Help! Heq5 making loud noises

[cuivenion]

26 minutes ago, spillage said:

ouch!! You might want to contact a supplier of this mount and they should be able to help with parts. Maybe flo?

Can you get it back on?

Not very far on no. To be honest the I'm sure the nuts replaceable, it's the thread on the end of the axis that the problem, I don't see how that's replaceable.

[Oddsocks]

2 hours ago, cuivenion said:

it's the thread on the end of the axis that the problem, I don't see how that's replaceable.

I can't see any damage to the axis thread in the picture, but if there is, and it only a very small section of thread, then the damaged piece can be safely filed smooth and thread-like again using a fine precision triangular metal workers file.

A good engineers workshop, car repairer etc could just run a metric die over the axis thread and restore it for a few pounds, this only takes a few minutes to do.

You can get a set of precision files for around £10 on Amazon, or maybe your local Halfords store.

TBH I think you will find the aluminium nut a harder repair, the only option for that is to either have it Helicoiled or bored out to a larger size and a threaded brass insert pushed into the nut.

Heli-coiling is a one time operation, once the nut is Helicoiled and back on the axis shaft it can never be removed again with out the Helicoil insert dropping out, if you wanted to pursue Helicoiling the workshop doing it would need to assemble the mount for you. Over-boring the aluminium nut and fitting a threaded brass insert would allow you to strip the mount again in the future. Neither option would be inexpensive, I'm around five years out-of-date with workshop prices these days but I can't see it costing under £125 - £175 pounds for either option. Just running a die over the axis thread would be around £10-£15.

You could try an ad in the wanted column here, or on AstroBuySell, maybe someone has an old EQ5 for breaking that you could salvage the parts from. Major mechanical parts for the Skywatcher mounts are simply not available from any principle dealer AFAIK, the only parts I have seen at a main dealer are the power board, polarscope, and hand  controller.

Astroboot may have something available but a quick look at their website didn't reveal anything, you could alway try an email, they may have a few odd bits and pieces lying around.

 

[Oddsocks]

Something you can try, seeing as you are stuck.

Completely remove the three set-screws from the nut.

Clean the threads of the nut with a tooth brush and inspect to ensure there are no jagged broken pieces of thread jammed anywhere, if so, prise them free.

Clean and inspect the threads of the axis shaft, remove any pieces of jagged broken thread by prising them free.

Apply plenty of grease to the axis thread.

Screw the nut to the axis shaft reversed (facing in instead of facing out!), tighten slowly and gently. this may be enough to flatten any irregularities in the thread of the nut.

If this works and the nut moves easily again, turn the nut the right way round and reassemble the mount, only put the set-screws back in the nut once it is fully assembled and adjusted.

HTH

[cuivenion]

Thanks I'll give it a try. I'm going to try and source the parts. The main shaft is bolted to the casing. It should technically be possible to replace both items.

[Oddsocks]

Just had another close look at the images. I can see that the set-screws were not backed out far enough prior to unscrewing the nut from the axis shaft and that is the cause of the damage. Astrobaby’s guide simply says to loosen the set screws before removing the nut but that is a little vague, it would be better if it said unscrew the set-screws ‘x’ turns to clear the thread, or just remove the set-screws completely.

As before, when I look at the image of the main axis thread I can’t see anything obviously wrong. I assume you aren’t thinking that the gap in the middle of the thread is damage because that is supposed to be there.

 

[cuivenion]

1 hour ago, Oddsocks said:

Just had another close look at the images. I can see that the set-screws were not backed out far enough prior to unscrewing the nut from the axis shaft and that is the cause of the damage. Astrobaby’s guide simply says to loosen the set screws before removing the nut but that is a little vague, it would be better if it said unscrew the set-screws ‘x’ turns to clear the thread, or just remove the set-screws completely.

As before, when I look at the image of the main axis thread I can’t see anything obviously wrong. I assume you aren’t thinking that the gap in the middle of the thread is damage because that is supposed to be there.

 

Ah right might be me being dumb then. It won't thread past that gap as it stands. But I'll try a my best to clear out the thread and use some lube on it.

[Oddsocks]

10 hours ago, cuivenion said:

It won't thread past that gap as it stands. But I'll try a my best to clear out the thread and use some lube on it.

