Re: [ap-gto] 600E Backlash Question


Oct 15, 2003

 


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#8953 Oct 16, 2003

In a message dated 10/16/2003 12:14:28 AM Central Daylight Time,

chrishet55@... writes:



> It doesn't continue when I

> run at .25x, .5x or 1x which makes be feel like it is SW related (if

> it is worm mesh why wouldn't the mount continue to move after a W-E

> at 1x?),



At .25, to 1x the motor simply slows down. It never reverses. At 12x and 64x,

the motor has to reverse. This unwinds the geartrain on the motor. Then when

you release the button, the geartrain has to take up the slack at only 1x.

Adding backlash compensation via the keypad in the Setup Menu gives the motor an

initial kick at 64 X for a very short time to help the motor geartrain reverse

and take up the slack. If you have the keypad set for either 900 mount or

1200 mount, the "kick" is very much shorter than if you have it set on 600 mount,

so check this setting on the keypad. You should be able to compensate for any

backlash by dialing in a 2 or 3 setting. Take a look through the spur gear

window on the side of the mount where the motor spur gear meshes with the worm

spur. With different settings of RA backlash, you will see the gears move more

and more quickly in the opposite direction when you let go of the E button.



If the worm is well in mesh, then the backlash delay is not coming from that

part of the mechanical gear train. It could very well be that the worm is in

mesh, but the spur gears are not. You can see whether they are in mesh through

the sight window. If they appear to be in mesh and they move quickly with some

backlash compensation dialed in, yet the stars still drift, then you may have

a loose setscrew on the spur gear on the end of the worm. To check that, you

will have to back off the worm housing and look underneath where you can see

the worm and spur gear. If the set screw has backed off, the spur gear will be

loose on the worm shaft and will rotate some distance before transmitting its

rotation to the worm. When you tighten this set screw you have to make sure

that you tighten it on the flat part of the shaft, otherwise it will not stay

put when the motor starts rotating the gear.



If you have any questions, please give Walter a call here at AP and he can

take you through the steps to check out your mount.



Roland Christen





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#8955 Oct 16, 2003

In a message dated 10/16/2003 3:22:39 AM Central Daylight Time,

Catterall@... writes:



> This doesn't sound like a backlash problem, but for some reason the

> motors continue to move the mount after releasing the East button



No, the motors do not move. The earth rotates, which makes the stars look

like they are moving in the eyepiece. This seemingly unnatural motion is quite

natural until the motor has fully engaged the worm gear and is finally driving

the mount again at the sidereal rate toward the west.



Roland Christen





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#8958 Oct 16, 2003

Thanks Roland!



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#8963 Oct 16, 2003

In message b0.3fd8cc8e.2cbfecb5@...>, chris1011@... writes >No, the motors do not move. The earth rotates, which makes the stars

>look like they are moving in the eyepiece. This seemingly unnatural

>motion is quite natural until the motor has fully engaged the worm gear

>and is finally driving the mount again at the sidereal rate toward the

>west.

>

>Roland Christen



I understand that, but in my case pressing the East button and then

releasing it, allows the star to continue moving in an eastern

direction. If the motors were not engaged, then the star should move

west, hence if the star is moving east, the motors must be engaged and

continue to operate even when no button is pressed.



The problem I have is that this is an intermittent fault and when I used

another handset, seemed to resolve the issue.



Adrian





--

Adrian Catterall

Amateur Astronomer

Hertfordshire UK

www.observatory.demon.co.uk/



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#8964 Oct 16, 2003

In a message dated 10/16/2003 4:40:49 PM Central Daylight Time,

Catterall@... writes:



> The problem I have is that this is an intermittent fault and when I used

> another handset, seemed to resolve the issue.

>



That may be, but the poster has a different problem and it would just add to

the confusion if you add your problem to his. I doubt that his motors continue

to run. Yours is the singular occurance of this phenomenon where the motors

actually continue to run after the button is released.



Roland Christen





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#8965 Oct 16, 2003

Update: and clarification...seems my brain doesn't work so well late

at night, especially during a baseball game! I worded my question as

if the motors were running after I let go of the East button. Today,

during daylight, I tested my backlash adjustments on a fixed object,

my neighbors gutter. Indeed it is not that the motor continues to

run but rather the RA doesn't catch up for a number of seconds, in my

case 8-11secs, after the button is released. This appears during the

night sky as a star drifting. My bad...



Now back to my backlash adjustment. I took your advice Roland and

called Walter. He walked me through your suggestions and a few

more. When I look through the site hole the spur gears appear well

meshed. I observed them and they look to be moving properly. They

engage immediately when I press the E or W keys and the RA starts up

with 2 seconds of releasing the E key. However I am still seeing a

delay of 8-11 seconds after releasing the E key which lead me to

believe there was something after the spur gears causing the problem.



I decided to take your advice and check the lower spur gear (the one

attached to the worm) To get to it I had to completely remove the RA

housing (?) from the mount housing. This wasn't too difficult but

beware the clutch has a small piece that can drop out so set your Alt

straight up if possible.



Once I got the RA housing off I removed the 2 flat head screws and

pulled the gear and setting circles away from the worm. This was

VERY difficult as it was quite stiff but I worked it back and forth

and finally got it off. Once I had access to the worm I checked the

spur gear set screw and it was fine. There also appeared no play

between the worm and the bearings. All seems to be perfect.



I reassembled and re-adjusted the worm. I've must have made 100

minor adjustments and no luck thus far (I'll keep trying). Most of

the time it takes 8-11 seconds, after the button is release, to re-

engage the RA. Occasionally is starts back up after only a few

seconds but goes back to 8-11 on the next test. I've tested every

setting on the RA backlash and tried different mount types as you

suggested.



It doesn't appear that the RA Backlash settings are doing anything.

Should I report this to the 4.05 Beta board? I've adjusted the worm

to the point of binding and it stills appears to have backlash. How

can this be? :o. Any thoughts would be greatly appreciated.



Heading to the Peach State Star Gaze on Wednesday so I still have

time....



Regards

Chris







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#8966 Oct 17, 2003

In a message dated 10/17/2003 12:27:09 AM Central Daylight Time,

chrishet55@... writes:



> It doesn't appear that the RA Backlash settings are doing anything.

> Should I report this to the 4.05 Beta board?



You can try different amounts of RA backlash settings and look into the sight

hole to see the action. Again, make sure that your keypad is set to 600

mount. I'm sure the software is fine. If the problem cannot be resolved there, then

I would suggets that you send the mount in to have it checked here.



Roland Christen.





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