STEP BY STEP

Sky at Night Magazine - - OCTOBER / HOW TO / SKILLS -

STEP 1

Un­screw one servo’s back (avoid dis­turb­ing gears in the top sec­tion). De-solder wires to mo­tor and re­move the three core ca­bles and cir­cuit board. Solder new ca­ble to mo­tor and re­fit. Re­peat for sec­ond servo. You may need to en­large ca­ble slot to suit new ca­ble.

STEP 2

Use the down­load­able plan/tem­plate to mark out parts – ad­just shape to suit your fo­cuser (see main ar­ti­cle). We used 18mm thick ply­wood made from some 15mm and 3mm of­f­cuts glued to­gether. Care­fully cut out servo mount from thin ply­wood or acrylic.

STEP 3

It’s eas­ier to drill holes in the ply­wood bracket and servo mount plate be­fore cut­ting out the fid­dly shapes as there’s more ma­te­rial to hold. The bracket holes ac­com­mo­date two trimmed nails, which pro­vide sup­port for the ca­ble ties. Smooth and paint fin­ished parts.

STEP 4

Make a round wheel from thin ply­wood with a dowel han­dle for speedy turn­ing. One of the servo at­tach­ments that comes with the kit is glued to the cen­tre. Su­per­glue a sec­ond at­tach­ment to the GT2 pul­ley (rough­ing up the sur­faces makes the joint stronger).

STEP 5

Make a thicker wheel with a 48mm di­am­e­ter. Drill the cen­tre to suit the fo­cuser knob. A small hole may be drilled ra­di­ally to ac­com­mo­date a grub screw so you can at­tach it se­curely. Glue the smaller GT2 belt in­side out to the cir­cum­fer­ence of the wheel.

STEP 6

Use ca­ble ties pass­ing over the nails to at­tach the bracket. A rub­ber strip un­der­neath aids the grip. Make sure the pul­ley and drive gear are in line be­fore tight­en­ing. Fit the larger belt and re­move slack be­fore fi­nally tight­en­ing the screws on the mount.

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