Graham Fletcher Posted March 23, 2021 Share Posted March 23, 2021 Hi guys i have a Skywatcher 250px flex tube dob and was wondering what you guys do to improve the altitude movement . I get a certain amount of “sticktion” making movement rather jerky. Are you supposed to have the clamping plastic handle on the opposite side to the focused relatively loose and just rely on the other clamping plastic handle to provide the correct tension? Is there any quick fix as to improving the “sticktion” situation at all? your help would be very much appreciated Graham Link to comment Share on other sites More sharing options...
Bottletopburly Posted March 23, 2021 Share Posted March 23, 2021 I believe some oeople use ptfe sheet cut into washers , some use milk bottle plastic Link to comment Share on other sites More sharing options...
Graham Fletcher Posted March 23, 2021 Author Share Posted March 23, 2021 They use these for the altitude bearing? Link to comment Share on other sites More sharing options...
Brantuk Posted March 24, 2021 Share Posted March 24, 2021 The alt axis should need minimum stcktion adjustment if the tube is properly balanced in any position. It's really just enough to hold in place cos gravity does the rest when you have a well balanced tube. When I had the 8" version it did have the tensioning handle opposite side to the focuser - I seem to remember it made a difference but can't recall why. Link to comment Share on other sites More sharing options...
Graham Fletcher Posted March 24, 2021 Author Share Posted March 24, 2021 That’s interesting Kim. I will give it a try although I cannot see why it should make any difference Link to comment Share on other sites More sharing options...
Brantuk Posted March 25, 2021 Share Posted March 25, 2021 I think it was the spacing between the supporting arms Graham. It had the effect of centering up the tube. I've been thinking overnight and I remember being totally surprised the difference it made. Of course the 12" may be built slightly differently so please treat it as a suggestion only, in the absence of anything else. 🙂 Link to comment Share on other sites More sharing options...
Graham Fletcher Posted March 25, 2021 Author Share Posted March 25, 2021 Thanks Link to comment Share on other sites More sharing options...
Daz Type-R Posted April 2, 2021 Share Posted April 2, 2021 I have the solid tube 8” so not your model but I balance the OTA best I can, then remove the black handle closest to me when observing and then tighten the other side just a tiny bit, works for me. Link to comment Share on other sites More sharing options...
Graham Fletcher Posted April 2, 2021 Author Share Posted April 2, 2021 Interesting. I will give that a try Link to comment Share on other sites More sharing options...
BAZ Posted April 2, 2021 Share Posted April 2, 2021 Whatever I tried with my 12" dob, it never seemed to be "Sticktion" free and when using high magnifications, it would jump all over the place. So I bought a ten quid skateboard and destroyed it to get the bearings out of the wheels. I then made an adjustable pair of rollers that sit just under the main weight bearing plastic mount of the tube assembly and these just take enough weight to make it silky smooth. A lot of work to solve a simple problem, but they work perfectly. Brantuk and +RonC 2 Link to comment Share on other sites More sharing options...
Graham Fletcher Posted April 2, 2021 Author Share Posted April 2, 2021 Wow Baz. I am trying to get my head around your method. Could the explanation be simplified at all? Link to comment Share on other sites More sharing options...
Graham Fletcher Posted April 2, 2021 Author Share Posted April 2, 2021 Is that complete addition including the mounting bracket off a skateboard? Link to comment Share on other sites More sharing options...
Graham Fletcher Posted April 2, 2021 Author Share Posted April 2, 2021 Is the hex had bolt at the bottom of the arrangement for vertical adjustment of the bearing? Link to comment Share on other sites More sharing options...
BAZ Posted April 2, 2021 Share Posted April 2, 2021 The bolt at the bottom allows accurate adjustment upwards. The two M6 nuts lock it off and keep it where you set it, this was all made down the shed. The only part off the skateboard was the bearings, I don't know if they are cheaper now, but that was a cost effective solution back then, all the other bits I made down the shed. There is a bearing both sides of the support structure so that they can be independently adjusted to get the tube to move just right. They do need to have just a little bit of friction or it rocks up and down with the slightest breeze, but a bit of fiddling and it has never had to be adjusted since I first set it. This of course was just me going off on one and probably going over the top to solve my stickiness issue. (Oh Matron!) 😆 Brantuk 1 Link to comment Share on other sites More sharing options...
Graham Fletcher Posted April 2, 2021 Author Share Posted April 2, 2021 Thanks Baz. There could be a plan developing! Link to comment Share on other sites More sharing options...
Brantuk Posted April 4, 2021 Share Posted April 4, 2021 Great solution Martyn - I see you're still innovative as usual 🙂 BAZ 1 Link to comment Share on other sites More sharing options...
Graham Fletcher Posted April 4, 2021 Author Share Posted April 4, 2021 Would it be possible to remove the 4 nylon bosses that the OTA trunnions run against and replace them with the same size roller bearings? Link to comment Share on other sites More sharing options...
Graham Fletcher Posted April 4, 2021 Author Share Posted April 4, 2021 Would it be worth me using Teflon altitude bearings instead of the 4 nylon ones? Link to comment Share on other sites More sharing options...
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