JohnTN

The Nuts tried above did not work out so well.  The one on the azimuth loosened as before and the one on the altitude actually tightened to the point the altitude would barely move!

So I tried another type I had on hand, these from Lowe's and plated instead of Stainless.  They look a lot like the two already tried so I have little hope...

While I was disassembling (I'm getting pretty fast at it!), I decided to take the blue base off to see what the other end of the axis looks like.   It appears to be only a screw head, driven in tightly.  I did not go any further, as it appears this has nothing to do with the adjustment in which I am interested.

I have had better success improving this mount since my last writing.  In summary, the adjustments for play and tightness on this Sparta mount are accessed by removing the dovetail saddle (4 bolts) for the altitude axis and by lifting the rubber cover exposing two bolts which can be removed to access the azimuth axis.  I adjusted both axes a couple of times but they loosened up after a short time.  I removed the factory M8 locking nuts and replaced them with the ones shown, which came from Home Depot.  I had to order them but they do not charge shipping.  The nut with the black insert is the original and with the white insert is the Home Depot replacement.  I adjusted them a little too tight at first but went back in and loosened them 1/16 to 1/8 turn.  This still left the altitude axis a little tight and I went back in and loosened it a bit.  At the same time I noticed the azimuth axis had a little wobble so I tightened it a bit.  The new lock nuts are better but still maybe not good enough! 

8 hours ago, Alan64 said:

I apologise for not explaining earlier.  This area, again...

...is a tying-off.  The nut and washer act as a bow-tie, if you will, to hold the components altogether, so to keep them from sliding apart and falling on the ground...

Thank you for the exploded photo of the assembly.  It helps my understanding.  It looks like there is a lock nut and washer on each end of a shaft.  Possibly many of these similar mounts have the same design.

5 hours ago, Alan64 said:

Yes, snakes have been a problem here on a few occasions as well, over the years.  Here's a copperhead, a pit-viper, although the mildest of same, sunning itself in my driveway right in front of my house, five years ago...

I drove it away, and haven't seen it since.  At one point I was about two to three feet away, with our staring at one another.

At other times it was one or two non-venomous, and in the house.  

The best scroll-saws have a solid table, not of flimsy stamped steel, which are prone to twisting and warping.  For example, this one, of stamped steel, an old Harbor Freight "Central Machinery", was abandoned to the elements well over a decade ago, then almost twenty possibly...

You wouldn't want that one of course, nor a new one of that type.  This is a new one, with a similarly shaped table, yet a solid table, likely of cast iron...

https://www.harborfreight.com/16-in-variable-speed-scroll-saw-71113.html

...and at a great price.  The reviews, although scant, offer only praise for the wonder.  You would need an adaptor for the fine blades without pins, at that price. 

A rotary-tool, a Dremel, or a generic with above-average reviews, is required, along with mandrels and sanding-drums, as the saw will cut close to the circles described by the tool-steel tip of a compass, but you'll need to grind the rest of the way to the line, then sand and polish.  I wear reading-glasses to get very close whilst working.

Phosphor-bronze is ideally placed, and in its element, when continuously immersed in grease, Super Lube or other.  It will tarnish otherwise, just like copper and brass.  Phosphor-bronze is seemingly brittle, very slightly, but it's a tough metal.  It's the small amount of phosphorus added to bronze that gives the metal its characteristics.

Good to know.  Thanks for the additional information.  I saw one copperhead here, many years ago.  I don't like to see them around!

On 28/08/2024 at 20:45, Alan64 said:

That washer that you see under the lock-nut is not to be discarded, by the way, or replaced.  It would cover and bear against anything placed underneath it.  If it moves, it moves.  Try a new lock-nut if the axis loosens up whilst rotating.

I haven't even made the washers yet for my Vixen Porta I mount.  I'm waiting on sanding-drums for my Dremel.  Do you have a scroll-saw, like this...

I make my own in a roundabout way, without a metal lathe...

I use fine German-made blades, the non-pin type; jewellers' blades.  Sometimes an adaptor is required for those.  

I do not have a scroll saw.  That looks like a great way to make the washers.  Thanks for the extra details.

I went to Home Depot yesterday and bought the last two M8 nylocs they had, with two different nylon colors.  They were zinc coated, not my favorite.  We shall see...  It must have been Lowes where the Hillman nuts were.  I was going to go there after a Physical Therapy session but my girlfriend texted me saying there was a snake in the kitchen and I needed to come right home!  You would have thought it was an anaconda from the way she talked!  Of course it had disappeared by the time I got there.  Later it surfaced again in the same place.  It had to be the smallest snake I had ever seen!  I swept it into a large storage tub and took it outside.  She was greatly relieved.

