I am preparing to purchase new form rollers for my 315. They are dented and also concave by 4 or 5 thou ( how much of a problem is this?). The question is, what is the correct diameter of form roller. If someone has the spec on this, it would be great to know. In the meantime, my existing rollers are about 2.9 diameter. But, since that seems an odd size, I thought that the geometry of the vibrator assembly in combination with the form roller shaft spacing would allow me to calculate the correct “theoretical” diameter. The attached drawing shows the stuff I can measure in black. The “theoretical” form rollers are also in black at 3.12 diameter (3-1/8 seems a nice roundish size). The rollers in phantom red are one existing roller and the vibrator shown to be “out of nominal position.”
The .5 dia. vibrator shaft rides in a .625 vertical slot in its carrier. Therefore the shaft is free to float +/-.0625 vertically from its nominal (centered) position. The existing roller being under-size requires that about 1/2 of the available float (.036) is used up.
The problem, as I see it, is that the horizontal beams that support the form rollers are currently adjusted near the top of their travel and, in addition, the rollers are adjusted about as high as they can go in their carrier. (The adjustment is done with a vertically oriented set screw which rides on the shank of the upper hex bolt. The rollers are shown in print position. )
If I purchase the theoretical size of roller, I may have to do a little grinding of the adjustment bolts shanks to get the beams up high enough to achieve correct roller clearance to the bed. Something seems amiss.
If someone has the specs for the rollers, that might help. Otherwise, any advice?
I did not say that the maximum size of roller which the vibrator assembly would accommodate was practical or would work on the press. Just that the vibrator would accommodate it (gotta wonder why, right?).
But, since you bring up the rack and pinion, I offer this last bit of information to the blog. And the only reason for doing so is because it seems to be forbidden, possibly of use to someone, and interesting:
1. Count the number of teeth on the form-roller pinion gear.
2. Add one tooth to that number
3. Measure the center-to-center distance of this new number of teeth on the mating rack.
4. Divide that distance by 3.1416
The resulting number is the diameter of the form roller.
As it may be said of Eric’s remarks, “spot on” as there is no reason to second guess, reinvent or interpret anew that which has already been engineered and designed. Vandercook went through many years of practical experience of what worked and what didn’t and as long as we have the bulk of their information still available in the Vandercook records that I maintain, the only things we should consider are new products or processes that weren’t around in Vandercook’s production days. Or how to redesign the pesky SP-15 roller block assembly. Photopolymer was kicking around back in the 60s and thin plate technology isn’t new, nor are patent bases, honeycomb bases or double faced adhesives. Ask Eric or Paul about my willingness to share information, or how I will spend hours digging for elusive blueprints. Probably 99% of the critical Vandercook information sits within 20 feet of my office desk and anything but manufacturing specifications can be had from me if for legitimate, non-commercial reasons. I’m getting a little slower and a lot more cranky in my old age, and tend not to suffer fools, but I’m here to help. Having spent time in the sun today reading a book at my favorite Victorian train station in Menlo Park, maybe I’m mellowing out too much.
Fritz
I do not believe that any Vandercook rollers have a practical working range of diameters such as suggested here. Even if the oversize/undersize diameters could be adjusted to type-height and still have contact with the distributors, there is the very real issue of the pinion gears and gear rack. These were engineered for a specific position and using off-size rollers will necessarily place the gears out of pitch; as they further off spec, undersize rollers will bottom out on the rack, oversize rollers will no longer mesh. I’ve seen an SP-15 bottom out with rollers just 1/16″ undersize.
Yes, and even the letpress thread on printing on ships and trains was thin–Miehle flatbeds in baggage cars, Kluges on US Navy war ships, Linotypes too, and probably some Vandercooks. The length and breadth of letterpress leading up to the 1950s was immense. I’ll scan some of this when I get home and post it. I especially look for Vandercook material in my reading and forward the most interesting onto Paul Moxon–Vandercook made machines for inserting pins into tank treads during the Korean War, as an example.
It is very reasonable that the Vandercook engineers would try for nice round numbers, though even engineers can’t always get what they want! You are right that 3.0 is the correct number for the rollers. At least that is the perfect size to mate with a vibrator that is 2-1/8. Mine is a bit under that, probably within tolerance, though.
Given the geometry, including the “vibrator float,” of this press, I see that rollers between 2.75 and 3.5 diameter will work with the vibrator assembly. So, reasonable roller diameter tolerances around 3.0 will be no issue.
Perhaps I should apologize for being as interested in the details of the geometry of the press as other people seem to be in the history of printing on trains, but the rubber will meet the road when I purchase new rollers.
Thanks for the information. It is very much appreciated. Tail slap is a problem I have encountered and it is good to hear that it is a common one and that there are ways to deal with it.
I think the engineers at Vandercook liked to work with logical numbers, like a roller diameter of 3 inches and not 2.9. Thus, the correct diameter is 3.00 with the allowable tolerances that roller makers build into their rollers. I don’t think there is a roller maker who would guarantee a precise diameter of 3.000, but that they will work to a + and – tolerance in the finishing of a roller. Since the tangent point of a soft roller and a steel roller is not exact, there has to be some compression of the rubber to allow transfer of ink, so that’s where the analytical, drawing board approach such as Russ is attempting is not practical for actual inking conditions. Vandercook’s roller specifications are all to the inch, i.e. 2.000, or half inch, like 2.500, and not some strange decimal point. As I told Paul Moxon, there is more of a blacksmithing approach to letterpress than there is a rocket science viewpoint.
Eric Holub and I just serviced the 3 Vandercooks at the San Francisco Center for the Book Art–and presses that are used to teach with and are rented out see various levels of abuse. The main complaint was sticky grippers or non-working grippers, or grippers that barely would open. On the 219, we cut away some the floor matting that was caught under the foot pedal, cleaned the grippers and the grippers sprang back to life. There was a bent stem on one of the #4 grippers and we were able to straighten it in Eric’s shop and get it working freely again. That took some effort. Roller racks were full of crud and we cleaned those out, and there is a stripped bolt on one roller rack assembly that I’ll send out a replacment for when I get home. The most obvious mis-use of these presses was not using the head bars and foot bars to establish the limits of plates and type, All too often it appears the folks printing use paper cut to the finished size and don’t allow for margins for the dead bars or grippers that can be trimed off later. The other situation is tail slur or slap on a sheet that is cut too tight to the final image area and that can cause a slur on type or the sheet can touch the ink roller and leave a nice stripe of ink. The best solution is to print a longer sheet and trim, but then a piece of 5 pica wide furniture turned on its side and locked in the form at the bottom edge of the plate or type often solves that problem.
And the other problem we encountered while demonstrating on the 10×15 C&P is plate bases that are way too big for the image being printed, and I see this as a common fault with folks getting Boxcar bases. An 8×12 base in a 10×15 chase leaves no place for grippers and gauge pins have to be set at the bottom of the platen and to the far left. While this is not so much a problem with Vandercooks,a base more suited to the image size makes for easier inking.