LARP Mini-Rifle Crossbow (V2/V3) with Prod

[This device is a work-in-progress and awaiting documentation, build instructions, etc.]

[Finally I think I have a reliable way to do arms.  Pulltruded carbon fiber bars covered with 3D printed skins for added protection.  Will be testing this out over the next couple of months and if it works out, I'll release the full design.  Right now I have three basic sizes that are in testing, this size (mini-Rifle) as well as a large Hand-Crossbow size, and a small Hand-Crossbow size.]

For the Prod (as pictured) cut and tape 3 fiberglass rods together.  I used a single solid white fiberglass from a driveway reflective sign post in the center, and two hollow green garden fiberglass rods as the outer ones.  It is not tapered in any way, not terribly efficient or elegant; it relies on simple brute force to do the job.  But in practice I've found this “minimal effort” prod to be more reliable and consistent than PVC.  In the future I'll experiment with shaping G10 (garolite) into a proper prod, but that is not something just anyone has the tools to do, or can do.  Most crossbow prods I can find online are simply too strong for this application, being between 80lbs to 150lbs or more.  The center rod should be slightly longer than the rest so that the string can be placed on the ends of the limbs.  Pad the prod with a little bit of foam on the front and back to absorb the impact, and so that it sits tightly in the front structure of the device.  

Alternatively, make something like a wooden prod from a highly pliable piece of wood, or use an actual crossbow prod if you can find one that is low enough draw weight.  

Velocity with the heavy bolt pictured (1550 grain weight) is ~44 ft/sec.  Better than the hand crossbow where the best case velocity is ~41 ft/sec (V3) and ~38ft/sec (V2).  With lighter bolts, the velocity increases, but expect it to peak out around ~70 ft/sec.  When tested with a 920 grain bolt the velocity was 53 to 57 ft/sec, depending on how tight the string was at the stoppers.  With a 460 grain bolt, it peaks out at around 68 ft/sec.    I have no idea if this device will work reliably with bolts made from 6mm diameter fiberglass shafts but I will test that in time.  It may require the newer “tooth” trigger design used in the V3 hand crossbow, which I expect is only strong enough for ~30 lbs.  So it would need to be a larger device with a longer draw length if this trigger is used. 

All models are designed to be printed without support, tested on a Mk3s.  Use PETG or better (no PLA) with at least 3 perimeters/walls and at least 6 top/bottom layers, 10-15% infill.  

There are several options available on features like the stock, riser size, and rails to accommodate different bolt diameters.  This device requires several sizes of both M3 and M5 machine screws.  

M5 Machine Screws:  7x 30mm and 4x 35mm on the top front; 2x 40mm on the understructure, 2x 50mm on the prod brackets, 2x 40mm on lower handhold nub (optional).

M5 Nuts (embedded):  2x in prod brackets, 11x in lower front.  

M3 Machine Screws:  

Some Amazon and other Links to the Kits I used to build this device.  Note these are just the ones I purchased for this project and many others.  Most of them contain way more than you need.

Ender 3 Spring Set:  https://www.amazon.com/gp/product/B07V6YCYP5

Spring Kit (1):  https://www.amazon.com/gp/product/B0002KO1X0

Spring Kit (2):  https://www.amazon.com/gp/product/B000K7M36W

M3 screw kit:  https://www.amazon.com/gp/product/B0812TYT5L

M5 screw kit (1):  https://www.amazon.com/gp/product/B08HXLQ7K5

M5 screw kit (2):  https://www.amazon.com/gp/product/B07HDJZ76R

Fiberglass Driveway Marker (strong):  https://www.homedepot.com/p/Everbilt-48-in-2-Sided-Driveway-Marker-Red-31454/304518983

Fiberglass Driveway Marker (weak):  https://www.homedepot.com/p/Everbilt-48-in-Reflective-Rod-in-Orange-31474/304685319

Garden Fiberglass Rods (medium):  https://www.amazon.com/gp/product/B08Q2Y6Y36

TODO:  Standard V2 trigger is good for ~35 lbs. reliably but not much more.  Add the improved V2 trigger and the V3 trigger.  

[Work in Progress, shares many pieces with the "Modular SlingXBow Family" Project and some of the shared files may not have been added yet]