EQ8: Dec binding or total failure?

[Dark Matter]

My EQ8 is only 2 months old and while it has been doing all it was intended to do, last night when I was slewing to Sirius for a 3-star alignment, the Dec made a terrible 'binding' or 'jamming' sound, as though the worm was too tight, a bearing had sized or the stepper motor is stuffed.

I'm now waiting from the SW engineers at Synta in Vancouver Canada to see how we can take apart the Dec and look to see what is causing this problem.

Anyone had any probs like this? If not, give it time. We get what we pay for. 

James

[ollypenrice]

You're not the only one. Scroll down this post on CN to find another victim. http://www.cloudynights.com/ubbthreads/modifypost.php

I also noticed my Dec motor was remarkably hot after some slewing. I wonder if, while being hopelessly slack on one side, it is far too tight on the other?

It is rather obvious by now that the EQ8 is in big trouble and what we don't want to see from Skywatcher is denial. They need to fess up and fix it.

Olly

[Velvet]

i wonder actually how many have been sold, this would give a clearer indication of the scale of the problem.

I have only seen half a dozen posts of problems, the others seem quite happy.  Hope its just

a duff batch, would be a shame if not

Velvet

[libraryman]

When  the EQ6 had it's debut, it had some issues with bearing quality and cleanliness of the assembly, these were well documented and resulted in strip downs, modifications etc.

i don't think EQ8 owners will be going down that road in a hurry! they will complain bitterly and may well negatively impact the Skywatcher brand permanently, Skywatcher need to watch their backs and get things sorted or explained, lest sales start to drop and owners mounts lose value.

At this time i have no overheating issues, just manageable backlash, can you be more specific on where and how the heat is being generated?

Ray 

[ollypenrice]

i wonder actually how many have been sold, this would give a clearer indication of the scale of the problem.

I have only seen half a dozen posts of problems, the others seem quite happy.  Hope its just

a duff batch, would be a shame if not

Velvet

This is a fair point but having spent most of yesterday on the net I've come across a lot more than half a dozen problems. What I have found is a very strong pattern.  Some have spotted the assymetry in mesh from one side of the wheel to the other physically, as I did. Others have noted a radical difference in guide speed calibration from one side to the other. During a shoot this means the guide speed needs altering. This would tally perfectly with a variation in mesh. While the seized Dec drives might have a quite different cause, an over tight mesh on part of the wheel would be perfectly possible as a cause. If this is the case an eccentricity in the wheel or the dec shaft could be the root cause.

I want to like the mount and I think they'll sort it but I'm not at all convinced that all is well at the moment. I think there is at least a batch out there with a fundamental machining error. What is clear to me, though, is that any half baked QC inspection would have spotted the error in my mount. It had been out of the box for about two minutes when Yves, Jeffrey and I all felt the saddle plate and said, 'Uh-Oh...'

What I might try is doing some unloaded slewing back and forth on the slack part of the wheel and then on the tight, to see if the motor gets hot only on the tight side.

Olly

[JamesF]

I'm sure I recall seeing pictures of the worm and part of the worm gear that someone had taken for a "tour of the EQ8" article.  If the gears are that accessible someone may be able to put a dial gauge on the gear to measure any eccentricity.

James

[Peter Drew]

I think you can check gear concentricity only by degrees of backlash/ tightness of the mesh. It is perfectly possible for the outside diameter of the gear blank to be eccentric but the teeth being cut concentric to the bore, and vice versa. This problem isn't confined to Skywatcher, The DEC gear on my Meade 16@ LX200 has a similar problem, however the worm assembly is spring loaded so backlash is eliminated, 

[Dark Matter]

Ok guys, here's what I got back from a Synta engineer re the EQ8 Dec seizure problem.

"Before you unbolt the Dec. assembly, would you please try to increase the backlash at the position where the axis got jammed?

On a conversation with our engineer on what is the proper backlash on an EQ8 mount, I was told these:

1. There is unavoidable machining error which lead to tiny centering offset of the axis of the worm wheel.

2. During the assembly process in the factory, our technician will find the maximum “high” point on the worm wheel and adjust the worm block to allow a small spacing for the worm-wheel meshing.