The bits of thread to concentrate on are the lead-ins, the first few mm of thread at the beginning of each threaded section, that is most likely where you will find a damaged piece and this will most likely be on the shaft. Temporarily reversing the orientation of the nut and screwing it on the shaft would realign a small damaged section on the aluminium nut as it is softer than the shaft but a damaged section of the harder shaft thread would not be restored doing this. A short damaged section of shaft thread can only be repaired by carefully dressing any damaged section with a fine file, running a die over it, or carefully prising away any broken section.

The gap in the thread on the shaft is where the set-screws in the nut are supposed to tighten on the shaft. When the factory assemble the RA axis they should ensure that when the axis pre-load is correctly adjusted then the set-screws are aligned with the middle of the gap, if they do not align then they would add one or two shim washers beneath the nut until the set-screws and gap in the thread were aligned. If you tighten the set-screws when they are not central to the gap then the shaft threads would be damaged.

(If you find you are missing some shims then you can make your own by cutting one from the wall of an aluminium drinks can using a pair of tough scissors, it needs to be the same diameter as the nut and the central hole needs to be a tight fit on the shaft to prevent it sliding about as the nut is tightened).

If you are unable to repair the thread after an hour or so then don’t waste any more time but look in your local area for any small workshops or independent car repairers and they should be able to run a standard metric thread tap and die over the nut and shaft in a few minutes to restore the thread.

If you had really broken all that thread away you would have had a great pile of broken bits on the floor when the nut finally came off!

———————————++++++++++++++++++————————————-

As an aside, we had a conversation at one of the clubs I belong to a little while back about the lack of engineering skills in the general population with, it seems, the majority of people born from the late sixties, early sevetnties onwards having no affinity towards engineering of any sort, so don’t beat yourself up, you are not alone!

 

[cuivenion]

5 hours ago, Oddsocks said:

The bits of thread to concentrate on are the lead-ins, the first few mm of thread at the beginning of each threaded section, that is most likely where you will find a damaged piece and this will most likely be on the shaft. Temporarily reversing the orientation of the nut and screwing it on the shaft would realign a small damaged section on the aluminium nut as it is softer than the shaft but a damaged section of the harder shaft thread would not be restored doing this. A short damaged section of shaft thread can only be repaired by carefully dressing any damaged section with a fine file, running a die over it, or carefully prising away any broken section.

The gap in the thread on the shaft is where the set-screws in the nut are supposed to tighten on the shaft. When the factory assemble the RA axis they should ensure that when the axis pre-load is correctly adjusted then the set-screws are aligned with the middle of the gap, if they do not align then they would add one or two shim washers beneath the nut until the set-screws and gap in the thread were aligned. If you tighten the set-screws when they are not central to the gap then the shaft threads would be damaged.

(If you find you are missing some shims then you can make your own by cutting one from the wall of an aluminium drinks can using a pair of tough scissors, it needs to be the same diameter as the nut and the central hole needs to be a tight fit on the shaft to prevent it sliding about as the nut is tightened).

If you are unable to repair the thread after an hour or so then don’t waste any more time but look in your local area for any small workshops or independent car repairers and they should be able to run a standard metric thread tap and die over the nut and shaft in a few minutes to restore the thread.

If you had really broken all that thread away you would have had a great pile of broken bits on the floor when the nut finally came off!

———————————++++++++++++++++++————————————-

As an aside, we had a conversation at one of the clubs I belong to a little while back about the lack of engineering skills in the general population with, it seems, the majority of people born from the late sixties, early sevetnties onwards having no affinity towards engineering of any sort, so don’t beat yourself up, you are not alone!

 

Good news! The thread and nut are ok. Once I'd followed the instructions and cleaned them out they where fine. One more question I have thats confusing me, is how do you know when the axis preload is set correctly? You're definitely right on the engineering skills lol, computers are more my thing. I am trying though.

[spillage]

Its a feel thing. You need to make sure there is no movement up and down the shaft and also when rotating the shaft there should be not tight spots. Secure but free moving.

I think of the top of my head you tighten it up till it is stiff and then slacken it off unit both clutch levers align.

I found this not to be the case on mine as it was about 90 degrees out.

[cuivenion]

16 minutes ago, spillage said:

Its a feel thing. You need to make sure there is no movement up and down the shaft and also when rotating the shaft there should be not tight spots. Secure but free moving.

I think of the top of my head you tighten it up till it is stiff and then slacken it off unit both clutch levers align.

I found this not to be the case on mine as it was about 90 degrees out.

Ok thanks, hopefully by the end of the day I'll have this sorted.

