Monday, December 24, 2012

DIY Tripod Spreader for Surveyor Tripod

Surveyor tripods are fairly common and can be repurposed as telescope tripods.  However a problem with many of these tripods is that they do not have a spreader, but rather have a chain to prevent the legs from splaying apart.

A spreader would be very useful for ensuring that the legs are perfectly 120 degrees apart (the chain offers no such constraints).  It is very easy to make a fixed spreader using a triangular piece of wood, but the problem with such a solution is that the spreader is a separate piece that must be removed for the tripod to fold, and attaching it to the tripod can be a cumbersome solution.

Here is a folding tripod spreader that I made from aluminum sheet and some cheap cabinet hinges.

The core of this DIY project are some 2.5" (60mm) cabinet hinges. I simply found the cheapest ones I could find. Three pairs (six hinges) are needed. In theory using piano hinges would be better as piano hinges have sturdier construction.

Take three of the hinges and bolt them together with M4 bolts (some filing will be needed to get them to fit nicely).

Next, take an appropriate length of aluminum sheet (I used some 70mm by 3mm thick bar stock). You would need three equal-length pieces. The actual length of the pieces would depend on how high up on the tripod the spreader would be fastened; and the height would determine how far apart the legs would be with the tripod deployed.

Make three holes in each end of the bars (that is 18 holes in total) to match the hinges.  Then bolt the bars to the triangular hub:

The other end of each aluminum bar would also have a hinge bolted to it; the other end of the hinge would then be bolted to the tripod legs.

It is necessary to drill holes in the tripod legs. In this case only the two outer bolt holes were used; this allows the tripod leg to extend (albeit not fully).  If the center hole was also bolted, the tripod leg would be fixed at its shortest position.