Linkage Design

Catherine Marshall was a suffragist. The suffragists believed in campaigning for women’s votes through peaceful, polite means. By contrast the suffragettes believed in deeds not words. In this model Catherine and a suffragette stand on either side of a donkey trying to get its attention with a carrot and a stick respectively.

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The women’s hands are moved via a cam and cam follower which in turn drives a linkage. I’ve used a heavy gauge wire to make the link. This part is made from a single wire bent into position over a template then fixed into position with a fine brass wire and some epoxy resin.link-01

A small screw fixed to a block on the box top provides a pivot point for the linkage.link-02

Then under the box the linkage is connected to a cam follower. All that remains is to see which is more persuasive; carrot or stick?link-03

Lead Weight – First Attempt at Casting

There are a pair of cam followers on the Colonel Rutherford model, one moves his head, the other his writing hand. The Colonel’s head has plenty of weight so it falls back into place on its own but the hand needs extra assistance to move back after the cam has released it.

A cam works in one direction only, the cam will push the cam follower up but something else is needed to pull it back down. I could use springs but I’ve decided to use weights in this model. I’ve collected loads of bits of lead over the years, mainly from wheel balancing weights found on the side of the road. My plan is try melting and casting the lead to form usable weights.

I used brass wire to create a hanger for the top of the weight.lead-a05

 

I then packed a tin can with white sand from the local builder’s merchants and made a hole in the centre with a 20mm dowel.lead-a06I pushed the wire into the bottom of the hole so the the arch of the loop was buried in the sand.lead-a07

I melted lead in a pan in the kitchen (#truelove was out) then #1son captured the moment I poured the molten lead into the mould.lead-a01After cooling for a few minutes I knocked out the sand…lead-a02…then washed off weight to complete.

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lead-a01I’ll probably try again to see if I can make a smoother finish to the weight but it certainly works well as is.
Total weight for this version 240g.

Any tips on smoother casting would be welcomed!

 

 

 

 

 

Laser Cut Wooden Chain and Sprocket

chain-a12The first version of the Colonel Rutherford model used a chain drive to transfer the drive from the motor to a gear rotating an airmail aeroplane above the model. I originally used a plastic snap-together chain that I bought from eBay. It worked well enough but some of the links were a little stiff giving the motion an uneasy, jerky look. Visuals are as important as how well the models work in these automata so I set about making an improved chain drive, this time using laser-cut wood. Here’s a rig showing the end result in action

chain-a01I cut out lots of little pieces on the laser cutter to construct the chain. For simplicity each link of the chain is constructed from four identical pieces.

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Two of these pieces are glued together for each side of each link. A cocktail stick through the small holes is used to ensure everything is lined up properly then the pieces are clamped up and left to dry .

chain-a03Lots of links are needed!

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The cross pieces of the chain are made from 10mm lengths of  9mm dowel. I drilled the dowel through the centre making a pilot hole for the screws. The screws are fitted using appropriate washers and tightened just enough so that the links are flexible.chain-a06

The sprockets are made from three layers of 3mm ply glued together.I sanded the side of the sprockets off to help guide them into the centre of the chain.chain-a07

Here’s one of the finished sprockets showing the tapered teeth.chain-a08

This version of the chain drive is a test bed to ensure that it works properly. I’ve mounted the two sprockets onto an MDF baseboard and added a handle. Looking good!chain-a09

Puppetry in Motion

puppets-a02I delivered the almost complete Mary Chambers automata to the Archives this morning. We need to make one small change before it is finished, the rower is at the wrong end of the boat. Oops!

Apart from that it is looking great. Dawn’s puppetry is fantastic and just look at those delicious gears!

We’re working on several models at once as we come towards the end of the first phase of the  Archive project. Colonel Rutherford is almost done, I’m just finishing off his plinth and connecting up the last of the linkages.

donkeyAfter that will be the suffragette model with Catherine Marshall. Dawn has pretty much finished the puppetry so it is down to me to bring the characters to life.
In this model the donkey (Ass-Quith, tee hee) will be sitting between Catherine, a suffragist and another character who is a suffragette. Catherine offers a carrot then the suffragette threatens a stick. Hence the angry eye brows.

Here are the various characters waiting to be brought to life. I love Catherine’s teeth!

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Gear Train for Mary Chambers Model

The Mary Chambers model was the first of the models in the Archive Project that we completed. As parts of the process of mounting the puppetry onto a plinth I wanted to update the mechanism so that the style matched that of the later projects.

There are three main movements in this model. The soldier rows the boat, the boat rocks up and down and the waves… well they wave. All three movements  can be based round a circular crank movement but they are all at different speeds. Fastest moving are the waves with the rocking of the boat slightly slower. The rowing movement is slowest. Slow and steady. I laid out this gear train which should so the job.gear-a05Time to transfer it to the real world.

I made a simple jig onto which I can build the gears.This keeps everything at right angles and makes sure that the key slots are aligned.gear-a01These pictures show the largest gear, the thirty seven tooth gear, being constructed. The gears are made up from three layers of laser cut ply . The gear part with the spokes is sandwiched between two disks and fitted onto the jig until the glue is dry.gear-a02

With the gear centre removed from the jig I fit the outer tooth rings into place front and back and clamp them into position whilst the glue dries. You can see the short section of rack in the picture that  I use to make sure that the teeth are lined up properly.

