Adjusting the Master arm forearm section for lighter camera loads

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2004Arms forum

22 years old. Gear and prices may have changed since.

The Master arm has a coarse adjustment mechanism that uses a long Allen wrench with a ball end to adjust spring tension for different camera weights.
The coarse adjustment bolt is located at the front end of each arm section where the spring or cable assembly begins and is approximately 2-4 inches long.
Releasing some coarse tension by turning the Allen bolt reduces constant strain on the springs and can improve arm responsiveness with lighter camera loads.
When releasing tension, the spring naturally contracts and cables can be held in place, but adding tension back is difficult because you must maintain spring position while tightening.
The Master Film Series arms have a minimum camera weight of 20 pounds, while TV series arms have a minimum of 15 pounds but maximum of 35 pounds, with spring tension being the physical difference.
Detuning only the forearm section closest to the body can help prevent lock-ups when experiencing varying loads from different arm angles and body positions.
The forearm section should be adjusted first to carry load both above and below horizontal, then the upper section should be adjusted to track the forearm as you boom up and down.
Each camera change, such as different lens setups, may require readjustment of the arm knobs to achieve optimal performance.
Detuning slightly reduces the arm's maximum lift capacity but makes it more centered and easier to control across its full range of motion.

The coarse adjustment should only be performed by experienced technicians, not in the field, and requires careful handling to prevent cable twisting.
When re-adding maximum tension to the springs, a strap wrench may be needed to hold the spring head while turning the bolt back in.
Heavy camera loads like Panavision BLs require the arm to remain at full tension and cannot be used with detuned arms.
Achieving optimal arm tuning requires experimentation and experience over weeks or months, not a simple one-time adjustment.
Unconfirmed claim that relaxing springs when the arm is not in use improves spring life lacks strong theoretical support since unloaded springs experience minimal stretch.