Mechanical problem with HEQ5 Pro

[raymo]

I have traced my tracking problems to the hand controller, and have bought a new V.4 one, but now have another problem. When tracking
with the counterweights pointing east, all is fine, smooth and quiet.
When tracking with the weights pointing west, the motor noise is normal, but every 10 to 20 seconds there is a loud sort of crack audible from at least 10 metres away, which I can just feel if I have my hand on the mount, so something seems to be slipping. As there is a little backlash in R.A. I thought that the R.A. worm might be moving longtitudinally, but it could only do that once, not repeatedly. Pushing lightly,or heavily, with or against the drive motor makes no difference. None of the gears are slipping on their respective shafts. Anyone else had this problem?
raymo

[jayconnor (Jay)]

how old is your setup mate?

I'm acutally looking at getting one!

[raymo]

2007 Jay. I've no doubt I'll sort out the problem eventually.
raymo

[JimsShed (Jim)]

As a mechanic in a previous life, I'd be telling you it's either a broken tooth on a gear, or a chip off a tooth that occasionally moves around and lodges itself between the moving gears. Either way, I would not use it again until I pulled the gearbox apart and cleaned and inspected it.

[raymo]

Thank you for your reply Jim. I would love to be able to confirm your
opinion, but firstly, the gears move so slowly that it would take many
minutes, or even hours, depending upon which gear, for the damaged tooth to come round, not 10 to 20 seconds. Also, the noise would be regular, and it is not, varying between the two mentioned figures.
A third problem is that it only happens when the weights are on one side of the mount; that changes nothing as far as the drive is concerned, it would happen all the time if a tooth was damaged. I may have to strip the whole thing. Incidentally, I inspected and greased the gears and
they look to be in mint condition. I do it regularly, as the gears are so
easily accessible.
raymo

[tilbrook@rbe.ne (Justin Tilbrook)]

Hi Raymo,

How well is your scope balanced??
It may need rebalancing to where you are pointing in the sky.
I know my Heq 5 pro will perform better when weighted slightly over balanced for objects on the rise but will need to be rebalanced for setting objects.
It will behave quite erratically will judder and slip if not rebalanced.

Cheers,

Justin.

[raymo]

That was in fact one of the first things I thought of Justin, so I have rebalanced it when suffering this problem. Made no difference. I then got a spring balance and artificially unbalanced it whilst tracking [and
cracking] by amounts up to 5KG both with and against the drive, and apart from hearing the motor working harder, nothing changed. Put the weights the other side, and all is fine. I'm mystified. As I said to Jim, I might have to strip it right down.
Until this arose it would track on either side o.k. without needing rebalancing.
raymo

[kens (Ken)]

A few months back I was on a bike tour and I started to hear a clicking noise coming from somewhere but not all the time. A couple of days later the seat post broke.
I'd be looking closely at the counterweight shaft and everything connected to it for stress fractures.

[raymo]

Something I hadn't thought of Ken. I 'll check it out. Thank you.
raymo

[glend (Glen)]

Geez Raymo you've had a bad run with that mount lately. You've reminded me that I occasionally hear a click from my NEQ6 when its being guided - I had sort of assumed it was a relay on the motor control board ( not that I even know there is one because I have not opened it up, but it sounded like a relay). It doesn't seem to affect tracking or guiding and is only noticable since I put it on the pier inside the observatory.

[jenchris (Jennifer)]

Are you biasing valance to keep the pressure on the front of the gears.
I always keep the east side heavy to ensure that backlash is always on the same side and the gears under load.

[Shiraz (Ray)]

maybe take the side panel off and have a listen and a look/feel. If it is mechanical and happening at 10-20 second intervals, it is most probably something to do with the transfer gears or the motor - maybe the idler gear is slapping up and down on it's axle for example.

