Inconsistant inking on sheet

light inking 4 inches from bottom of sheeteven inking at bottom of 15 x 22 inch sheet

On my Vandercook Universal 1 the printing pressure at the bottom of the sheet releases (sometimes but not always) at 4 inches from the end of a 22 inch sheet causing the printing to be lighter. There seems to be no consistency in its happening. Sometimes the printing is fine and sometimes its light starting at 4 inches from the bottom of the sheet. Is there something I can adjust?

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Eric Holub
Editor
12 years ago

Adjusting well-used bearings is very very challenging. In my experience the most careful setting to feeler gauges will still be off on successive passes. But small differences of one or two thousandths shouldn’t show the visible cylinder bear-off seen here. Worn spots might, if they didn’t always appear at the same place.
I’d use an inside caliper and see if there are worn spots on the upper rail corresponding to the bear-off. If there is also a worn spot on the bearer, when the two line up there would be bear-off on heavy forms.

Paul Moxon, Moderator
Admin
12 years ago

In an email exchange, I suggested Laurie read Gerald Lange’s article on carriage bearing adjustment https://vandercookpress.info/vanderblog/literature/articles/lange-adj/ , but have Dave Seat to do it.

Fritz Klinke
Admin
12 years ago

This press had its carriage removed to replace one of the bearings that was bad. I have a feeling that this may be of interest, but Dave Seat checked these, so I tend to rule that out. The reason I’d want Laurie to remove the trip rack cover plate is to see the condition of the bearings that the bolts go through–not to remove the rack. And to determine what level of lubrication there is on this assembly–the whole thing looks like it hasn’t seen oil for a long time. The backsides of Vandercooks, especially those up against a wall, often are neglected for maintenance, especially lubrication.

Eric Holub
Editor
12 years ago

If I was doing this, I would disengage the rack, first making marks to show the present timing of the teeth. Many other presses have timing marks made with a center punch, but for this I’d use a marker until I am certain of the timing. Then I would rotate the gear-and-eccentrics until I know the absolute topmost and bottommost positions of the cylinder. From those positions the correct mesh position of the rack would be determined by trial-and-error. If there is over-turning it might be an incorrect timing. But why that happens inconsistantly is more suggestive of Fritz’s idea of a worn cam follower (a worn or loose cam follower stud is possible too). The cam-follower on the gear rack is the most easily-ignored lubrication point on the old-style trip.

kyle van horn
12 years ago

Your photos didn’t link I think.

However, at those two moments where it is rocking back and forth the 1/4″, look at the round steel bearing at the bottom end of the trip rack. This should be lifting or dropping or rubbing against something if you’re seeing it turn the eccentrics at all, this could be the culprit.

Those clicks are happening as you travel through the trip paddles on the back. They’re the diagonal sprung paddles at the end of the press on the back. Each of them will have the same distinctive click.

It doesn’t sound like you need to remove the rack just yet – Watch that bottom bearing as the press travels past the paddles and see what it is hitting. It seems like it’s rubbing against something that is causing the trip to turn when it shouldn’t be.

The cover plate is on the left hand side of your previous photo with two hex-head screws in it – it is holding the trip rack against the press side. Don’t take it off just yet.

kyle van horn
12 years ago

The rack and gear are on the left hand side of your photo (round gear, straight toothed rack). The gear should align with a brass eccentric (round brass discs) on the inside walls of the cylinder, with a long steel cross bar that lies between your tympan and ink rollers, which has a matching brass eccentric on the other end. If you watch it as you roll down the cylinder, these eccentrics and the cross-bar will spin a half-turn as you start down the press, and a half-turn back on the return (this is the trip and print mechanics in action). This will all run in tandem with the rack and gear in your photo. This should be a very regular rotation at the beginning and end of the press bed, and nothing else happening anywhere in the middle.

What you want to look for is this rack and gear, or the brass eccentrics and steel cross-bar shift, moving, or rotating slightly at the moment you lose impression. It could rotate forward or backwards and produce the same loss of pressure. Look on the rack and gear for a worn or broken tooth too like Fritz recommended.

DON’T unscrew the rack and gear assembly in the photo (the rack is removable, allowing the gear to spin somewhat freely). They’re set together in a very specific pairing. I suspect Dave from Hot Metal could help out if it’s determined that adjustments need to be made here.

Sounds like we’re getting closer…

Eric Holub
Editor
12 years ago

I don’t see how short-trip (the impression part of it) could raise the cylinder while still on the impression stroke. It lifts on the return stroke, no?

Fritz Klinke
Admin
12 years ago

Sorry, I screwed up my post from last night and I didn’t want to be late for dinner. Vandercook lists for the Univ I a maximum form of 15×22, maximum sheet 15 1/4×24, and bed size 15 1/2×24. I’m not sure if the problem relates to too long of a form, packing, etc., but the cylinder trip rack, X–21774 that operates the X-10708 gear is where I would start. Early model Univ I presses had a wimpy gear rack with thin sides that often distort and to the point they will bind up. Later models had a much beefier, redesigned gear rack. The gear the rack turns that makes the cylinder go on and off impression also wears out and that may be inducing slop in the impression on some or all of the teeth. Wear may not be readily apparent. Then, the cam follower X-2726 on the bottom of the gear rack may have developed a flat spot and that could affect impression, so that may need replacing. That whole cylinder trip rack assembly takes a beating, and because it is covered, is often ignored when the oil can gets passed around. I suspect the problem is there.

fritz

Eric Holub
Editor
12 years ago

A short-trip only affects the gripper release.
First you need to determine whether the fault is with inking or impression. You are at the limits of the press, and in fact I’d have guessed beyond the 20″ deadline.

Fritz Klinke
Admin
12 years ago
kyle van horn
12 years ago

To me this looks like the trip mechanism is possibly rotating for some reason, either over-rotating, or possibly turning back. Next time you are printing, watch the trip eccentrics and axle (I don’t know the part number… Paul?) located directly behind the oscillating ink roller. It should make a half rotation as it goes into Print, and rotate back at the end of the press as it goes back into Trip.

The other big thing to look at are the bearers. Are all your rails clean? Are all the teeth on the racks clean? Is there anything wedged in between the bearer and rack on the end of the press?

Is the press possibly set to a short-trip?

Do you usually print forms this far down the bed? Is it possible this has been a long-standing problem that you have never experienced?

Tell us more!

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