The motor that came with my press.
Turns out there are two different springs. one. the shorter one for the double saddle post & rod:
Length 31″, 190 turns of 0.079″ diameter spring material, wound to 0.465″ inside diameter (0.620″ outside diameter).
The longer spring is for the single saddle post & rod:
Length 34″, 196 turns of 0.070″ diameter spring material, wound to 0.467 inside diameter (0.608″ outside diameter).
It’ll be fun getting the springs back on…
For a few days It’s been very cold. Since the press is still out in the driveway I haven’t got much done. Today was a good day. Worked most of the day on the press, removed the saddle stud & rods and the gripper bar. Noticed a difference between the double saddle stud and the single one. The double saddle stud springs are shorter than the single saddle springs. I wonder if that is because the single saddles were not used on the press (by the previous owner), thus never got compressed or cycled? Or is there a technical reason for it? Tomorrow I will measure and document the springs. Made good use of degreaser and cleaners today. The platen cleaned up real nice with the rust remover.
Made a decision on the oil holes today. While I have things apart anyway I will re-drill the top part of the oil holes and get oil hole covers to try to keep these locations from accumulating dirt, and make them more obvious for long term maintenance.
Interesting encounter today at the farmers market. When I was looking to sit down to enjoy my danish and espresso, there was no table free. So I shared a table with an older couple. We got to talking about things and surprise, surprise the gentlemen used to feed a C&P letterpress many years ago in a little town west of Red Deer. I asked about the speed, and he insisted that they were doing about a hundred pieces a minute top speed. Hm, that seems a pretty fast! The other production number I have heard a few times is about 2000 impressions per hour (iph), that comes to 33 pieces a minute.
I am going to aim for half of that, 1000 iph. My press has a 24″ diameter drive pulley. The smallest I am likely to get for the motor shaft pulley is 2″ diameter. So that works out to a 12 to 1 speed ratio.
With 7 turns per impression on my press, that is 7000 rotations per hour, or 116.7RPM.
On the motor side that is 116.7 times 12 = 1400RPM. For an 1800RMP motor, operating at 1400/1800 = 78% of maximum speed is not that bad.
But there is something else I have not mentioned before. I would like to increase the time available for the paper removal and placing task (while the platen is open) by manipulating (reducing) the drive speed depending on the press position (when the platen is open). During the three truns of the drive wheel while the platen is open I’d like to reduce the drive speed to about 40% (for a 1800RPM motor that would be 720 RPM). And during the four turns while the platen is closing/opening I’d like to run it at full speed. My plan right now is to use an inverter duty 3/4 HP motor driven by a VFD to be able to handle the cyclic acceleration/deceleration.
An 1800RPM motor actually runs at about 1750RPM at full load. Assuming that it will take half a turn (on the press) to accelerate from 720RPM to 1750RPM, and half a trun to decelerate back to 720, that makes one turn at an average speed of (720 + 1750) / 2 = 1235RPM.
So here is what my prediction is for overall rate:
3.5 turns at 1750RPM (at the press that is like running at 1250iph)
2.5 turns at 720RPM (at the press that is like running at 514iph)
1 turn at 1235RPM (at the press that is like running at 882iph)
Working out the average speed for the time weighting that each speed applies:
(3.5/7) * 1250 + (2.5/7) * 514 + (1/7) * 882 = 934.6 iph average speed, pretty close to the 1000 iph I was aiming at, and I gain a safety advantage with longer platen opening time. Let’s see what that would actually work out to: 720RPM / 12 is 60RPM at the press, that is 1 rotation per second, so for the 2.5 turns the platen is open – that makes it 2.5 seconds. Plus the bit of time the drive is speeding up and slowing down. So maybe close to three seconds time for the paper shuffle. That seems lots. We’ll see! One other feature I have been thinking about is to have two buttons on the feed table that have to be depressed before the press will return into the high-speed mode (or possibly if they are not pressed bring the press to an emergency stop via dynamic breaking). If you can think of holes in this reasoning, I’d like to hear what you are thinking.
