Pearl No. 11 Compatible O.S. Form Roller Wheel Design

Part No. CR5-2/71-OS

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1. Summary

In this Notebook I'll present a design for a roller truck intended to be compatible with an Improved Pearl No. 11 with "O.S." roller equipment. (As with my earlier "design" for a Pearl No. 1 Form Roller Wheel, calling this a "design" is a bit fancy - it is a straightforward modern implementation of the surviving data. Anyone with a Pearl No. 11, a lathe, and a chunk of Delrin® would make something very much like this. But I wanted to make it clear that this Wheel/Truck is not an indistinguishable reproduction of an original Golding part but rather a modern replacement intended to work equivalently.)

Thanks are due to Stephen O. Saxe for having preserved the original Golding & Co. drawings which made this possible, and for his very kind help in all phases of this project.

This design and drawing are an "open source hardware" project. Go up a level for a discussion of this.

The original Golding & Co. part number for this was 71 for both O.S. and N.S. trucks. This is my project ID CR5-2. So I'll call this part CR5-2/71-OS.

N.B., The use of the term "truck" or "roller truck" with regard to a Pearl is a modern convention. The Golding & Co. name for them was "Form Roller Wheels."

2. Drawing

In the Improved Pearl No. 11 with O.S. roller equipment, the same Roller Cores and Form Roller Wheels are used for both Inking Rollers and the Brayer Roller.

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CircuitousRoot Drawing No. CRD-9. The image above links to a PDF created from the CAD drawing. Here is the DXF-format CAD source: crd-9-pearl-no-11-os-truck.dxf In my experience the PDF prints well enough, but if you have the ability to read and print a DXF file that will be slightly crisper and more likely to be the size as drawn.

3. Discussion

The dimensions indicated in this drawing are to some extent idealized. There is a great deal of variation in existing equipment (especially since most Roller Cores are now reproductions), and the dimensions should be varied to suit the particular requirements of the press at hand.

3.1. Roller and Truck Diameters

The specified diameter of the Inking Rollers for a Pearl No. 11 is 1 1/2 inches. These would have been rollers made of "composition." The specified diameter of the original roller trucks is 1 3/8 inches. Various discussions online indicate that these dimensions are correct for composition rollers; the softer composition projects 1/16 inch beyond the roller truck (making the roller's diameter 1/8 inch greater than the truck's). These online discussions also indicate that rubber ink rollers, being harder, should probably be the same diameter as the trucks. However, I've also spoken with a very experienced retired printer who insisted that roller diameter should in general be 0.020 inch less than the trucks. You will have to draw your own conclusions.

3.2. Annular Recess

The surviving original drawings show an annular recess either cut or cast into the Roller side of the Form Roller Wheel. I am not sure why this recess is present; I will assume that it was to lighten the truck.

Many reproduction trucks have been made in solid steel, however, and they seem to work well. So, especially for trucks made in (much lighter) Delrin®, the solid design shown here would seem to be suitable.

3.3. Annular Relief

The original drawings indicate an annular "relief" with a fillet cut away from the larger section of the Form Roller Wheel at 'F'. I've kept this in the present design because it looks nice, but I don't think that it is necessary. If it is omitted, the larger section of the Wheel (diamter "A") should be turned the full length of "E".

The 1/8 radius for the fillet as shown in the drawing here is not specified in the original drawings. The exact radius almost certainly doesn't matter.

3.4. Pin Slot

The original (1898) Golding & Co. engineering drawing "Form Roller Wheels" indicates clearly that the Improved Pearl No. 11 truck for "O.S." roller equipment does not have a slot to accept a pin on the Roller Core.

Similarly, the original Golding drawing/table "Cast Roller & Roller Core Data" indicates clearly that the corresponding Improved Pearl No. 11 O.S. Roller Core does not have a pin.

(Improved Pearl No. 11 N.S. roller equipment does have a pin and slot, but that equipment is quite different from the O.S. equipment.)

3.5. Material

I have made these Form Roller Wheels in solid polyoxymethylene homopolomer ("POM", better known by the trade name of one version as "Delrin®"). This is a lightweight, strong modern machinable plastic.

You could also use steel, but it would be more work.

I don't think I'd try aluminum (I'd think that it might dent).


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