ok i know these are motors but ..... why the different lengths, does the 24 get a bit more of the arc than the 18 and the 36 gets more than the 24 and the H2H covers most of the arc.
18" 24" 36" H2h
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Different geometry requires different linear actuator lengths. To explain, a light dish (aluminum or small diameter steel) can use a short lever, which would use a short actuator. A heavy dish (fiberglass or large diameter aluminum or steel) would require a longer lever (more mechanical advantage) which would use a longer actuator. Designers have to factor the weight of the dish along with the desired arc and the power and length of the linear actuator. The linear actuators are safer pushing the load than pulling it. If there were a failure and the shaft pulled out, the dish could swing uncontrolled and cause damage. Most dish linear actuators us a recirculating ball device, which is less expensive to manufacture. The fact that they work better pushing makes them not very suitable for HH operation. As the dish swings the arc, east to west, the force changes from pushing to pulling as you pass true south for your location.
A HH mount, like the Birdview, uses ring and penion gears. This gear arrangement is reliable and not likely to fail, causing the dish to swing uncontrolled, damaging itsself. It is, however, very costly to manufacture.
A HH mount, like the Birdview, uses ring and penion gears. This gear arrangement is reliable and not likely to fail, causing the dish to swing uncontrolled, damaging itsself. It is, however, very costly to manufacture.
well i'm not understanding what it takes to make the mover, move at smaller incraments is it a different sensoror longer arm or would i need to go to the H2H to get the best tuning. are the clicks from the 4dtv (dsr-920) measured is there a way to make it move a 1/4 click....
Interesting explanation, caddata. The whole principle of pushing and pulling combined with safety issues must also involve the polar mount design? The mounts which are centrally located, ie located in the middle of the ring (e.g. Channel Master 10 foot), give you the choice of push/pull on the right or left depending on the intended arc segment you are after. The offset mounts, where the pivot point is on one side and the actuator hookup is on the other (e.g. Perfect 10, Kaul-tronics) gives only one choice. Presumably this has a safety advantage in that in the event of failure of the actuator it would be more likely to fall in rather than pull out?
Hey George,
I am no expert, but from my understanding of it, the movement per click is at least partially determined by two things.
1. The number of threads per inch on the actuator arm. Again with Harold's explanation, the amount of movement would change depending on how long the bar is the actuator attaches to. Short bar, lots of movement. Long bar, slower movement.
2. The number of pulses sent back which is determined by the magnetic wheel in the sensor.
The more pulses sent allows a more accurate point of stopping and starting. A set number of pulses for a set number of threads moved. More threads equals slower movement, but more accuracy. More pulses allows for a more accurate place to stop.
Many of the older analog receivers, and the 4DTV sends a large surge of voltage when the button on the remote is pushed sometimes pushing the actuator further than you wanted it to go. (two or three pulses at once) Sometimes a very quick push and release of the button will just nudge it.
That's part of the reason I like the VBox II. The button on the remote for it will allow a single pulse movement when fine tuning. Even then, all depends on the pulses and threads per inch.
As Harold said, when the dish is being pushed across the arc, everything remains pretty stable, but when the dish starts "falling" down the other side the pulses per degree starts becoming erratic.
With the Birdview, and AJAK H-H mounts and other gear driven positioners, the pulses per degree of the arc stays the same from one end to the other.
On the AJAK which I recently tuned in, 21 pulses will put you at the next bird if it is two degrees away. So 10 or eleven pulses per degree all the way across the arc.
Real life example: My old 10 foot Winegard had a 24" actuator on it. The attaching point on it was right at the base ring. I used it from 135W to 55.5 W with no problems. When I took that dish down and put up the 7.5' Perfect 10 which had a long bar hanging down from the base ring. The first time I used it, I ran the actuator all the way to the hard limit, and was only about half-way up the Western part of the arc going East from the Western limit. It took it down and measured the travel distance and discovered the previous owner had set the 24" actuator to only come out about 14". Thats all it took to move the Winegard as described above. To move the 7.5 footer the same distance takes about 20" of actuator sticking out.
Edit: Also remember that the Winegard was a center mounted dish, and the Perfect 10 is off-center mounted dish. That also makes a difference.
Hope that helps.
Fred
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If you want more pulses between satellites, make the actuator move further by:
(A). Making the rotating arm (attached to the dish) longer, or
(B). Relocating the fixed actuator connection, or
(C). Both A and B.
Either of the modifications would require a longer actuator.
Also, the stator (plastic wheel with magnets in it) inside your actuator may be available with different numbers of magnets. The more magnets, the more pulses per revolution. You might swap to a stator with more magnets than yours and not have to change the geometry of the polar mount arms. Finding another stator might be difficult without lots of old parts to look thru.
Harold
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