100-foot Inverted Tripod

[jimbobbus3]

For a Halloween display - a ghost that could fly around my entire front yard - I built an inverted tripod machine with a 100-foot base leg. Took a couple of months to do, but the project is mostly complete. Details have been assembled on a website here:
Snotrag the Ghost, 2007

I'm using a P3-667 computer running EMC 2.2 Beta built from source. The system uses the HALUI elements to allow wireless USB joystick control in World coordinates. I've got a mechanical resonance issue that caused me to miss the Halloween deadline, but other than that, the system works really well.

[samco]

That is awesome. I love it.

sam

[samco]

ps. I added a link to your site here
http://wiki.linuxcnc.org/cgi-bin/emc...l?Case_Studies

We are hoping that you would add a page to the wiki with more detail on how you calculated the kins and such. (maybe your ini and hal files also)

Thanks
sam

[LenMcC]

that's gotta be the sweetest halloween effect i've ever seen in someone's yard. nice work!

[jimbobbus3]

You probably already know this, but EMC comes with kinematics modules for a number of non-cartesian machines. I'm using the baseline tripodkins HAL module that's part of the distro. For reference, the stock kinematics modules are here in the source tree: http://cvs.linuxcnc.org/cvs/emc2/src/emc/kinematics/

I'm planning on posting more detail about the calculations for the scale factors on each joint. I wanted to get the basic information posted on the web before I get overloaded with family this week (Thanksgiving in the States.) I can post the INI and HAL files as well.

[unterhaus]

what stepper drivers did you use?

[jimbobbus3]

The stepper controllers are custom made. With traditional controllers, we haven't had good luck running stepper motors with long wire runs, and these needed to be about 150 feet. It took a little over a month to get everything designed and fabbed. We haven't had a chance to test for maximum length, but extrapolating the current results indicates that these units should be able to run up to 300 feet. That's largely limited by the I-R drop in the cable. If power is supplied externally, we should be able to operate over a couple thousand feet.