latest build in progress

I'm pretty pleased with the design and build quality generally, but there's a few kinks I need to iron out before I call this one done.

 The prod is from Slobows, the "SB BB": 3.5" brace height and 11" powerstroke, rated at 165 pounds. It's over 31 inches wide spanned, compared to less than 28 for the more typical steel prod from Alchem or Slobows, so it seems a bit of a monster compared to my previous builds.

 The main wood is Cherry, with accent pieces of Laurel. I really was focused on trying to keep a good balance and not go completely front heavy as is common with steel prods, hence the thick and meaty looking shoulder stock and cord binding. I planned from the start to use a red dot sight, though I have a rear iron sight that mounts to the same rail at the same height as a backup, I just need to come up with a front sight that will work with it. 

 Black Delrin roller nut, and the trigger mech is the same two-piece action I came up with when I rebuilt my first crossbow recently. It's a long pull, but very smooth and easy.
Didn't get a picture of this trigger mech, but here is a shot of the one it's a copy of:




 I'm pretty stuck on brass bolt tracks by now, but a new feature for me is accomodation for commercial, triple vaned crossbow arrows. This prod has enough upsweep in the tips to allow for a generous slot to be cut for the cock feather. The bolt track is made from two brass angle sections, screwed and epoxied to the stock halves before they were glued together.

 I thought the plate of Laurel on the butt of the stock looks particularly nice. I played with the idea of making the stock hollow for keeping spare strings and batteries and wax and whatnot, maybe I'll try that on version 2.0

 Here's where it gets a bit weird. I wanted the light weight of a cord binding, but I also wanted to be able to mount and unmount the prod quickly and with basic or no tools. This is what I came up with, given the materials I had on hand. It works pretty well, but I'm not in love with the look of it, and I'll need to do some field testing to see if it is sturdy and durable enough for long term use. If not I may convert to a more standard and permanent cord binding.


Gnome

Another nice job!

 Seems like how to mount the prod can be more problematic than trigger mechanisms.

Todd

very nice build! Elegant and imaginative design love it! Cherry is a very nice wood.
I am always surprised about what it seem like a very short band with the Slobow prod. Personalty I would  had add 1 or 2 cm of band and put the prod mortise a bit more high  this alloyd a smaller prod angle in the stock, less stress  and better efficiency for the prod harm. Prod mount  interesting and pretty, but preparing the rope like this is not longer then to do  steel stirrup? for about the same weight?
I am using the same trigger system I also think the pull bit long but it is efficient and easy to build.Wy do you choose this quite small poundage for the prod?

woooah... looks so smooth, how many hours do you use on crossbows like these?! i only use like 3-4 on my shitty crossbows....

Very interesting and artistic build.  Certainly the most unusual prod mounting I've ever seen.  Is that braided nylon prod mount cord?  Beauty aside, how does it shoot????

Thanks, all. How does it shoot? Ah, there's the rub. I usually put leather padding on my nocks to protect the loop ends. I've test fired this one four times, and four times the leather strip on one end has been cut in two under the string. Each time I've unstrung it and filed and polished the nock area and restrung it, the same way, and again it happens, always the same tip. So far the sting appears undamaged.

Any Ideas? This string is a bit thinner than I normally make, and the prod mortice seems like it might be a hair crooked. I plan on fixing both of those issues soon.

Kenh, the cord isn't braided, just the sleeve covering it. It's some kind of extruded core, can't remember where or why I got it. I originally set this up using loops of paracord, which worked fine, just looked pretty shabby. I imagine just about any type of string or thin rope could be made to work in a pinch.
Gnome

Ah!  Now I see it.  Like the cover over real paracord (not the thin stuff) only with a broader braid.  I wondered because I was thinking that a braided cord would have a lot of play in it and be a witch to tighten...

Hi gnome,a suggestion for securing your prod.Instead of using a turnbuckle,use a rectangular piece of metal.Cut a slot in the metal slightly larger than the width of a nut that that will fit the turnbuckle lashing screw.Cut away the surplus metal on both sides of the slot leaving two 'ears',one either side of the slot,about 1/8th inch thick,and a 'base' plate the same thickness.Drill a clearance hole through both 'ears' parallel  to the base of the fixture,so that the nut can sit between the ears clearing the bottom of the slot.Drill and countersink 2 holes in the 'base',for fixing to the stock.Place the nut between the ears,and screw on the turnbuckle lashing screw.When the turnbuckle lashing screw is through both of the ears,turning the nut by hand and with a wrench will tighten or loosen the lashing.You could inlet this fixture into the stock,which would make it neater.If you have threading equipment(suitable tap and wrench),you could make a larger nut,or other more suitable equivalent type of nut to go between the ears that would be easier to turn with your fingers.I hope this suggestion works for you,and helps to improve what is already an excellent job.
                                                                        Hermit.

