Engineering Help Calculating Length And Position Of Connections On Rotating Object

[carman435]

As for a plan view or an elevated view. This is a 2d rotational model I've been asked for help with. My friend believes they have other working models which they use to test things before furthering development but I'm being given limited info here

 

[carman435]

No.
The two equations are determined by the geometry. They have no names.
https://en.wikipedia.org/wiki/System_of_equations

Ah okay, does the above info help at all

 

[carman435]

Here's another photo showing just the arcs and there limit. It does not show the entire circle. Just the arcs the lines will follow

 

[Baluncore]

Ah okay, does the above info help at all

Not really, it just confuses more.
I understand the problem, and have sufficient information.

There is no point hitting my head against it now. I will be driving for an hour or two later, which will be plenty of time to relax the problem, and hopefully see an elegant solution.

 

[carman435]

Not really, it just confuses more.
I understand the problem, and have sufficient information.

There is no point hitting my head against it now. I will be driving for an hour or two later, which will be plenty of time to relax the problem, and hopefully see an elegant solution.

Thanks. I appriciate your help in this. I will stop supplying info as I get the impression I'm no help here at all!.

Thanks for your help and time

 

[Lnewqban]

...
The view we are seeing is a side view. The reason they won't hit each other is that they won't do a full rotation around the axis. I've simply put the circles on as I was trying to visualize it.
...
The links will not collide as they will be directly attached to the rotating lines.

Following your last dimensions, I have done this drawing at scale of what I understand.
Please, correct any error, and I will happily fix it.

Note that the two upper doors will need brackets (perpendicular offsets of 61 and 133) to reach the actual point of rotation for each of those.

The attached PDF file shows the drawing with better quality.

 

[carman435]

Following your last dimensions, I have done this drawing at scale of what I understand.
Please, correct any error, and I will happily fix it.

Note that the two upper doors will need brackets (perpendicular offsets of 61 and 133) to reach the actual point of rotation for each of those.

The attached PDF file shows the drawing with better quality.

View attachment 344237

Hi thanks that's actually spot on.

I don't suppose you got anywhere with connecting them?

I'm still working on that at the moment

 

[Lnewqban]

Hi thanks that's actually spot on.

I don't suppose you got anywhere with connecting them?

I'm still working on that at the moment

It is now late at my corner of Earth, but try finding points with common tangential velocity at each gate, in a convenient location, and connect those with a single link.
You can use the measured angles for that.

It is also important to consider the thickness of each gate, because different points hit the top and the bottom limiting surfaces.
A rectangle does not behave an ideal line in that case.

I may have time to help with that tomorrow.

 

[carman435]

It is now late at my corner of Earth, but try finding points with common tangential velocity at each gate, in a convenient location, and connect those with a single link.
You can use the measured angles for that.

It is also important to consider the thickness of each gate, because different points hit the top and the bottom limiting surfaces.
A rectangle does not behave an ideal line in that case.

I may have time to help with that tomorrow.

Not a problem thankyou for your help

I'm trying to find common points now but im unsure if there is a better way then trial and error!

Hopefully so!

Thankyou for all your help and time

 

[carman435]

I'm hoping for a tad of guidance here.

I believe the solution to this problem has mutiple answers. Is that the case? I think two of us could look at it and get two separate bars of different lengths and they would both work equally well?

If I'm right I may be close, if not I will revert back a bit.

 

[Baluncore]

There are multiple solutions based on where you attach the first connector.

I have some answers here to the original question, but I have not yet verified them.

 

[carman435]

There are multiple solutions based on where you attach the first connector.

I have some answers here to the original question, but I have not yet verified them.

I think I've managed to brute force a correct answer just by setting a constant and then guessing using an excel sheet.

That said I'm sure there is a more effective method

 

[carman435]

There are multiple solutions based on where you attach the first connector.

I have some answers here to the original question, but I have not yet verified them.

Did you manage to get any further on this?

 

[Baluncore]

Did you manage to get any further on this?