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The finished gear.gear-a04

I’ve then constructed an arch to hold all the parts into position. Here you see the assembled parts, almost complete apart from the keys which will be fitted to the axles.

Running smooth!

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Colonel Rutherford

colonel-a04I delivered the first plinth to the Archive this morning. Dawn met me there and after struggling with the heavy box from the car we set it down in a currently unused room.

The plinth, which will ultimately be painted white, contains a power supply in the form of a large lead-acid battery, a coin slot mechanism and a timer circuit. Drop a suitable coin in the slot and the motor runs quietly for a preset period.

Colonel Rutherford was the first to try out this privileged placement!
Looking good we both agreed.colonel-a01The good Colonel sits on his stool under the baking desert sun sketching and occasionally looking up at his subject .

colonel-a03Whilst the mail plane, charmingly decorated in copies of original hand written letters and airmail sticker circles overhead.

colonel-a02We were both delighted with how the plinth, the mechanism and Dawn’s fantastically detailed puppetry are looking.

Next time: Catherine Marshall and the Suffragette donkey!

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Battery Base

Each Automata in the Archive Project stands on plinth and will be covered with a protective glass case. Mounted in the plinth will be a coin slot. Tokens fed into the coin slot will trigger the performance of the automata.

Some of the plinths will be near to a ready supply of mains electricity but others will need to be self contained. I’ve opted to use a fairly meaty 12v lead acid battery as the power supply to maximise the time between charges. The batteries are heavy. Nearly 2kg in this case, so they need to be secured to the inside of the plinth.

I’ve constructed this battery holder on the laser cutter. It is shown here clamped up as the glue holding the three layers together, dries. battery-a05

A top view of the base shows that it is a shallow tray. Four small  rectangular slots on the base allow two zip ties to the threaded into place.battery-a01

Viewed from the underside you can see the two long slots where the ties fit. You can just make out the small holes at the end of each slot.battery-a02

Two long cable ties thread into place…battery-a03

…and the battery is secured. The finished assembly is screwed down inside the plinth and ready to go.battery-a04

Plinth

I’ve been trying out plinths for the automata. I made up a couple of drafts from corrugated card just to see if the size felt right. I’ve settled on 900mm for the height for the moment though I still have to check this with Dawn. Next step, see what it looks like made from more solid materials.

I’ve been to the friendly local wood merchant who cut me various pieces to size. There will be a pine frame inside but just to see what it looks like I’ve propped up these pieces and stuck them together with masking tape. I’ve stood the mechanism from the Catherine Marshall model on the top to get an ides of how it all goes together. The characters themselves will sit on the top of the box and the whole of the automata will be protected inside a glass cover. I’ve added skirting board round the base for the plinth which I think finishes it off nicely.plinth03We are planning to use tokens rather than just a push switch to start the automata, the thinking being that the tokens will encourage people to place a value on each ‘performance’ encouraging them to stand and watch rather than rushing off to press the next button. I’ve sourced some coin slot mechanisms and programmed them to recognise tokens. One of these will fit into the front of the plinth.

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The instructions for the coin mechanism appear to have been translated from their original language using Google Translate but after a bit of frustration I have got the machine to recognise or reject coins as appropriate.

For your interest here’s a closer look at the front half of the Catherine Marshall mechanism.plinth02

Motorisation

In the initial planing we talked about how the automata in the Archive Project would be driven. We decided against manually turning a crank handle because we were worried about damage caused by over-vigourous cranking, clock work was out for practical reasons leaving electric motors.  Some of the twenty models proposed need to be sited away from mains electrics so we plan to use 12v rechargeable batteries as the power source. I’ve sourced a suitable motor that is both powerful and runs quietly. The output shaft is 6mm in diameter and it runs at 145rpm, roughly two and a half turns a second. Pretty innit!? motor-a05

Now it needs a suitable mount.

motor-a01Here’s the cradle I’ve come up with, made from 3mm thick laser cut plywood. Notice the segmented segment in the cradle section. The gear box section of the motor sits here, the segments are glued into place and provide a surface to which the motor can be clamped.

motor-a03The motor fits in the cradle and a gear connects to the output shaft.

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The whole thing is clamped together with a jubilee clip allowing the motor to be removed and replaced in necessary.

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Linking a Gear to an Axle

While I’m prototyping the gears on the wooden automata I need to be able to assemble and disassemble the model so that I can experiment with designs.

I’ve tried all sorts of design variations. Brass axles, grub screws, flanges, perspex joints. Finally I feel like I have settled on a consistent design. I’m using 12mm dowel for the axles and a keyway in the gear’s axle hole to hold the gears in position.gear-a01

I drill a couple of small holes in the dowel in the place where the gear is being fitted. The holes don’t go all the way through the axle. I then make a curve-topped staple from a short length of 1mm diameter wire.gear-a02

The staple fits into the two holes, the fact that it is curve-topped ensures that the centre of the staple is raised above the dowel.gear-a03

The gear then slips onto the shaft with the keyway located over the staple. The staple works to stop the gear rotating out of position. Perfect!gear-a04

Here’s a sample of the gears in position. Looking good!gear-a05