58W (11 elevation from my area) is on the left side looking from behind the dish (My southern sat is either 121w or 123w). I guess I'll move it back to the left side then and try again looking for some sats.
So that would mean >70 degrees rotation from due south, I guess!
Going back to the left side with your actuator (as Titanium advised), without an extension bracket, would be a good solution indeed.
It would mean that the actuator-bracket should be right at the top of the actuator tube, I guess; or otherwise you might not reach 58W with fully retracted actuator.
(If you cannot reach 58W this way with the actuator bracket at the
left hole at the back of the mount, you could probably use the
right hole of the mount. But then your range to the other direction of due south will decrease a lot. I won't repeat the flopping risk...)
Many of us fabricated a new the arm connection point and added an "L" bracket (on the reflector end) further away from the mount. This would provide increased travel before the "flop", allow the use of longer actuator arms and increase the counts per degree for improved accuracy.
How I understand the actuator triangle goniometry:
-
total stroke length for the receivable arc is about twice the length of the shortest leg of the triangle;
- the actuator length must of course be a bit longer than this total stroke length;
- making the longest leg of the triangle longer, doesn't increase the total stroke length; it results in the possibility of having the actuator tube bracket not on the top of the tube, but more towards the base of the tube;
- with the two legs of the triangle equal in length, the
stroke length (and number of counts) per rotational degree (and therefore the positioning accuracy, and movement power) is highest at the fully retracted zone of the actuator;
- when having one leg of the triangle longer than the other, this zone of highest power and highest accuracy shifts more towards the halfway extended zone of the actuator;
- however, the longest leg would normally not be longer than 3 times the length of the shortest leg (resulting in having the actuator tube bracket at the base of the actuator tube); so I guess about
twice the length of the shortest leg would be a practical and sensible choice, to spread accuracy and power a bit.
When the leg lengths of the triangle are chosen (one leg almost half of the actuator length!), comes the actual choice/fabrication of the actuator fixing points, for the most retracted satellite position.
These points should preferably be as close together as possible/reasonable, possibly using extension brackets (L-shaped or other); so that you have more power and accuracy, and less chance of flopping, at the extended side of the actuator.
[ All these are approximations, as a rule of thumb, assuming the actuator tube bracket (as an influencing factor) has negligible dimensions.
It is not difficult to enter the size of the actuator tube bracket into the calculations, however, and do very precise calculations.
By the way, I've seen an example where especially the relatively greater size of the actuator tube bracket diminished the chance of flopping! ]
So if I had an polar mount setup with actuator (alas I have not), and wanted to make full use of it, I'd choose the fixing points of the actuator on the base of such an actuator triangle design.
I know this subject isn't discussed often, but I hope I've explained the principles and how I understand them somewhat understandable.
greetz,
A33
