Maintenance procedures

These should only be performed by qualified staff.

Setting drive belt preload

This section includes instructions for setting belt preload. BrecoFlex recommends belt preload be set equal to the highest load on the belt, which is estimated to be approximately 6200 N. This value was calculated using a 1 m² frontal area object with a drag coefficient of 1.2, moving at 3 m/s and accelerating at 2 m/s², assuming a total moving mass of 400 kg.

Using 6200 N as our target preload, we can calculate the necessary belt elongation by using the belt spring constant, 2358 N/in:

Since the belt tensioner assembly consists of two clamps, this means each clamp should be pulled towards the center of the assembly 1.31 in, starting with a slack belt. Note that to start the threads on the tensioning clamps, a bar clamp may be necessary.

Disassembly

1. Loosen the tensioning clamp bracket button head screws using a 6 mm hex key. Screws should be completely removed from their tapped holes, but can be left in their slots such that they will be placed back into the same holes upon reassembly. The location of each screw is important since they were ground flat in place upon first assembly.
2. Loosen the nuts on the tensioning clamp bracket to relieve belt tension. Loosen these until the belt is just about totally slack, but do not remove the nuts.

Reassembly

1. Measure the tensioner clamp overlap on each side of the bracket. Record both these numbers for reference. Better yet, take some photos.
2. Add the two overlap values together, subtract 2.63, then divide by two. The result is the new target overlap value for each side.
3. Tighten the tensioning clamp nuts until the target overlap value is reached. Be careful that the button head screw threads do not catch on the edge of the lower plate.
4. Tighten the 8 button head screws to secure the tensioning clamps to the lower plate and bracket.
5. Tighten the tensioning clamp nuts another quarter to half turn. This will make the lower plate slightly concave, which is desirable to prevent rubbing along the timing belt housing.

Aligning linear shafts

TODO

• Find gauge blocks for shaft height
• Add pictures
• Figure out how to fine tune levelness of shafts and describe here

1. Set the ends of the master shaft (the side the belt attaches to) parallel to the tank walls on the opposite side using a tape measure.
2. Straighten the shaft in the y-direction using a tensioned line attached to each end, displaced by a 1/8" thick bar. Adjust the shaft until the entire length is 1/8" away from the line.
3. Use the carriage with the slave-side linear bearings clamped tight to their brackets to set the y-location of the slave-side rail by moving it along the travel.
4. Roughly set the heights of the shafts using gauge blocks. Do this one or two mounting studs at a time (with others tight) so the y-location does not move.
5. Fine tune the levelness of the shafts.
6. Confirm adequate clearance along the entire carriage travel.