Trautman Hook (3d printed PLA, first bench test) [design]

From the idea of Open Prosthetics, I took the Trautman Hook stls (also published on Thingiverse [link][link]) and printed them using PLA on a Makerbot Replicator. Then I put them together and tried them out.

Strategy for using 3d printing in your overall problem solving process


Evaluating the shape and dimension as well as function of the Trautman hook

Print and assembly

The following image shows the print, straight from the 3D printer, including raft (a base plate) and supports (vertical support materials to allow for undercut or hollow parts).


Removing the raft and supports needs proper tools and time and care.

Lovingly but with determination, obviously, one will peel, push or otherwise twiddle off these plastic parts necessary for production but in the way of assembling and using the parts.

As it turns out, a Hosmer Model 5 split hook is most perfect for this task.

It leaves other options - placing the plastic into a vice, hacking away at it with a screw driver or scraper or other tool - far behind.

Raft/supports removal is a lot easier as a within-both-hands task where I can always determine how to best direct hook / metal force against the plastic parts in a best tangential or orthogonal way.


I assembled it using a few screws I happened to have lying around.

Alright I admit it, I have a well assorted choice of screws that I keep in plastic boxes almost all neat and tidy.

See the UNF 1/2-20 threading? Cuddly : )


Testing its function

This test has the goal to find out whether this device is so strange that I will not want one, or, what next.

And, .... mounted.

I never paid attention that this is a left handed model but I will mirror it before the next round.


The unique thing about the Trautman hook is probably that it is uniquely soft with its grip force, that it combines large grip areas with a roughened surface with slanted arching claw shapes that can reliably hold any bar shaped structure, and that it's opening swivels to the center of the body line, making two handed swaps uniquely easy.

In these aspects, is vastly different from other hooks.

Opening and closing, one can appreciate both the unique swivel of the overall shape during the grip action and the travel of the gripper shape combination.

While no one outside of my body gets this, this weird swivel is uniquely cool: with a body powered voluntary opening device, I will always extend my stump and possibly move it a bit to the right when opening it. At the same time, this hook moves its relative grip center to the left and closer to the wrist, so you can - possibly with visual reference to a background floor tile in the following video - understand that this essentially keeps the grip center at a stable center.

It seems to offer some insane gripping performance for bench or assembly type work as it picks up small objects with ease.

One has to accept that I find it a bit difficult to operate this reversed side plastic version here, because it is a really shaky first PLA assembly that I do not want to damage, and, it is a wrong sided model (left handed hook on right side).

You should also appreciate how these features were incorporated into the Retro [link]. The Retro however is small, cannot really go use a broom with it, and it is really also quite tight.

I find this Trautman hook's dynamic adaptation to my cable control VO caused extension of the arm, by counter shifting the center of the grip to keep it stable, so ingenious, that I decided to get myself a more robust version to test this in more extent.

Your next steps

Thingiverse archive where I placed the original left and added mirrored right parts here.

Shapeways is where I put up the parts so we can all get them 3d printed in really decent materials [link]. Such as matte black steel. Or really cheap acrylic so you can have a go at testing whether at all you like the overall shape and feel of it.

I put these up without any markup (added fee) so I won't be making any money from these manufacturing or 3d printing sales. Also this is an Open Prosthetics Project design so it would be fair to make this an affordable thing. As we can see, the overall cost of these parts, no matter what metal one chooses, is not extreme.

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Trautman Hook (3d printed PLA, first bench test) [design]; published 26/11/2016, 11:17; URL:

BibTeX: @MISC{schweitzer_wolf_1604167833, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Trautman Hook (3d printed PLA, first bench test) [design]}}, month = {November},year = {2016}, url = {}}