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OrionXT10 "The Dobsonian Base, fluid movements


Discussion:

MAURO DA LIO

I've never had problems of stability of the base. Instead the structure of the panels is a bit 'flexible: when you push in azimuth initially twists, until, at the threshold of the friction pads Teflon begins to rotate entire deformation and recovering well. (Stck Slip).

To work as much as possible, you can: a) stiffen the structure, b) improve the behavior of friction pads.

The point b is subtle (there is an article on S & T "Better donbsonian bearings" Martin Lewis in October 2003). Basically you need to reduce the friction of sliding but that of the first posting. The jumps depend on the difference between the static friction and one in motion. If you use a liquid or grease lubricated reduce the friction of sliding but not the first posting and the situation even worse. Solid lubricants (graphite and molybdenum disulfide should be had, but I have found on the market only in oil and graphite disulfide molibdenbo in fat). But it's well Teflon spray (found at the DIY with the other oils, I can not remember the name). And 'a spray that sprays like paint on the panel that slides over the teflon pads. Once sprayed, it formna a layer of Teflon particles attached. The flow becomes very gradual and slow, without the jumps of the first posting (up to 400x, then serve to stiffen the structure).


IO

Indeed it is almost impossible to move the base, much less to make sudden movements aiming at the zenith. The problem of breakaway della'attrito can be avoided by placing the pipe in position almost horizontal moving in this way far exceeds the threshold of friction, probably because it moves the CG (?).
course you can do so only for tracking of items with the Intelliscope. With the instrument pointed at the zenith of the threshold friction is virtually insurmountable instead (not applying the Teflon spary): in this case, the real risk that the base becomes unstable, rising in part. Also

Teflon friction pads, if the movement in azimuth is applied when the base rests on a smooth surface like a Pistrella, is that they can not be exceeded. In this case, the teflon pads completely adhere to the base and not allow you to slide in azimuth (if not taking an angle close to horizontal), but a slip of the whole base on the legs in contact with the ground surface.

This is just one example of the presence of this friction. Obviously, the observations are done placing the paintings on rough surfaces like asphalt with a terrace or a lawn grass. For this reason, I thought the instability of the base not necessarily related to the structure of the panels vertical.

So it's all in the attraction of breakaway as you said (ie static friction), suppose that the article was focused on the fact that the actress is always greater than static friction dynamic is also intuitive.
The force of static friction depends on the coefficient of friction statatico (or breakaway) and the normal force (the maximum friction force is proportional to the normal).
therefore reducing the burden on teflon pads also decrease the force required to start movement in azimuth. The most immediate solution is b) going to act only on the legs.

Regarding a): if I am correct in "XT12" (where the OTA weighs the XT10 " + Base) are two "spurs" side that stiffen the structure. I guess in order to solve this problem.