[cuivenion]

Unfortunately I'm getting to the point where I might have to give up on this. Here's the situation:

1. Put RA axis together worm is not engaged and the worm wheel turns freely.

2. Set the axis end float. Axis moves smoothly and there is no play.

3. Adjust the worm in the home position. No play, smooth movement.

4. Test with the motor. The axis binds in the same position as before with counterweight bar pointing to about 2 'o'clock.

5. Undo clutch and move the RA back to home position. There is now play in the axis when there wasn't before.

I'm out of ideas. Of course it would happen during the best run of clear weather in months too.

Thanks for the help up to this point, if anyone has any more ideas it'd be much appreciated.

[cuivenion]

For a bit more info the RA does a full revolution without binding in either direction when it's removed from the housing.

[Oddsocks]

15 minutes ago, cuivenion said:

4. Test with the motor. The axis binds in the same position as before with counterweight bar pointing to about 2 'o'clock.

5. Undo clutch and move the RA back to home position. There is now play in the axis when there wasn't before.

Without being able to see the mount it is difficult to make a diagnosis, from the symptoms you describe it suggests the casting of the RA hub, thats the bit bolted to the tripod that doesn't move, and the casting for the DEC axis, thats the bit that moves when you drive in RA or release the clutch and manually turn the RA axis, are rubbing together somewhere. Check the gap between the RA worm housing and the RA Hub, there should be a gap of a least 1.5mm to 2.0mm all the way around and the gap should maintain that distance as you either drive in RA a full rotation or release the clutch and manually turn the RA axis a full rotation.

If the gap is less than this the RA axis may bind if the respective castings come together and rub because of any sloppy manufacturing tolerances in the castings, or a bent axis shaft, causing the gap to open or close as the RA axis rotates, or too much free play in the RA main bearings, which you would see if tightening and releasing the clutch causes the gap to open and close.

It might just be that the shim washers, used in the RA Axis that we have referred to before are missing, were never there in the firsts place or were lost by a previous owner, I am curious to know if this was a new mount or a second hand purchase?

If you find it is simply a case that the gap between the two main castings, where the RA worm casting meets the RA hub casting, is too small, and the castings are rubbing then you can fix this by adding a suitable shim washer to make the gap bigger.

If the AXIS shaft is bent, you may still be able to add a shim washer or two to maintain a working separation between the two castings.

If this is a new mount I think I would be talking to the supplier by now...

[cuivenion]

Thanks, I'll try what you suggested. It was a second hand mount. To be honest if I knew then what I knew now I'd have some choice words for the seller. A 'hypertuned' mount this is not.

[Oddsocks]

In addition to the text above here are some pictures of my own HEQ5 with the gaps that need checking, if the gaps are smaller than shown, open and close together as the RA axis is rotated or the clutch is tightened and released then as above, the RA axis is missing some shims, the AXIS shaft is bent, or the AXIS bearings have too much slop.

My guess is that the RA axis shims are incorrect. If the mount was ever abused and dropped the RA axis shaft may be bent, or, the bearings in the RA axis are simply sub-standard.

[cuivenion]

Ah a new problem. The RA dial that previously fit over the pre load nut now won't. Awesome.

[cuivenion]

Just to double check are you suggesting shims that go where the red shim over the worm wheel goes, or where the pre load nut goes?

[Oddsocks]

7 minutes ago, cuivenion said:

are you suggesting shims that go where the red shim over the worm wheel goes, or where the pre load nut goes?

Could be either, it depends which parts of the castings, if any, that you find are rubbing when the the clutch is tightened or the RA axis is rotated past the 2 o'clock position.

[cuivenion]

Ok, I've tried shims just in front of the preload nut, no change. I used 25mm ID/35mm OD washers. They seemed to cover the area where the nut presses onto the tapered bearing, hopefully that was ok. The gap between the RA worm casing and the RA hub casing is never more than 1mm and doesn't seem uniform all the way round although this is hard to make out, so hopefully shims above the worm wheel will work.

[Oddsocks]

There are just a couple of points left to check/clarify.

You said that you adjusted the RA end float ‘till it was tight, turned the RA axis ‘till it became bound and then released the clutch, after which the RA axis end float became loose again.

