SP-15 rear trip pin wearing ink drum belt?

SP-15 rear trip pin

My SP-15 is showing wear on the rear trip pin from the ink drum belt. Photo shows wear from both trip and print positions. The belt touches the trip pin. Is this expected? And if not, what’s the best way to adjust this?

Additionally the trip arm had been touching the ink drum (wear from that is also shown in this photo on the drum – vertical line of wear on ink drum). There is now daylight between the two as I was able to slightly adjust the bracket under the plate the motor sits on (bracket accessible on upper left of first shelf). However, belt is still touching pin.  Is there a better way to adjust both of these? Any thoughts appreciated. Video


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Fritz Klinke
8 years ago

Additionally, the X-20805 plunger should not be painted as it slides back and forth to act as the cylinder trip. Parts that aren’t supposed to be painted are a sure sign of a rebuild. I would have to pull the print, but that sort of looks like a home-made replacement. Don’t forget the ink drum motor and ink drum are attached to the ink drum cradle so the motor moves as the ink drum is depressed by the rear ink roller.

Fritz Klinke
8 years ago

The change from the V belt and pulley was made on 2/1/62 to the timing belt arrangement. I wonder that the ink drum drive on this press is original but rather a retrofit based on the engineering change date and date of press manufacture. The ink drum spring is X-20772 for the SP-15 and though very close in appearance to the similar SP-20 spring X-20563, it is a lighter weight spring material. I can’t tell from the pictures, but I don’t think it is a spring issue. The timing belt arrangement used a cheezy plastic pulley on the ink drum and these regularly break with age and use and the replacement is a cast iron pulley we have to have modified to fit the ink drum, and it is costly. What I am thinking is this press was retrofitted back to a V-belt arrangement rather than sticking with the newer timing belt arrangement to cut costs. My initial reaction at looking at the photos was that the problem was not enough dirt and grease, lint, etc.

And on a technical note, the ink drum was specified to be “Ink drum to be .030 to .050 above bearing rail” and parallel with the bed. If not parallel, then shims were required.

Paul Moxon, Moderator
8 years ago

Revised: The pin (X-20805 Plunger) position is fixed, so it can only be that the position of the drum is too high. Knowing that this press has been refurbished, it could be for a couple of reasons. There should be a rubber shoe on the motor plate rest that prevents the motor plate rising too high. Perhaps the replacement shoe is too thick. Another possibility is that the drum springs (X-20771) were replaced with one’s that are too short.

There were several engineering changes for the SP15 during its production run. The serial number table says that #23700 was built in 1964. Sheet 248 of the manual shows an ink drum driven by a v-belt (X-21050) and pulley (X-21051). This appears to be correct in your photo.

Sheet 282-A was added to the manual in February 1969. It shows an ink drum driven by a thinner, toothed timing belt (X-21723) and pulley (X-21724). This change could have been made earlier and may be recorded in the engineers’ assembly drawings.

The census lists seven other SP15s (three with lower s/ns) in Seattle proper that you could visit. If you don’t know the operators, I’d be happy to email them on your behalf.

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