Lashing Block / Pulley Block with double ball bearing (6 mm plastic polished balls available on market)

WARNING - The mechanical resistance of this device is unknown and unpredictable, since it depends on the kind of material, 3d printer and 3d printing parameters used. Always assume that this device can fail suddenly, and always evaluate the consequences of this fail before using this device. Do not let anyone's  life, health, patrimony and/or achievements rely on this device!

I designed this pulley block for using  in the main sheet cable of a Ibis Rubra 3.5 dinghy sail boat* with 8 to 9 mm  diameter ropes.  It is a small balanced lug sail (5,2 m2) with bamboo mast and boom.  I use to sail this boat for day fun in a very secure lagoon, so there is no problem for me if the block fails anytime.

Lashing blocks are an ancient way of constructing pulley blocks with poor strength materials.  In a failure event, if only the block material colapses without leash or rope cut, the rope remains tied to the leash or loop . See ( https://es.wikipedia.org/wiki/Cuadernal#/media/Archivo:Bozzello_-_Museo_scienza_tecnologia_Milano_D1039.jpg) and (https://en.wikipedia.org/wiki/Block_(sailing)#/media/File:MaryRose-rigging_blocks2.JPG)

Plastic polished balls of  6mm diameter are available on market, since they are used as airsoft pellets and bb guns.  The name "bb" indeed refeers to  “ball bearing”.   I have bought some made of ABS.

The ball bearing geometry was inspired on http://www.thingiverse.com/thing:1799757

The use of a filament with high inter-layer adhesion is recommended.  I printed in PETG, with 0,2mm layers and 0,4 mm nozzle, in the maximum recommended temperature.

There is a small tubular 0,4mm thick column in the body piece in order to avoid the use of suport material in slicer. Remove this column before assembly using a utility knife and or trimmer. 

Each side of the block recieves 11 balls.

Assembling video.  Note that at times 3min15s and 3min34s I trim 1mm of the tips of the ball insertion hole caps.

After assembling, hang the pulley and apply  some load and speed with a rope and your arms to break in the bearings.

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*Ibis Rubra 3.5 is a derivative of Joel White's Shellback Dinghy designed by Wilson José da Silva. Different from Shellback, the hull of the Ibis Rubra boat has a higher freeboard and it has two watertight wooden cameras below benches, for navigating in wavier waters. For more sail performance, there is a option to use a genoa sail. Ibis are built in "paiol" - a permanent annual workshop promoted by ANI wich in 10 months, two times a week, the owner builts his/her boat (https://oficinanavalartesanal.wordpress.com). ANI is Nautical Association of Itajaí city (www.anitajai.org)(Santa Catarina State, Brasil), a non profit organization that aims to increase the popularity of sailing, with social objectives.