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Eric Holub
12 years ago

There is another thing that can cause the impression eccentrics to freeze: over-tightening the cover pieces. If there is no shim beneath, or the lock screws have been tampered with, then tightening the screws will bind the cover piece against the frame and the eccentric bearing cannot move.

Paul Moxon, Moderator
12 years ago

You are referring to the cylinder trip. This is a common problem that has been discussed previously. The mechanism may be gummed up, or more likely one or both trip springs. Below I have excerpted the repair instructions from my book Vandercook Presses: Maintenance, History and Resources:

SP Series Trip Assembly—SP series presses are in print mode when at the feed board, unless the lever is shifted to trip. The impression cylinder shifts into trip at the end of the carriage travel when the trip arm, inside the carriage side plate, contacts the white Delrin rollers (X-21119) at foot of press bed. If the roller is missing the cylinder will not shift into trip.
When in trip mode the trip arms, inside the carriage, contact the plungers (X-20805), which shifts the cylinder into trip mode. The plungers and linking can become clogged with ink and grime. If stuck—often on just one side—it will not trip the cylinder.
Position of the trip arms are stabilized by springs; without them, trip arms may slip causing the carriage to jam. There are two types of trip springs: coil springs (BRS -2) on an SP15 with a serial number before 23925, see manual Sheet 248; for flat or leaf springs (X-23790), see Sheet 287-A.
The SP20 and SP25 use coil springs (BRS-3) for presses up to serial number 23378 and 22837 respectively; later models use leaf springs (X-22980). See Sheet 245-A and 298.
If a coil spring breaks on any SP series press, accessing it requires removing one or both side plates by disassembling the tie rods and the oscillator assembly. If a flat spring breaks the looped end will hang from the steel dowel. See next paragraph.
Trip spring replacement: review Sheet 302 in the SP manual, but ignore the instruction to break spring loop with chisel because this may damage dowel “A”. Instead pry loop from dowel with a long 1⁄8″ screwdriver.
The assembly tool (J-19953) is available to rent from NA Graphics. It can also can be made from a 2 × 60 pica length of printer’s furniture. Place the loop of the spring against the side of the furniture and tap to indent, then drill hole with a 3⁄8″ flat bit and cut to shape. A flat segment of the broken spring can be used to create tension against the top of the loop.
Before installing, trip arm must be in print mode, see illustration below. Insert spring into tool. Raise oscillator and remove form rollers from press. From the feed board, insert a long thin screwdriver behind the side plate against spring and dowel, then hit with a mallet. To install a replacement spring insert spring over “C” and under “B.” Hit the assembly tool with a mallet until loop of spring snaps onto “A.”

Paul Moxon, Moderator
12 years ago

NA Graphics stocks replacement bearing blocks.

By the trip for paper release do you mean the L-shaped steel bracket hanging on the backside?

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