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Author Topic: Reciprocating Arms  (Read 2808 times)
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marklazarz
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« on: December 22, 2016, 05:03:03 PM »

I finally figured out how the reciproca ting arm escapemen t 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 recogniza ble therefore I feel comfortab le 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 observati ons:
1) The flywheels act similar to a pendulum in a recoil escapemen t.
2) Timing is controlle d 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 intereste d in this type of ticker.

Mark
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ArtF
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« Reply #1 on: December 22, 2016, 08:19:32 PM »

Mark:

 Very interesti ng. I think a few of David Roys sculpture s use the same type of mechanism ..

Ive always thought it looked real nice.. I may have to try something similar one day..

Art
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marklazarz
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« Reply #2 on: December 23, 2016, 10:19:14 AM »

The beauty of this mechanism is it's simplicit y.  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
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Dan Mauch
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« Reply #3 on: December 24, 2016, 11:46:16 AM »


 Very nice.! I am surprised by the thickness of the fly wheels. Are you saying that the heavier the slower?

Dan Mauch
I finally figured out how the reciproca ting arm escapemen t 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 recogniza ble therefore I feel comfortab le 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 observati ons:
1) The flywheels act similar to a pendulum in a recoil escapemen t.
2) Timing is controlle d 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 intereste d in this type of ticker.

Mark
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marklazarz
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« Reply #4 on: December 24, 2016, 12:59:35 PM »

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 considera bly lighter.

Mark
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John T
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« Reply #5 on: December 24, 2016, 02:12:31 PM »

Hi Mark,
Flywheels are really interesti ng 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 engineeri ng informati on on.

John
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drezal
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« Reply #6 on: March 04, 2017, 09:01:14 PM »

Really cool, Mark.  Not sure how I missed this from December. 

Dan
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marklazarz
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« Reply #7 on: March 05, 2017, 04:52:58 PM »

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
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drezal
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« Reply #8 on: March 05, 2017, 07:51:33 PM »

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 eventuall y 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 appropria te for kinetic art pieces. 

Dan
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Mooselake
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« Reply #9 on: March 08, 2017, 01:14:39 PM »

I too missed it the first time around; impressiv e.

Your shop in the backgroun d is impressiv e, too.  I don't think mine has ever been that neat and organized .  Is that a Grizzly wood lathe hiding in the backgroun d, only caught a quick glimpse of it?

Kirk
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marklazarz
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« Reply #10 on: March 09, 2017, 09:18:17 AM »

Kirk:

You opened a can of worms asking about my shop.  Others have commented on it from time to time so I will give you a little pictorial tour.  FYI, my shop is not overly neat, it varies depending on the state of my work in process.  I will probably have to post over three messages due to the number of photos.  Since I have limited space (don't we all), most stationar y tools are mounted on wheels and I move them into a clear space as needed.  One thing for certain, I have a very understan ding wife!

Mark


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« Last Edit: March 09, 2017, 09:23:04 AM by marklazarz » Logged
marklazarz
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« Reply #11 on: March 09, 2017, 09:20:24 AM »

More shop photos (2 of 3).


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marklazarz
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« Reply #12 on: March 09, 2017, 09:22:13 AM »

More shop photos (3 of 3).



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Mooselake
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« Reply #13 on: March 09, 2017, 02:45:17 PM »

I need more room and a bigger allowance Smiley

I looked at (online...) the tabletop Delta midi-lathe, but went with the 12" VS PSI since I've used one in the adult shop at the high school - if it holds up to HS students it should work for me.   Had it about a week now, even made a couple things that didn't go into the woodstove .

We have the same metal cutting bandsaw, but mine is red and had a 20% off coupon.  I'd like the Simpson metal rack, better than leaning it in corners against the wall...

Still impressed, and it's way neater than mine.  Gotta get out the broom and shop vac, not to mention another sort and put away session, longer than the last one.  Your pics are an inspirati on!

Kirk






* PSI Lathe.jpg (160.2 KB, 800x450 - viewed 78 times.)
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marklazarz
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« Reply #14 on: March 09, 2017, 03:42:36 PM »

That Simpson rack was on sale at a building center that closed.  I think I paid $10.00 for it loaded with all kinds of metal shapes and threaded rod.  You will also notice lots of General brand equipment, I believe it is all made in Canada - very happy with the quality.

I never touched a wood lathe in high school.  Purchased this one at a local hardware store for no other reason than I thought it would be fun.  I spent the first year discoveri ng that wood turning begins at the grinder, not the lathe.  Once I got over the fear of killing myself, it's great fun and easy to make something in a couple of hours.  It really comes in handy for making things like wooden clocks, kinetic sculpture s and incidenta ls associate d with Gearotic parts.  Shavings are used in my gas grill to flavor meat.

Whenever someone posts photos of their projects, I always look at the shop behind the scene.  Must be a guy thing.

Mark
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