The serious build

Had an appletree log lying idle for a few years.
Decided to put it to good use.
So this has been on the works last winter

Hunting weight bow. With low gear (1:12) windlass for safe and comfortable spanning.

This has been shot a couple hundred times and is holding together. Allthough practically every part needs to be replaced before this is finished.


Dodoo-list:

- "friction adjusted" Sight rail needs to be fixed to the mount with spring loaded button for quick range adjustment.
- Hemp cable windlass frame works OK, but could be nicer looking.


- Longer more ergonomical trigger lever.
- New trigger frame out of 4x20mm flat stock.

- Replace 70cm bundled bed spring bows with solid 80cm rowan staves to improve accuracy and allow increasing draw weight from 120#ish to couple hundred + .

Excellent, NF; really nice!  A great "upgrade" from the experimental platform to the
PaleoCompound Mark I.

Excellent, only the essential !! Do you have any idea of the arrow-speed  whit this system ?

Probably Mach 2 with a chopstick bolt!

jeep wrote:Do you have any idea of the arrow-speed  whit this system ?

Fast enough. 35 cm long 7mm hardwood shaft goes well over 100 m/s. While shooting to 40m, scope could be lined with bolt track like zeroing a rifle. Lightest bolts tested so far are about 2grams , under 40m range these were flying too fast to be seen with naked eye.
I have not had time to do any precise speed measures.
But calculated practical limit for this design with string of reliable thickness is about 200 m/s. - 230 might be doable.

- btw , use bbq sticks - chopsticks are too heavy.

Some progress

First version of range dial - military rifle style sliding bar.

Worked well on paper. But in practice , recoil kept shaking the dial button. ( plus new longer roller for windlass , to keep its edges from grinding the cables )

Second version is more traditional airgun style

Gear wheel can later be mated with second bigger wheel for a quicker dial.
Also filed a new scope rail out of solid 4x12mm. With some extra length for secondary open sights to be added.
Forward balanced heavy rail makes supporting spring unnecessary.
Those brass plates will later be riveted and epoxied after wooden parts are finished.

Lock

Same as the prototype . Just more durable build, carved out of 4x20mm flat bar. Nail hooks on tiller were also replaced with a solid bar.
Extenson of trigger on left side was intented to be waste. But I think I'll leave it there and try secondary flintlock style hammer mechanism on sight mount. This should make more comfortable and accurate triggering.

New set of bowstaves

120# Ikea caravan matress springs are to be replaced with solid wood prod. Allowing the weight to be doubled.
Bit longer string too. This should get off some MOA. Plus shorter arm stroke might improve dry-fire speed a bit. Lets see if this can go BANG!

Lookin' really good!  I think you need a bamboo housing for the scope though - to keep it as 'paleo' as possible!

Going bit slow, I like to keep this thing operational at all times


New bows installed.
Blobs of light paint on sight rail are phosphor paint. I live 61 north and this time of the year we have only been getting daylight during office hours. So some kind of nigt sight was necessary.

Those arms need to be replaced. They are not optimal as they were ment for a shorter and more flexible bows. With this set up there is nasty stack in late draw, well over 100kg with very little energy gain.

61 North?  Where ARE you?  Norway?  Sweden?  Finland?  I really like the way this project is developing, Nerd.  I gotta try building a trigger/cocking mechanism like that...

After some serious field testing the trigger mechanism provedto be too stiff for accurate shooting. Trigger pull was too long for the planned hammer mechanism to work reliably - hang firing crossbow is not fun.

So I decided to redo it once more. Special thanks to jaeger22 for encouragement. Seeing somebody else to succeed convinced me to try again.
This time with multi axle lock



And a secondary spring loaded hammer & pin mechanism through the stock.


And this time it works.
A true hair trigger , delight to shoot.
Trying to keep target in sights while sqeezing that Roman siege engine trigger was a pain. - But this is fun and easy.

( yellow blob in last picture is water scale for leveling sights )

Now everything works, just a matter of cosmetics to finish this.
Metal parts for lower trigger,
Stock needs to be shaped,
A yet new set of arms to rise weight from 120# to 200#
( allready made one but they came couple mm too long and narrow )
and some kind of wide field open sights to replace the narrow scope. Scope is sub-optimal aiming device in a field crossbow.

This is a very interesting build!   Lots of unique and innovative ideas all in one build. Great job!
Please keep us informed.

Allmost done. An elevated cheek plate and properly housed trigger lever are there.

As are new arms -the weight is slightly below 70 kg ( ~150# , extrapolated from power curve, I can push the string back against scale to about 60 kg ) , but cables bending to Z fatten power curve so energy seems to be same or more than with earlier unpleasantly stacking 200 pound version.

Ropes holding windlass look a bit ugly - need to remove those at least once to finish the stock. Hemp rope will probably be replaced with metal hooks.

Needs a trigger guard, some kind of safety glutches for both locks and wire diopter to be replaced with sheet metal.




Had a chance to try target shooting from 70m . Sight was zeroed to 30m so I aimed bit high. First bolt went over target and disappeared in the woods behind. Second one I aimed just slightly over target butt. It went over but I managet to find it stuck on tree stump some 10 paces behind at height of bullseye. So I guess this is good for 80 meter aimed shots.

It has been too windy to seriously test long range groupings , but 15m bench rest shots using a single bolt keep going through the same hole, wich is more accurate than my worn out bolts. So next project should be a set of match grade bolts.

What will happen to the power curve if the back bow is shorter one? Like this
" />
Not much of a doer myself but like to think of different setups. Admire your creativism Flintstone

In theory there would be more pronounced let-off at late draw.
In practice it makes the arms twist in vertical dimension.
And unlike normal compounds , there is no connection between cam and opposite limb. So if there is true let-off the arms easily "flip-flop" when triggered, leaving one side locked to back position and other one flying away.

My very first compund prototype of this type was in fact done that way, with only one bow. It was a conventional crossbow with cables fixed to the butt. - Sort of worked, but I abandoned it for reasons above.

Wow, very cool project you have here. An extremely interesting design...I'm pretty new to crossbows, but I must say I've never seen anything quite like this before. Is this based on any historical model, or strictly your own creation?

OrienM wrote: Is this based on any historical model, or strictly your own creation?

You could say it is my own design. Of course there are components that have been seen earliear: Inswinger ballista from late romans ,double bow from medieval china .

Fascinating design and work! I just started to dream about such a piece with heavy steel prods. It would be more than deadly.

Butt has been shaped bit narrower for better gripping -


Really helps, 10mm groups from 15 meters . Off hand , standing upright. I could not do better with an air rifle.
This is starting to be the way it was supposed to be.

This is the final update to this thread.


The PVC roller on windlass began to fall apart, so a replacement was bent out of 12x1mm tube. It now takes six turns to draw the bow, so reloading is bit slower but also easier due lighter transmission.
A ratchet bar has been added to sight to act as a range dial.
There is a small sliding loop of wire around trigger assembly that locks the intermediate trigger down - this makes good enough safety.

So this basically done. Guess somebody else could still see some cosmetic nonsense needing to be done, but I am really not gay enough to care about aestethics.

I zeroed the scope to 40m with 9gram bolt. A 4g bolt hits the same spot at 80 m distance. That is good enough. This would make nice "bird-rifle", now all we need is FEXIT so I could use it as one.