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Prototype Mechanical Crab

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Steve Crow15/07/2018 15:55:28
224 forum posts
70 photos

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".

crab_02.jpg

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.

crab_01.jpg

I originally made this to quite a high finish - months of testing and handling has left its mark.

crab_04.jpg

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.

crab_03.jpg

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

Michael Gilligan15/07/2018 16:41:39
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16365 forum posts
714 photos

Excellent project, Steve yes

Nice to see it done small.

MichaelG.

Adrian 215/07/2018 16:51:47
82 forum posts
19 photos

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

Adrian.

I.M. OUTAHERE15/07/2018 17:02:19
1468 forum posts
3 photos

Excellent work Steve!

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

Bob Mc15/07/2018 17:04:12
150 forum posts
1 photos

Beautiful Steve....!

Its Art...better than any Picasso.

Steve Crow15/07/2018 17:40:46
224 forum posts
70 photos

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

crab_05.jpg

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 Wyatt16/07/2018 17:12:10
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Moderator
18232 forum posts
714 photos
77 articles

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 Crow16/07/2018 17:42:39
224 forum posts
70 photos

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

crab_06.jpg

crab_07.jpg

Neil Wyatt16/07/2018 17:48:57
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Moderator
18232 forum posts
714 photos
77 articles

LOL... "The Onedin Line"!

Harry Mueller05/08/2018 17:08:00
2 forum posts

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 webster05/08/2018 18:57:32
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2795 forum posts
41 photos
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 Shaw05/08/2018 19:30:17
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1365 forum posts
373 photos

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 laugh

Rik

Mike Poole05/08/2018 23:41:20
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Moderator
2743 forum posts
64 photos
Posted by Neil Wyatt on 16/07/2018 17:48:57:

LOL... "The Onedin Line"!

Spartacus by Khachaturian

Mike

Hopper06/08/2018 02:08:07
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4804 forum posts
105 photos

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 Crow06/08/2018 18:58:03
224 forum posts
70 photos

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.

image1.jpg

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 Mueller07/08/2018 00:44:09
2 forum posts

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 Wyatt07/08/2018 11:03:29
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Moderator
18232 forum posts
714 photos
77 articles

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 Wyatt07/08/2018 11:07:01
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Moderator
18232 forum posts
714 photos
77 articles
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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