Have I broken my EQ2 mount?

[stu640]

PROBLEM FIXED

I'm pretty sure I have, but don't know if it's terminal! I have the EQ2 supplied with my Skywatcher Explorer 130. The Dec control stopped working last night. It winds until it hits its hard stop at either end, but only moves the mount under control if the end of the rod internally pushes against a just visible metal plate. When the Dec control is 'unwound' this plate and the mount/scope moves freely on the Dec axis by maybe around 10 degrees. Wind it in and the Dec axis is solid, and only movable by unlocking the dec lock screw. From what I've understood from google, basically, firstly I shouldn't have been using the Dec control for anything more than a few degrees of motion in the middle of its range and secondly, the 'return' on winding is probably meant to have been spring loaded against the back of that metal plate. If the latter there's definitely no spring in there anymore! And the system is not as I thought a worm screw like the RA motion control! This free movement of the mount renders the whole setup pretty useless.

If the diagnosis of a broken spring somewhere in the dec mechanism is right, is this easily reparable? And is it cost effective to do/easy to acquire parts?

Thank you in advance for any advice!

Edited February 16, 2018 by stu640
Update problem status

[Dr_Ju_ju]

Can we have some pictures, please, but it sounds like the drive isn't 'meshing' correctly

[stu640]

10 minutes ago, Dr_Ju_ju said:

Can we have some pictures, please, but it sounds like the drive isn't 'meshing' correctly

Hi Julian, thank you - I don't think meshing is part of this mechanism. The dec controller seems to be a push rod. It's not easy to see in the pictures, but the mechanism is under the plate, which you can see changes position in the first and second picture according to the declination motion. In the third of the pics you can see inside to the pointy end of the rod. Hope this helps!

[Peter Drew]

The DEC drive on these mounts has only a limited travel. Before use it's best to set it at halfway travel. You then loosen the DEC axis locking knob to point to the DEC position of the object you wish to observe and then tighten it again when in the field of view. Centering can then be achieved by turning the DEC operating cable. The RA control is a continuous action and will turn for as long as you wish or until the cable clashes with the mount, whichever is the soonest.  

[stu640]

1 minute ago, Peter Drew said:

The DEC drive on these mounts has only a limited travel. Before use it's best to set it at halfway travel. You then loosen the DEC axis locking knob to point to the DEC position of the object you wish to observe and then tighten it again when in the field of view. Centering can then be achieved by turning the DEC operating cable. The RA control is a continuous action and will turn for as long as you wish or until the cable clashes with the mount, whichever is the soonest.  

Thanks Peter - lesson learned! Just need to know if whatever it is I've broken in there can be fixed...

[RichM63]

Hmm, just remembered I have an old EQ1 or EQ2 in a cupboard.

From your pictures above.

The shiny sliver bolt thing on the opposite side to your hand controller contains a piston with an internal spring that forces the piston head against the casting thus giving resistance to the hand controller opposite.

The spring can not fall out on its own, nor can you see it unless you dismantle, but you may possibly have crushed it.

2 mins, unbolt it and pull out the piston to check the spring, bit like a bigger version of a ballpoint pen.

In your bottom picture it is the silver item top right. Nothing special about the spring that I can see in front of me. A good hardware/engineering store most likely will stock something to replace it if required.

Rich

[stu640]

18 minutes ago, RichM63 said:

Hmm, just remembered I have an old EQ1 or EQ2 in a cupboard.

From your pictures above.

The shiny sliver bolt thing on the opposite side to your hand controller contains a piston with an internal spring that forces the piston head against the casting thus giving resistance to the hand controller opposite.

The spring can not fall out on its own, nor can you see it unless you dismantle, but you may possibly have crushed it.

2 mins, unbolt it and pull out the piston to check the spring, bit like a bigger version of a ballpoint pen.

In your bottom picture it is the silver item top right. Nothing special about the spring that I can see in front of me. A good hardware/engineering store most likely will stock something to replace it if required.

Rich

Yes, fixed it! Unscrewed as suggested, but realised I could probably have just jiggled the piston rod back through its hole. Not pictured, but the spring behind pic 1 looks pretty heavy duty! Essentially, it looks like if you wind the dec controller all the way in, the metal plate can push the piston rod all the way its hole and the flat part of its face gets caught the wrong side (pic 3)... Some pics to help explain...

Thank you so much for your help Rich! I wouldn't have wanted to unscrew stuff without knowing it was going to be ok!!

[RichM63]

Glad you got it sorted.  saves figuring out how to post this complete one to you. 

Maybe add a smear of grease, spot of WD40 to the outside of the piston, can't hurt.

I'm a good 'unscrewer' of things, I always know that I can 'screw it up again' !  

Rich

[stu640]

Another holiday in Brittany would've been good, the skies were great when we camped there a couple of summers back! And thanks for the tip - I'll get the WD40 out! 

Thanks again!

[ericleo1]

2 years on from this post and I have had the same issue. It is clearly a flaw in the design of the mount which is otherwise robust. I extended the length of the spring by inserting a metal pin thereby increasing the tension but the idea that the whole mechanism is dependent on a small spring is the issue. Poor design; a weakness as you should not get any rocking of the OTA on scopes and you do with this set up.

[5/01/21] I have tightened the large bolt which compresses the spring and this seems to have 'fixed' it. The movement in declination is pretty restricted but manageable with out any shake.

Edited January 9, 2021 by ericleo1

[stu640]

On 05/01/2021 at 10:46, ericleo1 said:

2 years on from this post and I have had the same issue. It is clearly a flaw in the design of the mount which is otherwise robust. I extended the length of the spring by inserting a metal pin thereby increasing the tension but the idea that the whole mechanism is dependent on a small spring is the issue. Poor design; a weakness as you should not get any rocking of the OTA on scopes and you do with this set up.

[5/01/21] I have tightened the large bolt which compresses the spring and this seems to have 'fixed' it. The movement in declination is pretty restricted but manageable with out any shake.

It is very fiddly. Whenever I see anyone showing this mount off as a new acquisition, I always warn them not to go any distance with the dec controller to avoid this problem. Great starter mount for learning how the sky 'works' and not forking out too much cash before deciding whether it's for you, and then upgrade asap!!