4T gripper foot pedal slipping

I am trying to fix up a Vandercook 4T. When I press on the foot pedal, the pedal moves but the grippers don’t. At first I thought that the chain had stretched but when i look at the joint where the bar from the foot pedal connects to the bar that moves the chain, I can see that the joint is slipping.

I can pull on the chain and get the grippers to operate so I know they aren’t stuck.

How can I keep the joint from slipping?

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Fritz Klinke
17 years ago

Here are some details: The foot pedal is attached to the M-194 connecting link, on the outside of the press. At the end opposite the pedal, it is connected to the MR-173 rod that goes through the base casting with a #4 taper pin x 1.250″ long. On the inside of the press is a corresponding connecting link, MR-195, that Paul calls the “chain bar.” It is connected to the MR-173 rod with a #4 taper pin by 1.250″ long. At the opposite end of the connecting link, a .312-18 hex head screw with a .312 hex nut connects part MS-259, Clutch Connection Nut with part MR-153 that is threaded on one end and screws into the top of the MS-259 and on the other end of this round connecting link is attached the chain that then goes up through the cabinet and across under the bed to eventually the grippers. The MR-153 is held in place with a .312-18 Jam Nut. All of this shows in Paul’s picture except for the connection to the chain and that takes place above the base casting. The Jam Nut allows the connecting link to be moved up and down to adjust the chain for more or less pull. Paul should get a gold star for taking that picture.

It sounds like a taper pin has sheared, and if the one on the outside of the press is good, then the MR-173 shaft should move with the foot pedal, and that leaves the wonderfully convenient inner taper pin to be examined and be replaced if necessary. It could also be in the MR-153 adjusting link that needs adjusting. If the press is propped up to access this stuff, make damn sure it is safely blocked so the press can’t possibly slip and return to the floor.

Holes that accommodate taper pins are drilled and reamed with the 2 parts placed in the proper position. Thus, replacing one of the parts later and trying to match the taper pin hole and the taper ream is next to impossible. But, new taper pins can and will fit the existing holes. Those specifications have been around as machine standards for a very long time.

This entire gripper trip mechanism must have been designed as an experiment in terror because of its complexity, number of parts, and almost total inaccessability of some of the components. It involves chains, a spring (MM-147), castings, nuts, bolts, screws, taper pins, and at least one lock washer. This was all conceived by Vandercook in 1938 and 1939 as those are the dates on all the assembly and part drawings.

Paul Moxon, Moderator
17 years ago

The rod (“joint”) that connects to the foot pedal bar is fastened with a taper pin just like the crank handle on the carriage. I suspect this is the same for the chain bar on the underside of the press. My No. 4 manual doesn’t has a diagram for the foot pedal.

Which joint is slipping? If it’s the one that connects to the outer foot pedal bar you can try to drive the pin deeper. If that doesn’t work then you will need to raise the press up enough to tap out the pin from underneath. If the pin’s hole is reamed out wrap the pin with Teflon tape. You can also wrap the rod if needed.

If the slipping is at the inside joint to the chain bar you will still need to raise the press and to tap out the foot pedal bar’s pin, then disconnect the chain bar from the chain bracket, pull the rod and chain bar out, and then assess the wear. Here is a photo of the “chain bar”:https://vandercookpress.info/images/4parts/4chainbar.jpg that connects to the chain underneath the left drawer.

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