Jacob's Ladder No. 1

[gfish]

I got the device which I've taken to calling Jacob's Ladder No. 1 completely running for the first time tonight. It runs smoothly enough, but the ladder cascades just aren't starting reliably.

There are two possible ways to fix this that I'm looking at. Slower oscillations and wider (in angular terms) oscillations. Since I don't want to hunt down a new motor at this point, the first would require an extra gear reduction step, probably in the form of another set of chain rings which could float on the existing ladder axle. The most direct way to accomplish the later would also require another set of chain rings, plus a whole new axle. As that would mean a lot more work (plus would result in even more frenetic action, as it would be gearing up instead of down) I'm going to try the former approach first.

Other than that, the woodwork still needs to be finished (stained, and possibly some added trim), everything needs to be loctited and the raw iron sealed with beeswax, the connecting rod pivots needs to be improved, and the power supply/power switch need to be installed. At some point the stand goes away and it becomes wall-mount only. And if I have time, I'm playing with etching brass plates to create a handsome label. Sure would be nice to finish this before the NYC trip next week.

Comments

[niac.livejournal.com]

Awesome. :D

[niac.livejournal.com]

And a more useful comment: Have you considered using a microcontroller to drive a a MOSFET via PWM to control the speed of your motor? That might permit you to tune the performance much more easily, and with a minimal amount of code/time.

[gfish.livejournal.com]

Hrm. That's not a bad idea. (Particularly since I woke up realizing that I can't just float the reduction rings off the existing axle, as the large one would project behind the back of the structure.) But why use a microcontroller? I can wire up a 555 with adjustment pot easily enough. Instant PWM!

[niac.livejournal.com]

Well, I have more microcontrollers than 555 timers at home. :) That's one reason I look there. The other reason is I can do cleverer things with those, like detect lockup and do something about it. A 555 is also a great solution. :)

[randomdreams.livejournal.com]

Dude, drive it with PWM driven from the parallel port! using qbasic for the code!

[stolen-tea.livejournal.com]

Ooooh, next time you do another 5-spoked chain ring, may I make a request for a Tudor Rose? I've always liked them... :)

laddershaft

[capnblackberry.livejournal.com]

maybe shift the laddershaft rotation somewhat to the ccw - viewed fromthe side oposite the chain?

Re: laddershaft

[gfish.livejournal.com]

Trust me, I spent a lot of time trying to tweak that. I could get one reliable, or neither, but not both. But dropping the motor voltage to slow it almost completely fixed the problem, and adding a back to the thing (which reduces the swing of the ladder) seems to fix the rest.