Craig's Blog


I'm Craig, the administrator of this site. This page records my hurling events, ideas and stuff like that.

Current Plans

Gah. I'm busy. I do have some hurling projects in progress though. Top secret!


Very short descriptions for now. Longer descriptions will be written on their own devices pages soon.

Mini KA

See recent blog posts and the Mini KA page.

Onagenator 2

Frame is 1'*1'*1', arm is around 2 feet. Best throw was just over 600 feet with a golf ball. See the onagenator2 page for pictures.

Onagenator 1

My first torsion device. One foot long frame, 9 inch arm, 3/8 inch diameter bundle. Best throw of about 210 feet with a golf ball. Has also been used with a slotted arm to throw disks. Pennies disappeared, and one ounce washers flew nicely. I could even get the washers to air bounce, as in to be thrown downward and curve up before hitting the ground. I hope to test and film it skipping coins on water some time, but a new slotted arm, and probably bundle are needed.

K'nex FAKA

The first FAKA made. I don't remember the stats but they will be here eventually. It had about a pound of CW and threw 72 feet with a bouncy ball of around 1/2 ounce (recently lost by Mini KA impressive shot). Arm is somewhere around 16 inches long. I also made a floating everything whipper in the frame, which worked well, but was never perused.

Golf Ball Beast

Threw 310 feet with a 5 pound CW, and 690 feet with 15. It is a floating axle King Arthur with the rail at around 3'2" off the ground. See the Golf Ball Beast page for more information.


I have a un-named ballista. Shoots arrows 100 yards and has roughly 1/2 inch diameter bundles.

Tiny treb

Tiny treb was made out of boredom with a few feet of string and some bamboo skewers.

First treb

Well, not actually my first treb, it is the first one that worked well. Many years before there were pathetic attempts with k'nex. Made for a science fair project that got second in my school (out of several hundred), and placed in the top 10% at the district level. Not bad considering my experiment was fundamentally flawed (well, I realized there was an error, so the conclusion was just "I don't know why," not something incorrect), but I learned a lot about trebs, and scientific processes. My data contradicted my research and suggested that FCWs were better, and the longer the hanger the worse the range. I knew there was a flaw somewhere, but I did not fully understand until a few years later (thanks to the Hurl mainly) that the tuning is greatly different for FCWs and HCWs, and my treb was simulated and designed as a FCW first. I threw a golf ball (as an FCW) 20 meters (well, just over 19.5) with a one meter arm and 2 kg of CW. Not bad for a first treb. It had ball bearings on the axle, and a tapered fiberglass arm made from a fishing pole blank.

Mini Whip

A small whipper (16 inch arm) with a 15:1 arm ratio and 1 pound of counterweight. It has not had any real testing, but has thrown random small objects at good angles at high speeds in my basement. Still functional arm wise, but needs a frame, and maybe a new sling. The old frame was converted to k'nex FAKA's frame, and can still work for it.


Poor CW Energy Transpher

category: Blogs / Craig's Hurling Blog
07 Aug 2008 01:06

I spent some time today dry firing and taking video. I have to say that with a 5 pound weight (about 8.75 total CW) falling 7 feet, I only got a small portion of the energy into my light weight 2 foot arm. If built correctly with inelastic parts, 100% could be possible, so clearly there is room for improvement.

I have some ideas to help; I'm pretty sure I can get at least half of the energy by modifying some parts, though I will likely have to remake the complex trigger mechanism.

For now, I'm going to fix the few issues (slipping knots and such) then go throw some stuff. In the bright side, this machine could dry fire safely loaded with 50 pounds. A miss fire where the sling actually deploys could be an issue though.

Comments: 0

Dry Fires

category: Blogs / Craig's Hurling Blog
06 Aug 2008 03:43

I just did a few no CW dry fires on my treb. Seems to work right, though a few things need adjustments, and needs something to prevent it from falling over forward. I think I just make sure it is not on an uphill slope, and stake the back down or something like that.

As I have progressed with this implementation of the design, I have realized several flaws in my machine that should be changed for future ones. Changes can be made to tolerate elastic parts better at the cost of arm drag for example that would be good for a flimsy machine like mine, and least until I get some less stretchy string. Also, before the CW detaches, the transfer of energy may not be as complete as I want because of the same stretchy string and some minor building errors/choices. Again, the next one will be better in this respect.

I'm quite worried about the sling. With the axle around 3.5 feet off the ground, and a 4 foot sling, things could get ugly. 7 feet of string slapping the ground/treb! Also, the tuning literally chooses the release angle, though the first throw will basically be at a random angle, and the next one should fix it, but a random angle on such a machine is bad as it might just slam the sling and projectile into the ground!

