Flutterby™! : Tasks for the day

Next unread comment / Catchup all unread comments User Account Info | Logout | XML/Pilot/etc versions | Long version (with comments) | Weblog archives | Site Map | | Browse Topics

Tasks for the day

2009-12-13 18:22:04.142461+00 by Dan Lyke 4 comments

Sarada and I dipped over 150 truffles last night 'til we ran out of chocolate. Today I've got two projects:

  1. Get the train loop up on the wall around the tree. Think I've got all the measurements and issues worked out. It won't have a coat of finish on it, and the plywood won't have edging, but this is a prototype anyway (even though this prototype may end up being there for a year or two, which is why I do have the edge banding and intend to put something on it at some point).
  2. Build a couple of these Hila science camp tabletop trebuchets. I like the release mechanism, though I'll be doing the bucket slightly differently.

[ related topics: Chocolate Machinery Trains ]

comments in ascending chronological order (reverse):

#Comment Re: made: 2009-12-13 19:32:47.494702+00 by: Chris

is there any connection between the truffles and the trebuchets, can see firing them across the room aiming for a person's mouth...

#Comment Re: Trebuchet physics is *wicked* hard made: 2009-12-14 02:17:44.719052+00 by: ccoryell

My roommate in college modeled a simple trebuchet for his math thesis. (it used a fixed weight instead of a hanging weight to keep things easier.

The trebuchet is very interesting because it is theoretically possible to transfer 100% of the energy in the lifted mass into projectile motion (less friction and lifting of the arm etc).

We built a trebuchet with an ~10' throwing arm to prove his math. He'd weigh the the projectile (typically a watermelon) run off to computer lab to solve for the proper initial conditions (rope length, starting angle and release angle). When we fired it there was very very little swing in the arm after the projectile flew. It was spooky. The arm would go up and *STOP* while the melon went 200' down range.

So, when you mess with your tabletop trebuchets, know that it's possible to get the arm to have no movement after the projectile release.


Carl Coryell-Martin

#Comment Re: Speed made: 2009-12-18 19:57:25.301393+00 by: jeff [edit history]

I recently bought a used camera (Canon 1Dmk1) which has a top shutter speed of 1/16,000th second (it uses a hybrid shutter mechanism and electronically "gates" its CCD sensor on for this duration).

I'm struggling to find at least one everyday subject/object in motion which might require this speed to completely "freeze the action."

I'm also reminded of this video, which would be far outside the scope of what I'd technically be able to shoot (the 1Dmk1 is limited to 8fps).

#Comment Re: made: 2009-12-18 22:15:07.945188+00 by: jeff [edit history]

This gallery provides some examples of what the Canon 1Dmk1 and its in-camera 1/16,000th second electronically gated CCD exposure mechanism (hybrid shutter) can do.

CCD exposure taken with Canon 1Dmk1 @ 1/16,000th second (no flash):

By comparison a CMOS exposure taken with the newer (but slower) Canon 1Dmk2 @ 1/8000th second (no flash):

Quoted from the image comments: "With CMOS sensors and very short exposures the image is captured through a narrow gap between the moving shutter curtains. Obviously, this gap doesn't travel across the frame instantaneously and naturally results in an image that is captured sequentially from the bottom to top of the frame. This time lag between exposing the bottom of the frame and the top of the frame gives a distorted look to the muzzle flash, as seen in this image."