digital_davem Posted January 7, 2017 Share Posted January 7, 2017 Hi Anyone have any experience with reducing backlash in worm gear slow motion mechanisms? I have a vixen porta ii mount. I've replaced the aluminium legs with DIY non-adjustable height wooden legs so the tripod is very solid. However, I've noticed some unwanted play in the altitude axis of the mount. I took apart the mount to see how it works. There are two separate motion mechanisms on each axis. The first is the 'push' mechanism provided by a simple rotating bearing. This can be tightened with a hex bolt to adjust the amount of resistance to taste. Loosen them completely and the axis spins freely; lock them tight and axis cannot be pushed at all. In between settings provide resistance. The second motion is the slow motion control. This is provided by a brass "worm" and an aluminium gear. Turn the end of the worm, and the gear moves, adjusting the position of the axis. These two mechanisms are completely independent - if I lock the push mechanism bearing bolt tight, no movement is possible by pushing the scope but you can still move it using the slow motion control. There is no way to lock the worm drive in one place. The push mechanisms are fine on both axis with no unwanted movement. On the az axis, the worm drive is good as well. I can lock the push mechanism down and there is no play in the slow mo worm drive. However, on the alt axis, the slow mo worm has some slop. Even with the push mechanism locked, there is still movement if move the scope. What this means in practice is with my long classic f/16 refractor the mount is permanently wobbly in the alt axis. Given that the az axis is fine, this isn't simply a case the mount isn't up to the job - it is a fault of some kind in the worm drive. Anyone got any idea how to tune it? Cheers Dave Link to comment Share on other sites More sharing options...
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