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Essential Mechanisms: 3:1 reduction gear.

Not just a gear box though! The output gear (the large one in this case) is fitted with a crank so that a push rod can be connected to a character on top of the box. The gear box ratio is actually 10:29. The fact that the teeth numbers don't divide into each other exactly means that it isn't the same teeth meshing against each other all the time. This reduces wear and reduces that chance that teeth snag against each other.

 

 

3:1 reduction gear & crank. #mechanism #papercraft #automata #crank #gear #animation

A video posted by Rob Ives (@robivescom) on

 


The parts come as a four page file. Members can download them at the link for free. Non members can download them for £2.50.

I printed the parts onto coloured card for a colourful model. You can use white, coloured or patterned card. The best weight is around 230gsm or 67lb thin card.

Score the dotted and dashed lines and cut out the crosshatched areas before carefully cutting out the parts.


The twenty nine tooth gear is made from double thickness card. Fold over the card and glue it down leaving the centre tabs unglued. Once the glue is dry, carefully cut out the gear. You can cut out the holes to make spokes if you choose. They actually make the gear less strong but it does look nicer and it is still plenty strong! Your choice.


Roll up the four axle tubes gluing them down accurately on the edge of the grey area.


Make up the two crank pieces in these two steps.


The push rod ends are made from double thickness card. Fold over the card and glue it down. Once the glue is dry carefully cut out the piece.


Thread one of the crank pieces into the large gear and glue it to the marked area. Use the picture to ensure you have the correct orientation.


Assemble the push rod and push rod ends. Thread the shortest axle tube into place.


Make up the crank and gear assembly as shown fitting the two mid sized axle pieces into place.


Each of the ten small gear teeth is made as shown.


Glue the ten teeth together in a long strip.


Fit the gear inner to the square axle tube as shown.


Glue the gear fillets into place then glue on the second gear end.


Take the tooth strip. Starting at the end with the hanging tab, glue the tooth strip to the tabs on the gear inners.


Assemble the top and the base by folding over the side tabs to make right angled triangles.


Assemble the two box ends. This time the tabs fold round to make equilateral triangles.


Assemble the handle in three steps.


Glue the two ends to the box top. Use the two dots and the three dots on the parts for alignment.


Glue in the base and fold in and glue two of the side pieces. Leave the other two open.


Fit the two gears into place in the box.


Fold in and glue the sides.


Complete the model by gluing on the handle.

Use the model as an exercise in pure mechanism or as the starting point for your own character based automata!


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I'm working on the latest in my Essential Mechanisms series. This time a 3:1 reduction gear.


Rather than just reprising the 2:1 gear I wanted to add a little extra. To that end, the new mechanism includes a crank which can be used to drive your characters.


Here's the gears and crank fitted into a box and ready to go.

I have all the photography and parts layouts done so the finished project should be on the website very shortly.


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Sat 18th Oct 2014

Here's my standard quick-key that I add to the top of model instructions showing what the different line types on the downloads mean. You'll have noticed that I've added a new bit. To the right is a new crosshatched section. This is used to show areas that are to be cut out.


I've made it with a thin grey diagonal cross hatch (50% black 0.25pt line.) Surrounding the crosshatching are a broad white line (light grey in the picture here so you can see it) and closing it all in a 0.5pt black line.


Here's the end result in action on a model part. I think it looks rather good, or as #truelove put it: What? You weren't doing that already?


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£2.50
Download Gear Box
Become a Member for free access to this and other files on the site.
See the Membership page for more details.

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Essential Mechanisms: Gearbox.

This gear box features a two to one reduction gearbox. (The gear ratio is actually 23:12 so that the same teeth are not constantly in contact with each other) Use this model as an experiment in pure paper mechanism or as the starting point for your own character based designs.


Print out the parts onto thin card. I used coloured card to make a colourful model. You can use coloured, white, patterned or a mix of all three. Thin card, roughly 230 gsm / 67lb is ideal.

Score along the dotted and dashed lines and cut out the holes before carefully cutting out the pieces.


The teeth of the pinion gear are made individually. Don't worry, there are only twelve! Fold up and glue down each tooth then glue them together in a strip. Make sure that the teeth are just touching at their base.


Twelve teeth glued together.


Glue one of the gear centres to the pinion axle along one of the grey lines.


Glue the two gear fillets into place so that their ends touch the gear centre where the tabs stick out. (arrowed)


Glue the second gear centre into place.


Take the gear strip. Starting from the end with the hanging tab glue the teeth round the central core...


...finishing by gluing the end down to complete the pinion.


Roll up the two paper axles gluing their ends down lined up with the arrows.


Take the longer of the two axle tubes and thread it through the pinion. Line up the grey line with the end of the square tube. (Arrowed)


The larger gear is made of double thickness card. Fold the piece over and glue it down. Make sure that the central tabs are not stuck. Once the glue is dry, cut out the gear. You can cut out the four sector holes if you like although they are purely for decorative purposes.


