Burlington 2019

After several late-night fabrication sessions, Son of Pendragon was ready to go. I had no time for practice shots, so this would be interesting.

The firing line on setup day. Gourdinator had not arrived by the time we left. Only four machines this year, unfortunately.

SoP ready to go. I couldn’t figure out a cocking mechanism in time, so the counterweight arm was lifted manually and the weights added via ladder. Definitely not the ideal solution as far as safety is concerned, which we will have to change for next year.

“Gladiator Gourd Girls”, a traditional trebuchet made by Girl Scouts.

“Bad Wolf”, an onager (powered by twisted ropes).

And of course Gourdinator, a floating-arm-trebuchet that has competed every year.

SoP won its division with a shot of 447 feet (with a 1.4 lb. pumpkin). That works out to almost 5 feet per pound of counterweight (compared to about the 1.5:1 ratio Ballistikraft had). Can we improve on that? Find out next year!

Video footage to follow.

 

SoP Progress

I’ve been pretty busy lately and haven’t had time to post updates, but here’s a few photos:

Each “trolley” coming together. These are the “wheels” that slide across the tracks.

Please excuse the ugly bird-poop-quality welds- if I had the time I would have made them much nicer. But they’re strong, that’s all that matters for now.

I couldn’t find the right sized rollers for the arm fulcrum (aka the “FUBAR”), so I had to make them custom.

The frame is coming together.

The lengths of recycled Unistrut I used for the tracks ended up being more warped than I realized, so I wasted a lot of time straightening them out. Fortunately, once I was able to get the track/trolley assembly together, everything rolled relatively smoothly.

Hopefully I can post more updates when I can. Only 10 construction days left!

Son Of Pendragon

A lack of time and funds threatened to postpone construction of the new machine, but after a few issues were resolved I think it will be ready for Burlington in time.

Above you can see the 6.5′ pieces of unistrut that will be the tracks which the axle carriage will slide on. A third piece has been cut in half which will be welded underneath for strength. The unistrut pieces were salvaged from a previous job.

In the above photo, the piece on top is one of the reinforced tracks, with a WIP below it. The flat steel with the odd cut-outs is another salvaged piece that will be cut up and used for counterweight (each piece weighs 18 lbs, and I have 10 of them). The three pieces of unistrut below it will be made into the CW hangers, and finally the rectangular steel pieces will be main structure of the axle carriage.

Each side of the axle carriage will get three axles and bearings (as the main “wheels” to roll down the track) and four rigid casters will keep everything aligned.

Unfortunately the bearings I bought were metric, and won’t fit any of my axles without modification. As it turns out, the store I bought them from sells both metric and non-metric bearings and I didn’t notice. Oh well.

More updates to come.

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

 

Pumpkin Pitch 2017/18 Videos

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

Burlington Pitch 2017

Burlington Pitch 2017 (Slo-mo)

Burlington Pitch 2018

Burlington Pitch 2018 (Slo-mo)

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!

Oops

It looks like the arm couldn’t handle MORE POWER (*Tim Taylor grunt*).

So, that will need to be replaced. Fortunately, everything else seems to work relatively reliably.

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.