Introduction: Tennis Prosthetic

Hello and welcome to the Cambridge Bio-Augmentation System’s OpenSource tennis prosthetic. This project was born out of John Willis’ Road to Rio Challenge, where he participated in every Olympic and Paralympic sport in the lead up to the Rio 2016 Olympics/Paralympics. He wanted to show that sport doesn’t have boundaries and no matter the impairment, able bodied and impaired people can inclusively play together. So it is very fitting that the devices that we designed to help John hold sporting equipment, we are now releasing into the public so that true to John’s goals, the boundaries of sport are eliminated.

Step 1: Design Notes

Sockets

– This design will only work for sockets that use a 3/8 whitworth thread. It is possible to make alterations to this design to fit the US ½ inch thread, and European M12. The parts that will need altering are:

Threaded component.

– Socket section thread needs to be replaced with the desired thread type.

– Mid-section needs to have a larger thread type with a minor diameter that is less that than the major diameter of socket section and a pitch that is significantly different to the socket section (this promotes geometric locking and therefore security of the device).

Locking component

– Needs to have a thread that matches the mid-section on the threaded component.

Racket Size

– The plans in this document have been created around a junior racket size (that John used), which tend to have a shorter handle length. These designs can be used with adult rackets by using a longer carbon tube and following the same instructions.

– Tennis rackets come in a range of grip sizes, this device will accommodate the full range without needing alteration.

3D Printing

– The minimum printer requirements are:

Print Material (in order of preference): PLA, ABS

Bed Size: 150mm x 150mm x 140mm (height)

Printing Resolution: 0.2mm

Shell: Thick (2mm)

Infill: 30%

– We recommend looking on https://www.3dhubs.com for printers that can make these parts at a low cost.

Step 2: Labeled Device

1- Thread Component (Machined)

2- M12 Nut (search www.accu.co.uk)

- Fine Thread

- 6mm depth

- 19mm maximum width

3- Lock Component (3D Printed)

4- Bottom Clamp (3D Printed)

5- Carbon Tube (search www.ebay.co.uk)

- 12mm OD

- 10mm ID

- 240mm length

6- Lezyne Rubber Strap (search www.cyclesurgery.co.uk)

7- Top Clamp (3D Printed)

8- Washer (3D Printed)

9- M12 Bolt (search www.screwfix.co.uk )

- Fully Threaded

- Coarse Thread

- 40mm

Orange dotted line indicates how the racket is attached to the device.

Step 3: STL Files

Step 4: Manufacturing

- Using a lathe turn, a metal rod to the specification shown on the right.

- ATTENTION: the 30mm length on the far right is eventually going to be glued into the carbon tube. This section must be made to TIGHT PUSH FIT inside the carbon.

Step 5: Manufacturing

- Use Epoxy, glue the threaded component into the carbon tube.

- Leave to cure.

Step 6: Manufacturing

- Glue the bottom clamp to the base of the carbon tube, around the point where the threaded component meets the carbon.

- Leave to cure.

Step 7: Manufacturing

- Thread the indicated hole with an M12 coarse thread tap.

Step 8: Manufacturing

- Glue the M12 bolt into the hexagonal cutout in the washer.

- The bolt should go through the round hole in the washer component.

- Leave to cure.

Step 9: Manufacturing

- Put your tennis racket into the bottom clamp and secure it with the Lezyne strap. The straps loop around the small hooks located on either side of the clamp.

Step 10: Manufacturing

- Paste a layer of glue in the non threaded hole in the top clamp, then slide it onto the pylon.

- DO NOT LEAVE TO CURE – NEXT STEP.

Step 11: Manufacturing

- Locate the top clamp so the protruding section is sat comfortably at the base of the racket’s yoke.

- Screw the nut and washer component made in step 5 until the racket is clamped between the washer and top clamp.

- DO NOT LEAVE TO CURE, NEXT STEP.

Step 12: Manufacturing

- Rotate the top clamp so that the carbon tube and tennis racket handle are visually aligned.

- Leave to cure.

Step 13: Manufacturing

- Glue the M12 nut into the hexagonal cut out in the lock component.

- Leave to cure.

Step 14: Manufacturing

- Screw the lock component made in step 9 onto the M12 threaded component made in step 1.

Step 15: Full Assembly and Use

To fit

– Fully screw the the threaded component into your socket. Then unwind a fraction to find the comfortable orientation of you racket.

– Screw down the locking component so it is firmly pressed against the end of your socket. This will lock the racket in the desired position and prevent it from unwinding.

• There are two cup shapes in the top clamp that are for placing the tennis ball in to help serve.

Step 16: Additional Information

Liability

– Cambridge Bio-Augmentation Systems does not accept any liability in relation to these devices, or any of their remixed variations. Any breakage, injury or death are solely the risk of the user and by manufacturing you agree to relinquish Cambridge Bio-Augmentation systems of any responsibility.

The OpenSource license

– These devices are released under the creative commons license: attribute – noncommercial – sharealike.

Contact

– Any queries please contact contact@cbas.global.

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