Just Sharing This My Channel Master 1.8 project.

Manikm909

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before my new actuator arrives (which i am new to by the way, never used jacks before) i would like your advice on best position to place it.

i seem to have an EXTRA plate, shown here in pic2 - i dont think this is part of original CM polar mount.

first question: what do you think its for?
second question: should i leave it on, or remove it.
third question, in the first pic you can see that the actuator is mounted to second position from the end rather than the very end - should that change? ive basically copied how it came.

i have heard that its best to put the jack on the left, instead of on the right, but then again, maybe the additional plate changes things for my setup...?

FYI - its a 12" temporary jack at the moment

any advice would be very welcome.
 

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moonbase

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The shape and size of the imaginary triangle created in the plane of the two actuator fixing points and the rotational axis defines the sensitivity of movement.
It is a bit of basic maths for a scalene triangle. You want decent length movement to equal small degree movement.

Personally, I would use a fixing point that is further away from the rotational exis than the more central one in your picture.
If you aint got one on the left side you can drill a hole for one
 

Manikm909

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i have various points , i could lose the trianglular plate also. i know @nelson_b doesnt have this piece of metal on his setup.
i wonder why it was ever used \ included
attached are my options.
 

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Lazarus

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Are you going to transfer the spokes from the bicycle to the mount? :unsure
 

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1) Attach the motor end as far from dish centre as is possible and set the actuator limits to the furthest travel.

2) If you cannot get the arc that you require then move the end of the actuator towards the centre by one step and try again.

3) Repeat until you get the arc, or 3b )break the motor

If 3b) get a longer actuator and repeat 1-3)
 

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1) Attach the motor end as far from dish centre as is possible and set the actuator limits to the furthest travel.

2) If you cannot get the arc that you require then move the end of the actuator towards the centre by one step and try again.

3) Repeat until you get the arc, or 3b )break the motor

If 3b) get a longer actuator and repeat 1-3)


... and beware of the dreaded droop / dish flop at the extreme ends of the arc travel - a big heavy dish like that can give your positioner a heart attack when trying to pull back from the 'flop'
 

nelson_b

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i have various points , i could lose the trianglular plate also. i know @nelson_b doesnt have this piece of metal on his setup.
i wonder why it was ever used \ included
attached are my options.
Hi -
I don`t have the triangular plate that you have - but i have a bar fitted that does a similar job ( to get the motor end of the jack away from the center / rotational axis of the mount)

In your picture 2 above -- the jacks motor end is fixed away from the center axis - "and" forward and closer in at the dish end .... i think the user was maybe just trying to widest and most stable arc he could from a shortish jack ?
 

Manikm909

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thanks, so when my 24" arrives - i should follow Hoppers advice?
 

nelson_b

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Yes - .....
How your jack behaves in relation to its fixing points - and its pulse/ number counts will soon become clear to you once you start tinkering - i`m sure :cool:
Cheers.
 

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thanks, so when my 24" arrives - i should follow Hoppers advice?
I would order a 36" and start from there.

 

a33

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The shape and size of the imaginary triangle created in the plane of the two actuator fixing points and the rotational axis defines the sensitivity of movement.
It is a bit of basic maths for a scalene triangle. You want decent length movement to equal small degree movement.

Are there practical guidelines, to choose the ratio between the distances of the two fixing points to the rotation axis?

I noticed (by doing some rough calculations) that the 'zone of highest accuracy' shifts,
from the maximum retracted actuator zone when the ratio is 1 : 1;
to about 50 rotational degrees from max.retracted zone, when the ratio is 1 : 1,5;
to about 65 rotational degrees from max.retracted zone, when the ratio is 1 : 2;
to about 75 rotational degrees from max.retracted zone, when the ratio is 1 : 3.

(For the calculation approach, I've taken max retracted as zero degrees, and max extended as 180 degrees [no more triangle, but opposites]; as the theoretical maximum possible range.)