Fit the gear to the second square tube lining it up with the grey line then fit the white axle tube into place.


The two gears ready for action!


Assemble the handle in three steps.


Making the Box

Make up the two box side. The triangle sections should be right-angled triangles.


Make up the two box ends. This time the triangle sections are equilateral triangles.


Join the two ends to one of the sides. Use the two and three dot makings to ensure the correct arrangement.


Fit the second box side.

Glue in the side flaps from the box ends onto one side only. Make sure that the box stays square.


Fit the gears into place as shown.


Close the box over the axles and glue them down.


Complete the gear box by adding the handle to the pinion gear.

You can use this as a complete model, the gear is a rather satisfying mechanism in its own right. Or you can use the project as the starting point for your own character based design. I'll be adding a couple of examples of what you could do in the near future.


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All the parts layed out and ready for a (roughly) two to one gear box.


I've completed the computer files and taken assembly photographs. I just have the instructions to write.


The finished design will be a reduction gear box as part of my essential mechanisms collection. The plan is that you can use the mechanism as a starting point for your own designs, perhaps by adding a dinosaur as shown below. I'll be producing guides for each mechanism to show how to create your own paper animations as well as producing completed models as examples. Should be fun!


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The ever productive Mr Cool has been at it again! He's taken the static dinosaur models and made this super fun moving model. I love the way the dinosaurs are built so they curve round slightly. Nice work Coolio.


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Sat 11th Oct 2014

I'm still experimenting with gear design. In the previous version the pinion (the small gear) had the teeth wrapped around a central single flat disk. Simple(ish) to make but prone to tilt over. A disk at each end would keep the gear straight and level so here we go.

I've started with a short central core, added a disk at one end and some white support pieces...


...then added a second disk to the top making a sandwich core.


I've made the teeth from twelve individual triangle sections glued together.


The teeth are wrapped around the cental core.


And here's the finished pinion!

I fitted into the box from my previous model and it runs beatifully smoothly. I still have an issue where the pinion can drive the larger gear but the larger gear can't drive the pinion. Further experiments needed I reckon.


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Thu 9th Oct 2014

I'm sure you'll remember the SocketCircuit kickstarter I blogged about last month. Cory Russek has produced this fantastic range of paper based projects to introduce electronics. Despite attracting a healthy number of backer he didn't quite making the funding goal. Not one to give up, Cory has applied what he learned from the first round and relaunched an improved version of his KickStarter. I'm delighted to report that with twenty days to go he has well exceded his pledge goal!


As with the previous KickStarter one of the projects is this model, the BarriBot. Itis based on my paper robot model with the clever addition of a Barrier Grid Animation and internal LED illumination. Check out the KickStarter page - the animation is great!

SocketCircuit is a fantastic project to get involved in.

>> Visit the page here and sign up! <<


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Wed 8th Oct 2014

Experiments with paper gear design.

I've been looking at the gear in the Hippo model to see how it can be improved. In the current design there is this large gap between the teeth necessitated by the need to glue the teeth into place. I was wondering if there was a way I could construct a gear where the teeth are closer together.


This is what I've come up with so far:

The teeth are made from individual sections with tabs to the side to link them to the next tooth. I've printed out the parts twice on two different colours of card so that you can see the separate parts.


Here's a row of twelve teeth ready to be looped round and glued into a closed ring.


With a central support in place the result looks rather good.


I've then constructed a matching twenty three tooth flat gear from from double thickness card.

It feels like it runs smooth but I'll only really be able to tell if it works once it is mounted into a box. Back to the computer.


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£2.50
Download Dinosaur
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A paper dinosaur to print out and make.

Members can download the parts for free at the link, thanks for signing up! Non-members can join in the fun for £2.50. There are three versions in the download, two coloured and one line only version for you to print out on your choice of coloured or patterned card. Print out the dinosaur onto thin card (210gsm / 67lb) Score along the dotted and dashed lines and carefully cut out the parts.


Fold round and glue down the bottom tab of the centre piece.


Note these two marks on the body top...


Glue the centre piece to the body top between the two marks.


Starting from the end of the neck (arrowed), glue the two sides into place.


Work your way right down to the tail end gluing the tabs down two or three at a time.


Glue the two tail parts together using the tabs.


Using the small arrows for alignment, glue the body front into place.


The legs and feet are made from double thickness card. Fold the pieces over and glue them together. Once the glue has dried carefully cut out the pieces.

Glue the legs to the feet.


Glue the legs to the body on the grey areas.


Assemble the head then glue it to the top tab. Make up the eyes from double thickness card and glue them into place.


The arms are also double thickness. Once you have made them and cut them out, shape them gently for a realistic pose then glue them into place.


The paper dinosaur could be a good starting point to design your own animated paper character!


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