wrenchguy
Plastic
- Joined
- Dec 5, 2011
- Location
- NW Indiana
3 minute video pushing the shaft out the 24" pulley.
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Thoughts about these cast iron lineshaft bearings.
- Thread starter wrenchguy
- Start date
- Replies 27
- Views 2,546
Joe Michaels
Diamond
- Joined
- Apr 3, 2004
- Location
- Shandaken, NY, USA
I watched your youtube of pressing the shaft out of that pulley hub. A good close fit is needed when running a pulley of that size on shafting. When you make the new shaft, go for that same close fit for the pulleys. I find that using some heat on hubs with as close a fit as your youtube shows makes a world of difference. Years ago, millwrights taught me that when removing a tight-fitting hub from a shaft, put the heat at the keyway. They explained that the keyway is usually the thinnest section in a hub, and putting the heat there will create expansion akin to 'spreading a horse shoe'. Depending on hub size, I use anything from a brazing tip, cutting torch preheat flames, or rosebud. A little heat, properly applied to a hub can make things come apart or go together a lot easier and less danger of breaking a cast iron hub.
When I design and machine hubs and shafting to go in them, I often will design in a 'light shrink fit', even when there is a shaft key. Reason being I do not want to chance having a hub work loose on a shaft in service. The trick to this, particularly with cast iron hubs, is to design the shrink fit to stay well within the limits of cast iron's allowable tensile stress. In a circular or ring shaped part or shell, this is sometimes known as 'hoop stress'. About 40 years ago, I got a bit too generous in how much of a shrink fit I allowed in a cast iron hub when I machined a new shaft. The part (a crankshaft for a small "Marvel" lineshaft driven power hacksaw) had worked loose on its shaft and the journals of the shaft were also chewed up badly. I bored the hub slightly oversized and machined a new shaft, figuring on a shrink fit. I got too generous, figuring only how much the cast iron hub would 'grow' when heated and not figuring the developed tensile stress in the hub. As per the millwright, and 'spreading the horseshoe', the highest developed tensile stress was across the keyway. A crack ran from one corner of the keyway radially to the outer circumference of that hub. Nothing to do but remove the shaft from the hub, machine the OD of the hub and shrink a steel band onto it. Heat the banded hub back up and drive in the shaft with some light hammer blows.
The close fit you encountered with the pulley is a good thing. In subsequent years since the era of your saw rig manufacture, taper-lock hubs came along to insure a 'death grip' between hubs and shafts. Another timeless way to lock a hub onto a shaft is to use a tapered key and cut the keyway in the hub on a matching angle. The tapered key, while locking a hub onto a shaft, can move the hub to take up any slight clearance between hub bore and the shaft. On slow turning machinery, this is usually not a problem, but I've seen a tapered key and flywheel work loose periodically for this reason. On a heavy and large diameter pulley running with any kind of speed, this situation will cause rim runout and resulting vibration. Fortunately, this particular instance had the flywheel running at 200 rpm, and plenty of massive iron around it, tied to a solid foundation.
Even driving the tapered key with a sledge and brass drift did not break it of the habit of working loose. In another instance, I designed a flanged shaft coupling with 'spigotted fit' (male/female on the faces of the coupling flanges). I noted on my drawing that the shaft and coupling were to be machined to a shrink fit and gave the calculated diameters with tolerances. A local machine shop figured they knew better and machined things to a close slip fit. The shaft was about 3 1/2" diameter if I remember right. I was not happy when the parts arrived on the job and was told that was what it was, and the shop said it would work and words to that effect. I let everyone know my doubts. We locked the coupling hub onto the shaft with Loctite 603, I tapped in extra set screws and fitted the key so it had to drive in. In service, surprise ! The assembled coupling started working off the shaft with the 'close slip fit' (aka "wringing fit"). I was asked to do something about it. Only thing to do at that point was take things apart (hanging a chainfall and setting some wood blocking to support the shaft and the big belt pulley on it). I drilled some holes in the face of the coupling and shaft end, at the 'interface'. I drilled the holes as deep as a 5/8" UNF tap could reach, shank included. We then ran some long socket-head set screws in, more Loctite 603, and stacked a locking setscrew against each of the longer ones. These setscrews are tapped half into the hub of the coupling, half into the shaft. Millwrights sometimes call these "Dutchmen". Never had another problem with the coupling hub moving on its shaft. There was good reason I was quite specific in how I designed that shaft and hub. The local machine shop thought they knew better, and it came back to bite us. On higher speed machinery, such as your saw rig, a good close fit or light shrink fit is what I'd be going for.
When I design and machine hubs and shafting to go in them, I often will design in a 'light shrink fit', even when there is a shaft key. Reason being I do not want to chance having a hub work loose on a shaft in service. The trick to this, particularly with cast iron hubs, is to design the shrink fit to stay well within the limits of cast iron's allowable tensile stress. In a circular or ring shaped part or shell, this is sometimes known as 'hoop stress'. About 40 years ago, I got a bit too generous in how much of a shrink fit I allowed in a cast iron hub when I machined a new shaft. The part (a crankshaft for a small "Marvel" lineshaft driven power hacksaw) had worked loose on its shaft and the journals of the shaft were also chewed up badly. I bored the hub slightly oversized and machined a new shaft, figuring on a shrink fit. I got too generous, figuring only how much the cast iron hub would 'grow' when heated and not figuring the developed tensile stress in the hub. As per the millwright, and 'spreading the horseshoe', the highest developed tensile stress was across the keyway. A crack ran from one corner of the keyway radially to the outer circumference of that hub. Nothing to do but remove the shaft from the hub, machine the OD of the hub and shrink a steel band onto it. Heat the banded hub back up and drive in the shaft with some light hammer blows.
