Foot Treadle Presses

Just need some clarification on C&P presses, that have, or do not have a treadle?
Im confused, are all old style C&P presses designed to have foot treadles, or are there models that are only operated by hand, and/or a motor. What does “straight drive” mean exactly?
are you able to add treadles to presses with a straight drive setup?

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The “drive” refers to the shaft that runs through the press that’s connected to the flywheel. If it’s straight, it can only be run with a motor (or the flywheel turned by hand, I guess). If there’s a “U” bend in the shaft, you can hook up a foot treadle. I’m pretty sure you can’t add a foot treadle without a “U” bend in the shaft, but you can probably find a replacement shaft with a bend in it.

In theory you could do it on a straight shaft using an eccentric crank. Here is an example of one:

I put 4 (8x12 C&P OS) presses on a trailer with a lineshaft powering all of them and a real steam powered steam engine powering that. This was to demonstrate very visibly to the 100,000+ Bay Area Maker Faire (flagship) attendees the concept of running stock through multiple times to get multiple colors, in this case, CMYK process color.

Anyway, what has been said above about straight versus main shafts that have a crank, is correct. I’ll also add that when presses get dropped in a move, they invariably go down onto the flywheel side because it’s heavier and the weight of the press will, 95 times out of 100, break the crankshaft right where it goes into the frame, which functions as a sleeve bearing, and because the stress is concentrated there. Brazing the shaft back together and getting it straight enough to avoid objectionable runout (wobble) is difficult and rarely attempted and even more rarely accomplished. I own a couple dozen presses, maybe a dozen C&P’s and three of these had broken crankshafts, all at the same place- one of them even came with a hunk of metal the prior owner was going to turn into a main shaft and never got around to it. Since no one is currently making replacement main shafts with a crank, they invariably get replaced with a straight shaft. It’s pretty easy (relatively) to buy a hunk of round stock steel round bar and turn it down in a lathe to fit (the center of the shaft is a larger diameter than the ends where it sticks through and goes through the flywheel- I don’t remember the exact dimensions off the top of my head as it’s been a while). This is what keeps it captive). I made two shafts that way and two of the presses on that press-trailer have such shafts.

Anyway, the more this happens, the more presses get “converted” from shafts with cranks to straight shafts, which are not “treadleable”. I happen to also run a foundry and have a machine shop, in addition to my letterpress hobby and have been contemplating casting and machining brand new crankshafts with cranks in them. Not sure what the demand would be though as this is such a niche market. Most people are pulling parts out of donor presses before they are scrapped (flywheels, cranks, ink disks, chases- that sort of thing). I would have to get around $250 for a crankshaft to make it worth my while (-it’s a fair amount of effort to melt, pour, and machine that much iron) and a lot of letterpress printers seem to either be really cheap or on a budget so

…trying to get the picture attachment to go through… unsuccessfully. Says it’s uploading and then … poof… nothing. Anyway, the video is here, presses at about 1:50 minutes in. I know the flywheels are turning the “wrong” direction, but the actual difference in dwell time on the cam is minimal and this particular steam engine does not have reversible valve gear and the geometry on the trailer worked better this way…