Quote:
Originally Posted by Atmos
I think this is where the Linear will be better, having something like a four stage reducer it not only gets rid of backlash but should vastly smooth out all those little inconsistencies that cannot be guided out. The 30" PE that my EQ6 has is fine, that is not even noticeable, its those small bits in between  |
I'm not sure if the multi-stage reduction will have much of an impact there, maybe an engineer can chime in?
I've been thinking about trying to build my own mount (as a project, not a commercial endeavour), and having considered building a friction drive or belt driven system, I suspect that multi-stage reduction is simply there to keep the physical dimensions small.
You need a
really large reduction ratio to move something in small enough increments that it's suitable for tracking with a stepper motor.
Worm gears are great being a "simple" single-stage mass reduction step, but when using a friction or belt system, you need another way of creating very large reduction ratio.
To give you an idea, the EQ6 has a ~700x reduction ratio so it can move in steps of around 0.14" (from memory). Of course, if you tried to have a 700x reduction ratio with one pulley, you'd have a 7m pulley on one side and a 1cm one on the other (or a 70cm, 1mm for that matter, but you get the idea).
However if you use a multi-stage approach, you can greatly reduce the physical size by making a pulley version of a compound gear. Maybe it has some impact on high frequency noise as well, but I'm not sure about that (but then again, I know jack about mechanical engineering as well, so I'm keen to hear about it if someone knows more on this).
I'm actually a bit cynical on timing belts because they
must introduce some relatively high frequency noise into the system, so I'm still expecting some small-scale, high-frequency fluctuations, however I'm not expecting them to be significant enough to cause me issues imaging at 1.1"/px.
Quote:
Originally Posted by AndrewJ
Just for info, have attached a piccy of my AZEQ5 before and after tweaking the belt tension. The linear has much larger/stonger belts, and probably has a more precise belt tensioning system, but it pays to understand what can happen, even with belts 
Andrew
ie Some problems can be removed at the expense of possibly introducing new ones. |
Thanks for posting that, interesting graph! Excuse my ignorance, but can you please confirm the scales on each axis?
Edit: Soooooon