Prototype Mechanical Crab

[Steve CrowParticipant @stevecrow46066]

Hi all,

I've made a prototype walking mechanism. This is half a mechanical crab – an identical assembly and motor needs to go on the other end of its steel "spine".

It's based on the "Klann Linkage" (google it). You can find a few made examples on the net, mostly a lot larger than this.

I originally made this to quite a high finish – months of testing and handling has left its mark.

It works a treat. It was designed to cover its own length (100mm) in one second but with a 300rpm motor, it happily scuttles along at 150mm per second all day.

The main plates and the crank are made form 2mm engravers brass and the legs and linkages from 1/32" gauge plate hardened and tempered. The bridge plates are made from annealed 0.4mm Stanley blade then hardened, tempered and polished.

The crankshaft is 2mm silver steel running in miniature ball race bearings and there are brass bushes in all linkages.

I can't cut my own gears (yet) so they are bought in 0.5 mod brass gears.

All in all, there are 185 parts in this assembly and obviously the same again for the other side.

I've finished testing and I'm going to start on 2 complete crabs with a few modifications to improve on the prototype.

Cheers

Steve

[Steve CrowParticipant @stevecrow46066]

[Michael GilliganParticipant @michaelgilligan61133]

Excellent project, Steve

Nice to see it done small.

MichaelG.

[Adrian 2Participant @adrian2]

Beautifully made Steve . Can we see it in action please.

Adrian.

[I.M. OUTAHEREParticipant @i-m-outahere]

Excellent work Steve!

Are you looking a controlling the motors with a small microcontroller?

[Bob McParticipant @bobmc91481]

Beautiful Steve….!

Its Art…better than any Picasso.

[Steve CrowParticipant @stevecrow46066]

I did most of the testing using this Arduino and bridge setup.

I suppose I'll use something smaller on the finished item (which will be self contained).

I originally wanted to make this clockwork and only got the motors to test the mechanism!

I would love to post a video but my phone is an ancient Nokia with no camera.

[Neil WyattModerator @neilwyatt]

Lovely job.

Now you need to make a big one

Edit reading this Klann's linkage has many advantages over Janssen's (in the video).

Edited By Neil Wyatt on 16/07/2018 17:19:30

[Steve CrowParticipant @stevecrow46066]

Here's a couple more pictures of it under construction.

[Neil WyattModerator @neilwyatt]

LOL… "The Onedin Line"!

[Harry MuellerParticipant @harrymueller51767]

Great job Steve!!

I've recently dusted off a my Sherline mill/lathe and am looking for a project. What you've done has really piqued my interest and I'd love to see how this set of legs moves. Any chance you could borrow a friend's camera and post a video?

I've got a couple of servo powered hexapods from when I was active in robotics but your version has much more appeal. One of these with some sensors and the appropriate code could be a lot of fun.

Harry

[duncan webster 1Participant @duncanwebster1]

Posted by Neil Wyatt on 16/07/2018 17:12:10:

Lovely job.

Now you need to make a big one

Edit reading this Klann's linkage has many advantages over Janssen's (in the video).

Edited By Neil Wyatt on 16/07/2018 17:19:30

Wonderful, you need to get someone to do a construction series for a smaller one

Edited By duncan webster on 05/08/2018 18:58:07

[Rik ShawParticipant @rikshaw]

Nice work Steve and refreshingly different from model steam and mechanical engines (as much as I like both!). How about a nice big fiddler type claw on your next one. It could tighten up its own screws when they come loose

Rik

[Mike PooleParticipant @mikepoole82104]

Posted by Neil Wyatt on 16/07/2018 17:48:57:

LOL… "The Onedin Line"!

Spartacus by Khachaturian

Mike

[HopperParticipant @hopper]

A lovely bit of work. Work of art as said above. And annealed Stanley knife blades as a source of thin high-carbon steel, brilliant!

[Steve CrowParticipant @stevecrow46066]

Thanks Harry, I'll try to get a video up soon. In the mean time, there is a good animation on the net somewhere on which you can speed up or slow down the rotation so you can study the movement.

I'm attempting an "exploded view " of the mechanism. This is the crank assembly.

This is only a work in progress. I'm going to colour and shade it eventually.

I quite like the idea of using a small Co2 v-twin engine to power this. Has anybody made one?

[Harry MuellerParticipant @harrymueller51767]

Thanks Steve, appreciate your effort. Also like the idea of using a piston engine to provide the motive power. Perhaps a fuel cell? Electric is so nice though because you can use s/w to control it while pistons would require a mechanical control. Lots to consider.

Cheers,

Harry

[Neil WyattModerator @neilwyatt]

Looks like the BBC are watching this thread, the Strandbeest has been on the news!. You can buy an excellent Japanese strandbeest kit.

Neil

[Neil WyattModerator @neilwyatt]

Posted by Mike Poole on 05/08/2018 23:41:20:

Posted by Neil Wyatt on 16/07/2018 17:48:57:

LOL… "The Onedin Line"!

Spartacus by Khachaturian

Mike

I don't think I'd heard it since the 70s – until seeing that.

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