How much arc would I gain (approx) ?

[Vipersan]

I've put all my data in spread sheet. Can not find there linear sequence, I even think it is impossible.

Much closer to linear than mine tho' Rima
3 degrees of arc on the Western side on yours = 18
3 degrees of arc on the Eastern side on yours = 15

It would suggest that the actuator is on the western side of the mount ..if it's compared to mine.

 

[RimaNTSS]

It would suggest that the actuator is on the western side of the mount .

You are right, it looks like this

 

[Vipersan]

You are right, it looks like this

I thought so ..
..and I also suggest the reason for your more linear coverage is the motor end rose joint is closer to the centre pole axis ..
..which is something I cannot achieve If I want to see a larger chunk of arc ..as this would cause the actuator to physically come in contact with the mount itself shortly beyond True South travelling Eastward.
Hence I extended that joint outward from centre ..so as to allow the actuator to push to the East further...and of course less linear travel as a result.

Beautiful Dish by the way ..
Has she got a name ?

 

[Vipersan]

There is a way I could emulate your more linear tracking of the arc ..and that would be by referring back to an earlier post made by Huevos about getting the actuator higher ie raised from the current motor rose joint position at the back of the mount to 'clear' the mount itself when driving what is effectively Christinas back plate.
It could be done but would require some serious metalwork.

I'd need a roughly 8 inch length of 8 inch tall RSJ ..which I'd then cut off the back 'fins' to the shape shown in red on the photo ..
If anyone has such an offcut ..I'd have a go..
lol

 

[RimaNTSS]

Has she got a name ?

No specific name, just 150 :-per . Moreover, she probably feels that I have plans to replace her by 180.

 

[Huevos]

Like CJ says the G-box does high side and low side count so doubles the resolution without any modification to the sensor wheel. Also G-box doesn't wrap the count. It does negative count (going east) and positive count going west. Place due south at zero. On my setup (actuator on east side of dish) 57E is at -0744; due south (0.8W) is at zero; and 58W is at +0365... which shows just coarse the positioning is when the actuator is fully extended.

 

[Vipersan]

Like CJ says the G-box does high side and low side count so doubles the resolution without any modification to the sensor wheel. Also G-box doesn't wrap the count. It does negative count (going east) and positive count going west. Place due south at zero. On my setup (actuator on east side of dish) 57E is at -0744; due south (0.8W) is at zero; and 58W is at +0365... which shows just coarse the positioning is when the actuator is fully extended.

Thanks for the info Huevos..

I am giving serious consideration to raising the actuator as in the photo above ..thus I can get the motor rose joint closer to the mount pole axis..
I think this may well give me a closer to linear sweep ..though obviously this can never be perfect ..
I'd like your comments as to the accuracy of what I'm thinking ?

Also ..I do have a Gbox (500 ?) on the shelf ...currently driving the Gibby (KU) ..
If this one is suitable for higher res counting ..I may well swap them over and have The Vbox drive Neil ..and the Gbox Drive Christina ..
What d'ya think ?

 

[Captain Jack]

Yeah that's the one VS - I have that same one.

 

[Huevos]

VS, you have a span of around 130º of arc. The principle of the mount design is to open one side of triangle at a linear rate. With that design, over that span, there is no way to get the mount to rotate at a linear rate.

 

[Vipersan]

VS, you have a span of around 130º of arc. The principle of the mount design is to open one side of triangle at a linear rate. With that design, over that span, there is no way to get the mount to rotate at a linear rate.

Cheers CJ..

Yep I understand it's not possible to achieve a linear scan Huevos ...I just wondered if closer to linear (ie less abrubt coverage at my Eastern extreme) was possible by moving the motors rose joint further in toward the pole ..as it is in Rimas set up. ?
In other words ..anything to be gained ?

 

[Huevos]

VS, post some numbers and I'll do the maths.

I need:
distance from polar axis to spherical joint 1,
distance from polar axis to spherical joint 2,
min (closed) distance from spherical joint 1 to spherical joint 2.

Give me a few different combinations and I'll work them out into something tangible.

 

[Vipersan]

To be honest Huevos the measurements wont be whole lot different to those I already posted in reply #53 of this thread..
The weather is extremely foul here atm with high winds and rain ..but I'll measure them accurately again tomorrow if you require ..
rgds
VS

I'll measure A - polar axis
B- Motor joint
C- Backplate joint

and give the distances at Max jack extension (60E approx)
Min extension (58W)
and halfway (roughly) 1W
A B & C for Each
When the weather improves..