It's the first time that I did calculations on that, so I'd be curious to hear how people in praxis determine what ratio they choose for their actuator mounting points?

greetz,
A33
 
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Channel Hopper

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Are there practical guidelines, to choose the ratio between the distances of the two fixing points to the rotation axis?

I noticed (by doing some rough calculations) that the 'zone of highest accuracy' shifts,
from the maximum retracted actuator zone when the ratio is 1 : 1;
to about 50 rotational degrees from max.retracted zone, when the ratio is 1 : 1,5;
to about 65 rotational degrees from max.retracted zone, when the ratio is 1 : 2;
to about 75 rotational degrees from max.retracted zone, when the ratio is 1 : 3.

(For the calculation approach, I've taken max retracted as zero degrees, and max extended as 180 degrees [no more triangle, but opposites]; as the theoretical maximum possible range.)

It's the first time that I did calculations on that, so I'd be curious to hear how people in praxis determine what ratio they choose for their actuator mounting points?

greetz,
A33
I will have to check but I don't believe the full horizon arc on a prime focus dish (at this latitude) exceeds 155 degrees, any calculation is therefore going to be roughly 15% out.
 

moonbase

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before my new actuator arrives (which i am new to by the way, never used jacks before) i would like your advice on best position to place it.

i seem to have an EXTRA plate, shown here in pic2 - i dont think this is part of original CM polar mount.

first question: what do you think its for?
second question: should i leave it on, or remove it.
third question, in the first pic you can see that the actuator is mounted to second position from the end rather than the very end - should that change? ive basically copied how it came.

i have heard that its best to put the jack on the left, instead of on the right, but then again, maybe the additional plate changes things for my setup...?

FYI - its a 12" temporary jack at the moment

any advice would be very welcome.


'ere, cop for this picture of a Precision polar mount.
You can emulate the actuator fixing points on your Channel Master mount. The threaded rod in the picture is replaced by your actuator.

As you can see, the fixing point at the actuator motor end is offset from the centre of the dish via a plate.
The actuator retracting arm fixing point is out as far as it can go on the frame of the mount.

I think the receivable satellite arc you will get at the location of the installation will be catered for by your 24" QARL actuator.
You will probably have some line of sight issues at the extremes so a huge maximum possible theoretical arc is not likely.

.
Polar_Mount_02.jpg
 
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RimaNTSS

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Instead of threaded rod I use this, made a long time ago, device. It allows turning the antenna by hand from end to end or fix it in any position. It is good for adjusting antenna to the arc. After arc is set, the device can be replaced by an actuator.
 

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zorrin

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Shouldn't the jack be on the other side of the antenna for England?

1643194890656.png

something like that

1643195055365.png
 

RimaNTSS

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Shouldn't the jack be on the other side of the antenna for England?
It depends on what is your visible arc. I mean, what satellites you are going to receive? Most west and most East satellites?
 

a33

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... any calculation is therefore going to be roughly 15% out.

The calculation, however, has nothing to do with the satellite arc. Why would you think so?

It has only to do with the triangle(s), defined by its(/their) corners: the actuator mounting points, and the rotation axis.
Nothing wrong with the calculation, as far as I can see.


So I repeat my question: How do you, owners of polar mounts, in praxis determine what ratio you choose for your actuator mounting points?

Greetz,
A33
 

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The calculation, however, has nothing to do with the satellite arc. Why would you think so?

It has only to do with the triangle(s), defined by its(/their) corners: the actuator mounting points, and the rotation axis.
Nothing wrong with the calculation, as far as I can see.


So I repeat my question: How do you, owners of polar mounts, in praxis determine what ratio you choose for your actuator mounting points?

Greetz,
A33
To get a 180 degree movement the actuator arm would have to be on top of the polar bearing. In reality the maximum obtuse angle that can be obtained at this latitude occurs at around 150/5 degrees, as I recall on my own prime focus dish.

I would also expect a lower value on an offset reflector that does not have a counterweight since the actuator (and positioner) will struggle to 'pull' the mass of the dish back to the centre.
 
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