NEQ6 RA stiffness?

[sbooder]

This is a question for anyone really but Astro-Baby mainly, as she has probably disassembled and re-assembled more EQ6s than most.

Although I have stripped and rebuilt my mount about 6 or 7 times, I still have an RA that is stiff in places when the clutch is off.  I have tried all the suggestions to remedy this e.g. sanding down any rough parts in the RA casing.  But still it sticks at certain points (when the counterweigh bar is about horizontal).

The question is, if when I first stripped the mount (way back), if I had put the spacers in the wrong place, for instance, there are 3 spacers in my RA axis, and I always put them back in the same place, but, what if I had put them back in the wrong place the first time I stripped the mount, i.e. 1 where there should be 2 and 2 where there should be 1.  Could this cause the stiffness do you think?

[sbooder]

Hi All,
               thanks to some advice from my uncle, I think I have solved the tight spots people are finding in either or both axis of their EQ6/NEQ6 mounts with the clutch off.  I have not known for a year now if my scope to counterweight balance was good enough because of the two tight spots I had on the RA when horizontal.

And it has nothing to do with burghs or rough spots in the housings.  It is the taper bearing in each axis.

My uncle told me that as a long time mechanic the most precise part of putting the front drive of a car together was the taper bearing.  It could take hours of reseating, spinning, tightening, and spinning again, then starting all over because there were tight spots.

It seems that unless the taper bearing is seated perfectly you will always get these tight spots. I now know this to be true with the mount.

To run this test I did nothing but undo the taper bearing on the RA axis (which is where I had my two tight spots) and took out the bearing to give it some more grease.  I then replaced it and tightened the retaining nut bit by bit, spinning the RA after each turn and indeed the tight spots returned...but in different places than they were before.

So I started again and the same thing, but again the tight spots changed location.  It took half an hour until I could get the taper bearing under good compression and the RA running smooth all the way round.

The compression is important, because as my uncle pointed out, if a taper bearing is not under compression it can slip from true and the tight spots will return or even bind the mount completely.

This is why when you first strip these mounts you need a filter wrench to undo the taper bearing retaining nut.

I finished by spending a good 5 minutes spinning the RA and I am glad to say that it is free all the way round now and under good compression.

[Scott]

result

[Spikey]

Useful to know, thanks for sharing.

[sbooder]

Useful to know, thanks for sharing.

My pleasure.  It was so nice to be precise with the balance at last.  The tight spots I had made a 1cm difference for three 5kg weights on the counterweight bar!  For my money 15kg moved 1cm is a fair bit?

[nigelbeaumont]

I also wondered about how tight the axis nuts should be. Taper bearings are designed to take axial loads as well as radial loads, so a bit of axial preload from tightening the axis nuts shouldn't be a problem for them. However the other bearing on both the RA and Dec axes is a deep groove ball bearing, which I understood to not like axial loads at all. So I've always just tightened each axis nut just enough to remove any sideways or axial play, but with as little preload as possible. I then check for play again after a couple of days in case the bearings have bedded in or squeezed out some of the grease I applied during a rebuild. Have I got it all wrong? I tried turning the axes with the worms removed and found both moved easily - but as soon as I refitted the worms, there was some stiffness in the Dec axis when turning by hand with the clutch off (RA was OK).

[nigelbeaumont]

Meant to add that with the clutch disengaged and the worm in place, the Dec axis shaft and OTA clamp rotated but the big brass spur gear driven by the worm inside the clamp didn't; with the worm removed, both the shaft and the spur gear rotated freely. So I've always assumed that since there is only a small clearance between the spur gear and the OTA clamp, there is some drag when rotating the OTA by hand (eg grease in the gap between them). Hasn't worried me, since they don't move relative to each other when the clutch is engaged and the OTA being moved by the motors

[Astro_Baby]

Well I have done a fair few of these mounts and never really seen that problem - its interesting.  Thanks for sharing.

Mel

[SteveA]

Thanks for posting this...

I've had this issue with my EQ6 Pro since I bought it 8 years ago and I've never been able to solve the problem!

True serendipity this...as having just purchased the belt kit from Rowan Engineering I have the mount in bits and so will definitely be focusing on the taper bearings when rebuilding....thanks again!