On 28/08/2024 at 20:15, Alan64 said:

Do the cams require adjustment?  The four set-screws, two pairs, merely lock the cams in position, top and bottom. 

Are the worm-shafts difficult to turn?  

The worm shafts turn easily, but there is a little lash.  Probably acceptable for now, at least until I get the wobble problem ironed out.

On 18/08/2024 at 12:15, Alan64 said:

It appears that there's room enough to add extras under the steel washer...

You'd be amazed at how easy they are to make; well, not particularly easy, although not particularly difficult.  

Clean and re-grease throughout with Super-Lube, if you'd like.  It's not mandatory, or is it?

Then there are needle-thrust bearings, with mini-rollers integrated, splayed round, to place here and there perhaps...

My Porta I, so far, requires only one of those for each axis, and that happens to be at the same point as your own adjustment, not actually within the axes where light does not shine.

The bearings should be sandwiched within two phosphor-bronze washers, like this...

 

That one was for the DEC-axis of my Meade LX70 EQ5-class equatorial mount.  I will need to make two of those sets for the Porta I, one set for each axis.

Inside the axes, I will make those same washers, two for each axis, but without the bearing.  I could include bearings however, if the spacings and other will allow.  The increase would be negligible.

Such will eliminate any jerking, hesitations, stiffness, catching on this and that, during the motions.  Then, all aluminium surfaces having to do with the axes' motions should be smoothed and polished.

Iron-based metals, including stainless-steel, should not bear against aluminium surfaces, like this one...

Take from that what you might, and for an improved experience.

Concerning addition of your bearing sandwich under the steel washer, I have some questions.

When I adjusted the nut last time, I noticed that the washer does move sometimes when the axis is rotated and even more so when I rotate using a side load.  So possibly the more load is on the mount, the more tendency to unscrew.  Now the question.  Do you think adding your design bearing sandwich would eliminate entirely the tendency for the washer to move?  Is it possible that this would increase the load carrying ability of the mount?

Would there be room for it without removing other parts of the "stack?"

Third question.  I think you said you order the bearings, but how do you make the phosphor bronze washers?

Thanks,

John

On 18/08/2024 at 03:02, RT65CB-SWL said:

Just a thought @JohnTN - was the saddle secured by a ‘plain’ nut and bolt?

It maybe worth getting a lock-nut or ‘Nyloc’  nut as it may prevent it coming loose in the future… or apply some thread-lock to the bolt thread. 

The existing nut does appear to be the locking variety, but I will seek a better one as Alan64 suggested.  We have no local hardware stores anymore, a dying breed unfortunately.  Ace doesn't carry much metric.  But I have spotted a Hillman brand at Home Depot that appears to have a longer Nylon portion.  Next time I go out I will pick up a couple of those.  I also ordered a bag of Nylocs at random on the hopes that they might be better.

Thread lock is a possibility, I would think.  I can't see the harm using the Blue Loctite very sparingly so it doesn't go everywhere.  Maybe one drop on the inside threads of the nut and then reassemble.

I had thought of a jam nut arrangement using two thin ordinary nuts, but there really isn't room for tools to implement this.

12 hours ago, Alan64 said:

The Sparta mounts are known to have plastic parts.  The set-screws work in tandem with the cams to adjust and set the distance between the worm and gear, and for each axis.

I understand.  And is it true that all 4 set screws (two on the bolt side and two on the non-bolt side) have to be loosened to free the cam so it can be adjusted? 

Upon closer inspection, perhaps what I'm seeing on the "non-bolt" side is a thin plate cover whose holes don't match up with the set screw location.  I guess you have to pry off the plate to access the set screws.  I can't be sure as I can't get enough light in there to see properly.  So I guess there is no problem except a poorly made thin cover. 

Thanks,

John

On 26/08/2024 at 11:59, Alan64 said:

The set-screws can be deep inside the holes, and difficult to see.  I wouldn't adjust or remove those however, unless you've other plans.

I can see set screws on the side that contains the adjustment bolt, but not on the opposite side.  This is true for both axes.  Is this normal?

John

2 minutes ago, AstroKeith said:

Is the nylock nut actually loosening, or is just that the bearings are settling in? These castings often are poorly machines and a bit of working in can help.

But also try a new nylock, but before fitting make sure the thread on the axis is grease free.

I plan on digging into both axes in a few hours.  You pose a good question.  I'm not sure I will know the answer even after digging in as the adjustment required last time was so small.  I will make some marks on bolt and nut this time so I can tell next time.  Something tells me this will be an ongoing problem.  Thanks for your reply.

John

On 18/08/2024 at 12:15, Alan64 said:

I'd get another lock-nut from your local hardware store, not Home Depot or Lowe's.  It might be better than the original, and worth the bother.

