C&P Ink Roller Redesign
I’d value your input: For a 12x18 C&P that I’m rebuilding I need three new rollers. The original rollers for this press were 9/16” cores with rubber 2” OD. A mechanical engineer friend has pointed out that I would have a lot less roller deflection when inking if the cores were a tube rather than solid. I have come up with a design based on a 1”OD tube - which roller people are happy to build up to 2”OD (they point out that most modern print rollers only have 1/2” rubber on them). The reason I am fussing over deflection is that I will be printing zinc etchings (not type). And I will want the trucks the some OD as the rollers (which means I have to get the trucks made anyway as pre-made ones are under size). My plan is to have the 1” tube for the center 20” that is rubber coated, and have 9/16” shaft extensions on both sides to fit the original saddles.
Can any of you find fault with such a design?
Most modern print rollers are for offset, they are much harder than letterpress rollers, i like softer rollers for my letterpress printing, i don’t think 1/2” thick rubber will work. Why reinvent the wheel now, i’d stick with what has worked for the last 100 years. Dick G.
I totally agree with DickG.
I think you may be overfocused on the idea of roller deflection. It probably does not exist.
Good rollers of the conventional design and in good adjustment for correct roller height will print on type, poly plate, zinc cuts or petrified peanut butter if all are type high.
If you have the money and time, you could make the rollers you propose and try them.
If the rollers and trucks are the same O.D. they will work, but that is not the optimum situation.
When rollers ink a form, they sqeeze down on the form slightly. This slight pressure is needed to get good contact and good transfer of the ink from the roller to the form.
The reason rollers are slightly larger in diameter than the trucks, is that when they squeeze down on the form, then their diameter effectively gets slightly smaller. At that critical point when the inking takes place, they then ARE the same diameter as the trucks.
As the other commenters have said, the current methods have been perfected over a long period of time. While it may not be impossible to improve them, it is unlikely.
Hugo, Shop talk, well is what it is. I have had engineers my
grandfathers age impress upon me all the laws and physics of letterpress but none had ever run a press. My first concern with your friends comment that a hollow shaft
would reduce the roller deflection, a the while sacrificing the integrity of a solid shaft? Dick G has sound advice.
best james
Hollow core rollers are not just some engineer’s fantasy; that is how Heidelberg cylinder rollers are designed. As you get into longer lengths and larger diameters, properly-engineered hollow cores save weight and increase rigidity. And the 18” C&P roller is just slightly smaller than the Heidleberg KS roller.
Actually…. I can see some merit to Hugo’s idea. As rollers get longer, they get less stiff and a hollow core of larger diameter would indeed make for less deflection. I don’t see any reason why it wouldn’t work as well or better than the small diameter solid core rollers we all currently use. It would cost more to produce, but would indeed be a better solution.
As far as the thickness of the rubber covering goes, a half inch is more than adequate to allow the surface to fully engage the printing block or type, depending of course on the hardness of the rubber. I use a hollow core offset press roller as a brayer and it works just fine with only about 3/8” layer of rubber.
Hugo… I say Go For It!….. and after it’s up and running, let us know how well it works. THAT’s how letterpress progresses from yesterday into tomorrow.
posted twice by accident
Hugo -
As Dick G points out, offset rollers are much different. They are designed to roll against each other for milling the ink and across a flat plate for laying the ink.
Relief printing is different, and relief rollers are different.
The issue to focus on is not roller core, but rubber durometer. 20 - 40 is a common range. You may simply need rollers leaning more towards the harder 40 durometer.
Talk to Adrianne at RAMCO roller in California to get some real professional insight - from a man who makes rollers for printing presses.
Listen to Alan. Talk to a roller manufacturer. Se why they don’t already have that design produced.
Thanks everyone for your insight and commentary. I had a blackberry meltdown where I lost all info including passwords etc.shortly after posting my initial question - that and looking for paying work has taken more time than I care to admit to.
I’m ready to put the saddle springs back in this weekend and will see if I can measure the deflection of the roller in the center of the form using one of the original rollers.
Thanks again, I will keep you posted as I come up with new info.