Kinetic sculpture designed by Clayton Boyer

[marklazarz]

Eric:

Clayton specifies this spring for his Zinnia http://shop.sdp-si.com/catalog/product/ ... 3x51-20006

I wind the flywheel about 18 times for a full run with this spring so it's pretty long.  Run time is inversely proportional to friction, the number 1 factor for getting the most run time out of the sculpture.  There are not many parts to Zinnia so scroll sawing should be no problem although you will need a saw capable of reaching over 12" radius.

Mark

[Kineticrazy]

Thank you for the info. I'm surprised it's only a pound of force. I've got my first kinetic engine running on a drop weight of one pound, 30 inch drop. I tried upping the weight, for longer run time(presently 15-20 min), but my pawl would not disengage on the return rotation with more weight added. I assumed my ratchet design was at fault or I needed to add weight to one side of my wheel to disengage the pawl.
  Have you experimented with heavier springs? I accidentally bought a 4.5 lb. 40 inch constant force spring (not constant torque) and was going to attempt trying it by drawing it out linearly (one spool) and attaching a string to the free end and winding the string to my drive spool and ratchet.
Any thoughts on whether It will work? Will enough counter weight added be possible to disengage the pawl?

Keep in mind I have been using a pawl and ratchet of my own design (imagine a saw tooth ratchet with magnets embedded in the pawl) and not using David Roy's design yet. Do you think David's pawl design can handle more weight?


I've got 30 inches of throat on my Dewalt scroll saw (my favorite tool in my shop), and I can bend the blade ends 90 degrees if I have a long work piece. That gives me unlimited throat! (picture using the saw from the side, not the front)

Thanks again for the information, I hope you don't mind the questions...

Genuinely kineticrazy,

Eric

[marklazarz]

Eric:

No, I have not experimented with different springs.  Disengaging the pawls falls under the category of timing, and a lot goes into it.  The only advice I can offer is to build something and then tinker with it until it runs.  You develop a feel for timing variables when you see the mechanism in motion.  Proven commercially available plans still require some fiddling.  If you design your own, don't expect the first iteration to be your masterpiece.

I have not attempted to build any David Roy drive engines, maybe later next year.  Although I'm retired, I don't have enough time in the day to accomplish all the things I want to.  Busy with Christmas gifts, modifying the control on my CNC, learning Aspire, playing with Gearotic, and now shoveling snow.

Mark

[ArtF]

Mark:

All so true. I have a kinetic engine prototype half finished, lasers that need work, galvo cude to test with, and
the kinetic engine to complete, there just isnt enough time in the day.

  When building any kinetic object I really advise playing with every dimension in it.. you often improve it..

Art

[Dan Mauch]

Last year I posted my version of Zinna. One of the improvements I made that really helped increase the duration of the machine was to make the drive mechanism out of 5mm acrylic.
Dan Mauch

[ArtF]

Hi Guys:

  Heres a photo of the engine Im working on.. the top rotating stage isnt on it yet..

shows the spring arrangement though..

Art

[ArtF]

Couple more showing how the spring is used..

  This is a spring from vuclan springs, the constant torque, should give a few hours of motion..



Art

[Kineticrazy]

The Bat Returns!!

Looks well built Art, beefy !! I'm curious about your mechanism, I'm imagining pawls on the outer wheel, that will trip that pawl off it's pin on the backstroke? Does it advance one pin at the time? What size spring you got there? You've got me intrigued to say the least. Looking forward to pics of the outer wheel.

Good stuff,

Eric

[ArtF]

Eric:

  I got the springs awhile back, as I RECALL they are 4lb CT, about 160" long or something.. takes
20 winds on a 3" take-up spool. The outer pallet, as it spin's backwards grabs the pin the main ratchet is on, a magnet on the outer pawl then pulls the ratchet away leaving the outer pallet holding the pin on its own,This makes the outer pallet turn in reverse, and as it pulls away, the magnets separate and the main latch trips back in, thus one pin has turned. This means about 45 degrees of push per trip. This uses 2 magnets in a dual action, the first pulls the outer pawl in until it hits the pin, the magnet on the lower lever now is just offset enough to pull it outwards when friction releases it. This makes it dual action, the outer level pulls inwards to a limit, then the inner pulls outwards to the magnet, then it all reverses. 

  In testing, it seems ok but hasn't yet been fully assembled, I may end up switching the way it works as yet,
but I'm happy with the bottom, seems strong and has multiple possibilities for tripping.. just gotta find one..



Art
 

[Kineticrazy]

Art,
 I have nearly the same design. I'm wondering why you need the torsion spring to snap that pawl back in? wont gravity do the job?

I just attempted to post pics of my mechanism....Forgive me,I can't figure out how...I click insert image and then don't know how to place the pics file from there....any suggestions? (I did try the help function...all Greek to me) Sorry, I know I'm computer illiterate :-[