Help with calculating Backlash on Esprit 100ED & ZWO EAF

[Richard_]

It sounds like you're describing the part mentioned at 6:45 in the below video. 

 

 

Edited December 31, 2021 by Richard_

[scotty38]

In the interests of testing is it possible to connect the coupler without it entering the housing just to see if there's a difference?

[Stuart1971]

4 minutes ago, scotty38 said:

In the interests of testing is it possible to connect the coupler without it entering the housing just to see if there's a difference?

Well, simple but should be very effective, why did I not think of that….😂👍🏼

[oymd]

3 hours ago, Richard_ said:

It sounds like you're describing the part mentioned at 6:45 in the below video. 

 

 

 

2 hours ago, scotty38 said:

In the interests of testing is it possible to connect the coupler without it entering the housing just to see if there's a difference?

 

2 hours ago, Stuart1971 said:

Well, simple but should be very effective, why did I not think of that….😂👍🏼

Yes, the coupler does indeed rub on the inside of the housing. 
 

Before even installing the actual EAF motor, when I turn the COARSE knob manually, there is obvious resistance and a grinding sound. 
 

Not sure how to sort this. The only thing I can think of is using a file and trying to decrease the actual diameter of the coupler by a millimetre or so. 
 

With regards to attaching the coupler without  it being inside the housing, I do not think that is possible. The focuser’s shaft is deep inside the housing. 

Edited December 31, 2021 by oymd

[Richard_]

How old/new is the telescope? If its new, you could get in touch with the vendor and perhaps recommend a course of action. Perhaps they can provide you with a new focuser or something? 

[oymd]

4 hours ago, Richard_ said:

How old/new is the telescope? If its new, you could get in touch with the vendor and perhaps recommend a course of action. Perhaps they can provide you with a new focuser or something? 

The telescope is brand new. I do not think it’s the Esprit’s problem that the ZWO’s couplers diameter is a tight fit in the focusers housing. 
 

 

[oymd]

On 31/12/2021 at 12:57, Stuart1971 said:

On my Tak FSQ85 it goes in about 2-3mm

 

On 31/12/2021 at 12:57, scotty38 said:

Couldn't help but have a search and I found this on CN... I see what you mean now....

 

 

On 29/12/2021 at 12:21, Richard_ said:

Before you installed the EAF, how did the manual focuser feel on the Esprit? Is it stiffer than your Star71? If there's more tension/resistance throughout the travel, especially at the 2cm, 4cm and 8cm mark, then that may explain why your EAF is beeping all the time. 

Ok, so I removed the focuser and decided to start from scratch.

I can confirm that the 4 couplers provided by ZWO with the EAF are not precisely machined, as some of them are rough on the outside AND inside, and on looking at the inside and between the gaps there are some aluminium fillings here and there.

I have 4 EAFs in their boxes, so I had a total of 15 couplers to look at. (1 is fixed to the WO Star 71 and working perfectly well)

The first time around, I had used the coupler with the LARGEST hole to fit the Esprit's focuser shaft.

On further inspection, I think that was a little loose. The THIRD size is the correct one, but needs to be smoothed on the inside.

On trying different couplers from the 4 boxes I had, I believe the THIRD size is the correct one to use, but I needed to use a 2mm allen key to smooth the inside of it and flatten a lot of aluminium fillings.

Now the tricky part. The LARGEST coupler size I had installed on the EAF last week would not come off the focuser's shaft!! Even after completely removing both grub screws. It was STUCK, and I could only remove it after some clockwise and anticlockwise rotation, which was not a good thing for the motor inside, obviously.

On inspection, the EAF's arm shows deep grooves. Not sure why that happened.

Also, the coupler I removed showed friction and rub marks on the outside.

Anyways, Reinstalled the EAF using the Takahashi bracket, M4 35mm bolts, and used the size THREE coupler after cleaning up the inside.

I first made sure that when the coupler was fixed inside the housing, before installing the EAF, when I manually rotated the coarse focuser knob, everything rotated very smoothly.

Now works very smoothly, NO BEEPS, and Backlash is at 190-200. I believe when I forcefully removed the coupler off the motor's shaft, the motor developed some more backlash.

Zero is set at 0.5cm, and total travel is about 16500 steps, rough focus point of 6cm is at about 12000 steps.

 

[scotty38]

Good news that you have it sorted....