SP 20 Trip Assembly misaligned on one side

Hi all, I’m the new caretaker of an SP 20 (serial 23442). I’ve been investigating a carriage jam issue and have found that the trip assembly on the non-operator side of the carriage (X-21755) is sitting much lower than on the operator side. Because of this, the rogue trip arm has been scraping against the trip rollers (Z-21119) especially the one closest to the feed board. This damage is very noticeable since all trip rollers were recently replaced and the ones on the operator side are pristine. Additionally, when the Print/Trip lever is put in trip, the non-op trip arm just grazes past the steel plungers (X-20805) and does not shift the cylinder eccentric. The result is a half-trip half-print cylinder.

I have taken care to level the press bed. From what I can see peering inside the carriage, the trip springs are intact and in place. Could the carriage bearings be THAT out of whack? I have only attempted tentative bearing adjustments following Paul, Fritz and Gerald’s instructions. 

The first photo shows the trip arm assembly on the operator side when the carriage is at the feed board. Seems okay. The second photo shows the wacky trip arm assembly on the non-op side. 


Any advice would be super appreciated.

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Paul Moxon, Moderator
3 years ago

Yes, the top bearings are adjusted in print mode to a 0.003″ tolerance against the bed bearers.I

The rear studs for the trip rollers have a nut on the inside of the bed casting underside.

Andrea deBruijn
Andrea deBruijn
3 years ago

Thanks for the quick response, Paul. Yes, the bed bearer on the nonoperator’s side is showing prominent wear: two grooves corresponding to the path of the bearing (X-2672) that follows the cylinder as it travels away from the feed board. These grooves only appear between the trip rollers, so the wear must be happening when the cylinder is in print mode. The under rails on both sides are okay.

A question regarding the SP20 X-2672 bearings: They are to be adjusted in print mode to a 0.003″ tolerance against the BED bearers, correct?

The rear studs for the trip rollers look like they’ve been rotated to identical positions. I wasn’t able to get them to budge with a screwdriver though – I’ll hit them with a shot of penetrating lube and try again.

Paul Moxon, Moderator
3 years ago

The carriage bearings may be out-of-whack. Is there much wear on the under rails and/or the bed bearers?

The second photo shows that the trip arm on the nonoperator’s side is higher in relation to the trip roller (X-21119). Note that the rear studs for the trip rollers are are eccentric and can be rotated. Compare the position on the farside to that on the operator’s side.

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