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I spent the morning measuring parts with vernier calipers and calculating timing belt lengths.
The Helical focuser drum is 70mm in Ø. It rotates very easily compared to the PST etalon band.
The PST etalon band is 61mm in outside Ø. It has an embossed finish to provide friction.
The bare, etalon drum is 58.5 with the band removed but has a tiny raised ridge to keep the band in place.
My smallest GT2 pulley has 14 teeth from memory.
The drive belt for the FT focuser is 100mm long.
Next I needed to arrive at a suitable center to center distance for the motor pulley[s] relative to the diameter of the driven circumference.
I reasoned that driven diameter x Pi/2 would give me a nominal tooth count to use in an online belt calculator. They usually want a tooth count to make any progress.
I ended up ordering a 280mm belt and a 300mm. These lengths do seem extreme but they have to divided in half and wrapped around the transmission components. Circumferences always use up a lot of length. The belts are really quite inexpensive. In fact the postal charges were slightly more than the two belts put together.
I can progress with testing drive reliability once I have the belts here by using my existing Skywatcher motor. The belts will arrive tomorrow thanks to online dealers who care about rapid turnaround of orders.
I have searched online for suitable 60-61mm clamps to fit the AOK Swiss PST etalon adapters. The loads on the clamp are low. So a reasonable cosmetic appearance is arguably rather more important than sheer strength. Nobody wants to see an ugly exhaust clamp half way down their H-alpha telescope! Nor a screw hose clamp.
It would be easy to simply bolt the motor mounting plate [provided] to the AOK etalon adapter. However, this is a rather fixed arrangement. Rotation of the two motors, relative to each other, becomes awkward. One motor will face the talon. While the other will face the helical focuser. I'd much prefer a neat clamp for each. A visit to a large DIY outlet is indicated.
I could bore a 60mm hole in a piece of black plastic sheet and then cut it in half. This is what I had to do with the FT clamp. I wanted a compact arrangement with the motor laid low over the pinion housing. The difficulty lay in drilling down 2" [50mm] through the edge of the plastic to take clamping bolts. The FT has a stainless steel conical section behind one focusing knob. I decided to use that as my clamping surface. Not an easy task. Because the parallel section was narrower than the plastic sheet. The conical shoulder didn't help.
Despite all this, the focus motor worked very well and looked fine from a distance. Providing a revolution in my ability to focus precisely without touching the telescope. I was sidetracked by a focus motor control box which promised much but instantly crashed SharpCap. A recent software update seems to have overcome these difficulties.
It would be easy to simply bolt the motor mounting plate [provided] to the AOK etalon adapter. However, this is a rather fixed arrangement. Rotation of the two motors, relative to each other, becomes awkward. One motor will face the talon. While the other will face the helical focuser. I'd much prefer a neat clamp for each. A visit to a large DIY outlet is indicated.
I could bore a 60mm hole in a piece of black plastic sheet and then cut it in half. This is what I had to do with the FT clamp. I wanted a compact arrangement with the motor laid low over the pinion housing. The difficulty lay in drilling down 2" [50mm] through the edge of the plastic to take clamping bolts. The FT has a stainless steel conical section behind one focusing knob. I decided to use that as my clamping surface. Not an easy task. Because the parallel section was narrower than the plastic sheet. The conical shoulder didn't help.
Despite all this, the focus motor worked very well and looked fine from a distance. Providing a revolution in my ability to focus precisely without touching the telescope. I was sidetracked by a focus motor control box which promised much but instantly crashed SharpCap. A recent software update seems to have overcome these difficulties.
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