Kevin's Tripod Wedge for Barndoors

Page last updated: 2002 April 15

Variable Wedge

wedge_13.jpg wedge_12.jpg

Start of the Project: 2001 Sept 16

Intro

After building the fixed height tripod last week, the next step was to build a variable tilt wedge to allow the use of the barndoor tracker. I should have looked at a map first however, as I ended up with a wedge that goes from 35 degrees to 65 degrees latitute and I am at 45 degrees. I don't even know where 35 degrees is!
In any event, this wedge will allow you to mount securely a barndoor tracking mount, at various latitudes.

Benefits

  • The tripod is pretty useless as is except for as a base for a small voyager style portaball telescope with it's own base, unless you already have a wedge, like many smalled Schmidts have.

    Design

    This was designed and built in about three hours. Once you have the plans you should be able to shave this down to 1 or 2 hours.
    The larger the wedge, the more accurate the latitude setting can be, but we don't want the edge to be to large or heavy, and small enough to fit on the top of the tripod without edges sticking out.
    So this base design is for 35 to 65 degrees of latitude. It can be modified for lower latitudes (all of the way down to 0 in fact).
  • Parts List

    x1  1/2" plywood (or 7/16") approx 24"x24" (sides, top, base) (approx $6)
    x4  1/4-20 bolts 2" long
    x5  1/4" washers        ($0.10 each)
    x3  1/4-20 wing nuts    ($0.11 each)
    x2  1/-20 locknuts      ($0.13 each)
    x1  1x2" pine 9" long (ledge)
    x12 #4x1" wood screws
    x1  1/4-20 carriage bolts 2.5" long
    
    
    Supplies needed:
    carpenters glue
    tape measure, tsquare, protractor, drill, jigsaw, palm sander
    #80, #240 sandpaper, clamp, counter sink drill bit, 1/4" drill bit, small 1/16"
    drill bit
    
    

    The Assembly

      The sides
      wedge_01.jpg wedge_02.jpg
    1. Cut four identical side pieces. Base 6.75", left side 2", right side 6.25" and the top is a line from the left to right sides about 7.25"... this should form an angle of 35 degrees as measured from the left side to right side. You can cut two of these from a single square of 6" x 8.25" plywood.
                 /|
                / |
               /  |
              /   |
             /    |
            /     |
           /      | 6.25"
        2" | +    |
           |      |
           --------
             6.75"
      
    2. Mark a point on the left side, 1" from the bottom and 3/4" from the left. Get out a protractor and mark out 5, 10, 15, 20, 25 and 30 degree marks and draw lines from the hole mark all the way out to the right side. From the hole mark, measure out 4.5" along each line and put a mark.
    3. Stack the four pieces apart each other, clamp and drill a 1/4" hole through the mark. This will be bolted and become the mainpivot point. Insert a temporary bolt to keep the clamp and alignment.
      With the 4 pices still stacked together drill a 1/4" hole at each of the "top" degree mark. Then remove the two bottom pieces , reclamp and drill a 1/4" hole at each of the 4.5" x degree increment mark. Using a jig saw, cut out a long slot big enough for a 1/4-20 bolt to move along. Test fit an inside piece and an outside piece to see how a bolt can move along the slot. This may require a little sanding down to allow for clearances. Sand all edges, sides, surface with rough (#80) then fine (#200+) sandpaper.
    4. Assemble a pair of inside and outside pieces. The slot pieces are on the outsides. The pivot point bolts insert from the outside with washer and nuts on the inside. The slot bolt inserts from the inside with a washer and wing nut on the outsides.
      The base
    5. Cut out a square 6.75"x9.75". Mark the Center. Mark lines along the short edges (top 7.25x8.75, so the outer side is 8.75/2=4 3/8" from the centre. Remove the thickness of the two sides (2x1/2"=1") and you get 3 3/8".
      ---------------
      | |         | |
      | |         | |
      | |    +    | |
      | |         | |
      | |         | |
      ---------------
         < 3 3/8" >
      
      wedge_05.jpg Drill a 1/4" hole in the centre. Place on the tripod, align with a bolt and mark the 4 corners that hang over the tripod. Remove from the tripod and cut the corners. Sand all edges, sides, surface with rough (#80) then fine (#200+) sandpaper.
    6. Predrill 6 fine pilot holes (1/16") for the inside sides. Drill countersinks as the base must rest flat against the top of the tripod. Add some #4 by 1" screws, sticking out enough to grab the wood and hold it in place. Glue the inside sides, align, hold in place and screw in 3 screws. Repeat for the right side.
      The Top wedge_06.jpg
    7. Cut a rectangle 7.25"x8.75" from the plywood.
      Sand all edges, sides, surface with rough (#80) then fine (#200+) sandpaper. Prefill pilot holes (1/16") to attach the top to the outside pieces of the left and right sides. Align, glue and add 3 screws on each side.
      The ledge wedge_09.jpg
    8. Cut a 1x2x8.75" strip and attach it to the bottom of the top surface of the wedge and secure with glue and pilot holes and three #4 x 1.25" screws. wedge_11.jpg Once secure, lossen the wing nuts and open the wedge so that the glue does not glue the wrong pieces and let dry. wedge_12.jpg
    9. Place the finished wedge onto the tripod and insert a 1/4-20 carriage bolt from the top through the base and through the tripod. Use a washed and a wing nut underneath to hold in place.

    Click here for a gallery of all of the photos, not just the ones display here.

    After the Fact

    Take apart the top and bottom levels, remove metal bits and varnish all surfaces. When dry add velcro (a small 1x2" male strip (hooks) to the underside of the top surface. Secure with staples, screws and or glue. Secure a long (12") strip of velcro (female) to the underside of the top surface with enough to loop through a barn door arm over the top end and onto the male velcro. This will hold the barn door securely in place.

    Total Cost: under $10
    I actually built this without having to buy any new parts at all. It is nice to have accumulated various spare parts enough to actually build something useful from scratch!