Nice build Gnome

Chaz

Hermit can you draw a picture, sorry not following what your saying.

Todd

Hi Todd.
          Nothing would give me more pleasure(and save me much intellectual pain!)than to publish a drawing,but at the moment,and for the immediate future,I have to rely on words.we all know what happens when you screw a nut onto a bolt,or threaded rod,the nut travels down the rod,until it is stopped.If you confine the nut between 2 fixed plates,with clearance holes for the rod,and sufficient clearance for the nut to rotate,and hold one end of the rod(in Gnome's case,put a hook on the end that will attach to the prod securing cords),when the nut is turned,the rod will not rotate,but will be pulled through the 2 fixed plates,and the whole fixture will become a tensioner.I hope that this posting,along with my previous posting makes things clearer,and am I ever glad that I don't have to write assembly instructions for Ikea furniture!!!!    

Gnome, that's awesome. I love the shape of the stock, and that quick-release binding is really sharp. Great stuff.  

Greetings;

 It has been a while since I have logged on the site, boy have I missed a lot! Great build love the look!!!

jds6

jeep wrote:very nice build! Elegant and imaginative design love it! Cherry is a very nice wood.
I am always surprised about what it seem like a very short band with the Slobow prod. Personalty I would  had add 1 or 2 cm of band and put the prod mortise a bit more high  this alloyd a smaller prod angle in the stock, less stress  and better efficiency for the prod harm. Prod mount  interesting and pretty, but preparing the rope like this is not longer then to do  steel stirrup? for about the same weight?
I am using the same trigger system I also think the pull bit long but it is efficient and easy to build.Wy do you choose this quite small poundage for the prod?

Jeep, I've got the prod mounted low so to allow clearance for the cock feather slot. I could have put it maybe a quarter inch higher, but didn't want that slot to go all the way down to the top of the prod for strength. The binding I have now is much lighter than anything that I could do with steel, the body of the turnbuckle is aluminum. 165 pounds is plenty strong for my purposes, and the strongest available from the vendor for a steel prod with this powerstroke.
Gnome

Hermit wrote:Hi Todd.
          Nothing would give me more pleasure(and save me much intellectual pain!)than to publish a drawing,but at the moment,and for the immediate future,I have to rely on words.we all know what happens when you screw a nut onto a bolt,or threaded rod,the nut travels down the rod,until it is stopped.If you confine the nut between 2 fixed plates,with clearance holes for the rod,and sufficient clearance for the nut to rotate,and hold one end of the rod(in Gnome's case,put a hook on the end that will attach to the prod securing cords),when the nut is turned,the rod will not rotate,but will be pulled through the 2 fixed plates,and the whole fixture will become a tensioner.I hope that this posting,along with my previous posting makes things clearer,and am I ever glad that I don't have to write assembly instructions for Ikea furniture!!!!    

Hermit,
I get what you're saying and I'm going to give it some serious thought when I get back to the lab- I'm on a driving tour of the Midwest at the moment. Probably not exactly as you describe, but the same principle could possibly be applied and end up a bit simpler and more elegant than what I've got now. Thanks for the input.
Gnome

Samuel Wilhelm wrote:woooah... looks so smooth, how many hours do you use on crossbows like these?! i only use like 3-4 on my shitty crossbows....

Thanks, Samuel, and I'm not even done with the finish on this one, LOL. Once I get down to the final shape I probably don't spend more than 3 or 4 hours sanding. I did treat myself to a new batch of sandpaper for this project, instead of the box of torn up scraps I've been hoarding for 20 years! I got every grit available from 80 to 600 and used them on this stock, I guess it shows. I put one coat of linseed oil to get an idea of how the grain would look, but I still need to do a final rubdown with steel wool, another coat of oil, and then beeswax.
Gnome

Very nice looking build!    
I think it is an interesting combination of old school and new school and you pulled it off well.
On your Black Delrin roller nut, did you reinforce the nut with some kind of steel at the tickler contact point or will the Delrin handle the wear?