3. The result is that the backlash at the “low” point of the worm might be higher.

A spring loaded worm might be the way to solve the problem, but it was not implemented on the EQ8 mount.

My suggestions are,

1. Do not seek for zero backlash on the EQ8 mount when users try to tune the backlash by themselves.

2. Slightly unbalance the Dec and RA.

If you extended the backlash and find the problem is still there, please let me know. I will try to find out to what level that we can release the technical document..."

If what they are saying is correct and the Dec wheel is eccentric to the Dec shaft, the wheel in fact is rotating a 'cone' pattern which will lead to stripped teeth and a burnt out stepper motor.

Had it been a car, it would have been recalled and fixed at the car makers expense. So now we're been asked to 'fix' their problem?

So if you know any EQ8 users please make them aware of this.

cheers,

James

[swag72]

If their workmanship is likely to lead to the issues you suggest in time - a burnt out stepper motor or stripped teeth - this is surely serious and devastating news for all those who have the EQ8 even if at the moment everything looks fine.

[FLO]

Olly, if your mount has a fault then we are here for you. You received it only three days ago so all options are available including free collection and full refund. Please don't let this spoil your Christmas 

James (Dark Matter), it is good to see Skywatcher have responded quickly to your questions. I hear their distributer for Australia have a good reputation for service and support so you are in good hands. 

The EQ8 has had a remarkably successful launch and the internet is full of praise from owners so if there is a fault then it has only just become apparent. Let's give Skywatcher a chance to digest the information and respond. 

Steve 

[FLO]

PS: Apologies in advance if I am not online over the next 2-3 days. My youngest Son is bouncing on the bed telling me it's only 15 hours til Christmas and my wife is giving me one of 'those' looks because my laptop is open! 

[knobby]

Flo... Its Christmas mate, you don't need to apologise... You already GI above and beyond what should be expected of a retailer.

you and your family have a great Christmas!

(But I'm sure you'll sneak in here anyway :-) )

[Dark Matter]

Thanks everyone and to FLO. Yes I'm dealing with this issue with Synta and hope the 'cancer' hasn't spread to other EQ8 users. If it does, it will become pandemic.

I tried both motor firmware updates. Its original 2.09 and then 2.10 and I still had the same issues. Even the RA has started to play up like its mate, the Dec.

Now this may come as surprise. All this 'jamming' as I call it, only happens at Rate 9 or when it slews at high speed which is Rate 9 or 3.3 D/sec. All other speeds it purrs like kitten.

I even loosen off the Dec worm and still had this intermittent stalling or jamming.

So I'm now at point of either sending it back to my supplier for refund or hope to God, Synta can solve this issue. To the latter I think they will but how?? Build a new mount with NO faults? Hha hha..

Anyway, as veteran of 60 in astronomy, I've built dozens of Eq mounts in my day some to tale 300kgs payloads and never ever had anything like this happen.

I won't give up on this and will keep all of you posted.

cheers and a Merry Christmas to all.

James

[Naemeth]

Does seem odd that if they knew of an unavoidable machining error that they didn't just change the design, or change to a spring loaded worm

[ollypenrice]

Olly, if your mount has a fault then we are here for you. You received it only three days ago so all options are available including free collection and full refund. Please don't let this spoil your Christmas 

James (Dark Matter), it is good to see Skywatcher have responded quickly to your questions. I hear their distributer for Australia have a good reputation for service and support so you are in good hands. 

The EQ8 has had a remarkably successful launch and the internet is full of praise from owners so if there is a fault then it has only just become apparent. Let's give Skywatcher a chance to digest the information and respond. 

Steve 

Guys, none of this is your fault and I wasn't contacting you because I wanted you to have a break. Forget it over Christmas and we'll discuss it later. Our Christmas is fine. Enjoy yours!

Olly

[Prador]

The machining error is very much avoidable. Unfortunately, closer tolerances inevitably mean higher manufacturing costs.

I machine all kinds of things on a manual Colchester lathe to a tolerance 0.005mm. I am pretty sure the allowed tolerances in these suspect mounts would have to be terrible for worms to bind onto its corresponding wheel.