 

[Huevos]

Sherical joint to Sperical joint

Dish due south is 50cm
Fully closed 11cm

polar axis distance with dish due south ..
To joint one jack end 44cm
To joint two ..motor end 38.5cm

These measurements are with the jack located in the recently drilled hole ..not the original mount point hole.

Okay, I couldn't find them earlier.
Right, converted to inches, 4.32"; 17.29", 15.13".
That gave this:

• Inch 1 = 4.01º
• Inch 2 = 3.87º
• Inch 3 = 3.81º
• Inch 4 = 3.79º
• Inch 5 = 3.79º
• Inch 6 = 3.81º
• Inch 7 = 3.82º
• Inch 8 = 3.86º
• Inch 9 = 3.91º
• Inch 10 = 3.95º
• Inch 11 = 4.02º
• Inch 12 = 4.09º
• Inch 13 = 4.17º
• Inch 14 = 4.26º
• Inch 15 = 4.37º
• Inch 16 = 4.5º
• Inch 17 = 4.63º
• Inch 18 = 4.81º
• Inch 19 = 5º
• Inch 20 = 5.23º
• Inch 21 = 5.52º
• Inch 22 = 5.87º
• Inch 23 = 6.32º
• Inch 24 = 6.91º

 

[Huevos]

BTW, that gives total travel of 108º, so by the looks of it either your measurements are off or you are only going to reach about 50E.

 

[Vipersan]

Certainly it's possible that I can only achieve 50 East now ..
Having relocated the mount points..
Definately I previously reached from 58W to 57 East as you know ..on account I posted images from TeleChad.
Problem now is I have this heavy duty Jack which is thicker and and the mount bracket is wider thus positions the jack slightly more westward..
It worries me that I may now be restricted somewhat as I can't mount it in quite the same way as it would definately bind on the mount whereas the TD24 didn't but at full stretch was so very close to the polar mount.
All I want is the same arc coverage with the QARL ..but might now have issues.
I'll get more accurate measurements as configured currently with the QARL ..
I'll do this tomorrow morning ..and if you cound just work out my -current- Eastern arc limit..
btw ..it currently doesnt come close to the mount body ..and if the limit switch can be adjusted another click ..just possibly a couple more degrees to the East as a result.
Your efforts ARE appreciated mate.
rgds
VS

 

[Vipersan]

Looking casually at a glance your figures indicate as I suspected the dramatic arc coverage per inch seems to kick in after 19 inches extended and accelerate rapidly from there..

 

[Huevos]

Looking casually at a glance your figures indicate as I suspected the dramatic arc coverage per inch seems to kick in after 19 inches extended and accelerate rapidly from there..

Yes, any time the mount is open more than 90º it starts accelerating. In your case 19" = 92º.

If you want to try any other combinations just post them and I'll crunch the numbers.

 

[Vipersan]

Weather had improved a bit this morning so went out and got accurate current numbers with the QARL fitted ..
Distances in cm ..A > B > C
I dont know if this is relevant but it occurred to me that this triangle shown in purple on the photo has to fixed sides..
Whereas the introduction of a 4th point D ..forms a second triangle (shown in green ) which has 2 variable sides.
So I've included this data as well..

Fully extended jack

A > B fixed 38.7cm
A > C fixed 34 cm
B > C Var 67.9cm


A > D Var 40.6 cm
C > D Var 67.6 cm



---------------------------
Dish halfway 1W


A > B fixed 38.7cm
A > C fixed 34 cm
B > C Var 46.7cm



A > D Var 43.2 cm
C > D Var 46.5 cm

----------------------------------
Almost closed 58W


A > B fixed 38.7cm
A > C fixed 34 cm
B > C Var 13.0cm






A > D Var 41.5 cm

C > D Var 11.5 cm

--------------------------

Thanks for taking the time Huevos.
No rush ..as I only really want to know my Eastern arc current limit

 

[Vipersan]

Ok ..I have a pack of Neodymium magnets on order
1mm dia x 0.5mm thick ..
..and have cast a new disc in liquid plastic which should be rock hard by tomorrow..so that I can tidy it up ..and hard enough to drill.
Here are the pics so far..

 

[Captain Jack]

Your ingenuity knows no bounds...