It appears that there's room enough to add extras under the steel washer...

You'd be amazed at how easy they are to make; well, not particularly easy, although not particularly difficult.  

Clean and re-grease throughout with Super-Lube, if you'd like.  It's not mandatory, or is it?

Then there are needle-thrust bearings, with mini-rollers integrated, splayed round, to place here and there perhaps...

My Porta I, so far, requires only one of those for each axis, and that happens to be at the same point as your own adjustment, not actually within the axes where light does not shine.

The bearings should be sandwiched within two phosphor-bronze washers, like this...

 

That one was for the DEC-axis of my Meade LX70 EQ5-class equatorial mount.  I will need to make two of those sets for the Porta I, one set for each axis.

Inside the axes, I will make those same washers, two for each axis, but without the bearing.  I could include bearings however, if the spacings and other will allow.  The increase would be negligible.

Such will eliminate any jerking, hesitations, stiffness, catching on this and that, during the motions.  Then, all aluminium surfaces having to do with the axes' motions should be smoothed and polished.

Iron-based metals, including stainless-steel, should not bear against aluminium surfaces, like this one...

Take from that what you might, and for an improved experience.

Unfortunately, there has been a step backward.  The wobble has come back in the altitude axis and in the azimuth axis as well, after only a little bit of use.  I will go in search of a proper locking nut as you suggested as I suspect it has loosened.

Another potential problem I noticed is that the set screws near the slow motion shafts are missing.  I'm beginning to think my copy of this mount didn't receive a proper QC at the assembly line.

Thanks,

John

All very interesting, Alan.  Perhaps I will "super modify" my mount someday, but, for now, I am just glad it works!

I took it out last night, along with my "work in progress" Frankenstein telescope, for about an hour.  First light, I think it's called!  Mount and scope performed well viewing the moon!

John

Thank you Alan64 for sharing this.  I'm beginning to see what you will do with the bearings.  Will the bearing and shim assemblies replace the wave washer, or do you still have a spring of some sort for tension?  Very interesting how you have planned this all.

John

Thank you both for your encouragement!  The dovetail saddle is attached by 4 metric socket head cap screws with 6 mm allen size.  The central nut (13mm) exposed when the saddle is removed makes and holds the adjustment for play or wobble.  It is somewhat critical.  You have to adjust it tight enough so there is virtually no play but not so tight that the mount has too much resistance to turning.  The adjustment nut appears to be of the locking variety.  If it starts going out of adjustment too often, I will get a tighter locking nut.  Feedback on the Sparta would indicate that going out of adjustment is one of the problems of this very inexpensive mount.  I think I can live with it now that I know how to adjust!

John

Thank you Alan64 and RT65CB-SWL for you comments and suggestions.  It is within return period, but I got such a good deal on it that it would cost a bit more to get a replacement.

As it turns out, I don't have to remove that cap or logo just yet.  I had posted this on Cloudy Nights almost a week before I posted here and had no reply until today.  Antal on that forum came up with the solution to adjusting the play or wobble.  The key was to remove the dovetail attachment plate and adjusting a nut exposed in the center.  I removed the 4 bolts with 6mm hex key, and then adjusted (just slightly) the nut with a 13mm socket.  All works well now!

John

Hi and thanks for the welcome!

I have been following that thread from Alan64 and it is very interesting, especially because of his detailed photos of the inner mechanisms.  But I think the method of cover attachment was different on the Porta's vs the Sparta.   The Porta's I have seen in various threads have a steel disc with a thin logo piece glued on (and the steel disc has to come off to gain access).  The Sparta seems to have a plastic cap with the logo glued on.  I may try getting the logo off, but I doubt it will give me any better access.  I think I have to get the plastic cap off and the answer may be to just pry on it until it comes off!

Thanks for your comments!

John

I have a new Sparta WD006 mount with some play in the altitude axis.  I'm wondering if someone has experience removing the plastic cover over the altitude axis.  Note this is made differently than the Porta's that are similar.  The cover interface is marked by the green paper clip in this photo.  There is a gap if you pull on it, but it does not turn loose easily.  Just trying not to destroy the cover if there is a trick.  Thanks for any help you can give me.

I am following this thread with great interest.  Keep up the good work!  When finished, you will have a "better than new" mount.  I can't wait to see how you implement the roller bearings.

Your photos of the internal mechanisms are especially interesting to me as I have a Sparta WD006, which may or may not be a copy of your mount, but it is similar.  When I received it new a week or so ago, it exhibited significant play in the altitude axis.  Your photos will help if I decide to repair it myself.  Thanks for posting this.

John