Nylon bearings/bushings: How to use best?

[archive10]

On a recently acquired polar mount for a Prodelin dish, I have discovered Nylon-like bushings (or bearings, if you like). They are on the main pivot axis of the polar movement.
See attached pictures.

Question 1: Can/should I do anything to recondition / lubricate these?

The original config is a separate bolt in each of the bearings (roughly , but only just so, aligned on the axis of swivel). I am considering stikcing a threaded bar through both, effectively giving an axis.

Question 2: Would the threading on the rod dig into the nylon compared to the flat surface part of the bolts that were there before? (and even then one end had a third of the bushing "threaded", while the lower ones had all of it.

The alternative would be to get a really long bolt, and use that instead of off-cut from threaded bar. Not sure it would be worth it though.

Any advice from you mechanical experts is much appreciated.

 

[Gerry55]

Hi st1
What ever you do don't put a thread any were near a nylon bush it will cut it , grease is good for the bush.

 

[archive10]

I figured something like that.
I need to rethink how the swivel axis is implemented with a bolt.

 

[RimaNTSS]

Take bolt with part of it without thread. #1

 

[archive10]

Take bolt with part of it without thread. #1

Yes, that's how the original config was for the upper attachment point.
The lower attachment was just a bolt with thread all the way.

The original configuration had the bushings fastened individually with two separate bolts.
See first sketch and picture.

I was thinking to replace the two, separate attachement points with a single long bolt (or piece of threaded bar, which I have now abandoned). I am seeking to stabilise the swivelling, and perhaps have better load-bearing. See second sketch.

When I got the mount, the swivelling was really tough, I put this down to the bolts and nuts being a but rusty (most of the iron is OK). After dismantelling it, I realised that the axis of the upper and lower attachment points are slightly mis-aligned. My interpretation is that although this difference is allowed because two separate bolts are used, it imposes a constant stress on the nylon in the bearings, so that it moves less easily.
Is was therefore thinking to align the axis of the two attachment points, and replace the two individual fastening bolts with a single long bolt ensuring both a) alignment of the axis of the two attachment points and b) a bit more rigidity in the swivelling axis. (Just how to implement align the axis of the two may be a separate issue).

From squinting at the construction, it now seems that the upper attachment is designed to take the full vertical load, whereas the lowermost mostly provides balancing (i.e. horizontal force from the dish hanging in front).

NOW, therefore:

If i DO replace the two bolt with a single, long, 34 cm bolt with only threading at the end, I get no threading in the bushings, which should work better presumably. However, I also get no nut under the upper attachment point, so that the bushing merely rests on the upper steel lip of the mount, rather than being fastened to it (and boy was it fastened when I took it apart).

I can't figure out which part of the bushing is supposed to move, sliding around what. And if the misalignment of the attachment point axises is simply sloppy welding, or actually deliberate to obtain some sort of twisting action in the nylon bushings.

Can any of you engineering experts provide some advice on what would be the best approach to obtain a smooth but firm swivelling action from this piece of steel?

 

[RimaNTSS]

It is probably not so difficult to make long long bolt by connecting two separate ones with long nut. Like on my picture (I just do not have proper ones at home to demonstrate), just an idea.

 

[Channel Hopper]

From memory, the polarmount was a horrible affair, manufactured for a dish supplied under the name Echostar.

They also tried selling a post adapter kit (to extend the existing 1m dish to a 2m version) with an eight nut clamp arrangement, making everything even more bouncy-bouncy on the arc.


Cut your losses and weld something better to the back of the dish