Trebuchets, Geohashes, and Richmond, VA

A while back, I was home in Virginia for a little while, and my friend James decided it was time to build a trebuchet

Pictured: James, Doug

I say measure once, cut eighty or ninety times.

As you can see by Doug’s hat, trebuchets are very serious business.

I had to leave before we could test it, but they finished up the last touches in my absence. This week, we got a chance to fire it for the first time.

The projectile (three full Dr Pepper cans taped together) vanished off into the woods. Firing successful! In the video, you can see falling leaves cut by the projectile.

In other news, Geohashing is working out wonderfully. At the most recent meetup I attended, we flew a camera from a kite and then tried to spell words under it.

There’s a new feature in the map-locating program where you can suggest and vote on alternate meetup sites for a given day. So far, the pattern is generally that we show up at the location, then find a nearby park or restaurant to hang out at. Bringing games and activities is encouraged.

I wasn’t able to make it to the most recent meetup because I was at MoCCA. By the way — thank you to Chris Hastings of Dr. McNinja for his generous hospitality. He gave me a place to sleep with no advance warning and didn’t even get mad when I spent the night sick on his couch, beat him at Mario Kart, and stole half his stuff. (If anyone wants a good deal on some of his erotic Batman fan art, let me know.)

This afternoon (starting 4:00-ish), some friends and I are heading to Belle Island in Richmond, VA, which is an alternate location for today’s geohash. I hear there are fireworks or something?

151 thoughts on “Trebuchets, Geohashes, and Richmond, VA

  1. There aren’t really any building plans, and if there were you wouldn’t want them. James used some random online trebuchet simulator to work out the basic dimensions, and we ballpark-calculated everything else on backs of envelopes.

    It was basically an experiment to see if we could build a trebuchet in a couple days days for a couple hundred dollars.

  2. How did you get the camera to take pics? Either you precisely threw a rock at the shutter button, or you had some sort of special camera.. or you used the 10 second wait time and got that kite flying extremely fast. Thanks, Brian

  3. Thanks for the link Tim,

    Do you have any info on exact camera, or circuit?

    A friend is off to study engineering at Oxford Uni, and we thought it would be great to get some pictures of the great architecture from the sky


  4. Oops, thought I was getting the security phrase wrong each time, so I kept trying.. lol?

  5. Hopefully similarly frivolous geohashing adventures will be had when I make it back to Boston in the Fall. :-)

    Randy: do you have any kind of geohashing worldwide success statistics? I.e. how many geohashers are there in total, what’s the average group size, how many groups actually meet, etc.?

  6. @Brice

    Finding trebuchet plans online isn’t very difficult, just google it and you’ll get a good enough idea that you can make your own blueprints. I teach high school physics, and in one of my classes this year, I helped a team of girls and a team of boys each built their own trebuchets (our physics room has its own workshop, so the kids did all the design and construction there at school). The boys’ trebuchet was much larger than the girls’, but the girls still kicked their butts :) Wish I had some video to share, but with school privacy practices these days, I probably wouldn’t be allowed to anyway!

  7. I WAS AT MOCCA! I would have loved to meet you. I was telling my girlfriend how awesome it would have been to see an xkcd table there. Please go next year!!!

  8. I am not going to lie…I am trying both of these things as soon as I can.
    The trebuchet will be for pumpkins that my neighbor sells every fall. I don’t know what adventure I will use the camera for. *!@IDEA!*@ Shoot the camera from the trebuchet and rig a parachute to deploy all the while it is snapping pictures of the whole thing!

  9. Holy cow, I found where the Firefox logo spends it’s time, on Doug’s head!

  10. aw, are you kidding me, I was going to see the fireworks at Belle Isle yesterday but couldn’t go because the car was in use.

    and hey, it’s Doug. Hi Doug!

  11. @John haha, that’s the same thing I was thinking. That’s some big hair there Doug :)

  12. I like Doug’s hair…

    The trebuchet looks awesome. I want one! And I’m considering trying the kite + camera idea around my local area to see what it’s like from the air. It’s probably cheaper than renting a helicopter or light aircraft, no?

