Wobble Stick Overview:

The MTS Wobble Stick, as with all wobble sticks, is a 4 DOF (pitch, swing, twist, and plunge) manually actuated Atmo-to-XHV mechanical passthrough. It features an all 300-series stainless steel central vacuum chamber weldment that forms a contiguous leak free envelope. The coupling mechanism is comprised of permanent magnets which couple through the wall of the tube which comprises the body of the central vacuum chamber weldment. The in-vacuum actuation is carried out by means of a 0.25” diameter rod welded to the internal magnet shuttle.

The central vacuum chamber weldment for the MTS Wobble Stick is designed for reliable long term operation with minimal service. As the core functional component, the metal bellows are guarded and supported by the yoke assembly, protecting from accidental damage during mounting. However, as with all vacuum bellows, FOD becoming lodged in the bellows convolutions can cause a puncture during operation, resulting in a loss of functionality. Ensure that the Wobble Stick is covered when not in use. Ideally, store in clean-room conditions.

The yoke assembly provides support to constrain the motion of the wobble stick to prevent the bellows from becoming over-strained. The yoke assembly also has multiple locating features to optionally further constrain the motion of the wobble stick.

The wobble stick is intended to be actuated using the barrel. Use the minimal required force to avoid deforming the mechanism (pitch and swing) or de-coupling the internal magnets (twist and plunge). If unexpected resistance to motion occurs, check that the barrel lock is loose, the Yoke Lock screws are not tightened down (the washers should be loose) and the four hardstop jack-screws are sufficiently backed out. If the centering spring detent action is not desired, the ball detents may be backed out to disengage them. To lock the motion, these same lock screws can be tightened finger tight.

Should it become necessary to disassemble the wobble stick, the external components can all be removed (except for the flange-side yoke) without breaking vacuum. See Figure 2, for the components.

1. Remove the rear shaft clamp by loosening the cap screw and sliding the collar off of the tube.
2. Remove the barrel by pulling firmly towards the narrow end of the tube to decouple from the internal shuttle. This should take less than ten pounds of force.
3. Remove the front shaft clamp with the same procedure as step 1. Note that after this step - and especially after step 4 - the bellows will not be supported and extra care must be taken to avoid damaging the bellows by over-deflection.
4. Remove the two thumb screws, two socket head cap screws, and two shoulder bolts which secure the yoke assembly to the flange-side yoke. If present, remove the jam nuts on the inside of the yoke assembly before attempting to remove the screws. Note that the tube-side yoke screws are identical, so look inside the yoke assembly to ensure you are removing the correct screws.

The interior of the assembly may also be removed, though this is only recommended after un-mounting the wobble stick. Using caution to avoid damaging the internal bellows convolutions, remove the internal retaining ring with an angle pick. The central rod, bearing, and shuttle can then be pulled out of the central vacuum chamber weldment.

Wobble Stick Troubleshooting:

If the Magnets Coupling Becomes Weak

A weak connection between the barrel (on the air-side) and the rod shuttle (on the vacuum side) likely indicates a half-coupling condition. This occurs when only one of the two pairs of magnets are aligned, which pushes the magnets 180° out of phase. This can be corrected by pulling or pushing (depending on the position of the half-coupling) the barrel approximately 0.75” and allowing either the rod and/or the barrel to rotate 180° about axis. If pulling is required, remove the rear shaft clamp first to allow sufficient stroke. If pushing is required, press the rod against a suitable rigid surface.

If the Wobble Stick needs to be secured

To more securely lock the pitch and swing axis than can be accomplished by using the Yoke Lock thumb screws, the four Yoke SHCS  can be tightened. These screws are normally locked in a “loose” condition by jam nuts on the interior of the yoke assembly so that they act as locating pins for the adjustable hard-stops. In order to tighten the four Yoke SHCS, first loosen the jam nuts, then tighten the bolts with an allen wrench, and finally re-tighten the jam nuts. Reverse the process to release these locks.

To Disable the Hard Stops

The hard stops may be optionally removed if their functionality is not desired. They may also be disabled by removing the Yoke SHCS as described above.