No More Tendon Knots !

For discussion of hand designs.
droomurray
Posts: 69
Joined: Mon Feb 16, 2015 4:04 pm

No More Tendon Knots !

Postby droomurray » Tue Apr 28, 2015 8:31 pm

Chaps,

One problem I have had when building hands is the knots, I have some kind of mental block and no matter how much I practice I always struggle with getting the knots, tight and looking good. I have previously looked at jewlry bracelet solutions but in testing found them to be no good under stress.

My most recent build for Stephen brought this question back to my mind when Stephen stated he wanted to get into building devices for people; I was thinking hmm I could do with 3 hands to tie the knots, how will he do it with one.

Anyway the solution I found was part of the Bill of Materials used by Open Bionics - http://www.openbionics.com
(Myself and Stephen are planning to go see them in the future as there work looks pretty cool and there only a few hours drive away.)

The solution is using .8mm nylon coated steel cable, its VERY strong and with the coating does not seem to eat at the plastic.
The crimps are copper, 5mm in length.
The crimp tool is a little bulky but well made, one thing I know from previous work is a good set of quality crimps pays off in the long run !

These pics are showing fitting on a Raptor Reloaded printed at 100% size.

IMG_0969.jpg
IMG_0969.jpg (94.52 KiB) Viewed 3255 times

IMG_0968.jpg
IMG_0968.jpg (99.04 KiB) Viewed 3255 times


So I can take no credit for finding the cable, crips etc but can confirm that this does seem a very good knot free solution !
Later in the week I will try the crimps with my normal 1mm elastic but think its to bulky; I probably need the next size crimp up.

Elastic wise I want to give Jason's experiment with dental bands idea taken from the Falcon hand a try, that to me offers several advantages over strings of elastic anyway.

Cable - http://www.tecni-cable.co.uk/0-54mm-7x7 ... 43-000-540
Crimps - http://www.tecni-cable.co.uk/Code-0-8-D ... 15-000-800
Crimp tool - http://www.tecni-cable.co.uk/TECNICable ... 15-007-023

IMG_0970.jpg
IMG_0970.jpg (95.39 KiB) Viewed 3255 times
Last edited by droomurray on Thu Apr 30, 2015 7:03 am, edited 2 times in total.

Peregrine Hawthorn
Posts: 64
Joined: Mon Feb 16, 2015 5:49 am

Re: No More Tendon Knots !

Postby Peregrine Hawthorn » Wed Apr 29, 2015 2:49 am

This is pretty awesome. Pretty much no one likes the knot tying aspect of making these hands. It looks less accessible, and requires some more specialized equipment, but it's a good alternative to tying crazy knots and melting beads.

Just curious, could that work without elastics? Those cables look non-compressible, they could probably push fingers open, as well as close them. Maybe if they were thicker?
Heavy duty hand user, and co-designer of the Talon.

I break hands and then tell you how I did it.

droomurray
Posts: 69
Joined: Mon Feb 16, 2015 4:04 pm

Re: No More Tendon Knots !

Postby droomurray » Wed Apr 29, 2015 7:58 am

Peregrine,

The small diameter does mean i think it will just bend along its length if pushed but I will order a few different thickness's over the next few weeks and try them out. If you can describe a "push test" I would be happy to try it out.

Drew.

Docdavies
Posts: 2
Joined: Wed Apr 29, 2015 4:15 pm

Re: No More Tendon Knots !

Postby Docdavies » Wed Apr 29, 2015 4:18 pm

I notice the text say's 0.8mm cable but the link brings up 0.54mm. Is one better than the other? The link cable does not appear to be "plastic" coated. And with the 0.8 or 0.54 mm cable....what are the appropriate ferrules?

Finally, is there a good American supplier for the products? UK is ok, but I'd like to have a source in the US as well.

Doc

droomurray
Posts: 69
Joined: Mon Feb 16, 2015 4:04 pm

Re: No More Tendon Knots !

Postby droomurray » Thu Apr 30, 2015 7:06 am

Docdavies wrote:I notice the text say's 0.8mm cable but the link brings up 0.54mm. Is one better than the other? The link cable does not appear to be "plastic" coated. And with the 0.8 or 0.54 mm cable....what are the appropriate ferrules?

Finally, is there a good American supplier for the products? UK is ok, but I'd like to have a source in the US as well.

Doc


Doc, well spotted, i have updated the link to the correct wire i am using. I did some searching and could not find a US supplier but will be speaking to them sometime soon so will ask if they have a distributor closer to you.

Drew

mjculpepper
Posts: 3
Joined: Thu Apr 30, 2015 7:39 pm

Re: No More Tendon Knots !

Postby mjculpepper » Thu Apr 30, 2015 7:43 pm

Docdavies wrote:I notice the text say's 0.8mm cable but the link brings up 0.54mm. Is one better than the other? The link cable does not appear to be "plastic" coated. And with the 0.8 or 0.54 mm cable....what are the appropriate ferrules?

Finally, is there a good American supplier for the products? UK is ok, but I'd like to have a source in the US as well.

Doc



I think I found one, the items will be arriving tomorrow and then will be able to follow up for sure.

Look for American Tackle Supplies or something like that. Metal leader rigging are the thickness and are said to have the flexibility.

droomurray
Posts: 69
Joined: Mon Feb 16, 2015 4:04 pm

Re: No More Tendon Knots !

Postby droomurray » Thu Apr 30, 2015 9:01 pm

Can you post links to the products so I can compare ?

mjculpepper
Posts: 3
Joined: Thu Apr 30, 2015 7:39 pm

Re: No More Tendon Knots !

Postby mjculpepper » Fri May 01, 2015 2:16 pm

Here a link to the Company's Web site, it has the specs.

http://www.afwhiseas.com/Surflon-Micro- ... s/1993.htm

TO be noted, I ordered if off of Amazon here...
http://www.amazon.com/gp/product/B0000A ... UTF8&psc=1

droomurray
Posts: 69
Joined: Mon Feb 16, 2015 4:04 pm

Re: No More Tendon Knots !

Postby droomurray » Fri May 01, 2015 7:28 pm

I'm confused, the point of this thread is eliminating knots, that wire / cable etc is just that, I assumed you had found another source of crimps ?

Drew.

mjculpepper
Posts: 3
Joined: Thu Apr 30, 2015 7:39 pm

Re: No More Tendon Knots !

Postby mjculpepper » Sat May 02, 2015 5:33 am

Sorry, I thought you were asking about the line.

I bought these kind of crimps to test.

American Fishing Wire Single Barrel Crimp Sleeves, Black Color, Size 4, 0.071 -Inch Inside Diameter, 100-Pieces https://www.amazon.com/dp/B003FYD136/re ... rvb06B5B1H

Also have double barrel as well.

The sizing of these may be off, but I got got an assorted pack to try different ones.

User avatar
vindicarblack
Posts: 4
Joined: Wed Feb 18, 2015 9:36 pm
Location: Phoenix AZ
Contact:

Re: No More Tendon Knots !

Postby vindicarblack » Mon Jun 01, 2015 10:40 pm

do you think this cable would be equivalent?

http://www.ebay.com/itm/0-8MM-PVC-Coati ... 4aeaa6267a

I was still a little confused whether you use .53 or .8mm coated cable

droomurray
Posts: 69
Joined: Mon Feb 16, 2015 4:04 pm

Re: No More Tendon Knots !

Postby droomurray » Fri Jun 12, 2015 7:41 pm

The steel cable is .53, with the nylon coating it comes with makes it .8mm

Drew.


Return to “Hands”

Who is online

Users browsing this forum: No registered users and 1 guest