Jaeger,
I always put a steel sear plate on the roller nut, except with a couple of small pistol crossbows where the rest of the trigger mech is either also delrin or brass, and the pressure is not as great. I'm thinking I might post my process for doing that here, but it will require some illustration because I don't think I can explain it very well.
Gnome

Finally had a free afternoon I could back to work on this one. Happily productive: I fine tuned the prod mortice and got straight and true, and decided to use shrink tubing around the prod tips instead of leather. I just got a half a dozen test shots out of it without any sign of damage to the loop ends of the string. Next up: the "iron" sights. I have an adjustable rear peep sight that mounts on the scope rail, but I'll need to fabricate the front sight. I'll probably start by repurposing a pin or three from an archery sight and see how well that works.
Gnome

Back to Kenh's question, how does it shoot? Only OK. I'm going to rework the front end pretty severely:

My experimental prod binding was a good learning experience, but otherwise a waste of time, it doesn't really hold this steel prod securely enough for more than a couple of shots before the shock loosens things up. I think I'll see if I can get some screw-type irons from Slowbows, or see if I can rig up something similar myself.

The mortice for the prod is too low (you're right, Jeep!) so I'll be fixing that as well, which will mean splicing some wood in but I think I can handle that without it looking too bad.

The stirrup is awkward, and ended up not being big enough for me to get the toe of my hiking boot in and out of without getting stuck. That was probably a comical sight the first time it happened, if anybody had been there to see it. Worked fine with the sneakers I wear around the shop!

It might be easier to start over, but I'm so happy with everything else, the look and feel and balance of the stock, the lock mech, sighting system, etc, that I think it's worth salvaging.
Gnome

So I gave up on my prod binding experiment and ordered some screw down irons from Slobows. Here are the parts provided, plus a standard foot stirrup, not pictured:

 
Never content to leave well enough alone, I felt the need to customize the parts. The decorative pointy bits had to go because they just wouldn't fit on the stock, but that got me thinking: how much of that metal behind the threaded bit was really necessary? The only reason I could figure you'd want it would be the added stability, keeping the irons flat against the tiller. Turns out I was right, but I had to go ahead and chop off a bunch of metal to prove it. Here are the parts after I got through with them, including the foot stirrup which at the last minute I decided to skeletonize rather than just trim down. A spur of the moment decision, turns out the be the thing I'm happiest with on this build, it's lighter and a stable platform, and I just like how it looks.

 
So of course I had to modify my tiller, and I had planned on raising the prod mortice up to a better angle anyway. I cut out the top of the morice and fixed the angle, then glued in a block of laurel wood on the bottom. The square hole for the screw anchor is half on top of a half inch dowel, don't think that hurts anything. So now the only really noticeable remnant of the previous prod mounting method is that aluminum lined hole where the original stirrup was mounted. Not sure what to do with that, maybe a sling mounting point.

 
and here it is, back together again in firing order.

 

 
I mentioned that lopping off so much metal off the irons wasn't the greatest idea, when tightening them down the tension pulled them away from the tiller at an angle, and when the weapon was fired they moved away even more. I had to think about a solution for that for a few days- wish I'd thought it over that much before I busted out the angle grinder in the first place! Here's what I came up with, a hole drilled in each iron and a skinny little bolt. Self inflicted problem solved.

 
I carved some pretty major finger grooves into the tiller, which gives a more comfortable grip and better "memory" about where to put my fingers to keep them safely out of the way.

 
I also carved out a channel to bury the picatinny rail a bit to bring the profile down.

 
I had a red dot scope in mind from the beginning for this build, and I've been playing with a telescopic sight on it, but I want simple iron sights as an option as well. I've got the rear set up, the last step on this build is coming up with a front sight. I don't want it in the way when I'm not using it, and I'd rather have it swivel or fold out of the way than come off entirely, so it may take some design time and trial and error to come up with something I like.


Gnome

Hi Gnome,
Just beautiful, love the design,it look more functional  ,perhaps,to say something, I still think the brace height is a bit small: inch or inch and half more would have given possibility to low down the prod angle and increase the pretension.

Hey Gnome,

  Cool is Cool

Chaz

Thanks, guys. Jeep, right now the brace height is 3.5 inches, pretty much exactly what is reccomended for the prod. I do plan on trying a thicker string at some point, and will make that string slightly shorter so that I can keep the downforce on the bolt track light without altering the prod angle. And of course that will raise the brace height a bit and correspondingly adjust the pretension. This one is working too well for me to make any more major changes, I'm callig it done! But I do have a second, identical prod on the bench. Maybe I'll play with a taller brace height on the next build!
Gnome

Wow, great looking bow! I just love this stock, it's like a sculpture with the deep grooves. The cutouts in the stirrup look fabulous, as well. Very inspiring work, thanks!