Today was another day of rust removal. Now my order at Acklands came in and I have better emery-cloth and some rust remover to try out. Had bought a new set of wrenches at Home Depot, an open end – close end ratchet combination set in the typical heavy plastic packaging that you need a set of shears to open. When I came to use the 9/16″ wrench I find the ratchet did not work, and looking at it closer it was a used wrench of a sightly different style (still a Husky though). Back to Home Depot for a refund, but that was not so easy. Even though the packaging claims lifetime warranty there was a lot of waffling going on, I felt they were of the opinion that they were letting me get away with something. Frustrating.
Then a slight, could have been bad mishap. I had attached the throw-off lever linkage and left the lever pushed forward. Then I worked on cleaning rust off the platen and the tympan bale areas. I left the top bale folded down while I got busy with something else. As I turned the flywheel cleaning the main rocker shaft I felt a bit of resistance on the flywheel. Hm that’s not right. As it turns out there is just the right amount of extra space left in the throw-off position so that the bale just gets squeezed a bit – without damage.
Note to self:
1. Never leave anything on the platen that could cause damage.
2. Always turn over the press for a full cycle by hand, and check if anything seems to take too much force!
3. Never leave the platen bales open!
After a fair bit of reading and searching I have found the right lubricant for the press. When you look for machine oil to day (the way it was available in the days when the press was new), you find that it is all detergent based today. Today’s engine oil is way too thin for the cast iron journals with their rather generous clearances. The oil would just drip away. The oil I found is made locally, for metal working machinery where the oils has to stay in place, even on vertical sliding surfaces, and has to maintain lubricating film properties even under high loading and slow movement. It is called “way-oil” and has just the right properties. Likely a better oil than was available at the time the press was in production. I am hoping use of this oil will extend the usefull life of the press far beyond my own. Only problem, you have to buy a 5 gallon pail of the oil! But if it works out as I’m thinking now, I will package the rest of the oil in half liter bottles and make it available for anyone who would like to try it. But I have to try the extended run time motor driven test run first.
When I first laid eyes on the press I was looking for evidence of oil remaining at the journals and linkages. There was a lot of oxidized oil heavily caked with dust and dirt in those places, a good sign. When I removed the retaining bolts for one of the connecting rods, sliding the rod off a bit, the journal area was still shiny with good oil. Then I cleaned out all the oil holes with metal drill-bits, twirling them by hand – finishing with a q-tip to get all the gunk out. I filled every one of the oil holes and proceeded to move the flywheel back and forth just a few inches. Hearing no noise, and feeling no resistance, I increased the rocking motion until I finally made a whole turn. Seeing the oil in the oil holes sink down a bit gave me the assurance I was looking for: The oil was flooding the journals. The press moves with absolutely no noise, smooth as silk! The only thing you hear is the little clack of the ink disk advancing ratchet action.
I was surprised about how the platen mechanism stays open for quite a long time. One press cycle on my press takes seven turns of the flywheel. For three of those turns the platen is wide open. The drive wheel is 24″ in diameter. Next I want to work out what speed motor I should get. The original motor is a 1926 half horsepower motor that looks like the size of a new three to four HP motor today. I will not be using it since I will want to go with variable speed drive and that requires the use of an inverter duty motor. Those have a lot better insulation than a standard motor and vastly better than what was available even just twenty years ago – never mind eighty years ago.
Many many years ago as a first year Electro-Mechanical Engineering apprentice I cleaned a lot of machine parts. And before embracing this endeavor I looked at some old presses, read a lot about the methods other people use. And then I went out to the local industrial supply store and got some emery cloth, scotch-bright pads and wire-brush. And then I met reality! The unmovable hulk of rust. A couple of hours every night, I promised myself. You can believe me, its quite satisfying to climb into bed with sore arms, sore hands and sore fingers – leaving behind another small reclaimed spot on the press. At this rate I hate to even project how long it might take. Long!
I’ve read about a shop that undertook a recovery and rebuild of a press very similar to my model, also a C&P 12″x18″. You can read about it here. They really did some detective work on the surface treatment and paint. Their final result looks like a piece of art. My primary motivation is to make the press productive, create art with it – but not make it into a work of art. My paint job will be more utilitarian, but with some appropriate highlights. We’ll see if I can do justice to it before I say too much.