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folding chair - checking how it folds

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folding chair - checking how it folds

Postby Robert » 06 Apr 2019, 18:13

I'm thinking of making a couple of folding Adirondack chairs.

Ages ago I made 2 normal ones - which are now in my daughters garden. They were given to her mainly because they take up so much room when stored over winter.

Having sat in folding versions whilst visiting the Virginia last year I took some pictures of how it worked.

I'm guesstimating my way towards sizes based on my fixed version and the pictures.

I can test the folding by rotating things about a pivot location but then I have to change selection and rotate some more parts and so on until I get to the last move and can compare the holes to see if they line up.

This is a similar chair I found in sketchups 3D warehouse. the sizes don't match but you get the idea from it
Image

Is there an easier way to move things the way they would when folding the chair?
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Re: folding chair - checking how it folds

Postby Dave R » 06 Apr 2019, 18:37

You might have a look at MSPhysics. I believe it could do what you want. I've never really had the need for it and haven't looked at it much since it was first released so I can't give you a lot of guidance in using it.

If I were going to make the chair fold up, I would make nested components to make selections easier.
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Re: folding chair - checking how it folds

Postby Robert » 07 Apr 2019, 10:36

Tried to install it but it says not compatible with my version. I'm using the last stand alone make version.

Maybe I'll try working in a web browser sometime but not yet.

Didn't think there was an easier way than grouping components but no harm in asking. thanks anyway.
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Re: folding chair - checking how it folds

Postby Dave R » 07 Apr 2019, 12:30

Robert wrote:Tried to install it but it says not compatible with my version. I'm using the last stand alone make version.


What is the error message you get when you try to run it? The last "stand alone make version is SketchUp 2017. According to the author of the extension, it is compatible with that version. There's also a required library file which is linked to in the Compatibility and Requirements section of his first post.
Screenshot - 4_7_2019 , 6_35_29 AM.png
(24.7 KiB)


Robert wrote:Maybe I'll try working in a web browser sometime but not yet.


What do you mean? I'm not sure how that is related to your question.
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Re: folding chair - checking how it folds

Postby Robert » 07 Apr 2019, 22:43

The not compatible message came up when I went to install. Think it said I could try it anyway but given the likely learning curve for something that may have a problem I didn't.

The web comment was because I thought that was what 'make' is now - a web browser page app. I admit I've never tried it to find out how it works.

I think for the chair folding right it is the small link at the back that makes the most difference. If it comes to it I could adjust the length and lower pivot position of that when making.
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Re: folding chair - checking how it folds

Postby Dave R » 07 Apr 2019, 23:27

Robert wrote:The not compatible message came up when I went to install. Think it said I could try it anyway but given the likely learning curve for something that may have a problem I didn't.


I expect the message was indicating that the extension hasn't been signed. That doesn't make it incompatible. But since the learning curve is an issue, then it's probably best you didn't proceed.

Robert wrote:The web comment was because I thought that was what 'make' is now - a web browser page app. I admit I've never tried it to find out how it works.


The web version has its strengths and weaknesses. I guess like any other program. It currently doesn't have a provision to utilize extensions but the vast majority of users don't use extensions anyway. Since it runs in your browser, though, it'll run on Linux machines and on cheapo computers like Chrome Books.

Robert wrote:I think for the chair folding right it is the small link at the back that makes the most difference. If it comes to it I could adjust the length and lower pivot position of that when making.


You could work out how long that link needs to be without any extensions. If you want to share the SKP file, I could show you.
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Re: folding chair - checking how it folds

Postby Robert » 08 Apr 2019, 09:45

Dave R wrote:You could work out how long that link needs to be without any extensions. If you want to share the SKP file, I could show you.


Appreciate the offer but I'll get there. I will do a WIP thread for it sometime and will share the file then. I'm in no hurry so may not be for a while yet.
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Re: folding chair - checking how it folds

Postby Simon_M » 13 Sep 2019, 22:08

Perhaps a bit late, but if you can't get the program or data or extensions to load, all is not lost.

With a chair like this the operation can be understood by simplifying what you are working with. In the chair it's unlikely (I don't know) that it relies upon anything that cannot be explained in one plane e.g. the side elevation?

If you look at the way it works, you will see that there are only two types of parts: fixed length parts and fulcrum (where things rotate). So in this chair there is an arm - which can be approximated to a "rod".

Using the arm as an example, there are two fulcrum where the part is attached and free to rotate. The arm is more than a rod, but its operation can be understood from thinking about it like this.

It might help to think wha happens when someone sits in the chair, the force on the chair back pushes back and the chair is stable. But when you lift the arm, it also pulls up on the back and there is the option to move the base of the seat.back to get into another stable position.

By modelling a chair by using simple approximations, it becomes easy to move these about e.g. pick up one end of a line and drag it to a new position. It may help to look at other parts e.g. draw a circle to show the rang of movements possible on two parts and where the circles cross there are a number of positions where it's stable.

Of course the model of the chair may omit some detail that also needs to be understood.
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