[Zakalwe]

If their workmanship is likely to lead to the issues you suggest in time - a burnt out stepper motor or stripped teeth - this is surely serious and devastating news for all those who have the EQ8 even if at the moment everything looks fine.

Lets not jump to conclusions just yet.

[Tim]

Now this may come as surprise. All this 'jamming' as I call it, only happens at Rate 9 or when it slews at high speed which is Rate 9 or 3.3 D/sec. All other speeds it purrs like kitten.

I suppose the good news is that you can get by without using the high speed. You shouldn't have to, but at least you are not sitting on a dead duck as it were.

[Tim]

The machining error is very much avoidable. Unfortunately, closer tolerances inevitably mean higher manufacturing costs.

I machine all kinds of things on a manual Colchester lathe to a tolerance 0.005mm. I am pretty sure the allowed tolerances in these suspect mounts would have to be terrible for worms to bind onto its corresponding wheel.

I think you just found yourself a new venture

[Prador]

I think you just found yourself a new venture

No problems. Everybody send your EQ8's to me. I promise a speedy two year turnaround 

[JamesF]

Now this may come as surprise. All this 'jamming' as I call it, only happens at Rate 9 or when it slews at high speed which is Rate 9 or 3.3 D/sec. All other speeds it purrs like kitten.

I'm not sure that's a surprise, to be honest.  Certainly in some cases gears that are a less-than-brilliant match will mesh ok at low speeds because there's sufficient play in the system overall to allow them to move a little to accommodate each other.  The increased inertia and reduced time available at higher speeds can result in the same gears jamming.  Either way it's going to result in increased wear, which is not good

James

[Dark Matter]

No problems. Everybody send your EQ8's to me. I promise a speedy two year turnaround 

Awww doncha love the English SOH?   hahahahaaaa.. I love it, mate. Mine is on the flight deck to you... can you replace the worms with spring loaded ones?

Listen to this audio I made of it. It has been sent to Synta.

James

[barkis]

Why can't Skywatcher build a jig to lap out any eccentricities they find during inspections. After all, the deviations can't be that large,

and it wouldn't take too long to remedy. A DTI guage atop a  lapping worm would indicate when the anomaly had been removed.

The wheels ought to be scrutinized before assembly, and the duffers taken to the lapping shop.

Not a criticism, just the offer of a solution to the problem., but perhaps there is a reason why it isn't practical.

[Dark Matter]

Why can't Skywatcher build a jig to lap out any eccentricities they find during inspections. After all, the deviations can't be that large,

and it wouldn't take too long to remedy. A DTI guage atop a  lapping worm would indicate when the anomaly had been removed.

The wheels ought to be scrutinized before assembly, and the duffers taken to the lapping shop.

Not a criticism, just the offer of a solution to the problem., but perhaps there is a reason why it isn't practical.

Maybe it was to a price and not to a quality standard, which I don't think exists in China.

Had it had spring-loaded worms and more QC, I might not have this problem but then, I may not been able to afford it either. 

[Steve 1962]

I'm sorry to hear of the problems that people are having with the EQ8 - it must be very disappointing for everyone who has been looking forward to playing with their new mounts over the Christmas and New Year break.

My finger was posed over the "buy" button, so I'll be watching progress with interest - this mount promised to be really good value for money. (If the term "good value" can be used in reference to "a tripod with a head motorized in two directions" (to quote a popular and well known SGLer in another related thread) costing the best part of £3k!

It strikes me that the there's always a risk for early adopters of new equipment, but really, the whole point of a mount is to drive a scope across the sky, so why does Syntra / Skywatcher apparently have such poor QC that an issue so apparently obvious / predictable can make it out to customers?

But then, we are participants in a hobby where supposedly reputable manufacturers seem to think they can get away with selling flatteners that don't flatten, mounts without functional ASCOM drivers and equipment that doesn't allow spacings to be achieved (to name only a few of the issues which regularly seem to crop up) - all at exorbitant prices.

Let's hope Syntra step up to the mark in an appropriate, timely manner...and the guilty others do some decent testing and QC rather than using us all as beta testers.

There - rant over!

Have a good Christmas everyone.

Steve