One of the harder aspects of these scopes has been getting the bearing surface in place.
To start with, it is necessary to cut a piece of 1 inch black poly pipe in half, diameter-wise
It comes with the curve from being rolled up which complicates running it through the saw.
I have used band saws and table saws, with both it's difficult to keep the width of the cut even because of the existing curve.
I actually found the table saw easier. Either way, it is a two person job!
Even with the built in curve it is necessary the heat the poly pipe to get it to take the smaller curve of the rim.
Surprisingly, using the opposite curve works best, here's why.
When you heat the correctly curved piece, the center wants to collapse and go flat.
If you carefully heat the edges of the reverse curve the half pipe keeps its round shape.
I included some pictures of the stands' construction.
Sizing the half pipe to the rim is another tedious job.
After I've formed the pipe to the rim I've found if I wrap tape, then string around the pipe and rim and overlap the ends, I can get a tight fit.
Then you have to mark and cut the overlapping end of the pipe to mate up, also a difficult procedure.
It only takes two tiny screws at the joint to keep the pipe on the rim, if you get a tight fit when forming.
I have tried PEX pipe, but it is too thick and hard to work with.
The Poly seems to work the best, the action of the contacting bike rims is smooth and light.
This scope only goes down to 30 degrees for horizontal.
This is because I went with smaller diameter rims in relation to the socket rim.
It's necessary to put the ball deeper in the socket if you use a spring instead of counter-weight.
I live in the forest and the sky starts around 30 degrees, so this isn't a problem for me.
Also,in a pinch you can block up one of the legs to view lower.
If it's necessary to pivot to the horizon, design the ball higher in the rim and go with counter-weight.
This scope is still a work in progress.
I wanted to go with the original Orion parts, but later discovered the high profile of the focuser is vignetting the primary.
I need to go with a lower profile focuser and lengthen the strut.
It is my intention to do that in the future, but the scope currently functions fine.
It is just not utilizing the full 8 inches of primary.
Also, I have spent a lot of time exploring scope vibration.
The bike cables are covered in small surgical tubing that keep the wire vibration in check.
But there is an inherent vibration of the scope as a unit.
I would imagine anyone who has built a scope has discovered this.
I had already put Sorbothane pads under the feet and that took care of it, but I tried a couple of ideas just for the fun of it.
I read an article that explored the fact that if you break spaghetti by flexing it, it will always break into more pieces than just in half.
It was discovered that if you "twist" the spaghetti, and keep the tension on it, it will break in two pieces, the torque absorbs energy.
So, I tried "winding" the cables.
It helped some, but hard to keep the cables from winding up.
It would seem that the total scope acts like a piece of piano wire.
if you clamp it in a vise (like a scope connected to the ground, no flex) the whole wire vibrates.
If you hold it in your hand, your fingers absorb the energy.
It makes sense that the most effective place to the vibration is at either end, because that is where the "movement" of the wave is the greatest.
Chuck
2018 Sep 1