Pearl No. 1 Compatible Form Roller Wheel Design

Part No. CR5-1/162

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1. Summary

In this Notebook I'll present a design for a Form Roller Wheel (i.e., Truck) intended to be compatible with a Pearl No. 1. Actually, calling it a "design" is a bit fancy - it is a straightforward modern implementation of the surviving data. Anyone with a Pearl No. 1, 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 162. This is my project ID CR5-1. So I'll call this part CR5-1/162.

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

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CircuitousRoot Drawing No. CRD-2. The image above links to a PDF created from the CAD drawing. Here is the DXF-format CAD source: crd-2-pearl-no-1-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 Rollers for a Pearl No. 1 was 1 1/2 inches. These would have been rollers made of "composition." The specified diameter of the original Form Roller Wheels was 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 rollers, being harder, should probably be the same diameter as the Wheels. However, I've also spoken with a very experienced retired printer who insisted that the roller diameter should in general be 0.020 inch less than the Wheels - and indeed the rail height for the one Pearl No. 1 that I have examined is lower than the type height. 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 Wheel.

Many reproduction Form Roller Wheels have been made in solid steel, however, and they seem to work well. So, especially for Wheels 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 No. 1 roller cores have two "pins" in them used to key the Roller Cores to the Form Roller Wheels. ("Pin" is just a name I made up; this part is not named in the Golding drawing). As noted in the discussion of the surviving original drawings, the size of this pin is unknown. (It was specified by number, but the gauging system for that number was omitted and there are many possibilities; its height was never specified.)

The Form Roller Wheels have a corresponding "slot" (again, "slot" is my own term) to receive this pin. The slot is completely dimensioned on the drawing (although its shape is not - it is not clear if the outside of this slot is flat (unlikely), concentric with the Wheel's diameters (possible), or a 3/32 radius (formed by a 3/16 mill). In the design here I've shown it as formed by a 3/16 mill.

The puzzle is that this slot is almost certainly much larger than the pin which fits into it. This permits some (limited) rotary motion of the Form Roller Wheel relative to the Roller Core; this would seem to be less than ideal. Modify pin and/or slot to suit.

3.5. Material

I have made these 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 suspect that it might dent).

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