Pop up Robot prototype...
...and here it is squashed down and ready to pop!
The core of this project is the pop up mechanism from the previous post, inverted.
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I'm working on a pop up character. Elastic band powered. The character has a head and body, folds flat and pops up when released. The face on the front isn't the final design (!) it is simply there to help with laying out the parts once I've dis-assembled the project for scanning and final design.
I've use two nets like these ones one slightly smaller than the other. The design is based on the pop up cube I made some time ago.
The trouble is, the tension of the elastic band pulls at the corners, peeling them apart.
Time for a redesign.
I've split the sides in half so that the joint is in the middle of the sides rather than on the edges.
That way, the tension will be pulling straight rather along than trying to peel apart.
The single elastic band hooks in the corner of one cube, threads through a hole between the two then hooks onto the other side.
...and the result, the slightly collapsed old model on the left. The new version on the right.
Sorted.
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Vertical pendulum, Move the box and the main shaft at the front rocks up and down. This mechanism is destined to be used in the heart of a paper animation, perhaps a hopping frog or a moon walking spaceman. Build the project and bring it alive with your own character!
As usual, members can download the project for free, thanks for signing up. Non-members can download the parts for £2.50
Vertical Pendulum in action.
Print out the first two parts sheets onto thin card (230 micron / 67lb), the third sheet contains hinges, it should be printed onto standard 80gsm printer paper. Paper makes a good flexible hinge.
Glue the two pendulum pieces back to back then glue down the two side flaps.
Glue the paper hinge into place.
Fold the feet round and glue them down. Note that the creases are valley folds.
Glue the two sides to the grey areas on the base. Note that the writing faces towards the longest foot of the base.
Assemble the two struts and glue them into place on the grey areas.
Assemble the top piece and glue it into place using the grey areas for alignment.
Glue the pendulum so that it hands from the front strut.
Assemble the top link as shown. Note that the tongue is completed by folding over the tab and gluing it down to make double thickness card.
Assemble the bell crank as shown. The tongue is the same as the previous link. Glue two paper hinges into place as shown.
You'll need four coins as weights. UK 2p coins are perfect. 25mm in diameter, 7 grams in weight. Wrap each pair of coins tightly in an off-cut of card as shown.
Glue the coin packs to the pendulum front and back.
Glue the bell crank to the lower strut
It needs to be free to rock back and forth.
Connect the upper link to the upper strut with a paper hinge.
Thread the vertical shaft onto the two tongues and lock it into place by gluing the two tabs into place.
Glue the lower link to the front of the coin pack using a paper hinge.
Connect the lower link to the bell crank via the other paper hinge so that the top of the bell crank is sitting horizontally.
There it is! Move the model and the vertical shaft rocks gently up and down. Next step, add your own character!
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Here's the completed prototype for the vertical pendulum mechanism I'm working on. It's done and ready for photography but that's going to have to wait until morning. To keep you going in the meantime there are a couple of interesting issues that came up in the design/construction of the model.
Two design features: 1) A vertical shaft that moves up and down whenever the project is moved. 2) All wrapped up in a narrow package.
I've folded a bell crank back on itself which seems to work quite well. I'd still rather that the shaft was more central in the mechanism, ideally directly over the pendulum, but it is certainly useable as is.
Okay, first issue. You need a lot of weight to do anything useful. The greater the movement of the vertical shaft, the more weight is needed. This is an issue of maths and physics. The only way round it is to have the pendulum swing further causing other problems elsewhere. (Just had an idea about flywheels though - make a note!)
Second issue it to do with the stability of the model. I have four 2p pieces in the prototype, over 28 grams of your Sterling currency! All that weight tends to bend the card, just slightly, but enough to cause problems. The base flexes slightly causing the model to rock back and forth slowing the pendulum swing and stopping the movement early. (Picture above left) To get round this I've added feet front and back. (Right hand picture above) these provide a solid base for the rest of the model to sit on.
Feet under the base help keep the model steady.
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Corrugated Card and Paper Tape Truncated Icosahedron
I'm pretty sure it is one of the laws of thermodynamics, perhaps the forth. If not it is certainly one of the fundamental attributes of the Universe.
"In a closed system the number of single, unpaired socks always increases."
And so with the inevitability that accompanies physical laws, here at robives.com towers we have a pile of unpaired socks known to us as the sock orphanage. We currently inelegantly store them in a plastic bag while we wait for the return of the sock siblings.
Obviously we "can-nae break the laws of physics" but here's a possible work-around.
Like many bibliophile families, we have a lot of used Amazon packages ready for reuse. Time to press them into service. I decided to make a nearly spherical store pod thing, the actual shape I used is a truncated icosahedron, the same shape as a carbon 60 molecule and the classical soccer ball. The shape is made from twelve pentagons and twenty hexagons.
I made pentagon and hexagon templates. (Members can download the file at the link.) If you make you own template make sure that the side lengths on both are the same. Time to switch to instructional writing style...
Collect together several sheets of corrugated card. Using the templates, draw out twelve pentagons and twenty hexagons.
Carefully cut out the pieces using a ruler and sharp knife.