Comments: 0

Axle assembly and frame progress

category: Blogs / Craig's Hurling Blog
03 Aug 2008 00:40

I just have two uprights to cut and install, and the counterweight arm to cut and install. If all goes well, I might have it finished tomorrow.

The CW came out more compact than I thought, so it should hole a few extra 5 pound disks if desired, but I will have to modify it to work with my planned initial test weight (5 or less pounds) because the CW arm would not properly clear the arm assembly if I simply make it skinner when I remove weights as planned. Also, the primary trigger needs to be designed, but it should be trivial.

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Sling and pin finished.

category: Blogs / Craig's Hurling Blog
31 Jul 2008 03:08

I just finished the sling and adjustable firing pin. Adjusts across about 90 degrees of angle. The sling came out to 4 feet long. I have to wonder about the effects of having a 4 foot sling on a 2 foot LA.

I also gathered the remaining parts of the frame, though I still need to locate some hardware and such. I'm really looking forward to getting this thing tested, though I will have to start with just a few pounds of CW so wont out throw my local park. Looks like the treb might actually work!

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Triggers work!

category: Blogs / Craig's Hurling Blog
04 Jul 2008 21:04

My new treb may have a complex hacked together unstable trigger system, but it works. I clamped the axle to the work bench and spin the arm around. Even the sling holder and new sling configuration seems to work great. Now I just need full length sling sling lines, a firing pin, and the upper part of the frame.

Now, I think it will work. I always can confidence in the concept, but my implementation of it has left me wondering it it would actually work. Maybe as soon as next week I will be able to get some real throws off.

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Springs and things

category: Blogs / Craig's Hurling Blog
03 Jul 2008 03:34

I just added the tab that lets the tertiary trigger get released after the secondary has released. I also spring loaded the secondary and tertiary triggers. Now I just need the sling box, and hook that up to the tertiary trigger and the trigger system on the arm will be complete. Well, the firing pin for the sling could be considered the quaternary trigger, and it is not done, but I'm not worrying about it now.

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Treb Construction Progress

category: Blogs / Craig's Hurling Blog
20 Jun 2008 22:40

Yesterday I built most of the arm, and designed the sling holder. Today I started building the secondary and tertiary trigger assembly (they are timed separately). When discussing the design with my dad yesterday, I think we came up with a better way to hold the sling, and also a possible design modification. This thing is complex enough that I'm having trouble visualizing it working. Mathematically it may be the simplest treb, but mechanically it is quite the opposite. On a related note, I think I finally understand how to model arms and slings mathematically.

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More Pictures!

category: Blogs / Craig's Hurling Blog
16 Mar 2008 03:59

I just uploaded 28 new pictures of my hurling devices. I now have a much better work flow for uploading and tagging pictures. Check out the new pictures on Fickr or just look on any of the pages with image galleries. Some of the pictures are of my new treb.

Comments: 0

Next Treb

category: Blogs / Craig's Hurling Blog
10 Feb 2008 21:55

I'm not going to release too many details at this point, but I have a new design and I am planning on building it. Here are the stats:

  • LA: 2 feet
  • CW drop: 6 feet
  • CW: 15 pounds
  • Projectile: Golf ball
  • Sling: 4 feet
  • Maximum possible design efficiency: 100%
  • Axle height: 3 feet
  • Total frame height: 3 feet

I'm quite happy to finally have a design where the efficiency is only limited by how well it is built (friction etc). That 100% requires no friction and perfect tuning, but not a massless arm, or anything like that. It also looks like the 100% efficiency should be possible with much higher mass ratios, and even more drop (CW drop is easy to add). I would also like to say that the only long beams in the whole design contribute to the CW, have no bending load (possibly a slight bending load during cocking depending on how it is cocked), and only a mild compression load. The whole machine should fold up very well (could be made to fold up just like merlin, but easier) and could be easily scaled up to trailer size. It has no rolling or sliding parts, and no moving parts that can hit each other excluding the sling and projectile. This means no arm vs. hanger whipper death, no FAKA end of track slamming, and no rolling axles, CW guides or anything like that at all. Because of this, and some other reasons, it should be relatively easy to build. There are some small complex parts, but nothing too bad really.

Also, it should be the easiest treb design to tune that I have ever seen. It should be able to be fully tuned by adjusting two things (one is the firing pin) which do not effect each other. You can literally adjust the release angle forwards of backwards any number of degrees (no guess and check ether!) with out messing up the other tuning (consisting only of the firing pin angle).

The one main issue that I see is that the sling can potentially hit the ground before and/or after the release. It is similar to a whipper in this respect.

Comments: 4

Old Blog

category: Blogs / Craig's Hurling Blog
10 Feb 2008 21:33



September 29, 2007: Burlington!