[raymo]

Jennifer, I have unbalanced it by small, medium, and HUGE amounts
both with and against the drive. No effect at all.
Ray, I have adjusted out almost all of the backlash, [couldn't quite eliminate it altogether without getting a tight spot], and cleaned,
inspected, and lubed the gears. They are level with each other, and tight
on their respective shafts. The intriguing part is that the problem only occurs when the weights are on one side of the mount; on the other side, it tracks beautifully. Every cracking sound causes stars to elongate
massively, so something is jerking, but when watching the gears
nothing visible to my old eyes happens. When the R.A. clutch is released the mount swings freely through 360 degrees.
I don't think that there are any relays Glen ;I think everything is solid state.
raymo

[MattT]

Had 2 HEQ5 mounts and an NEQ6 none of them have done this....so Ramyo lie down on the couch and tell me....when did all these troubles begin?

You mention a new hand set and this cracking problem after that....works one side but not the other...

To me it sounds like binding or worm and ring gear are not aligned, close but not good enough perhaps?

How good are your strip down and re-builds? How many times have you done this in the past?

Could be crack in the ring or worm gear too...highly unlikely but you never know. Never had a seat post on my bikes crack but they are all top shelf Campagnolo, one from the mid 80's.

Just brain storming

Matt

[raymo]

Hi Matt, Being a retired Flight Engineer, and after being medically grounded, becoming a Marine Engineer for the rest of my career, I know
my way around mechanical and electrical equipment.
The first problem I had was bizarre readouts of polar alignment
error, and faults such as the hand controller freezing up so that all buttons were inoperative, so it had to be switched off and rebooted.
The next problem was the tracking went haywire, with the scope seeming to be tracking at about 20% of the required speed.
The irregular cracking noise and accompanying star elongation
started about three months ago. [ I apologise if I misled you about when the cracking started, but I was ignoring it until I had the other more important issues sorted.]
I borrowed a H/C from a kind IIS member, and voila, no more bizarre readouts, and great tracking, but the cracking continued [ still only on the one side, and not every time].
I have not stripped the mount down, just adjusted the backlash on both axes. Almost all backlash is gone in R.A. Not quite all as it then
develops a tight spot when the weights are almost directly above the mount. It now runs freely through 360 degrees by hand or motor.
Getting new H/C tomorrow. Will have to strip down I suppose.
raymo

[Shiraz (Ray)]

If you haven't done so, maybe try adjusting the RA worm clearance to make it sloppy and see if that helps. If the drive is binding because there is not enough worm gear clearance, you could possibly get buildups and sudden releases of tension in the gear train (or maybe the motor?). The ring gear is not perfectly concentric with the bearings, so you could have binding only on one side of the mount - that might not show up in a rapid slew. If the worm is binding, external variation in load will have little effect - as you note. Another possibility might be that you have a damaged worm bearing, although it is hard to see why that would only have effect on one side of the mount. Clutching at straws here, but something has to be cactus and there is not much that it could be in such a simple mechanism.

[raymo]

I had thought of drive train wind up like you can get in car transmissions,
but I can turn the mount easily[ but tediously] through 360 in either direction by turning the wormshaft gear with my fingertip, with absolutely no sign of binding. As an aside, my wife brought me a you beaut
Super Polaris from the U.K. when they were the best thing since sliced bread for the price. I had to put up with massive R.A. backlash to avoid binding. So much for Japanese quality. I couldn't afford to send it back
under warranty. I will, as you suggest, slacken the worm and see what happens.
raymo

[MattT]

Hi Raymo,
A full strip downand re-build of the RA is what I'd do...lots of fun. Take photo's and post them. On my old mount if the worm isn't contacting the ring gear perfectly I get the same sort of clicking noise. As I built it, it is easy to adjust which solves the problem.
Don't forget photos. I want to see what you find.
Matt

[traveller (Bo)]

Raymo, are there any movement in the RA and Dec axis when they are locked down? If so, then you will need to adjust for the mesh between the gears and the worm via the thruster bearings.
Does the cracking noise happen when there is no load and when you speed up the slewing? Again, I'd be looking at the interface between the gears and th worm as the first culprit.
Failing that, strip down the mount and inspect the tapered bearings on both axis and also check out if the shims are worn out.
Good luck
Bo

[raymo]

The noise and jerk only happen when tracking, not slewing, which suggests that a build up of tension occurs, and is periodically released
with a jerk, as Shiraz suggested. I don't know when I'll get to
stripping it, as I have a lot going on, including a sick wife. Thank you all so much.
raymo