I forgot that I hadn’t uploaded any footage from the 2017 event, so I finished that while editing this years’ videos.
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.
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.
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.
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!
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.