Flying Buttresses, Solid Buttresses, & Tripods

Flying Buttresses, Solid Buttresses, & Tripods

Okay, the square tube is plenty stiff; the 1/4" thick L-brackets that link the square tubes to the vertical tube that holds the tripod isn't.

It occurs to me that nearly all tripods use some variant of a triangle. Either they have the legs going out at a angle, or they use a triangular bracket to tie each leg to the vertical tube. The reason is that the diagonal distributes the load.

I am thinking that perhaps what might be the right way to do this would be to either add a diagonal from the top of the tube (which is 10.5" tall) to the end of the leg, so that most of the load would be distributed directly to where the casters are located, or replace the L-bracket with a right triangle 3/4" thick, and perhaps 10" high.

The right triangle is much easier to make, although the material cost if made of aluminum is substantial. I could drill out lightening holes to get the weight down.

Adding a diagonal member might not be so difficult. I could use some square tube (I still have plenty), cut it at the correct angles to make the L-brackets be the right angle. Somewhere there must be something that shows how the load works for cathedrals, flying buttresses, and solid buttresses.

The good news is that it won't be written in Latin; medieval cathedral builders did everything like this by experiment. The cathedrals that stayed up inspire wonder in us today; a number didn't stay up. You could say that they buried their mistakes.

UPDATE: I went back out to the garage, took another look at everything, and had a sudden inspiration. Dobsonian telescopes (as Big Bertha 1.0 was) consist of:

1. A flat base.

2. A cradle that rotates in azimuth on the flat base.

3. The telescope tube that rotates in altitude on bearings on the cradle.

I thought about it for a couple of minutes, and realized that I had already put the casters onto the flat base--which is two inches thick of solid oak. Hmmm. I think that would hold the 5.5" ID tube into which the CI-700 mount should go. All I had to do was:

1. Remove the casters that I had removed from the flat base, and put them back in the flat base.

2. Remove the square aluminum tubes from the L-brackets.

3. Drill and tap (yes, you can tap oak) the flat base to match the holes in the L-brackets that were attached to the square aluminum tubes.

4. Screw 3" long 3/8"-16 bolts through the L-brackets into the flat base.

5. Put nuts on the bottom of the flat base to hold the bolts--in case, for any reason, the threads in the oak give way.

It is an elegant reuse of materials! It might look better to use a 1/4" thick stainless steel square instead, and it would certainly be resistant to the weather, but I already have the oak, and I know that it will handle the load--it has been handling the far greater load of Big Bertha 1.0.

Tomorrow: I need to drill and tap 3/8"-16 holes at the top of the 5.5" ID tube for the bolts that hold the CI-700 equatorial mount head into the tube. At that point, it's just a matter of moving the mount, bolting everything together, and then moving Big Bertha 2.0 into the saddle.