New Trigger

The Ballistikraft originally used a smaller quick-release trigger from an earlier machine, but I decided to make a larger version to handle bigger loads.


The main body is made from 3/16″steel and cut with a hacksaw. That took a while.


I wanted to make it look fancy so I added some mesh to the outside. In retrospect I probably should have used bolts to hold it together rather than welded pins, but I don’t anticipate any reason to take it apart again.


The safety has two pins: One keeps the jaws closed and one keeps the trigger handle shut.


This trigger is based on plans from this website, which originally came from the old Catapult Message board:

Trigger Plans



Update 2018

I haven’t had a lot of time to work on catapult stuff over the last few years, but I hope to be able to update with new projects/info over the Fall/Winter/Spring.

Current plans are to make a medium-scale (about 4.5 foot axle height) version of my floating-axle modred trebuchet, designed to throw 1.5 lb. pumpkins.


R.A.M. in Action (Video)

So the plan is to update as the new machine is being built. I’m most likely going to start with the rolling axle and their tracks. I also have video of past Burlington events which I still need to edit and upload.

New Arm


The arm has been replaced and seems to be strong enough. A new piece of thin rectangular steel was cut, and reinforced via a smaller, but thicker, piece of steel placed inside it.


The arm also has 3 solid guy wires instead of rope. The tower that supports the guy wires has been lengthened for better leverage. The counter-balance for the arm was moved outward to account for the heavier arm.

Quick-Change Disposable Sling

For smaller catapults, I like making slings out of duct tape- it’s easy to make and relatively strong. But they are prone to tearing and can be bulky (especially after being repaired). This was a problem with Drill Sergeant, but I think I’ve come up with a good solution.


A combination of Tuck Tape (a strong polypropylene sheathing tape) and duct tape makes for a very strong, lightweight and flexible sling material. Wrapping the Tuck Tape sticky-side-out around a piece of drain pipe gives the perfect shape / size, which is then covered with duct tape (sticky side in).


A small wire frame is then taped on. The sling lines tie onto the frame. That way, if the sling needs to be replaced, all you need to do is cut the tape off the wire frame and tape on a new one. Even if the new sling had to be made from scratch, the whole replacement process would take less than ten minutes- useful in a competition scenario!

Drill Sergeant, Pt. 3

After a short (well, maybe not so short) hiatus, I finally have some time to work on catapult stuff.


The new chain drive works really well, and the drills don’t seem to mind being bound together (both drills are the same make, voltage and speed so I didn’t anticipate any problems). With just the one drill, the average max. RPS of the arm is 5.7, and with two drills this increased to a nice 7.5 RPS (450 RPM).

I also tried different ratios between the winch drum and the arm, but it didn’t make too much of a difference.

The next task is to improve the sling design- at high speeds the projectile wants to be forced out of the holder. This was a problem at Burlington, with pumpkins falling out prematurely. Once that is done I’ll be able to test the range.