What the thread found

• The M-1 Preston Gear Adapter Kit allows snap-on M-1 style gears to work with Preston DM-1 or DM-2 motors and includes six different gear sizes ranging from 0.4m to extra wide 0.8m pitch.
• Larger diameter gears provide more convenient motor placement and better clearance between mirror housing and accessories on cameras like the Arriflex 535B.
• Using the regular output gear on the Preston motor paired with a regular gear on the M-1 adapter produces better results than combining extra wide gears on both motor and adapter.
• Large gears can create clearance problems with the Hill PAM bracket in some configurations and may cause the gear to rub against Rosetta adapters.
• A DM-2 motor with extra wide 0.8 pitch M-1 gear failed to turn a 65mm Zeiss lens in at least one instance, though the cause could not be definitively confirmed.
• Very large gears significantly increase the torque demand on motors, potentially causing performance issues or motor failure.

Depends on

• The single motor failure with the DM-2 was not reproduced or investigated in detail, so the cause remains unclear.
• Experience was limited to a 535B camera with specific bracket configurations, which may not represent all use cases.
• The observation about old large gears relates to different historical motors, not the Preston system being discussed.

Parts

Low Mode, Follow Focus

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