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Tue 27th May 2014

One starting point mechanism can be used for all sorts of different paper automata. Take, for example, the four bar linkage mechanism. This project was originally used as a pointing finger for my YouTube video outro,


With a little extra work it makes this rather fetching dancing figure.


No sooner had I posted the Instagram animation above than I received a tweet from @loobydotlu suggesting it could also be a goal keeper. Nice idea!


I'll be releasing the plans for this character shortly. I'll keep it blank so you can choose how to dress it. Dancer, goal keeper, person dodging bees... it'll be up to you.


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Tue 27th May 2014

I've long been intrigued by the idea of making sounds with paper models. In a previous post you'll have seen that I was retrying my old train whistle project using an improved bellow. I'm aiming to get the pitch of the pipe much higher so that it can be used as part of a bird model.

This model uses a 7mm square tube for the pipe. It works nicely and could be even higher pitch with a shorter tube.


My next step is to try driving the bellows from a mechanism. The obvious choice is my new favourite, the Scotch yoke. Its up and down movement matched nicely with the needs of the bellows. I should also be able to fit a second bellow on the other side so that it sounds in both directions.

Here's a first draft.

From a lower angle you can see the crank that is used to drive the yoke up and down. I have a couple of other ideas for mechanisms and layouts. Expect to see more soon.


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Two new video from friend-of-the-website, cool022883. Firstly, with remarkable alacrity here is Mr Cool's version of the four bar linkage mechanism with added Chameleon.

A charming little project I'm sure you'll agree!


Secondly, and beating me to the punch, as it were, here is Mr Cool's version of the intermittent drive that I'm working on with the Eagle project but this time used for a vampire model. Nice work and thanks for sharing!


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Sat 24th May 2014

Back to the Eagle project. I've worked out the Geneva part of the mechanism and how it will drive the Scotch yoke. I've also worked out the design for the rack and pinion. My next step is to link the Scotch Yoke to the rack and pinion so completing the drive chain. You can see in this picture that the rack is connected to the Yoke and is moved back and forth with the yoke as the crank is turned.


Viewed from above you can see that the rack is floating free and is joined to the yoke only by the ends. This allows it to be threaded through the box containing the pinion. I'm not sure if I will be keeping this layout or whether I'll be holding the pinion wheel into place in a different way.


From the end you can see the pinion wheel in place against the rack. The vertical shaft will be used to mount he Eagle's head once the mechanism is completed.


The Geneva drive fits on the outside back of the box. It will divide the movement by four . Next step is to finalise the layout of the parts and try to fit them into a box as simply/elegantly as possible.


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Sat 24th May 2014

There are two main types of projects on robives.com. Firstly, there are the complete animated character model like the Giraffe in a Box or the Press-Ups Robot. These models are usually fully coloured and have a completed project with a character performing a little story.

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Four Bar Mech Rack and Pinion Geneva / Crank Rotating Vertical Shaft
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Twister Stepped Rotation Scotch Yoke Ratchet

The other type of project is the starting-point kits. These downloads feature a mechanism or group of mechanisms in a box ready for you to add your own characters. They are the perfect starting point for the maker, hobbiest or student as a spring board for creating your own paper automata.

I've collected a few of the mechanisms together here. They are all free to download for members and I'm very happy for them to be used in schools. I suggest a Membership Plus subscription for school. If you are a member you can make as many copies as you need for your class.

I've collected together links to some of the recent mechanisms here, follow the links to see them in animated action.

What are you waiting for? Become a member now!


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£2.50
Download Four Bar Mech
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This interesting four-bar linkage mechanism produces a movement that swishes back and forth in a rather charming way.

Use it to explore the mechanism or as the starting point for your own animated paper character.

Members can download the parts for free at the link, non-members can download the parts for £2.50ukp


Print out the parts onto thin card. I printed them onto coloured card to produce a colourful model.

Score along the dotted and dashed lines, cut out the holes then carefully cut out the parts.


Fold up the base with right angle triangles at the side.


Repeat the process with the box top then fold out the flaps on the hole in the box top and glue them down as shown.


Fold over the tabs on the box end with the circular holes to make triangle shaped tubes. These will strengthen the box as it is assembled.


Glue the box end to the box top. Use the picture to make sure you glue the correct ends together.


Join the remaining box pieces together. Take care to align everything as accurately as possible.