Burlington was great! I will get some videos up eventually, but I don't have room to edit them now. A ton of great pictures were uploaded. See them on the main page for now.

September 22, 2007: Pumpkin On A Stick testing!

First we bent the arm on deceleration. After fixing that we eventually cut the sling loop for the firing pin, then we tried 3 pullers and broke a pulley and bent an upright. I guess I will be buying 4 stronger pulleys and a new upright. I don't think I will try more than two people again unless I can find a stronger replacement for the uprights which I don't think I would have time to install anyway.

Also, the arm got a bit screwed up when the pulley broke because the load became unbalanced because it rubbed on the screws.

The disadvantage of the double redirect system is that it triples the load on the frame which seemed to be too much with 3 people.

On the bright side, it actually worked and threw around 20 yards with a completely horizontal release. We might get 100 feet with just 2 people which would be cool.


August 28, 2007: Traction!

No traction treb yet, but the frame is nearly done (it needs 4 safety pegs installed). Plans for the arm are developing. I have some great plans, but nothing is sure yet. It will be cool; I can say that.

August 21, 2007: Onagenator 2 broken

Today Matt and I set out to test the minor changes to Onagenator 2 including a reinforced draw down loop on the arm, pins to prevent the bundle from unwinding and a longer sling. Because of space limits we used a heavier 5 ounce lacrosse ball rather than a golf ball as a projectile. The sling was too long for the heavier projectile, but the the changes worked well, too well. We increased the bundle twists in large increments to quickly get up to last times failure point where the modulus slipped. Our new pins worked (but bent) however with our greatly increased torque there were problems. First our spanner has some minor problems, but that would be easy to fix. More importantly one of the pegs in the modulus that the spanner hooks up to got pulled out of alignment as the oak deformed. This did not stop us, and nether did the breaking off of one of the onager's feet which don't do much now. What did stop us was much more impressive, the sliding release trigger rated at 150 pounds failed. I don't know how, but the trigger clearly released while we were cocking the onager. As always during the cocking and loading process all people were clear of the plane of rotation and no one was hurt, but the most amazing thing happened: we broke the arm into three pieces! The bottom break was just past the end of the bundle in the steel reinforced section. The steel clearly need more wrapping to add sheer strength as it was intended to resist compression which it did. Video will be added soon! (Sorry, no video of the break) See onagenator2 page for pictures

August 17, 2007: Burlington Info Received

Today I finally got the information I needed about the Burlington Pumpkin Pitch. If all goes well there will be a youth division 11-17 throwing 4 pound pumpkins which I will compete in. Should there be less than three entrants in the division it will not exist and I will be throwing 8 pound pumpkins in the adult division. I may take action to make the youth division exist by finding some other people to enter it and/or entering more than one device. Should this status change it will be updated here.

August 2, 2007: Mini KA day Two

Matt and I did some more testing with Mini KA today. We tried the racket ball with some more room and threw 63'4" and tested a smaller bouncy ball some where around a half ounce which got lost on top of a 31 foot high building 124 feet away. The throw would have gone about 200 feet. This shows that my Mini KA can be very efficient through a wide range of mass ratios through the adjustment of the arm ratio, secondary trigger, sling length, and pin angle.
Here is today's video. As you can see I'm getting better at video editing.


July 31, 2007: Blog Creation and Mini KA

Today I created this blog about my hurling. For earlier information see my blog on the hurl.


My Mini KA:

The day before yesterday I started making a small King Arthur inspired by the great CW I had laying around: A 3 1/4" long 2" diameter can filled with 3 1/2 pounds of solder. I grabbed a few pieces of 1/4" by 3/4" wood and started cutting with no real plan. A bit different from my normal computer modeling then building process. I finished the trebuchet yesterday and tested it today.


CW: 3 1/2 pounds
Projectile: 1 1/4 ounces (roughly)
Axle Height: 13 1/2"
Long Arm: 12 3/4"
Short Arm: Adjustable (4 1/4")
Sling: Adjustable (13 3/4")
Wheels: Yes!
Frame: 1 1/4 pounds (roughly)


Test went well. Tuning was very good, but room was lacking. My joke desktop trebuchet with almost an equal sized counterweight and projectile, but 45:1 mass ratio, threw through part of a tree and uphill for a range of roughly 50 feet. I hope to do some testing with more room soon.
Frame seems quite strong (Took a few misfires and getting flipped) but the original axle bent, probably when the frame bounced; it gets about an 1 1/2" of air under the back wheels on a regular throw. New skinnier and stiffer axle works great.

Short Video

A single shot at real speed.
Long Video

Contains some pictures and slow motion.

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