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Old 04-06-2022, 06:53 PM
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Ironman Ironman is offline
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Default Math help needed.

Likely Arizona Bill can figure this out.
I am sending in some drawings of the mechanism, a side on view to give an idea of the setup.
I am working on this mechanism, and I would like to have a stroke of 2" or 3" on the cutting blade. Present throw on the crank is 6", I can't reduce that as components start to interfere.

By changing the lengths of pivot points, I believe the end goal can be achieved.
No need to worry about it's strength etc, all will be revealed in the future, once I can proceed without trial and error construction.
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  #2  
Old 04-06-2022, 07:55 PM
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Quote:
Originally Posted by Ironman View Post
Likely Arizona Bill can figure this out.
I am sending in some drawings of the mechanism, a side on view to give an idea of the setup.
I am working on this mechanism, and I would like to have a stroke of 2" or 3" on the cutting blade. Present throw on the crank is 6", I can't reduce that as components start to interfere.

By changing the lengths of pivot points, I believe the end goal can be achieved.
No need to worry about it's strength etc, all will be revealed in the future, once I can proceed without trial and error construction.
Some one call my name? Let me download them and have a minute to study what is what.
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Old 04-06-2022, 08:03 PM
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arizonian arizonian is offline
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The thing to focus on are the pivot centers and distances. Also, the point of the cutting edge. Is the 6" crank location fixed? Is the frame elevation and horizontal distance fixed also?
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Old 04-06-2022, 08:22 PM
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Quote:
Originally Posted by arizonian View Post
The thing to focus on are the pivot centers and distances. Also, the point of the cutting edge. Is the 6" crank location fixed? Is the frame elevation and horizontal distance fixed also?
Crank location is fixed. Horizontal distance is not fixed. Frame elevation is fixed in relation to the pivot points, as the whole thing is raised and lowered on a 3 point hitch.
Pivots can extend horizontally away from the crank and the upper end with the con rod can be as high as you want.

And thanks, Bill.
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Old 04-06-2022, 09:22 PM
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I took 2 shots of the same page...

ASSUMING: The cutting edge is directly under the pivot point and is held at 22" swing, AND and the crank is centered horizontally on the frame pivot point. To get 3" swing we need to extend the top out to 44". That is Position 1. We can fold over the arm and the intersection of the center of arm to the crank stroke is approximately 90°, that is Position 2.

If a 2" stroke at the cutting edge is mandatory, we need to extend the top out to 66" and then fold it over, which will also increase the horizontal distance.

If the cutting edge is not directly under the pivot, it will still work but now your cutting edge is moving at an angle.

The centers and the point of the cutting edge are all that are needed for now. You can add in any offset as long as they return to the same point. Think of pivoting C-channel on one lip, the other lip returns to the same plane. Only the web is offset. The dotted lines represent the linkage but is offset from the center pivot. Add in whatever is needed to make it work.
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  #6  
Old 04-06-2022, 11:54 PM
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Quote:
Originally Posted by arizonian View Post
I took 2 shots of the same page...

ASSUMING: The cutting edge is directly under the pivot point and is held at 22" swing, AND and the crank is centered horizontally on the frame pivot point. To get 3" swing we need to extend the top out to 44". That is Position 1. We can fold over the arm and the intersection of the center of arm to the crank stroke is approximately 90°, that is Position 2.

If a 2" stroke at the cutting edge is mandatory, we need to extend the top out to 66" and then fold it over, which will also increase the horizontal distance.

If the cutting edge is not directly under the pivot, it will still work but now your cutting edge is moving at an angle.

The centers and the point of the cutting edge are all that are needed for now. You can add in any offset as long as they return to the same point. Think of pivoting C-channel on one lip, the other lip returns to the same plane. Only the web is offset. The dotted lines represent the linkage but is offset from the center pivot. Add in whatever is needed to make it work.
The cutting edge is 4" wide front to back, so count the center as 2" back of the front edge.
Somewhere between 2 and 3 inch stroke will be good as it will keep vibration down and add leverage to the thing.

I should be able to take it from here and see what I can do with this.
Thanks
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Last edited by Ironman; 04-07-2022 at 12:01 AM.
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  #7  
Old 04-07-2022, 12:10 AM
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Looking this over some more, seems if there is a way to do the pivot point as less than 22" up from the cutter, that would have a definite effect on stroke
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Gerry
You got freedom of speech, if you don't say too much.
Aaron Neville.

When a liberal screams racism, you can bet they were also born with white skin.

The countries whom the gods would destroy they first make green. Rex Murphy
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  #8  
Old 04-07-2022, 01:48 AM
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I've made cardboard templates to figure out how to attach an rudder angle sensor to a rudder shaft arm because of different swing angles. Poked a nail through the cardboard to visualize the pivot. I've honestly forget the specifics but I know the bracket and arm came nice with the arc of the rudder just smaller than the arc or the sensor and slots for adjustment and to center. This was before smart phones or I probably would have taken pictures.
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  #9  
Old 04-07-2022, 06:38 AM
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When I have these to doo, I use CAd, and represent arm lengths as circles, with the arm length being the radius.
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  #10  
Old 04-07-2022, 06:42 AM
JBFab JBFab is offline
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That's what I do as well. Makes it pretty easy. I'd do that for Gerry, but I don't think I fully comprehend what needs to happen.
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Originally Posted by digger doug View Post
When I have these to doo, I use CAd, and represent arm lengths as circles, with the arm length being the radius.
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