Time for my first serious crossbow build

So I just got back from the wood store. I have a great piece of Bocote for my tiller, some ebony for the trigger parts and a couple nice grained pieces of hickory for the prod limbs.

Here's my plan in a nutshell. Split limbs, fiberglass backed hickory (with metal prod limbs to follow if the bow proves worthy), I will be making this a single shot with a slide mechanism and handle cocking device. There will actually be two handles that join into one when fully cocked. I don;t know if this design or parts of it are unique but I am really looking for design feedback. I know some of my elements are not the usual crossbow fare so I am really open to idea or concerns about the design.

Basically I have a sort of "reed trigger" design that I have been working on that I think will work well scaled up. Basically, it's the repeater style cocking with a slide that moves back and pulls the string. I won't be building a fixed hopper on this because I want to use fletched bolts but I want to build an optional hopper attachment that can be mounted for "automatic" style shooting with fletchless bolts.

The reed trigger is just a flexible piece of reed material that slides with the assembly and comes to rest over the trigger pin which levers the string out of it's catch. I will start drawing up some design ideas and posting them here...if I don't just go ahead and build it.

Either way, pics to follow!

Wow, Jake: You have chosen some seriously hard-to-work woods for your first crossbow project. I would have recommended something a little lighter and easier to cut. Your finished product will be heavy as bricks, but very pretty, once you get the finishing done to perfection. Hint: Wear a good respirator when working with ebony and any sort of rosewood, in particular. Geezer.

I knew that the hard woods would be a problem but I am not afraid. I have my dust masks and vacuum sander ready to go.

I am off to the tool store to get a heavier blade for the bandsaw and some chisels this morning. Are there any special tools you recommend Geezer? Where do you find a spoke shaver? Also, where do you go for your wood working tools? I am in N Austin, Wells Branch.

Oh, and I think I am ditching the split limb idea. If I switch to a metal prod I don't think I will want a split limb design.

Jake: Being in Austin Texas, I usually get my woods from Fine Lumber and Plywood on Dungan st. (North Austin) You should be able to get a decent spokeshave from Woodcrafters on 183, but I have found Breed's Hardware, just N. of the university to be substantially cheaper. Get a Stanley or Record spokeshave and you'll be fine.
As for very hard tropical woods: The bocote is a sort of rosewood, which will be Very Hard to Cut, Hard to plane, hard to finish, etc. It requires extra work at every stage and will make a Very Heavy finished piece, but if done right it will look very nice. Oh, and did I mention the silicates in the wood, the allergenic properties and mild toxicity? Well, that's another issue.
From a purely commercial point of view, buying a fresh bandsaw blade every time I want to cut out a stock is pretty prohibitive. So THAT's why I don't work in rosewoods, lignum-vitae, ebony, etc. Even so, if you keep your tools really sharp and keep at it, you'll turn out a very nice product... eventually . Have fun stormin' da castle. Geezer

Yeah, that's where I got my lumber as well.
What about metal, spring steel and such? I have found a few places, most are closed today though...

So far the Bocote has been ok, to work. I have the basic tiller shape done and I am making the slide channel now. This wood is BEAUTIFUL! I can't wait to get some good shots of it up.

If I may chip in on the fun

Steel is good, but heavy(if you know a little about bowyery, then you'll know that heavy limbs move slower ), you will get better velocity from a fiberglass prod, there are 150lb replacement prods being sold on e-bay for around $20-25 vs. steel $60...not to get on the bad side of the Alchem, it's just that for a beginner project it might be a little easier on the budget + these limb's dimensions allow for a three-fletch arrow track design that you want.

Let me know if you'll be using the fiberglass prod, there is a specific mounting angle and draw length for it.

Definitely post a pic of your trigger and spanning lever!

Ivo

I think I am going with a pecan (hickory) and fiberglass design. I will be starting a bit oversized and cutting it down as needed. If I do go to metal the tiller and slide mechanism should be overbuilt enough to handle it.

I got the rough tiller and the shuttle slide done yesterday. I will take shots today as I place the trigger and reed assembly and start on the bow shape.

Oh...and the spanning lever will be built in and operated by a handle that splits out and locks forward into a front mounted handle receiver. I have the basic idea down but the details are still coming together.

So I finished but I neglected to take very many mid-build shots. I have a few and a vid of the first firing tests that I will post when I get a chance after rennfaire.

Here's the bow, need to get some better shots of the wood. I decided to ditch the crank and made it cock like the gastrophetes. It's simpler, lighter and definitely more beautiful. I estimate the draw at around 130-140# and it shoots very nicely. I was able to get a 6" grouping at about 40 yds with my funky homemade arrows. I am definitely going to be working on better bolts.

