Broken press shafts

Ive gone off on this odyssey…

This weekend at Maker Fair in San Mateo, we will have qty4 C&P all on a row driven off a central line from a steam engine.
Kinetic Steam Works is going to do cmyk printing.

The presses are all early 1900s C&P and all have something in common.
During handling in the past, they have all had their crankshafts broken.

The presses with broken shafts were cheap because they had broken shafts.
With milling equipment in the shop, they are all working again.
We installed the last replacement straight shaft last week.

We arent pouring iron yet, but aluminum casting is getting us in practice.
When the iron furnace is working, we are talking about possibly casting replacement iron crank shafts to restore the presses to treadle capability.

Broken cranks are all to common in vintage letterpress.
The topic has come up, of whether people would be interested in purchasing a KSW replacement crankshaft for their presses as part of a fundraiser for KSW.

Fabricating straight shafts is doable immediately.
Its going to be a while before we are ready to try doing crankshafts, but its time to research demand.

This is still in the talking stages.
So I come to you and ask how many are in need of replacement straight shafts and how many need replacement crankshafts?

Log in to reply   3 replies so far

You might want to see if you can determine what the material is of the C&P crank shafts from the factory. Cast iron is more brittle than cast steel, so I would expect that in spite of the greater difficulty of manufacturing with cast steel, the advantage of greater “ductility” means that the shaft would be less likely to break under stress, though it would break if stressed enough, and as happens often enough with C&P flywheel shafts. Forged steel would normally bend under such stress, so the fact that the shafts break, but not as easily, I suspect, as if they were cast iron, probably means they are cast steel.


i can see where casting your own parts would be pretty neat. The “elephant in the room” however raises its head during the sale of these items. are you willing to accept liability for failure of the part. Part failure can cause some things. Down time; replacement cost, (who bears it, IE “It just failed, no, you over loaded the press, thus the shaft.”), associated parts damaged due to the failure, and most importantly, injury. these things must be considered even between the best of friends. i am not an attorney, and, i don’t know your goals. just throwing out considerations i take into account every time i repair a machine.

Cast iron requires around 2200F.
This will be a huge step up from 1300 for aluminum.

Low grade steel brings up around 2500F and better grades bring us up to 2900F.

Ductile steel might be doable at 2500.
I dont think we can hit 2900.

If someone is foot treadling, low grade steel should do the trick.
Restoring presses to treadle is the goal.

It would have to be an “as-is” sale with a specific void if the press is powered by anything other than a single human treadling.

Of course, this is most premature.
The purpose of my post was to start a list of people who want to regain foot treadle capability.

There is no point in swapping back to a crank if you are going to power it.
If you are local to the bay area, these guys have some left over shaft material and can machine a straight shaft for presses with broken shafts.
They are hoping to recover some of their investment for other projects.

So I guess nobody on here is forced to run powered by a straight shaft that wants to convert back to treadle?