This could just be because the extra loading you place on the taper bearing when you tighten and release the clutch is forcing the taper bearing into alignment. When you tighten the nut to carry out the initial pre-load then the RA clutch must be released, otherwise the brass gear won’t be able slide up the shaft to take up any slack, so you make the initial nut tension adjustment with the worm tension released a liitle and the clutch undone, tighten the nut set-screws and then the correct procedure is to manually rotate the DEC housing around the RA shaft while every 20 deg or so tighten firmly and then release the RA clutch, then release the nut set-screws and adjust the nut tension again. Keep repeating this until the RA pre-load remains constant for whatever angle the RA axis is turned to. Then adjust the RA worm tension with the RA clutch released. Finally power up the mount, engage the clutch just enough to secure the RA axis from slipping and adjust the RA worm tension under motor drive to minimise backlash and ensure the worm does not bind and stall the motor. In normal use the clutches should only be applied with just enough force to prevent the axis slipping, too much force on the clutches will tend to push the brass axis gears out of line and lead to the worm binding at the point on the brass gear exactly opposite to the clutch lever.

Adjusting the worm tension is a balancing act. The Synta mounts are not made to a high enough standard that worm mesh will be constant for a complete revolution of the axis so you need to make the worm backlash adjustment to accommodate this non-linearity and adjust for a compromise so that the worm does not bind at the tightest spot and is not too loose everywhere else. Over-tightening the clutches will affect this adjustment by distorting the brass gear so don’t overdo the clutch tension.

If you follow the above procedure but every time you make the nut tension adjustment the RA axis becomes loose again and can not retain it’s tightness then there are only three possibilities I can think of, either you are not tightening the set-scews enough in the nut, and the nut is unscrewing it’self from the shaft when you apply load to the RA axis or the threads of the nut are stripped, are not gripping the RA shaft tightly and the nut slips across threads when tightened or the RA shaft is loose in the DEC casting and is unscrewing it’self from the DEC casting (though I do not know how the RA shaft is secured to the DEC casting so this may or may not be a valid surmise).

If the RA end-float becomes stable after the above adjustments then drive the RA to the 2 o’clock point where it used to bind.

If it still binds in the same point then this can only be a shimming issue where the RA and DEC castings are rubbing together, the brass worm gear is misaligned to the worm, or one or more of the RA axis bearings are defective.

A point to check that may shed some light is when the RA axis is disassembled look at the painted surfaces of the DEC casting, RA worm carrier, RA hub casting and the meeting faces of the brass worm gear where it butts up against the DEC casting. Any sign of rubbing away or gouging of the painted surfaces where the various components meet would indicate a problem with insufficient shimming, too much free play in the RA bearings or simply a high point on one of the castings that needs dressing.

If you were a bit closer I would have liked to have been able to give the mount a look over, most likely it would have been a simple problem to resolve with the appropriate tools and mechanical experience but a seven hour drive is a little too far far for me these days. Are there no local astronomy groups close to you? Many astronomy clubs will have at least a few mechanics in their membership that would be happy to help.

I see you have opened another thread asking for recommended service providers.

You could try contacting Peter Drew at the Todmorden Astronomy Centre, you can PM him here on SGL, I believe Peter used to service and repair telescopes and he may be able to suggest a good engineer that is close to you.

The only two companies I know of are SCTelescopes in Kent and Dark Frame Optics in Hampshire.

SCTelescopes have been around a long time and are well known and respected. Dark Frame Optics appeared out of nowhere a few years ago but apart from the claims on their website I know very little about them.

I can’t think of anything else to suggest and will step aside, maybe there is someone else here on SGL, a bit closer to you and better able to offer support, or who can explain how to make these adjustments a little more understandable than I can, sorry I haven’t been able to help you on this occasion 

 

[cuivenion]

Thanks for the advice and you've been a great help, it's much appreciated. I'm going to try a few more of your suggestions but the reason I'm looking for a service centre is my limited engineering skills, tools and patience. The more time I work on the mount the more likely I am to permanently damage it. Also someone such as yourself would likely sort the problem pretty quickly if working on it in person. Thanks for the help again.

[cuivenion]

Thanks for the help everyone. Got the HEQ5 up and running again. Turns out the brass worm wheel in the RA was a very poor fit for the RA housing. As soon as I swapped it out for the dec wheel it was easy to set the RA axis up. The offending wheel fits the dec better. It's not perfect but theres no binding. I'll replace the worm wheel at a later date. Fully regreased with WS2 oil and ready for the Moon and Jupiter tonight! Wish me luck. Thanks for all the help guys!