A few notes on up/down balancing

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alt-az-builder
Posts: 83
Joined: Wed Mar 22, 2017 2:12 pm

A few notes on up/down balancing

Post by alt-az-builder » Tue Aug 15, 2017 1:31 pm

The Hitch Hiker (with either the payload platform or the side-saddle) provides for two-axis balancing -- which includes both fore/aft positioning of the load and up/down movement of the saddle. The objective is to place the center-of-mass of everything that rotates on the altitude axis directly on the center-line of the altitude axis.

Assuming the fore/aft balance is properly adjusted, if the saddle is set too high, the load will tend to pitch either forward or backward (with equal propensity) when the altitude axis is rotated slightly forward or back. The situation could be compared to a person standing up in a canoe -- the center-of-mass is too high. A little displacement to one side or the other causes the canoe to tip.

On the other hand, if the saddle is set too low, the altitude axis will tend to rotate back to horizontal whenever the instrument is pointed upwards or downwards.

When the up/down position of the saddle is correct, the altitude axis will remain pointed at any angle that the user sets. Note that while the altitude friction control can be used to compensate for SMALL variations or errors in balance, it should NEVER be used in attempt to overcome large errors in balance. Doing so will sacrifice the fine motions of the Hitch Hiker and may lead to sudden pitching of the altitude axis which could result in damage to either the payload or the mount.

One new feature of the production Hitch Hiker is the ability to bias the saddle's up/down position slightly downward or upward -- thereby increasing the total range of available up/down adjustment. The four tapped holes in the face of the altitude axis hub which are used to attach the saddle to the hub are slightly offset from the center of the hub. Before attaching the saddle, one can rotate the altitude axis to set the four tapped holes towards either the top of the mount (creating an upward bias in position) or towards the bottom (to create a downward bias in saddle position). Hitch Hikers are generally shipped with the bias set downward.

One other note of importance: To create the lightest possible mount, the axis shafts of the Hitch Hiker are machined from aircraft-grade aluminum. Aluminum is rather a soft metal -- so extra care should be taken to not cross-thread any screw in any in any of the tapped holes in the axis shafts. Never tighten one screw in the four-screw pattern until all four screws have been started into the threaded holes -- allowing each screw to be precisely aligned to the hole. Also, be careful not to cross-thread the tripod's hold-down screw into the base of the mounting. Always follow the important general rule of never forcing anything!

Charles

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