GearHeads Corner

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

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

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

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

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

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

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
 

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 :-[

Hi:

  To place images, there is a "additional options " button below your message. Click it and a browse button will appear so
you can attach an image ( or 4)..

  I used a spring, because the ring of brass pins are always under tension from the CT spring, and the trigger can happen at any angle
so long as the two platforms are spinning in reverse direction with the bottom turning cw. Alway hard to explain these things :),,
which is why I hope to be able to allow simulations of mechanisms like this one. Kinetic triggering can be so nonintuitive that
Id like ot have a tool where I can play with shapes and how they interact as they spin .. might help creativity some.

Art

OK Art, gotcha. I get the jist of your engine. They are hard to describe, but here goes....

Here are pics of my unfinished project. The upper (inner) pawl is lifted by magnets glued to small dowels inserted in the outer wheel. They are adjustable, hence the extra holes. In the pic in the following post you can see the outer pawl catching the ratchet as the magnets lift the inner pawl. Gravity drops both pawls. The magnets are placed opposite the heavier end of the arm, to get the most from the back swing.

A couple more.....

Sorry for the huge pics, again, I don't know what I'm doing...... :-\

Huge pics are fine, I liek them that way, allows me to zoom in on detail.

You work as I do, experimentation, changes, more experimentation till it works. I
respect the process. I too tend to work that way, though the new bat was drawn and
conceived on paper, its the first one that was. Scimitar was seat of pants with many variations
whicgh is why the drawings and such are piced together. Im hoping the bat is better
able to be documented.

  Good work, keep it up..

Art

Art, I was thinking that David Roy's pawl is shaped to avoid slipping off it's pin. If you wanted to eliminate that spring you could sand the end of your pawl....

these pics show the wheel coming to rest, reversing position, and starting again.

Sorry posting when you replied....Thanks for your comments. Your seat of the pants design of scimitar is the reason I'm here!

Im not so sure that would work for this design..because of the way I designed the action of the trigger
it needs that spring to pull it back in just to eliminate the possability fo runaway ratchet.. but we'll see, that design
may see many changes as I piece things together..

Ill post videos as it starts to run.. if it starts to run.. :)

Art