topic Re: Soss Hinge Joints in Fusion Design, Validate & Document Forum

Soss Hinge Joints

Anonymous — Thu, 03 Jan 2019 23:50:25 GMT

Hi All,

I'm having trouble getting a soss hinge to move correctly in Fusion. I've been playing around with the joints to no avail - I can't seem to get the motion correct. Does anybody have tips for defining the joints for the following hinge:

https://www.mcmaster.com/1612a2

The part number is 1612A2 on McMaster Carr

Alternatively, if someone with experience with soss hinges could give me advice on how to position the bodies properly corresponding to the hinge being closed, that would suffice. I'm having trouble visualizing exactly how these hinges work.

Thanks

Re: Soss Hinge Joints

davebYYPCU — Fri, 04 Jan 2019 05:40:34 GMT

Rigid Grouped the blocks and pins on each side, and both pairs of arms, 4 groups.

The 4 pins all have Revolute Joint with the arm/s.

I could not make it work until I ignored the centrë pin, which maybe an Assembly item.

Some parts hidden for clarity.

Might be wrong Cause I can get unusual movement, when grabbing the wrong bit.

Re: Soss Hinge Joints

jeff_strater — Fri, 04 Jan 2019 06:11:27 GMT

right. I got to the same conclusion. Without that center pin, it kinda works. I don't understand these hinges - I suspect that there are springs and/or some "slop" or sliders in the real item that make this work, but such things are not apparent in the McMaster-Carr downloadable geometry.

Re: Soss Hinge Joints

davebYYPCU — Fri, 04 Jan 2019 06:35:53 GMT

With my left side grounded, pull the arm on about my red spot, all works perfect, right hand block swings the required 180 deg.

Can you point me to an intuitive way to set Joint Limits, my model needs 0 and -104 or 76 depending on which joint.

I have not found a repeatable way to set these buggers - in my 3 years.

Re: Soss Hinge Joints

Anonymous — Sat, 05 Jan 2019 18:21:05 GMT

Thanks for checking it out. The two faces which have countersinks in them are supposed to be flush (or nearly flush) when the hinge is closed from my understanding of how soss hinges work (see attached picture). I just can't determine how the arms are supposed to move to accommodate this. If you look closely beneath the arms (other picture) it looks like there is a rod attached to each that is supposed to roll under the other arm (they are intersecting in the model, circled in green). I tried using a contact set but still had some trouble!

Re: Soss Hinge Joints

Anonymous — Sat, 05 Jan 2019 18:23:57 GMT

Thanks for giving it a look. I could get the arms to swing but there is some other motion that is not being taken into account because the faces of the big components should be flush at the end of the 180 degrees. See my previous reply if interested. I tried looking up a video of a real soss hinge being opened and closed for clarity but it didn't help much!

Re: Soss Hinge Joints

davebYYPCU — Sat, 05 Jan 2019 22:12:37 GMT

Me too, I had ti find what was required, cause the inserted model was freezing up if I used the centre pin for anything, and I agree with Fusion, until shown otherwise, impossible, with that model, using 5 pivot pins, works with 4 pivot pins, but Jeff’s observation about how accurate from McMaster, is also to be considered,

At the time I posted my take on it, I was happy to embed the hinge a little deeper than flush to make it work, but now I realise in the real world you could not do that, without board interference on the arms.

My take now is the McMaster model is good enough for an open static representation, cause when closed you can’t see it.

You’ll need to reverse engineer a real one, or find good documentation on the mechanism’s Geometry, was my first step, but didn’t get far on that when seeing a vid on the how it works.

Edit : Found the Geometry onthe Net, duh, there is 3 fixed and two moving pins, just had to jump out of the square a minute. Back later, see if I can make it work.

Re: Soss Hinge Joints

davebYYPCU — Sat, 05 Jan 2019 23:31:18 GMT

With proper homework done, works, there is now only a 2mm airgap to the faces,

mechanics are

117 degrees on the inner pins.

54 degrees on the centre arm pin

Motion link, 166 to 360, for both sides

The moving pins describe what looks like an ellipse, so they are having an air swing in the model. Fusion doesn't have a joint for them, I put them in the arm rigid group.

Might help....

Re: Soss Hinge Joints

jeff_strater — Sun, 06 Jan 2019 00:29:26 GMT

I found this on Grabcad: https://grabcad.com/library/soss-no-212-hinge--1 that is a different example, but shows what is missing - a groove where the pin slides on the outer sides:

However, I tried to create joints for this in Fusion, and I think I need more joint limits to get it to work correctly - this mechanism is definitely stressing out Fusion's joint solver. The Pin-Slot joint comes in handy here

Jeff

Re: Soss Hinge Joints

davebYYPCU — Sun, 06 Jan 2019 00:50:19 GMT

This is the original model, it's geometry requires a Pin / Curve track Joint, and the Planar will just be redundant.

Re: Soss Hinge Joints

MichaelT_123 — Wed, 09 Jan 2019 02:46:19 GMT

Hi Fellows,

A Soss Hinge is tricky, isn't it?

Please find attached the example of another one in the form of video files. Hopefully, it will allow you to better understand how it works without going to a hardware store. Please note pin channels there. They are not straight but a little bit curvy (might be straight or even different for both halves though). The channels control the dynamics between a hinge scissor and hinge mounting bodied. The shape of them can be to some extent (within a range) modified, giving some kinetics variations possibilities. The one in the example implements linear angular relations between moving elements with some haptic kick at the end.

SossHinge

https://a360.co/2CXOT5g - SossHinge_A_mono.mp4

https://a360.co/2CYDr9E - SossHinge_B_mono.mp4

https://a360.co/2Fhvw98 - SossHinge_arcd.mp4 - requires stereo media viewer (e.g.VLC) and red/cyan anaglyph glasses

Regards

MichaelT

The model is based on the files (with some modifications) by Mr. Edmund Lively.

http://www.3dcontentcentral.com/secure/download-model.aspx?catalogid=171&id=772975

Re: Soss Hinge Joints

jeff_strater — Wed, 09 Jan 2019 02:58:47 GMT

thanks, @MichaelT_123 - that is certainly helpful, and does explain why I couldn't get my model to work - those slots are somewhat curved!

Re: Soss Hinge Joints

MichaelT_123 — Wed, 09 Jan 2019 03:28:44 GMT

Hi Mr.Strater,

As I indicated channels can be also straight, at different angles, etc.

Together with the rest of hinge's geometry, they contribute to the overall kinetics.

Together here is an important word.

Regards

MichaelT

Re: Soss Hinge Joints

MichaelT_123 — Thu, 10 Jan 2019 11:24:21 GMT

Hi Mr.Strater and Fellows,

… adding a little bit of substance to the notion, that the Soss Hinge kinetic characteristic can be modified by a shape of its sliding pin channels, please find attached ‘seeing is believing’ resources.

They represent two hinges one with a curvy channel (the same as in my previous post) and the other with a straight channel (as you would probably find in a hardware store).

Dynamic characteristic of both of them can be ascertained from the chart

and the video.

https://a360.co/2FoI7XZ - SossHinge_C_mono.mp4

On the side note, the AI (artificial intelligence) of the current Motion Solver, although works in typical situations, has problems with slightly more complex scenarios (at least automatically). Maybe it is good, as FI (ficial intelligence) still has its use.

Regards

MichaelT