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Ski pole

Ski pole

Manon, hope for the 2030 Olympics ?

Our previous design of the ski pole aimed at Pierre-Luc, based on the principle of ball joint that enclosed his palm, does not seem appropriate to us in Manon’s case, because her clamp function can be performed by his thumb and his pinky. Of course the strength of this clamp is clearly not sufficient to hold a ski pole, so we keep the principle of using a socket build around her hand.

We therefore define new specifications intending the left hand palm to have the same feelings of touch as her right hand.

Scan of the left hand, equipped with a muffle

Pour ce nouveau projet, nous essayons de nous passer de l’étape moulage, en réalisant un scan de la main in-situ, en position de maintien du bâton de ski. La main étant équipée d’une moufle qui sera ensuite bien adaptée par la couturière de la famille.

For this new project, we are trying to work without the molding stage, by performing an in-situ live hand scan, right in the position of holding the ski pole. The hand being equipped with a muffle which will then be well adapted by her family’s seamstress (grand’ma).

The scanning operation is not as easy as expected, but after 3 attempts we got a good quality mesh file.

 

Another evolution of our process, we will not transform the resulting mesh (STL format) into a B-rep file for importing into our usual CAD software (Onshape).

Once the STL is imported into an ONshape’s “part studio”, an enveloping surface is made around the mesh, made of multiple ‘Spline’ curves (generalization of Bezier curves) drawn over successive cut planes. These curves, building a group of sections, each of them wrapping the glove, are then connected (joined) to each other by ‘lofts’. A loft is a surface obtained by interpolation between the different curves, in the form of a NURBS surface (cf wikipedia).

 

A pile of parallel planes will slice the fist holding the pole. All plans are referenced on remarkable points of the muffle.
On each plane, a closed curve is drawn to surround all boundaries of the displayed STL, thus creating a section. By interconnecting the successive parallel sections by lofts (3D loft function), we obtain the blue envelope (as a surface) which will then be transformed into volume using the “thicken” function.
After having created thickness to the developed surface, having cut the end of the socket to allow the thumb to come out of it, the socket is ready for integration into the new holding system.

Highlights of the device including a (simple) system.

The new device is therefore no longer based on the ball joint principle but on a two-element system :

  • an element on the stick (host)
  • a detachable socket for Manon’s hand.

The cohesion of the two elements is achieved by neodymium magnets, powerful enough for the stick to follow each hand’s movements, but detachable enough to allow the release of the socket in case of fall.

The host frame is attached to the stick. The vertical side of the host is on the outside to allow ejection of the interlocking (inwards) in case of any fall. On the inner side of the host, we can see the location where the small circular neodymium magnet aimed at vertical support will be screwed, and the rectangular magnet, more powerful, dedicated to lateral support.
L’emboitement est “collé” sur le bâti grâce aux forces d’attraction des deux aimants.
The hand-socket is “glued” to the host-frame thanks to the forces of attraction of the two magnets.
  1. The correct positioning of the interlocking is ensured by a centering dome, and a calibrated location
  2. The holding of the interlocking on the frame is the attractive forces of the main rectangular magnet (40x40x4)
  3. The second magnet (circular) facilitates vertical support and centering of the hand-socket.
-The first prototype validated the functionality of holding the ski pole and its test on a ski slope confirmed our technical choices.

Some small improvements were made to give more room for the thumb and the final version of the interlocking was printed using semi-flexible material (BASF Fusion, with shore mark 65D).

The success of this new concept quickly attracted other parents. So we reviewed (cleaning) the design scripts, so any new requests would be made quickly. The frame (HOST on the drawing) is almost generic, its adaptation to the hand-socket is minimal. On the other hand, the hand-socket being 100% adapted to the size/aspect of the hand and the type of agenesis of the child, its design will be a little more touchy.

Ces adaptations de système à la main d’un autre enfant nécessitent de maitriser l’outil de conception CAO, mais n’est pas aussi compliqué qu’il y paraît. Les fichiers STL du système développé pour Manon ne seraient d’aucune utilité pour un autre enfant. Par contre, nos développements sont open-sources et disponibles sur la plate-forme Onshape, et nous sommes toujours prêts à donner un coup de main 🙂 [© E-nable France]

These system’s adaptations for another child’s hand will require some skill using a CAD design tool, but are not as complicated as it seems. The STL files of the system developed for Manon would be of no use for another child. On the other hand, our designs are open-source and available on the Onshape platform, and we are always ready to give a helpful hand 🙂

Let’s keep in touch.

 

 

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