Looks good and sounds interesting

"No lever" decision could mean a number of things
How long is the draw on this bow?

I'm also wondering about "cocking like gastrophetes", I don't get it, is the trigger mech/rail assembly a moving component?
6" groups at 40yds...I can't find any sights on it...how did you manage that?
String looks pretty thin for +/-150lb, what material did you use to make it?
Also I believe I missed the trigger type on this one?

All in all, the way you explained it, this little jewel holds some interesting details...please shine some more light on it and do a few more close up shots...and when you are uploading the photos, simply set "Resize image" to "No"...the forum will fit what ever size image in to the window with an option to expand to full size.

Ex.

Yes, the top deck with the bolt path and trigger catch and "reed" (diaphragm?) slide together. I have a rear sight and I just line it up with the front of the arrow groove and it is sighted almost perfect for 40 yds...just a click down gets me dead center....I didn't measure my range though, it may be closer to 100feet. The thing I noticed most was that horizontal axis was almost perfect at all ranges but the vertical axis was a different story.

The decision to leave the crank out was just the elegant solution. The crank would have added a ton of weight that really didn't need to be there. Secondly, the steel in the channel would have been pulling upward and placing lots of strain on the body guide edge. Lastly, it was just too much weight to pull easily and work the way my smaller repeaters do. It was easy to add the bumper out front and just push it down to cock....so that's how I use it. The draw length is 13" and the string is 10 strands of dacron, it may need more. I may be off on my draw# estimations, I am definitely not very experienced in this matter.

when I get home I will do more precise testing with a better bunch of quarrels and post more details.

jake-owa wrote:It's simpler, lighter and definitely more beautiful. I estimate the draw at around 130-140# and it shoots very nicely. I was able to get a 6" grouping at about 40 yds with my funky homemade arrows.

6" at 40 yards is excellent grouping, good enough for any production crossbow with factory-made bolts.

Checking more it looks more consistently like 10" grouping @100'.

Working on aluminum bolts now, need to get a tap and die set.

That really is a cool looking bow. I must say well done Very tactical looking, now it just needs to get some Picatinny rails on it so you can hang all the little do-dads on it like a proper tactical weapon
And 10" groups at just over 30 yards aint to bad either.

Thanks Basllisk! I have made up a bunch of feathered bolts and I am going to test some more today. I will post some pics and results by the end of the day. Just have to get a couple trigger details worked out. Trying to shave a few lbs off the response. Luckily, this place is a wealth of information.

I am cracking up...I was freaking out that the bow was shooting slower today, a little less power. I got home and pulled the string off and checked it in the string jig and it actually stretched about 3/4" since I set it up.
I guess this is why crossbows have such thick strings! Duh.

If after 300 or so shots I gained 3/4" I guess I will try to double the strands, to 20.

Anyway, sorry to link but here are some shots of my wife cocking the bow (in our daughter's jacket ) to give an idea of operation...if anyone is interested.

Opening the slide

cocking slide back

Locking slide back

Loading 8" aluminum bolt

And of course aiming...actually that is an older wooden bolt in there.

Nice bow I like the spanning mechanism. Not very traditional but looks simple and very easy to use

Thanks, that was the goal. My biggest problem now is trigger load. I am going to make a few changes and see if I can get it down some. Seems to be around 15 lbs now...ugh.

Did a pseudo-speed test today by recording. The 411 grain bolt shot 100 feet in .750 seconds, minus 10% for returning sound at 1,100feet per second gets me, by my very rough calculations, in the range of 135 fps. Not bad for a home made crossbow and a fat aluminum bolt I think. The471 grain bolt spanned the 100' in .778. I guess I should make some 340grain arrows and try them. I assume it will be around 160-170fps which should be workable for rabbit hunting...no? I bet with the right shot Icould take a small deer at 15-25 yards. I am able to get very tight groups of 6" of so at 20 yards.

I see that the problem with this method of speed measurement is that it takes an average of the entire arrow flight where a chrono placed 10 feet from the muzzle would take a max speed reading. If anyone in Austin with a chrono wants to humor me I would love to get a "real" speed reading of this puppy.

Anyway, not exactly suiting up to go hunting yet but having fun so far.

So I guess that about wraps it up. I added a piece of springsteel from a sawblade to the reinforce and add some #age to the trigger reed and it lightened the trigger up considerably, feels like around 10 lbs now which is acceptable. I shaped the tiller butt a bit to fit the hand better so smaller hands can handle the trigger better. Fastened the bow on better (thanks for the tips) and oiled it up one last time.

I am calling this one done, for now. Moving on to a recurve model for the wife. This will have the same slide action cocking but different mechanics and a different trigger.