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Reciprocating Arms
Posted: Thu Dec 22, 2016 10:03 pm
by marklazarz
I finally figured out how the reciprocating arm escapement works with a little help from a Turkish friend I met on YouTube. He did not want me to share his design so I modified it to the point where his design is no longer recognizable therefore I feel comfortable revealing bits and pieces with this little community. My "proof of concept" mechanism can be seen here
https://youtu.be/O2JafxJ8yuM. It's very crude and downright butt ugly but it works!
Here are some observations:
1) The flywheels act similar to a pendulum in a recoil escapement.
2) Timing is controlled by the spacing of the cage gear pins, placement of the pawls, and length of the string.
3) The mass of the flywheels control how fast things move.
4) The arms need to be weighted with the center of gravity offset so they retract far enough.
5) The string should not slip on the flywheel pulleys.
I hope this helps my fellow gearheads who may be interested in this type of ticker.
Mark
Re: Reciprocating Arms
Posted: Fri Dec 23, 2016 1:19 am
by ArtF
Mark:
Very interesting. I think a few of David Roys sculptures use the same type of mechanism..
Ive always thought it looked real nice.. I may have to try something similar one day..
Art
Re: Reciprocating Arms
Posted: Fri Dec 23, 2016 3:19 pm
by marklazarz
The beauty of this mechanism is it's simplicity. It's easy to construct with a couple of parts, no springs, no magnets and it can be used to drive any flywheel design. I forgot to mention that the flywheels work best when balanced so there is no need to use offset weights. Pawls are triggered by the recoil generated by the flywheel's momentum.
Mark
Re: Reciprocating Arms
Posted: Sat Dec 24, 2016 4:46 pm
by Dan Mauch
Very nice.! I am surprised by the thickness of the fly wheels. Are you saying that the heavier the slower?
Dan Mauch
marklazarz wrote:
I finally figured out how the reciprocating arm escapement works with a little help from a Turkish friend I met on YouTube. He did not want me to share his design so I modified it to the point where his design is no longer recognizable therefore I feel comfortable revealing bits and pieces with this little community. My "proof of concept" mechanism can be seen here
https://youtu.be/O2JafxJ8yuM. It's very crude and downright butt ugly but it works!
Here are some observations:
1) The flywheels act similar to a pendulum in a recoil escapement.
2) Timing is controlled by the spacing of the cage gear pins, placement of the pawls, and length of the string.
3) The mass of the flywheels control how fast things move.
4) The arms need to be weighted with the center of gravity offset so they retract far enough.
5) The string should not slip on the flywheel pulleys.
I hope this helps my fellow gearheads who may be interested in this type of ticker.
Mark
Re: Reciprocating Arms
Posted: Sat Dec 24, 2016 5:59 pm
by marklazarz
Heavier wheels take more force to get going, so drive weight and flywheel weight are related in that regard. It's all part of the fine tuning process.
What you saw in the video was my first attempt at the flywheels so I made them thick to give them some mass (had to start somewhere). Next time, I will work on a pleasing design and I'm sure that they will be considerably lighter.
Mark
Re: Reciprocating Arms
Posted: Sat Dec 24, 2016 7:12 pm
by John T
Hi Mark,
Flywheels are really interesting things. I remember from my school days (long ago) that it was the weighted rim that was critical for stored momentum.
Anyway its worth while looking up some engineering information on.
John
Re: Reciprocating Arms
Posted: Sun Mar 05, 2017 2:01 am
by drezal
Really cool, Mark. Not sure how I missed this from December.
Dan
Re: Reciprocating Arms
Posted: Sun Mar 05, 2017 9:52 pm
by marklazarz
Thanks for the comments. I have a fairly decent sculpture nearly completed. Just waiting for the warmer weather so I can spray paint outdoors.
Mark
Re: Reciprocating Arms
Posted: Mon Mar 06, 2017 12:51 am
by drezal
Sounds good. Looking forward to seeing it. I purchased Clayton's Zinnia a while ago primarily to see how the mechanism worked. I cut much of it on a small 3040 CNC, scaled way down, and will eventually get to it's assembly. Over the last few months I built a larger Solsylva CNC with a cut area of around 2' x 2' which would be much more appropriate for kinetic art pieces.
Dan
Re: Reciprocating Arms
Posted: Wed Mar 08, 2017 6:14 pm
by Mooselake
I too missed it the first time around; impressive.
Your shop in the background is impressive, too. I don't think mine has ever been that neat and organized. Is that a Grizzly wood lathe hiding in the background, only caught a quick glimpse of it?
Kirk