SP-15 carriage problem

We have recently begun having an intermittent problem with our SP-15. After printing, when the cylinder is returning to home position, it hits some obstruction about 12″ away from the feed board that causes a jolt and a significant bang. It doesn’t do this all the time (maybe 1 in every 4-5 print passes), and I cannot see any parts that would come into close contact at the point where it happens. Of course, much is hidden. I have taken a photo to show the point in the travel at which this collision occurs. Will try for further diagnosis tomorrow. Any suggestions on experiments to try or elements to look for?

9 thoughts on “SP-15 carriage problem

  1. Paul Moxon, Moderator - February 25, 2011

    Great news. I did use canned-air to blow out the dust bunnies and dug them out with a toothbrush, but guess it wasn’t enough. It was a grimy machine, but we, Katie had several issues to tackle. As Eric noted earlier the eccentric needs to be oiled weekly. Still, the plunger cylinder trip mechanism is clunky.

  2. Katie Harper - February 25, 2011

    UPDATE: The oiling really seemed to help. Maybe the trip assembly was not being moved far enough out of the way by the plunger, due to gunk on the mechanism? Anyway, much better now.
    BTW, our press does not have the roller support assembly, nor any place for it.

  3. Katie Harper - February 25, 2011

    After some testing, I think I have found the source of this problem: the rh trip assembly in the carriage sometimes hits the trip plunger on return to home. Most of the time, the “arm” of the trip assembly misses the plunger; after a few rolls, however, the assembly seems to drop down so that the arm starts to graze the top of the plunger, and then it gets so low that it bangs into the plunger. I oiled everything, but when I look at it all with a flashlight, that whole assembly is very dirty, full of old ink and lint and other crud. Not sure if that could be causing the problem? I sure wish my SP-15 looked like the one just recently posted!

  4. Paul Moxon, Moderator - February 25, 2011

    I did a tune-up on this press during a visit in January. The Serial number is 22182, which potentially brings Eric’s comment about the trip springs into play.

    Sheet 287-A of the manual (circa 1969) shows “flat” spring (X-23790) for trip arm X-22753 R.H. and X-22754 L.H. and states: “Machines before S.N. 23925 use X-20482 R.H. & X-20483 L.H. trip arms”

    So this press uses coil springs instead of flat or leaf springs.

    Sheet 248 of the manual (circa 1962) shows the coil spring (BRS-2) for X-20482 R.H. and X-20483 L.H. trip arms.

    In the illustrations below note that the bottom of the older style trip arm (at right) doesn’t project as low. This is the part that contacts the Delrin Trip roller (X-21119), see Sheets 247 and 282-A.

  5. Eric Holub - February 24, 2011

    I don’t think a broken trip spring would cause an intermittant problem. Wouldn’t that side of the cylinder just stay wherever it was when the spring broke?
    So far I’ve only seen the spring break when it is the leaf spring. Some models have a coil spring, and I haven’t seen any of those go yet. A serial number would be a clue to that.

  6. kyle van horn - February 23, 2011

    Hm, I wonder – it’s possible that you might have a broken trip spring…

    Anyone else more familiar with this want to chime in?


  7. Katie Harper - February 22, 2011

    I completely forgot to mention that when I did this yesterday, I was in TRIP mode. Would that make a difference? We don’t short roll in PRINT mode, but we sometimes do it in TRIP just to ink up the form.

  8. Eric Holub - February 21, 2011

    Yes, as Kyle says, short-rolling will cause this for sure. Another thing to check is the condition of the nylon wheels at the end of the bed on each side. If they are worn or their studs are loose you might also have intermittant problems. And it can’t repeated often enough to lubricate that cylinder eccentric. The oil notch is so small that the slightest amount of crud and it won’t be noticed.

  9. kyle van horn - February 21, 2011

    It sounds like you’re hitting your trip pins on the return with your press halfway between trip and print.

    I *think* that the trip mechanism is the same on your press as on an SP20.

    The carriage goes to into trip mode at the end of the bed (away from the feed board), and then back to print mode when it returns to the feedboard. If you don’t roll the carriage all the way down, it has a tendency to jam, on the return, catching the mechanism halfway between the trip and print settings.

    To test it, roll it ALL the way down, and back – it should work fine. Then roll it *mostly* to the end (I describe the Trip to students as a ‘speedbump’ you need to roll over) – you should be able to replicate this problem.

    If you watch the side of the press, you’ll see the center ring behind the handle (an eccentric) make a half-rotation back and forth from trip to print.

    You’re just catching the press on a quarter turn of the mechanism, and yes, it is jarring when you hit.

    Hope that helps a little!

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