Orion VX10 Dob friction plates….

[Ande]

Hi all. Recently purchased a VX10 dob, and have just used it for the first time. Once I’ve got a decent sized eyepiece in, plus my RACI and a Telrad I’m struggling to balance the scope.  It was sagging whilst looking at M42, so I moved it back in the mounting rings to achieve balance. However, once I swung it upwards for a look at the Pleiades it wanted to swing back the other way again. I’ve tightened up the friction knob as tight as this 17-stone bloke can, but to no avail. Any tips for making the clutch more effective? I can’t keep sliding the OTA up and down in the mounting rings.

[johninderby]

Are you balancing it with the tube at a 45 degree angle? If you balance it with the tube horizontal then you will have balance problems in use.

[Mr Spock]

Try a magnetic knife rack attached to the tube. Have a weight you can move up and down.

I believe OO's solution to this problem is a friction brake you can purchase separately.

[scarp15]

Hi, interesting, I had developed a similar conundrum with my VX14 dob mount friction brake. Similar to yourself, it is weighted down with finder scope, telrad, then extension tube or paracorr and usually a hefty 2" low power wide field E.P. Required max tightening and would still start to motion backwards. Initially I thought that the PTFE bearings were worn (being a few years old), or maybe some grease or such like on the trunnion block. 

Anyhow I did consult by email with OOUK, whom had been helpful and like you, slid the OTA upwards and also ensured that the tension screws are such that the PTFE brake bearings are completely flush in gripping against the the trunnion block - please refer to picture one.

One other suggestion was to create a course surface on the PTFE bearings by using some fine sandpaper, thus potentially creating better grip and stiction. The problem here is that it can pick up residue paint off the trunnion - refer to picture two. 

The next thing I employed was to beef up the bearings slightly with the addition of a 2mm deep PTFE washer as sourced off ebay - picture three.

Well in part because of the circumstance with the PTFE bearings, OOUK kindly sent out replacement bearings, I have switched the old ones with these and retained the washers. By itself it wasn't quite enough and so incrementally slid the tube upwards a little more (and tilting the focuser angled a bit more upwards) thus finally achieving good balance and without over tightening.  when as you point out, the tube is angled more upwards then it retains position also with light compact E.P's. 

Therefore just keep tweaking the adjustments, check the alignment screws are set correctly, that there is no wax or grease residue, but mostly just nudge the OTA upwards yet a little more. The jury's out concerning the benefit for adding the two washer bearings but hey-ho. 

The final picture inserted illustrates the not quite concluded balance proportion.

As a footnote, OOUK stipulate that the PTFE bearings ought never show signs of wear, therefore as tough as old boots after years of extensive use.

 

[Stu]

On my 8” f8 I have a couple of additional rings and a dovetail running between them, wide side outwards. I use this to carry a weight which I can slide up and down to adjust the balance.  I just happened to have the rings available so it made sense, and being f8 it needs a bit more weight than an f6. Otherwise the magnetic knife holder is a great idea.

[Ande]

2 hours ago, johninderby said:

Are you balancing it with the tube at a 45 degree angle? If you balance it with the tube horizontal then you will have balance problems in use.

I probably balanced it at about 70 degrees, so not ideal. I shall retry at 45. Thank you 🙂

[Ande]

2 hours ago, Mr Spock said:

Try a magnetic knife rack attached to the tube. Have a weight you can move up and down.

I believe OO's solution to this problem is a friction brake you can purchase separately.

That’s a pretty good idea, and something I can do “on the fly”.  Thanks 🙂

[Ande]

2 hours ago, scarp15 said:

Hi, interesting, I had developed a similar conundrum with my VX14 dob mount friction brake. Similar to yourself, it is weighted down with finder scope, telrad, then extension tube or paracorr and usually a hefty 2" low power wide field E.P. Required max tightening and would still start to motion backwards. Initially I thought that the PTFE bearings were worn (being a few years old), or maybe some grease or such like on the trunnion block. 

Anyhow I did consult by email with OOUK, whom had been helpful and like you, slid the OTA upwards and also ensured that the tension screws are such that the PTFE brake bearings are completely flush in gripping against the the trunnion block - please refer to picture one.

One other suggestion was to create a course surface on the PTFE bearings by using some fine sandpaper, thus potentially creating better grip and stiction. The problem here is that it can pick up residue paint off the trunnion - refer to picture two. 

The next thing I employed was to beef up the bearings slightly with the addition of a 2mm deep PTFE washer as sourced off ebay - picture three.

Well in part because of the circumstance with the PTFE bearings, OOUK kindly sent out replacement bearings, I have switched the old ones with these and retained the washers. By itself it wasn't quite enough and so incrementally slid the tube upwards a little more (and tilting the focuser angled a bit more upwards) thus finally achieving good balance and without over tightening.  when as you point out, the tube is angled more upwards then it retains position also with light compact E.P's. 

Therefore just keep tweaking the adjustments, check the alignment screws are set correctly, that there is no wax or grease residue, but mostly just nudge the OTA upwards yet a little more. The jury's out concerning the benefit for adding the two washer bearings but hey-ho. 

The final picture inserted illustrates the not quite concluded balance proportion.

As a footnote, OOUK stipulate that the PTFE bearings ought never show signs of wear, therefore as tough as old boots after years of extensive use.

 

Thanks for the extensive reply. I had considered “roughing up” the PTFE washers, but now you’ve pointed out the possibility of losing paint I’m not so sure.  I’d also thought about gluing good, old fashioned tap washers to them to see how that might pan out? You’ve certainly given me plenty to think about anyhow. I’ll have a bit of a play tomorrow in the daylight.

[Ande]

1 hour ago, Stu said:

On my 8” f8 I have a couple of additional rings and a dovetail running between them, wide side outwards. I use this to carry a weight which I can slide up and down to adjust the balance.  I just happened to have the rings available so it made sense, and being f8 it needs a bit more weight than an f6. Otherwise the magnetic knife holder is a great idea.

That looks to be an excellent solution. The scope I bought actually came with additional rings married to a dovetail. It’s certainly another option if I can’t beef up the friction brake.

[Ande]

Happy to report that I’ve completely resolved the problem. And in a non-destructive way too, which makes me a happy bunny.  I happened to have some self adhesive circular, soft felt/fibre furniture protectors kicking around. I stuck one to each of the two PTFE washers, and Bob’s your uncle 😃. They are quite soft, so no chance of roughing up the paint. But, more importantly, they can be compressed quite nicely.  I now have no sag, regardless of how I align the scope.  I’m well happy now, and looking forward to getting it back out there. 
 

 

Edited January 30, 2022 by Ande
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