No 4 Grippers not engaging

I’m having some troubles with a Vandercook #4, and I’m more or less completely inexperienced with it. The trip mechanism is not connecting enough when the foot pedal is depressed. There is about a centimeter of space between the trip assembly and the rod when not engaged, so when you hit the pedal, it just gives it a light tap, not enough to move the grippers. I’ve got a diagram here:

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I found it in the Vandercook maintenance guide, however I unfortunately am very new at this and I don’t know enough about the parts to really understand what it all means. The guide indicates that this can be fixed by “tightening the clamp bar” but the clamp bar is not labelled in the diagram. Can anyone give me more detail on this? Seems like it shouldn’t be too complicated.



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Paul Moxon, Moderator
16 years ago

Another solid hypothesis from our Mr. Holub. However if doesn’t prove to be the case, it may be that there is something obstructing the foot pedal. A floor mat is obvious, but a large type sort or small piece of furniture underneath the pedal would inhibit the action as originally described.

Eric Holub
16 years ago

Yeah, Paul, I’d also have to be looking at a similar press to follow the linkages. I just don’t remember what is between the pedal and the opposite side. Looking at the parts drawings, the only thing that comes to mind is that if either of the LR-4 pins–the bolts that act as pivot-pins in the center and top of the MS-125 gripper trip lever–were backing out, then the lever would not have its full movement. Or, if the holes there are worn significantly larger.
I’d also try putting the grippers on automatic and see if they open the same amount, and whether they open adequately at the end of the bed. At the end, the wedge can be pulled off and set in holes timed for long and short sheets, and shims can be put under the wedge to adjust amount of gripper opening. I don’t recall any such adjustment at the feedboard end.

Paul Moxon, Moderator
16 years ago

Because the distance you describe is so slight it may be that excessive grime is inhibiting the push rod. It could also be that the trip bar end is worn down or that the push rod is bent. Also, you should follow the connecting components to see if there is some slack at any point.

I will not be in front of my No.4 for a few of days and so cannot accurately describe other causes and all the connectors are not illustrated in the manual. Perhaps in the meantime, another blog member can step up. (Eric? Fritz?)

BTW: Your original title: “Vandercook Grippers – Trip assembly not engaging” confuses two independent mechanisms. (Yes, the verticle bar connected to the push rod is called the “gripper trip lever”, but generally when someone is referring to trip they mean the mechanism that raises the impression cylinder as it rolls over the press bed during the print stroke.) The clamp bar is the name used for the gripper bar in the No.4 operator’s manual. Your reference to “tightening the clamp bar” is out of context. My point in the handout is that it is possible to misalign the trip bar so that it is tilted and does not make contact with the push rod. This may not be readily apparent to an experienced operator.

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