Twenty hexagons, twelve pentagons and a roll of brown paper tape ready to go. For ease of assemble it is worth spending a little time cutting the paper tape to length. You'll need ninety strips each the length of one side.
Start with a single pentagon, tape five hexagons round it as shown.
Fold the hexagons up and tape then together.
Add five more pentagons between the hexagons. Be as accurate as possible in the alignment of the pieces. Small inaccuracies multiply!
Work your way round the shape adding hexagons and pentagons as appropriate. Each hexagon touches three pentagons on alternate edges. Each pentagon is entirely surrounded by hexagons. Use these rules to help you choose the appropriate shape for each position.
I finished off leaving one hexagon off as an access hole. The finished shape makes a fantastic sock orphanage, a stylish litter bin or a play house for a curious kitten.
The spare hexagon makes a rather natty coffee mat.
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Friend of the website Dan, aka waterrocketsrule has been busy making some fantastic paper projects over the last few week. His latest is this mashup between the Snowman sculpture and the mech from the disagreeable sheep.
I'm sure you'll agree he has created a fantastic new project!
Earlier, he created a cam powered set of chomping teeth, a project which spurred me into finishing of the pendulum powered gnashers I had in an almost complete state. Nice one Dan!
Go and subscribe to his channel on YouTube where you can also check out his fabulous flapping trout model (I wish I'd thought of that one!)
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A pendulum powered pair of gnashing teeth! Move the box and the pendulum swings, opening and closing the box. Nom nom nom!
Members can print out the parts for free, thanks for signing up. Non members can download the parts for £2.50 at the link at the top.
Gnashing teeth in action!
Print out the first three sheets onto thin card, note that the colour version has both front and back pages. Print out the front of the sheet, flip the sheet round and return it to the printer to print out the back.
The forth sheet is for the hinges, print this into paper. The more flexible paper makes a better hinge than card.
Fold up and glue down the tabs at the bottom of the boxes to make triangular sections.
Join the two halves of the box together. Glue the box lid into place with the grey rectangle to the back of the box.
Fold up and glue together the pendulum hanger. Glue the hanger into the box so that the front edge lines up with the front of the box.
Assemble the pendulum. Glue the hinge to the grey area. Make sure you do not get any glue on the crease line.
Attach the pendulum to the pendulum hanger.
Assemble the lower jaw box. Glue the teeth into place. The grey face on the box is the lower face.
Glue the lower jaw box to the grey area on the top of the main box.
Assemble the upper jaw as shown above.
Glue the teeth into place. Note that the top of the box lines up with the top of the teeth.
Connect the two jaw pieces with the paper hinge.
Fold the coin holder tightly round two 25mm diameter coins. (approx 7 grams each) UK 2p coins are perfect for the job. Glue the coins to the front of the pendulum.
Assemble the push rod. Glue the hinge to the grey area as shown.
Glue the push rod to the grey area on the upper jaw as shown.
Close the jaw, threading the push rod through the hole in the box top.
Done! Once the glue is dry, move the box and the gnashers gnash!
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Further experiments on the theme of pendulums. I really wanted to create a pendulum powered model that bobs up and down when it is moved. Obviously, the first person that sprang to my mind when thinking about this possible mechanism was Ada Lovelace, mathematician and steam-punk computer programmer. And so we have, forthcoming project of a pendulum powered Ada Lovelace who bobs up and down whenever she is moved. Perfect.
Okay, mechanism time.
If I could use springs a vertical moving pendulum would be trivial but with card it is less straight forward. I need to convert the back and forth movement of a pendulum into up and down movement, and all within the space of Ada's conical section skirts.
My first draft is shown below with a bit of explanation as to why it was unsuitable. And so onto mk2. The go-to mechanism to change direction of movement by 90 degrees is the bell crank. The problem (there is always a problem, that is where the fun comes in :-)) being that the bell crank necessitates extra width in the model, making it hard to fit everything under the skirts. Above right and centre are my proposed solutions. Firstly, a pendulum with a cut out in the centre. Secondly, a bell crank that doubles back through the hole in the pendulum wrapping the mechanism neatly in on itself.
Notice also that I'm linking to the end of the main pendulum so getting the maximum amount of movement from any swinging going on.
I have bits cut out and ready to go - I'll be reporting back in the tomorrow.
Here's one that didn't work.
Well, it did work but it is far too bulky.
In this mechanism, the pendulum and the bell crank are a single piece. To get a reasonable amount of vertical movement the side arm needed to be long making the project over wide. To minimise the width I moved the pendulum right over to the side which also meant that the whole thing was unstable. Pah.
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Friend of the website, Waterrocketsrule sent me the link to these YouTube videos of the modified T.Rex he has created based on the original from the Flying Pig site. Nice work!
Happy New Year!
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Happy New Year!
Welcome to 2013.
A New Year's competition. The first person to sign up for standard membership in 2013 (GMT/UTC/UK time) will have their account upgraded to Membership Plus! Happy New Year!
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...and we have a winner! Steve Leach signed up first and has has his subscription upgraded to Memmbership Plus, thanks Steve and thanks to everyone who signed up. Happy New Year!
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