  13. # John Says:
    June 14th, 2008 at 3:06 pm

    Doug’s hair is AWESOME!

    fix’d. My friend was doing something like this, but smaller. Trebuchets kick arse.

  14. His hair makes me think of a young Donald Trump… and a young Head of Hair on Donald Trump, of course… We all know it’s its own entity.

  15. Well, Geohashing sure does sound fun to me. BTW, how exactly did you fly a camers using a kite and how did you get it to take a picture from that high above the ground?

  16. Apparently those pics were taken quite a while ago, as Richmond has been setting new records lately for heat. That hat would have resulted in a heat stroke any time in the past month.

    I don’t suppose that your friend lives on Huguenot Road near the Bon Air Baptist church, does he? I’d swear there’s a trebuchet sitting at the end of someone’s driveway up there. I’ve been meaning to stop and ask them about it.

  17. I think i speak for all your lovely fan girls when i say that you most certainly need to keep the pics coming. There’s nothing sexier than a man with raw building materials. mmmm….

  18. I think i speak for all the lovely lady fans of this site when i say that you most certainly need to keep the pics coming. There’s nothing sexier than a man with raw building materials and a mission in mind. mmmmm…

  19. that’s right, I’m one of those “cool” SUV-driving, non-skateboard-smug people that you xkcd “people” make fun of all the time. And you know what? I like it, so you can take your “maths” and your tricky “science” and eat it, because I don’t need no fancy “studies” to stay groovy.

  20. We made a trebuchet in our garden. The main arm was an old telegraph pole, so it was rather larger than yours here. The weight we used was actually a victorian curling stone- it had a convenient metal handle already embedded!

    Unfortunately, though the mechanism worked, our “sling” design was pathetic and just kept getting tangled. We swapped it for a basket just to get the satisfaction of launching something, but it didn’t lob out turnips nearly as far as we were hoping.

    We then took it apart and chopped it up for firewood. To this day I get irritated because I didn’t take a photo and no one believes me that there was, for a brief time, such a big siege machine in my garden. *sigh*

  21. On the trebuchet; you will get dramatically increased range if you add wheels.

    They don’t have to be particularly big, as long as they allow the frame to move perpendicular to the axis of rotation of the arm.

    I forget the exact mathematics, but it has something to do with momentum transfer or conservation or something. Momentum at any rate.

    Depending on the efficiency of your sling, you could get a doubling of the range, apparently.

  22. Doug scares me.

    He has so much hair, but so little happiness. Big-haired people are supposed to smile. :shudder:

    All said, though, it’s pretty neat to see it work, especially knowing that it was built haphazardly. :)

  23. Suggestion for trebuchet ammo: take 1 gallon milk jugs and fill them with water. They explode on impact. Also cats work well if you can sedate them slightly.

    Our record was 106 feet with the 1 gal water but our trebuchet was capable (according to said random online trebuchet simulator) of propelling the potent potable 315 feet with the planned 600 lbs counterweight. That is until it broke.

  24. I wish I had the space and budget to randomly make trebuchets that size.

    Adding wheels usually helps, but not always. Based on the reasonable counterweight stall timing, sling adjustments would probably be more useful. Too bad the sling is cut off in the video. I can’t offer any tuning advice.
    My analysis of the subject ( – section on Axle Movement) covers how wheels help if any one is interested.

  25. We built a treb this year just before school got out. It was around 5 1/2 ft long and 6 ft tall, so a bit smaller than what you guys had. We were able to throw a can of Dew about 100 yards with about 180lbs of freeweights as the counterweight. Ours had wheels, but more for ease of movement than aiding in throwing. Ah… she was such a beauty until the bolt holding the weight broke :( RIP Dillymonger, you’ll be resurrected one day.

    I highly recommend building a treb. So long as the builders are careful not to let unweighted arm smack them on the head (happened twice) its a blast!

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