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    First Forged Prod

    OrienM
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    Post by OrienM on Sun Aug 10, 2014 1:44 pm

    Hi folks,

    Continuing my crossbow obsession over here...I wanted to show my first attempt at a fullsized, forged prod. Unfortunately it was a bit of a semi-failure.  pale  I underestimated the thickness I'd need, used 1/4" thick stock and ended up with about a 90# draw weight. In an effort to boost it back up I added a set of saw-steel leaf springs...this sort of worked, and the finished prod appears to pull about 200# with a 6" powerstroke. I was hoping for around 300#, but 200 is adequate...if the cast seems reasonable I will likely build an xbow around this thing.

    Pix:
    First Forged Prod <a href=First Forged Prod Prod1_zps8739bf48" />

    First Forged Prod <a href=First Forged Prod Prod3_zpse3c51094" />

    First Forged Prod <a href=First Forged Prod Prod2_zpsef53f909" />

    The forged part (front bow) is made of 5160 leaf spring, with rolled nocks, and is about 22" wide across the string. Tip rise is 1/2", and the prod is slightly under 1/4 thick by 1 3/8" wide at the center, and 3/16" x 7/8" just behind the tips. The triple layer of sawblade steel  in back boosts the thickness at center up to around 1/2".

    The extra leaves and steel clamps creak like crazy  Shocked  but do look kind of cool, I think. All in all this was good practice, and I'll know better what to do next time (use 3/8" or 1/2" stock, for starters!)  Rolling Eyes 

    Comments, questions and advice all welcome; thanks for looking!
    -Orien
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    Post by Nick D on Sun Aug 10, 2014 1:52 pm

    I like the nocks.  How did you temper the main piece?
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    Post by OrienM on Sun Aug 10, 2014 2:03 pm

    Thanks! Making this required me to build a charcoal-burning "ground" forge, with a perforated pipe about 3' long running down a dirt trench, and hooked up to my hand-cranked blower. I got the prod heated to critical temp as evenly as I could, quenched it in used motor oil, and tempered it to a shade just past the blue range using a propane torch. It seems to have worked well, just about the right springy temper I was after.

    It was also the longest piece I've ever heat treated, by a pretty big margin. I'm kind of psyched, now I can HT swords and machetes fairly easily, as well as crossbow prods.
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    Post by Nick D on Sun Aug 10, 2014 2:45 pm

    Funnily enough, that's the more or less the method I had decided on for hardening my prods.  I'll build a temporary ground forge with firebrick and pipe, though I'm going to have a T connector in the center to the blower to make sure the air pressure is even at each end (I don't know if that's really necessary, but just in case.)  I do want to temper in an oven so I can control the temperature more closely and perhaps run it through a couple tempering cycles.
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    Post by OrienM on Sun Aug 10, 2014 3:22 pm

    That should work great. I was impressed by the even airflow I got with just the plain slotted pipe, and also by the crazy fuel consumption (1 1/2 bushels of wood in under an hour, yikes!). I like heat treating 5160, I've made a lot of blades from it and find it pretty forgiving.

    I probably should have done another tempering pass myself, but one seems to have been OK...when I make a thicker bow it will be done twice if not 3x, for safety. A tempering oven would have been awesome!  Very Happy  My shop is a pretty simplistic setup, nothing has temperature controls. I've been tempering with a torch for a long time...it's a fussy, kind of risky way to do it, but it works fine if done very carefully.

    Thought I should add, I used the Payne-Galloway prod design as a rough basis for my limb tapers. The limbs reduce in width by 1/3, in thickness by 1/4. The tiller or bending shape of the bow is quite nice, to my eye, and I will use similar proportions when I attempt another prod.
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    Post by kenh on Sun Aug 10, 2014 7:37 pm

    Is it just the bands that are riveted together, not the laminations of steels?  I love "loose laminate" prods precisely because they can be easily "tuned" to a desired draw weight.  The Chinese were doing them 3000 years ago.  

    If you feel the need to part with that "semi-failure" of a prod, I'd be happy to take it off your hands... bounce
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    Post by OrienM on Sun Aug 10, 2014 8:15 pm

    Hi Ken,

    Yeah, it's a loose laminate setup...the steel strips are separate, just clamped together so the layers can slide. Each belly lam has a clamp riveted onto each end, which then wraps around whatever's in front of it (so, clamping all four layers at the inner pair, then three layers, then two). The outer ends don't need any extra pressure, so the clamps there are shorter and just hold the sides in alignment.

    I've played with these some in wooden bowmaking, and it is neat to be able to add and subtract elements to change the weight and bending shape (the wood-lam handbows all creaked like mad when drawn, too, just like this does  Razz ).

    I might consider parting with it, actually  Very Happy ...what I'm really after is to produce a crossbow I could potentially hunt with, and I'm not sure this has the power I want/need. I'll probably end up trying again, and can hopefully produce another prod more in the range of 300-400# (or whatever the maximum is I can span with a wippe lever). PM me, if you want, and we can talk...
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    Post by Rizzar on Mon Aug 11, 2014 12:13 am

    Hey there!

    Nice work you have done with that prod.

    But as considered above I´d suggest you to build a new one from one piece.

    Loose laminates are always slowing things down.
    The fact that steel prods are already very slow the laminating will contribute its part.

    Considering the time effort on making a finished crossbow my choice would be to use the sufficient parts and no compromises. The thing that you seem to be able to build your prods quite easily would help me with that decision if I were you.

    I did not make a calc since the lack of many relevant information, but 90# on a short bow like that seem to be too low, even with 1/4". 

    I´d like to get a closer look on the tip ends from different angles, they really look very good as far as I can see, could you please provide some detail shots?

    greetings Rizzar
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    Post by OrienM on Mon Aug 11, 2014 8:27 am

    Thanks Rizzar! Yes, having built a few full crossbows now, I am very reluctant to build something so elaborate around a less-than-ideal prod. This will throw a bolt, I'm confident, but it feels inefficient...it weighs more (physically) than a one-piece, 1/2" thick prod would, with a far lower draw weight. I can still string it by hand (the "step-in" method), and can pull it back by hand about 4".

    I wouldn't call forging one of these "easy", exactly  Wink  but since I made this one successfully I know I can forge a better version as well. I want to start with a fairly powerful prod, or it's not going to be worth the effort and expense to build up.

    I was very surprised by the low draw weight, honestly...I'm terrible at math, and I don't have a bow scale so all weights are estimated, but it was certainly pulling less than my body weight (140 lbs). I thought the shortness of the prod would make up for the thinner steel, but I guess I was wrong.  Neutral 

    I'd be happy to get some close-ups of the nocks, they turned out nice and seem to work well. I'll snap a few photos in the next day or so, with the string off so you can actually see the shape.

    Thanks again!
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    Post by OrienM on Tue Aug 12, 2014 12:31 pm

    Some nock pix here. I already had some experience forging sockets (on chisels and spearheads, and as knife handles), and these turned out to be much the same idea. Forge out a little spatula-shape, then roll it up....

    It was little tricky to get a sense of the right shape just from pictures, handling an original prod would have been very helpful indeed. These work fine and look OK, but the next pair I do will be wider and flatter in the 'ears', and bent down slightly to follow the line of the string.

    [img]First Forged Prod Nock1_zps6037b6e6[/img]

    First Forged Prod <a href=First Forged Prod Nock4_zps968f2553" />

    First Forged Prod <a href=First Forged Prod Nock2_zpsb61fdb6d" />

    First Forged Prod <a href=First Forged Prod Nock3_zps16bc946f" />

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