Yes, but I was not in any hurry to solve your exact problem.
Instead, I was looking at the bigger picture of solving linkage puzzles.

With your challenge for example, I do not know if the rotation of the lines requires they be fixed bars that end at those defined points, or if they are virtual lines, that are projected through those points without defined ends.

 

[carman435]

Yes, but I was not in any hurry to solve your exact problem.
Instead, I was looking at the bigger picture of solving linkage puzzles.

With your challenge for example, I do not know if the rotation of the lines requires they be fixed bars that end at those defined points, or if they are virtual lines, that are projected through those points without defined ends.

Fair enough.

The lines are fixed bars that end at those defined points.

I think I've got far enough that I could recreate it which is what I hoped for.

Thanks for you help.

 

[Lnewqban]

Hi thanks that's actually spot on.

I don't suppose you got anywhere with connecting them?

I'm still working on that at the moment

You are welcome.
I have not had access to CAD since my last post, sorry, but I will continue working on the problem soon, I hope.

Do you have access to AutoCAD?
If so, this may help:
https://dynref.engr.illinois.edu/aml.html

Did you progress on the interconnection of the gates (I have assumed those are gates)?
Did you consider the actual thickness of each and the stand-offs at the pivots of the upper ones?

 

[carman435]

You are welcome.
I have not had access to CAD since my last post, sorry, but I will continue working on the problem soon, I hope.

Do you have access to AutoCAD?
If so, this may help:
https://dynref.engr.illinois.edu/aml.html

Did you progress on the interconnection of the gates (I have assumed those are gates)?
Did you consider the actual thickness of each and the stand-offs at the pivots of the upper ones?

They are interconnected gates! Yes. I will have a look over that site and see if it helps.

I do have access to AutoCad, although I was using Webcad as I was at home. I've installed proper AutoCad onto my home pc now which is making life easier.

In terms of the thickness of each I'm not sure what you mean? Do you mean considering the thickness of the lines as to prevent collision? I think I sort of get this. The lines are representative of position not the actual dimensions of the gates so collisions could happen before the maths say it would?.

Not sure what you mean by standoffs

Sorry! I'm a tad useless at this.

 

[Lnewqban]

No collisions, but doing a lot of work based on unreal center-lines, is what worries me.

For example, we are assuming that the represented center lines are hitting the top surface at certain angle, but if you consider the actual thickness of one gate, its top edge will hit that top surface short of the considered angle (based on the that ideal center-line).

I am sorry, I am probably not being able to explain myself properly with words (English is not my native language); that is one of the reasons I prefer showing my ideas in the form of diagrams or scaled drawings.

In CAD, you could create an array of opening positions simply by dividing each arch in several equal portions.
That may help you visualize what points at each gate is more suitable to locate the links.

 

[carman435]

No collisions, but doing a lot of work based on unreal center-lines, is what worries me.

For example, we are assuming that the represented center lines are hitting the top surface at certain angle, but if you consider the actual thickness of one gate, its top edge will hit that top surface short of the considered angle (based on the that ideal center-line).

I am sorry, I am probably not being able to explain myself properly with words (English is not my native language); that is one of the reasons I prefer showing my ideas in the form of diagrams or scaled drawings.

In CAD, you could create an array of opening positions simply by dividing each arch in several equal portions.
That may help you visualize what points at each gate is more suitable to locate the links.

Ah I follow I think. Yes I understand the concern.

The centre lines are just the basis here and its mainly just to help describe the formula and calculations I was looking for.

This likely won't be put into production but was a test case to help us explore 4 bar linkages.

If we were actually going to create this we wouldn't use centre lines outside of initial drawings.

 

[Baluncore]

Given the simple problem, without offset centres of rotation.
For red, green and blue lines.
The independent connector links are shown in magenta and yellow.

Red pin is 476.815 from red centre.
Green pin is 500.000 from green centre.
Blue pin is 544.910 from blue centre.

Red to green link length is 323.914
Blue to green link length is 544.910