SP-20 Inking issue

Hello all,

I’ve owned a Vandercook SP-20 since April of this year, and it’s been, to this point a beautiful machine. About a week ago, I started getting a strange issue that I have not been able to decipher, and is not covered in any of the books I have looked at. Here is what’s happening:

1. When the machine is ON impression, the form rollers seem to lift up when they are at about 10″ into the printing cycle (so about 10″ from the feedboard end of the bed). If I’m printing something where the form is longer than 10″, there is a distinct line where the rollers stop applying ink. I have verified this with my roller height adjustment tool. At the beginning of the print bed they are adjusted perfectly. At 10″ and beyond they don’t touch the tool.

2. This problem is confounded by the fact that when the machine is OFF impression, on Trip, the rollers maintain their proper height for the entire length of the print cycle, and ink the form correctly. The cylinder still makes an adequate impression, so it’s not moving… just the rollers.

So, the only think I can surmise is that there is something going on with the trip/print mechanism that causes the whole carriage to somehow shift part way into the print cycle. I haven’t been able to find an exploded diagram of the internal cylinder mechanism to even try to start deciphering the issue. I would be grateful for anyone with more service experience with the machine that can possibly point me in the right direction for tackling this issue.

Thanks,

Mike

Clawhammer Press
www.clawhammer.ca

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kyle van horn
11 years ago

That CLUNK on the return to the feedboard is actually your press returning on a ‘half-trip’ setting. This means you did not fully reach the foot of the press to engage the Trip eccentrics (or possibly that your nylon trip rollers are maladjusted — they’re on tiny eccentrics too!) I notice this problem a lot with students printing on our presses when they simply haven’t pushed the carriage fully to the foot of the press.

This could be related to a broken spring possibly, but is most likely just user error (for better or worse).

You should be able to replicate the issue by running the carriage down and carefully engaging the trip eccentric (the ring that spins around the cylinder axle, behind the hand-crank) halfway through its movement. This may take a couple of tries to figure out where that halfway-point is. Upon return to the feed board (carefully) you should be able to reproduce the clunk / stop.

Still doesn’t fix the inking problem, but at least it’s another issue solved.

Fritz Klinke
Admin
11 years ago

The only scan I have posted of the SP-20 cylinder blueprint is this one:

http://www.flickr.com/photos/53177163@N00/296258089/

and I don’t think anything would be solved by taking apart the cylinder assembly. I would check that the cylinder trip springs are intact on both sides of the press as a starter, then look elsewhere. We have new springs, so those are replaceable. My scanner is down at the moment, so I can’t scan any other prints, but I can look stuff up if necessary. I would check the two upper bearings, X-2672 on each side of the press as they control racking, or the levelness of the cylinder assembly. Both bearings are supposed to be snug but not tight to the bed rail and I have a feeling the front bearing on each side is set too tight to the bed rail and that could cause the front of the cylinder assembly to lift if the rear two bearings are set too loose. Just a thought.

Paul Moxon, Moderator
Admin
11 years ago

It could be the carriage bearings adjustment like Eric said.

Mike, the serial number 23766 indicates that your press has flat trip springs (X22980) so it shouldn’t be necessary to tear down your cylinder. Coil springs were discontinued on the SP20 after serial number 23378. See Sheet 245-A. I’ve seen several SP presses function with missing or broken trip springs, but slippage of the cylinder eccentric can occur and cause the carriage to get stuck.

The floating racking is a holdover from the Universal series presses. It was eliminated after serial number 23905. See Sheet 244-A. (Kyle: this should indicate that in your shop SP20 #22466 has this mechanism, but that SP20 # 28222 does not.)

I don’t plan to see an SP20 until late January. Hopefully you have this solved by then.

Eric Holub
Editor
11 years ago

The parts diagrams in the SP-20 manual (copies available from NA Graphics) show some details of construction.
There are two slightly different designs for the cylinder eccentric bearings, one using a coil spring, the other using a leaf spring. The serial number of the press would indicate which type.

kyle van horn
11 years ago

Mike – this is a really mysterious issue.

When the press is on Print, there is nothing in the way that should cause issues as you roll down the bed. As both you and Eric mentioned, this press idles in Print at the feedboard, and only switches to Trip when the lever is set. The one thing I can think of is the Rear Floating Rack, the sprung bit of geared rack (found on both sides at each end of the press) that assists with the trip/print transitions. My best theory is that something is perhaps wedged under the sprung portion of the rack that is throwing the carriage off kilter. This would have a corresponding issue with the bearings, but might explain why it’s not an issue in Trip (the carriage would be lifted up already and riding over the ‘bump’.

Can you feel anything at the time the rollers lift off of inking? A knock or bump or anything? If you are, you shouldn’t.

To answer your questions on the mechanisms on the trip/print triggers: When in print, Trip / Print is dictated by the four nylon wheels at the head and foot of the press. The wheels at the foot of the press throw it into trip as the sheet is released, and the wheels at the head of the press reset it to Print when the carriage returns to the feedboard.
When the press is set to Trip, two metal pegs stick out from each side of press (above the washup tray) which throw the press into trip as the carriage approaches the press bed.

I’ve also uploaded a photo of the Rear Floating Rack and one of the Trip pegs (it is recessed, in Print setting). If I was looking for a culprit, I’d see if anything was weird or off with the floating racks. You can remove them easily, just don’t lose the springs.

Eric Holub
Editor
11 years ago

I’d forgotten that feature of the SP print/trip mechanism. But it reminds me that the upper bearings control roller height on trip, and there is a delicate balance to be found for roller height at both positions.
Not sure why rollers would shift moving forward on print if the carriage stays in print position, but it seemed to me that ten-inch location is just about where the mechanism would come into play.

Eric Holub
Editor
11 years ago

Maybe the rollers are being lifted when the cylinder comes onto impression? And the impression bearings (the lower ones) are misadjusted?

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