HEQ5 mount RA bearing

Startrek (Martin) · #1 16-09-2019, 01:20 PM

Does anyone with a HEQ5 mount experience the issue below ?
When I balance the mount in both RA and DEC , I find that the mount rotates in RA quite freely when the counterweights are pointing west and this allows fine balancing but in the opposite direction ( counterweights east ) I find that the RA motion is not as free , it’s a bit stiffer compared to the other side which makes testing your balance more difficult
I assume the weight is the same over both sides so why would the RA bearing be tighter on one side
My only explanation is that it’s a cheap mount with cheap bearings
Does anyone with a HEQ5 experience this ?
Comments welcome

Atmos (Colin) · #2 16-09-2019, 01:33 PM

I have an old HEQ5 that suffers from the same issue, cannot remember if it’s the same or opposite direction. Never noticed an issue with tracking though.

Saturnine (Jeff) · #3 16-09-2019, 11:10 PM

My HEQ5 does the same, when the scope is on the western side of the mount the movement is looser than when rotated in R.A. to the opposite side , where it stiffens noticeably. That meaning it takes a little extra push to get the mount to move. Doesn't seem to affect the drives and guiding.
Would be an interesting exercise to measure the current when on one side and then the other to see if there is an increased load.
I suspect the cause may be machined surface that the button of the clutch lock rides against being slightly eccentric, would only need to be a fraction of a millimetre out of round to feel it.

doppler (Rick) · #4 17-09-2019, 12:01 AM

Have a look at this guide, you might be able to adjust it.

"Run the mounts RA motor a full 360' to make sure there is no binding at any point in the cycle.If binding occurs you will need to readjust the set screws. This can be a long process to get the perfect balance between no play in the axis and smooth motor running."

http://www.astro-baby.com/heq5-rebuild/heq5-we1.htm

The_bluester (Paul) · #5 17-09-2019, 06:54 AM

It wont be that adjustment, that is to adjust the mesh of the worm on the ring gear which is not part of the train when the clutches are released to balance the scope.

I would suspect if you pulled it apart and put the shaft in a lathe you could find things are not quite concentric or straight, it could even be as simple as an imperfect bearing.

doppler (Rick) · #6 17-09-2019, 07:12 AM

The worm carrier pushes the worm against the ring gear which is connected to the RA shaft and bearing, so if a bit tight might put a bit of pressure on one side of the shaft even when unlocked.
http://www.astro-baby.com/heq5-rebuild/heq5-ra1.htm

Startrek (Martin) · #7 17-09-2019, 08:10 AM

Thanks All for your comments
I did find a few posts on CN about the HEQ5 RA motion being ok on one side and stiffer on the other plus a great YouTube clip where a guy demonstrated an inherent problem with the rotation of the mount in RA
His HEQ5 has an identical problem as mine and others on IIS
He pulled the whole mount apart literally and showed the issues along the way
Yes most of the problem is in the quality and precision of the design and parts used
The main bearings and the small worm gear shaft bearings are the main problem. They have too much slop and play when fitted on the shafts, he demonstrated the amount of movement which was evident. The ring gear is not the main issue as they can be adjusted to some degree to remove some out of tolerance play
When he rebuilt the mount he used new quality bearings, reused the old worm gear shafts and ring gear plus use a high quality lithium grease
When finished the mount it rotated perfectly in RA and DEC using only two fingers , free wheeling in other words right around
The mount was powered up and it ran smoothly and a lot quieter
He said the total cost was about $900 plus his time ( 3 days )
Since the mounts are only worth $1300 is it is worth the bother
He never mention about tracking or guiding performance
So the stiff RA rotation boils down to cheap poor quality bearings and possibly poor installation as he found a lot of muck in the mount when he pulled it apart ( probably from the factory in China )
At the end of the day even though these HEQ5 mounts do a reasonably good job and are extremely popular , they are entry level mounts for AP compared to what’s on the market

Thanks again
Cheers

doppler (Rick) · #8 17-09-2019, 08:28 AM

Interesting, but I wonder how a couple of bearings cost $900 he must have outsourced some machining work or something. I will have to check my mount out now, the stiffness is not something I have noticed in mine but may be present. My mount was really noisy when I got it (secondhand) but after adjusting the worms and motor cogs and a re grease it was a lot quieter and smoother, so well worth the time having a tinker.

The_bluester (Paul) · #9 17-09-2019, 08:56 AM

Quote:

Originally Posted by doppler

The worm carrier pushes the worm against the ring gear which is connected to the RA shaft and bearing, so if a bit tight might put a bit of pressure on one side of the shaft even when unlocked.
http://www.astro-baby.com/heq5-rebuild/heq5-ra1.htm

Looking at it that way I suppose it could, it still needs one of the bearing surfaces on the shaft to be out of true but any one of them has the potential to be less than perfect, including the bore of the ring gear itself. A good machinist could tell in minutes but the mount has to come apart for that sort of check.

Atmos (Colin) · #10 17-09-2019, 09:27 AM

Wow, those new bearings are worth more than mine did when I bought it

Saturnine (Jeff) · #11 17-09-2019, 11:36 AM

Would have to wonder if the $900 was the initial cost of the mount and repairs in this case, a few ball bearings would only cost $50 I guess. Does make me think that I should have a tinker with mine but it still runs reasonably well and I need to pay more attention to my EQ6 at the moment.