Wanhao di3 x-axis belt spacer

This is another way of solving the problem of the x-axis belt rubbing against the bearing housings of the Wanhao di3. The concept relies on two home-made "rollers" used to push the upper part of the x-axis belt that tiny bit required not to rub against the housings, while at the same time reduces wear on the belt which is now in contact with a rolling, not a sliding surface
This approach is less intrusive than the one involving trimming of the upper bearing housings with a hacksaw in order to increase clearance from the x-axis belt, but there are some things to consider (see further down).
You will need 2 of each:
The .stl file,
M4x30 bolt and nut,
nail about 1.2mm diameter and 23mm long,
18mm of plastic tubing 1.3mm inner diameter. (For this last item, I cut away the tubing of an ordinary used ballpoint pen...)
Assembly:
Print two spacers, pass the nails through the plastic tubing and snap them in place on the spacers as shown in the pictures. The plastic tube should be rotating freely round the nails. Then, put the spacers at the two ends of the upper housing blocks, aligning the openings with the lower, outer holes on the blocks. Tighten in place using the M4 screws or equivalent - see further below.
You should end with the upper part of the belt touching the freshly added rollers, just 1-2mm below the bearing housing. Move the extruder assembly back and forth with your hands, the belts should move freely now without touching the bearing blocks and the ballpoint pen rollers should be rotating along, driven by the belt movement.

And now for the fine print:
1. I noticed that the spring tensioner of the x-xis belt was installed spring-up, reducing the clearance between the upper and lower parts of the belt, so I reinstalled it upside-down. This gave me some 2mm of clearance between the moving belts....
2. The spacers need to be secured (i.e.bolted) tight so that they can maintain the distance from the bearing housing during operation. I chose to use two M4 bolts through the lower outer threaded holes of the housings. The hard part was to extend the thread throughout the housing width using the right die, but it worked out fine without taking the extruder asssembly apart. Mind you, you need to make careful, slow and patient moves in order to avoid breaking, snapping or displacing something. Also, it would seem better to keep the extruder closer to the end of the rods, where they are stiffer and can withstand more pressure (when turning the die). Of course, you can save yourself the effort if you can use M3.5 or M3 screws, which should go through the existing holes without messing with the existing - partial - thread (only thought of this just now)

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