# Ploopy BTU Mod

The roller bearings used in the Ploopy Trackball are nice, but with the standard ball they might not feel as smooth or as low-friction as you'd like. The prompt for this mod was "what if we replaced them with ball transfer units?"

It turns out - good things happen!

Ball transfer units (or BTUs) are omnidirectional bearings, as opposed to the single-direction roller bearings the Ploopy Trackball uses by default. This means you're never rolling the ball in the "wrong direction" for one of them.

This mod is a new 3D-printable top piece for the Ploopy which contains holes for ball transfer units instead of roller bearings.

Designer: [George Bryant](https://github.com/gbrnt) with help from [/u/d4baller](https://reddit.com/user/d4baller)

## Versions
### v3
This version was designed in Rhino and so isn't really editable for most people. It works well though.

### v4
This version was redesigned in FreeCAD and the various dimensions are now editable in the FreeCAD file.

Currently untested! It might collide with something internally, particularly if you've soldered in a programming header for the microcontroller.

## Buying the BTUs
The particular BTU this mod is designed for is the Bosch-Rexroth R053010810, or KU-B8-OFK. A set of three is about 20-30 USD, depending on where in the world you are and where you buy them from. Here are some sources we've found so far:

* [Bosch-Rexroth](https://www.boschrexroth.com/en/xc/products/product-groups/linear-motion-technology/ball-transfer-units-and-tolerance-rings/ball-transfer-units/r0530-with-sheet-steel-housing/r0530-1-with-sheet-steel-housing)
    * UK (and worldwide?)
    * Requires you to be a company (have a VAT number)
* [Livhaven](https://store.livhaven.com/r053010810-bosch-rexroth-ball-transfer-unit)
    * US-based
    * Doesn't require you to be a company, but overseas shipping is expensive
* [L-System](https://l-system.nu/webshop/linear-technology/ball-transfer-units-and-tolerance-rings/ball-transfer-units/type-r0530/ball-transfer-unit-ku-b8-ofk/)
    * Sweden-based
    * Allows you to select "private customer" but still has mandatory field for VAT number
* [Spareparts](https://www.sp-spareparts.com/en/p/r053010810-bosch-rexroth)
    * Ireland-based? Ships to UK, and maybe elsewhere.
    * Does not require you to be a company.
* [Rodivago](https://rodavigo.net/es/p/bola-transportadora-con-carter-de-metal-laminado-ref-053010810/557053010810)
    * Spain-based
    * May require being a company.