| Body is 2 inch I.D. PVC conduit cut to 2.125 inch length. Mark body at 12:00, 3:00, 6:00, and 9:00 o'clock position. Saw halfway through the tube 0.5 inch from the top and 1.375 inches from the top. Drill holes at mid point so as to seperate the two arms |
| Building a PVC Focuser |
| Body is 2 inch SCH 40 PVC conduit. Drawtube is 1.25 SCH 80 PVC pipe. Rubber tubing on .250 inch steel shaft presses against drawtube. Steel tube rotates in arms that are bent from the body by heating in boiling water. Friction on drawtube can be adjusted by sliding rubber tubing closer together or farther apart. Drawtube glides on bearing surface cut from a plastic milk jug and held in place with double-sided tape. Wooden toy wheels are pressed into place. Another style of focuser is shown at the end of this page. |
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| Construction: |
| Heat in boiling water and bend arms straight. A candle can also be used if you go slowly. Take care to not distort body out of round. |
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| A jig is used to ensure the arms are parallel . |
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| A steam fixture is useful when constructing multiple units. |
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| Heat and insert rings inside of body. Be sure they conform to the inside of the body. Cement into place. Next, drill .250 holes for the axle 1.03 inch out from the body centerline. A round file will be used later to make final adjustments. Trim ends of arms. |
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| Cut two rings of 2 inch PVC. One 0.5 inch and one 1.250 inch. Then cut a 1.125 inch segment out of each. |
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| Cut a 2 inch wide strip from a plastic milk jug. Use double sided tape and secure to body in location shown. Be sure rougher surface of milk jug plastic faces drawtube. |
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| Use a round file to enlarge holes so that the shaft turns smoothly and does not touch drawtube. Insert shaft and install two .5 inch lengths of rubber tubing. Lubricate tubing with water to ease installation. Press wooden wheels into place. If wheels slip, sqeeeze the ends of shaft tightly with pliars to create ridges. If draw tube is hard to move, slide rubber tubing apart and ensure drawtube is touching only the plastic bearing and the rubber tubing. |
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| A mounting plate is built from scrap PVC. Heat and form it on your telescope tube to ensure a precise fit. |
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| Glue mounting plate to focuser body. |
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| A screw in a slot limits the travel of the drawtube . Make the slot with a ruler and a sharp knife. |
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| Here is another style of focuser using molded PVC. |
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| Question or comments? email scope_maker@hotmail.com |