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First Flip Face prototype for members to download and try.

I'm trying out a few different mechanisms so see which works best and thought you might like to play along at home so if you are a member you can download the parts at the link and make your own. 

This is a successful mechanism. Turn the handle on the back of the box a full turn and the face turns 180°. The mechanism keeps the face in position when it is supposed to be stationary. The only downside I see is that turning the handle a full turn then stopping isn't the obvious thing to do. Ah well, you try it and see what you think.

Print out the parts onto three sheets of thin card (230 microns / 230 gsm) Score all the dotted lines, cut out the holes the carefully cut out the pieces. Dotted lines are valley folds, dashed lines are hill folds, solid lines show where to cut. Fold up and glue together the side pieces making right angled triangle sections top and bottom.

Glue together the drive stiffeners.

Glue the drive stiffeners to the drive wheel on the grey area.

Fold up and glue together the two axles.

Tightly roll up the two drive pins and glue them shut.

Thread the drive wheel sides onto the drive wheel axle lining them up with the two grey lines

Glue the sides of the drive wheel into place so that they are curved.

Expand the cross holes at the ends of the drive wheel with a cocktail stick then thread the drive pins into place.

Fold over and glue together the geneva wheel so that it is double thickness. When the glue is dry, cut out the piece then fit it to the second axle lining it up with the grey line.  

Assemble the handle as shown above.

Glue the two halves of the box together at one end only. Thread the geneva wheel and drive wheel into the correct hole using the picture above as guidance. Glue the washer into place. 

Glue the box closed then glue the washers into place on the back. Glue the handle to the axle then glue the face to the tabs on the drive wheel.

Done! Turn the handle a full turn and the geneva drive advances two quarter turns flipping the face over. Rack and pinion next.

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The continuing adventures of the Flip Face Mechanism.

Here's another possible solution I could try. It is sort of half way between a rack and a gear. It has the advantage of going back to what I was originally aiming at, press down one hand for happy, the other for sad.

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Further adventures with the Flip Face Mechanism.

I've started off by adapting the bi-directional ratchet mechanism so that it turns a full 180° degrees for each cycle. I've done this by reducing the number of teeth on the wheel to four.

Here's the result. It works, sort of.  I could connect a pair of arms to the cross bar, (Under my finger in the picture.) which would then rock back and forth to rotate the face.

The downside is that it really is at the edge of what the mechanism will do, it works, but not easily, not smoothly. 

Two more mechanisms to try. A double ended geneva drive mechanism modified from this mechanism. I have the parts cut out for this, ready to try. I think it will be a good solid mechanism. I plan to put a handle on the back of the box and the face connected to the axle running though the cross piece on the front side of the box, one turn of the handle would make the face on the front turn 180°.

Alternative three, a rack and pinion drive. Also promising.  It could work quite nicely. The face would be attached to the gear with the rack running through the body as a set of arms with hands on each end. It would then just be a case of pushing the arms one way for happy face, the other way for sad face. Watch this space.

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Progress on the Flip Face project.

Okay, so it sort of works. You press down on one arm and the place where the head will be mounted rotates 180° one way, press down the other and it does the same the other way. 

The trouble is, as soon as I let go of the hand the head bounces back perhaps 20°. You might think it would just look wistful but no, it looks crooked. Pah.

Also, the friction on the paper belts is a little high so it jams up very easily.

I think I'll mark this down as a dead end and try replacing the mechanism. I have a few possible ideas to try. Either a very short rack and pinion, some sort of long action ratchet or perhaps as Pookafletch suggested by email, some sort of adapted pop up mechanism. 

A happy mix of frustration and fun.

Expect to see a happy face in the thumbnail next time. :-)

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I'm working on the flip face mechanism again. In this model you press down on one hand and the face turns 180°, press the other hand and it turns back.

It turns out to be surprisingly difficult to make a mechanism that turns a piece through 180°. Here's what I'm working on with the moment, let me know if I've missed an obvious easier solution. 

The face is fixed to the semi-circular shape at the top of the sketch below. This part can turn through 90° left and right from its currently position. It's joined to the arms by a long thin paper strip threaded over a couple of rollers. the rollers direct the paper, ensuring that it is being pulled straight down.

(Apologies for the rather rubbishy sketch! I'll try harder next time :-)

Semi circles are hard in paper, I've gone for a simpler semi-octagon which is a close corollary and works just as well.

Here's the rotating part fitted into place with the paper tape threaded through the support piece and under the first (not actually rolling) roller. 

I'm worried that the rotary piece won't stay in position when pressure is taken from the hand. We'll find out soon!

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I really need to keep a scrap book. I mean, I stick things in my notebooks that I find interesting but what I really need is a systematic scrap booking system for all the bits and piece of interesting ephemera that I see, enjoy and promptly forget. The other I saw a picture of a little brass figurine with one of those rotating happy/sad optical illusion faces on the front. He had his hands out in front of him palm up and when you pressed down on the palms his face rotated. And for the life of me I can not remember where I saw it! I've been thinking about how it would work in paper on and off for a couple of days. There are a couple of interesting problems that might make for a fun project. So here's my first draft:

The face (which I drafted in Illustrator) is fixed to an axle centred between the eyes. Press one arm down and the head rotates 180° one way, press the other and it rotates back again.

The two main problems as I see them:

The head need to rotate exactly 180° them stop. Shouldn't be two hard with a suitably placed stop but I do need to make sure that is stays in place and doesn't 'bounce' back.

Secondly, the arms move only a short distance yet the head has to turn a full 180°. If I was using brass and steel I'd probably use a chain and sprocket.

This is where the interesting mechanism comes in. There are a few different things I could try. My first draft has the arms as a single unit pivoting about their middle. Connected to the arms and running over the head axle is a thin paper belt. As the arms move the belt turns the axle, rotating the face. I'm in the process of putting this together so I'll get back to you on how well it works.  

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I've been finalising the colours for the faerie project.

...and trying parts out to see what they look like. 

I've settled on a completed colour scheme and have cut out all the parts. Once I've hit publish on this post I'm off to set up the studio flash to take pictures for the construction instructions. 

Big hug!

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Poseable faerie. Final stages of assembly.

I once saw a mushroom that was this big!

Care to dance?

Taxi!

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Factory robots use arms with many joints to that they can reach into awkward places. Each axis on each joint counts as one degree of freedom so, for example, a joint which rotates and moves up and down, like Surly Jack's head, has two degrees or freedom whereas an simple elbow type joint has only one. In the faerie model I'm aiming to create an arm with two joints and three degrees of freedom. 

Degree one the upper arm rotates. This joint uses a couple of flat plates with the arm joined to one side. The long tabs in the picture will fix the plate into the shoulder.

The second degree of freedom is an elbow joint. Again, tabs in a circular hole.

Here, the arm is fitted into the shoulder showing the first degree of freedom.

For the final freedom, the shoulder swings back and forth.

The prototype works nicely, time to incorporate it into the complete model.

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After the fun with Surly Jack I'm back on finishing my Faerie project. I think it will probably end up as a static model but with poseable features.

I've used the same poseable head joint as with previous projects but with a slight change. Instead of making the head so that it can nod and rotate, I'm making it so that it can rotate and tilt. Yaw and roll if you like. This is fairly straightforward to achieve, I just fit the joint side to side instead of front to back

After the usually struggle getting the hair design sorted I have a head I'm quite pleased with.

I've mounted the joint across the head and fixed it into place with the chin raised slightly.

The result is this rather coquettish tilt of the head.

Looking good so far, its going to look great on the top of our tree!

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