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Originally Posted by danielsun
Can you tell me what size threaded rod and pitch is needed for this manual design?
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I made the barn door last year so the bits of paper I did my calculations on are well, they're around here somewhere
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No drama, it's easy to start from scratch. Go to Bunnings and get a long bolt. The long bolts are usually displayed prominently in the aisles nearest the "nuts and bolts". The long bolts come in different diameters and are about 2 feet long, so you'll have to cut yours to size with a hacksaw. I cut mine to about 18 cm which left heaps of room for movement plus attaching a handle, etc.. I put a rounded cap nut on the upper end of the bolt on which the moving board rests. This rounded nut limits area of surface contact and really cuts down on friction as the bolt turns. I used two plates from the bottom of lounge-chair legs to hold the bolt to the bottom board. These plates come with a threaded hole in the middle of them which holds the bolt in place. By holding the bolt in the bottom board the bolt as it turns is able to apply force and lift the upper board. If you look in the picture you'll see one of these plates screwed onto the bottom side of the lower board.
Getting the tape measure onto the bolt it's about 5/16" diameter and, just checked, appears to have a thread of about 60 turns per 84mm. Working out the distance for 60 turns is the key to your calculations.
60 turns will be 60 minutes which is 15 degrees sidereal movement.
Using X= Y / tan (15degrees) yields distance X from hinge to bolt hole of around 313 mm. (i.e. Y=84mm)
Just used the tape-measure on my tracker and that's about right.
Hope this helps. If in doubt, use the formula and work it out on paper before drilling. Besides if you put the hole in the wrong spot you could always drill another.
p.s. Note that the hinged board is tilted to 37 degrees (Canberra's Latitude) and the door hinge MUST be arranged as shown otherwise the tracker will be turning in the opposite direction to the movement of the sky...
p.p.s. I chose to hinge the lower board (see the two small hinges attaching it onto the stool's seat) and used a protruding bolt to set the latitude (tilt) just in case I move or travel and I can adjust latitude accordingly.
p.p.p.s. I use a bungy strap to secure the lower board these days to prevent the weight of the cameras from tipping the boards backwards.
L.