Glue the box sides into place.


Assemble the linkage support as shown.


Glue the linkage support into the box as shown.


Glue together the linkage.


Glue the linkage to the linkage stand.


Assemble the dog-leg bar as shown.


Fold over and glue down the two crank ends to make double thickness card then cut them out.


Roll up and glue down the three pins. Use the arrows and grey areas to line up the ends accurately.


Glue the crank ends to the long arm of the dog-leg bar.

Find the pin with four arrows and thread it into the crank ends. It should turn freely.


Assemble the two crank pieces.


Glue the short ends of the crank to the pin lining them up with each other.


Glue together the handle following the three steps shown above.


Hold the crank assembly into position inside the box and thread the two remaining pins into place gluing them to the inside of the crank.


Glue the end of the linkage to the dog-leg bar.


Glue the handle to the box to complete the model. You can use this as a starting point for your own character or as a demonstration of how four bar linkages can work.


I used mine as an animation to go on the end of my forthcoming YouTube videos. You can see an animation of it in action here.


I've also tried creating my own character that uses this mechanism. Look out for a finished version in a download shortly!


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Thu 22nd May 2014

I really liked Patrick D's ideas of using the Four Bar Linkage mechanism I'd animated a while ago as part of my YouTube outro. To that end I've made up a paper model version so that I can give it a screen test.

I was rather pleased with this box design which clearly shows all the working parts whilst being solid feeling once put together.


Here are the four parts joined together ready to accept the paper engineering mechanism.


The four-bar linkage fits neatly into the box.


A hand and a "Subscribe" sign finish off the model. I've put together a quick Instagram video so that you can see it in action. I'll have a go at a proper screen test shortly.


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I'm planning on adding a set of wave on the sides of the the rowing project I'm currently working on.

I have a single drive point at the end of the waves, the slot in the middle allows them to rock up and down. I've stacked two layers of waves out of phase with each other, the result is quite pleasing.


The drive pin is in the foreground of the this picture with the alignment pin in the distance.

Check it out in animated action.


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This ratchet mechanism is part of the forthcoming Eagle project. Having put it together I think that it could have all sorts of uses in other projects so I'm releasing it now as a standalone download. Paid members can download the parts from the link, thanks for signing up. If you'd like to become a member you can sign up here.

I printed the single parts sheet out twice onto two different colours of thin card (230 micron / 67lb) then cut out some parts from one sheet and some from another.

Score along the dotted and dashed lines, cut out the holes with a sharp knife then carefully cut out the parts.


Pre-crease the folds on the rack teeth strip then glue them into place. Glue the grey glue areas and grey lines to help with alignment.


The completed rack strip.


The pinion wheel is made from a regular twenty four sided shape each side 3mm long. Every other side it marked with a 3mm equilateral triangle. The triangles are cut away leaving the pinion wheel perfectly matching the rack.

 


Fold over the pinion wheel part and glue it together to make double thickness card. Cut out the pinion wheel then glue in the pinion centre.


Fold over and glue down the box ends.


Fold round and glue together the box.


Roll up and glue down the axle tube using the grey areas and triangles for accurate alignment.


This is how the pinion fits against the rack.


Hold the pinion into place in the box then push the axle through. The pinion should be fixed to the axle and the axle itself should turn freely inside the box.


Thread the rack into place. Move it back and forth to turn the pinion wheel. As mentioned, this mechanism will be at the centre of the upcoming Eagle project. It will also be handy for all sorts of projects where you need to convert from rotary to linear motion or from linear to rotary. I hope you find it useful!


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The eagle mechanism is a made up of three basic mechanisms. A Geneva drive which divides the rotation by four, a crank and scotch yoke to convert the rotary motion from the drive to a back and forth motion and finally, a mechanism to convert the back and forth motion of the scotch yoke to the rotary motion of the vertical shaft. My first draft had a peg sticking out the side of the vertical shaft and a simple link joining them together. It worked but the extreme ends of the yokes travel the motion of the vertical shaft slowed right down.


I wanted to make the rotary motion more consistent so that it didn't slow down at the ends of the range of travel. To that end, I've put together this flexible rack and pinion drive


By fitting the drive parts inside this box section the rack is held against the pinion wheel. Pull the rack back and forth and the pinion turns. Next step, fitting the various mechanisms together into a whole unit.


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