet snugly in such a manner as to lock it from any movement on the tiller. Thoughts? In the instructions this prod has a 11.5" full draw, so it will be about 12" to the front of the tiller. Any idea what the proper projectile length should be?

    Don't feel bad for 'doubting' me...I doubt myself frequently. scratch My wife reminds me often that this was supposed to be a winter project Shocked ...And even though I am itching to proof the whole thing it will be awhile before it is ready to shoot. Carving on two sides will be time consuming. Which brings me to another question, Are there any pictures showing the detail on the head of the hawk you posted for me IVO? My imagination has failed me...

    Thanks, Tinker
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    Re: Suggestions, Corrections ot Input appreciated

    Post by Basilisk120 on Mon Aug 16, 2010 2:24 pm

    Wow if ever a piece of wood was asking to be made into a crossbow Smile Looking forward to seeing this project completed.



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    projectile length?

    Post by Geezer on Tue Aug 17, 2010 12:52 pm

    Tinker: You asked about Alchem prods with the rubber coating and projectile length.
    The prod will work fine with the rubber left in place... though the rubber may have to be cut away on the edges if you're mounting the prod with Alchem's small bow-irons. The rubber between the prod and stock will slightly reduce noise and apparent recoil, but it certainly isn't necessary for satisfactory shooting.
    For projectiles, you might as well start with 11/32nd inch standard arrow-shaft with 125 grain heads. (100 grain may give you slightly better velocity at shorter ranges, but will wear strings out faster) Medieval bolts generally run anywhere from 12 to 18 inches long, with an average of about 15 inches. My SCA customers, who shoot in target competitions at 20 to 40 yards generally prefer longer bolts rather than shorter. 16 inches is the most you can get from arrow-shafts if you cut two each. I make a lot like that. Theoretically longer still should be more stable, but they will have more surface friction as well as weight, so they'll lose velocity faster at longer ranges.
    You definitely want your bolts to have a forward weight bias (which is a fair argument against using butt-caps). The experts say the balance point on your bolts should be about 1/3 of the way from the front.
    As for thickness, many of the bolts you see in museums are very thick, 1/2 to 3/4 inch seems about average, and the preferred woods for medieval bolts were ash, birch or oak, but for the sort of lightweight bows we shoot, you'll want to stick with standard arrow-shaft to begin with. Spine weight doesn't particularly matter, so long as all the bolts are spined the same. Of course it's possible to get a shaft that's simply too wimpy, but if you get shafts spined for 40 to 50 lb or thereabouts, you'll be fine.
    Remember that crossbow bolts must be very straight, have the heads on straight, and if you're using un-nocked bolts, make sure the butts are square as well. If have seen un-nocked bolts cut with a slight hollow in the butt. That seems to work out well, and it may be a cure for a marginal misfire problem.
    I'll think about it, maybe come up with more ideas, but that oughta be enough to start with. Geezer
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    Re: Suggestions, Corrections ot Input appreciated

    Post by Tinker on Wed Aug 18, 2010 10:21 am

    Thanks guys, I value your help and encouragement.

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    Re: Suggestions, Corrections ot Input appreciated

    Post by Pavise on Wed Aug 18, 2010 12:57 pm

    One other little detail you might wish to consider:

    If using wood, the grain lines (annular rings) of the shaft should be vertical, or in other words at 90 degrees to the string. This means that the string will then be crossing these lines of weakness and that the slight bending of the shaft (which does take place) will be consistent and your shafts will all fly about the same.

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