The close fit you encountered with the pulley is a good thing. In subsequent years since the era of your saw rig manufacture, taper-lock hubs came along to insure a 'death grip' between hubs and shafts. Another timeless way to lock a hub onto a shaft is to use a tapered key and cut the keyway in the hub on a matching angle. The tapered key, while locking a hub onto a shaft, can move the hub to take up any slight clearance between hub bore and the shaft. On slow turning machinery, this is usually not a problem, but I've seen a tapered key and flywheel work loose periodically for this reason. On a heavy and large diameter pulley running with any kind of speed, this situation will cause rim runout and resulting vibration. Fortunately, this particular instance had the flywheel running at 200 rpm, and plenty of massive iron around it, tied to a solid foundation.
Even driving the tapered key with a sledge and brass drift did not break it of the habit of working loose. In another instance, I designed a flanged shaft coupling with 'spigotted fit' (male/female on the faces of the coupling flanges). I noted on my drawing that the shaft and coupling were to be machined to a shrink fit and gave the calculated diameters with tolerances. A local machine shop figured they knew better and machined things to a close slip fit. The shaft was about 3 1/2" diameter if I remember right. I was not happy when the parts arrived on the job and was told that was what it was, and the shop said it would work and words to that effect. I let everyone know my doubts. We locked the coupling hub onto the shaft with Loctite 603, I tapped in extra set screws and fitted the key so it had to drive in. In service, surprise ! The assembled coupling started working off the shaft with the 'close slip fit' (aka "wringing fit"). I was asked to do something about it. Only thing to do at that point was take things apart (hanging a chainfall and setting some wood blocking to support the shaft and the big belt pulley on it). I drilled some holes in the face of the coupling and shaft end, at the 'interface'. I drilled the holes as deep as a 5/8" UNF tap could reach, shank included. We then ran some long socket-head set screws in, more Loctite 603, and stacked a locking setscrew against each of the longer ones. These setscrews are tapped half into the hub of the coupling, half into the shaft. Millwrights sometimes call these "Dutchmen". Never had another problem with the coupling hub moving on its shaft. There was good reason I was quite specific in how I designed that shaft and hub. The local machine shop thought they knew better, and it came back to bite us. On higher speed machinery, such as your saw rig, a good close fit or light shrink fit is what I'd be going for.
wrenchguy
Plastic
- Joined
- Dec 5, 2011
- Location
- NW Indiana
While pressing the shaft out I thought for sure the pulley been onand off several times with a galled shaft from set screws. Thats why I was surprised at the end seeing the results of the pulley put on once and not removed till yesterday. There was bit of gall from 1 screw, the other 1 on the key slightly marking it. thx.
wrenchguy
Plastic
- Joined
- Dec 5, 2011
- Location
- NW Indiana
How is the centered 3/4" wide oil gallery with oiling ring bringing up oil from the reservoir configured in the scenario?
"Overhung loaded pulleys" because the pulleys on the optional jointer and boring attachment are outboard the saw frame. At this time if I redo it, I'm not putting the jointer back on the saw frame unless i find/acquire the boring attachment. I'm planning to have the new jackshaft built to accommodate those pulleys, prolly overhanging the stands. thx.
This ad is the only one i have showing jointer with boring jig on other side.
Joe Michaels
Diamond
- Joined
- Apr 3, 2004
- Location
- Shandaken, NY, USA
Wrenchguy:
In answer to your question: Ring oiled one-piece bearings were quite common. Bronze electric motor bearings having ring oiling were made as a one-piece bronze bushing with a slot cut in the top (approximately between 10:00 and 2:00) for the ring to ride the shaft in. Babbitted one piece bearings were made for ring oiling as well. This was done in a few ways depending on size of the bearing and slot for the ring oiler:
-the ring oiler slot in the cast iron 'box' or shell was plugged with babbitt damming compound (a putty used to seal or dam off molds and bearing housings when pouring babbitt). A mandrel, which could be at the same diameter as the shaft journal, or a bit smaller (if the bearing were to be bored to finished diameter) was centered in the bearing shell. The mandrel was given a coating of carbon soot (aka "lampblack") to keep the babbitt from sticking to it. The mandrel was clamped to hold it centered in the bearing shell, the whole works was preheated, and the babbitt was poured in. After the babbitt and the bearing had cooled, the mandrel was pulled out of the babbitt. The damming compound was removed from the slot in the iron shell. The slot for the ring oiler was then cut in through the babbitt, hacksaw, coarse files, or by milling. The inside of the babbitted bearing at the ring oiler slot opening was cleaned up with scrapers to get rid of burrs
- a piece of steel was cut to the size/shape of the slot and fitted closely into it. After the mandrel was in place, this piece of steel, also smoked, was placed in the slot and sealed off with damming compound. The steel fitted snugly against the mandrel (curve machined on the end of the steel form to saddle onto the mandrel).
The whole works of bearing shell, mandrel and steel slot form (a core in foundry terminology) was preheated and the babbitt poured in. The mandrel and core for the slot were then pulled once the bearing had cooled.
-Some babbitted bearings are poured using centrifugal casting, also known as "spin babbitting". This gives a harder and totally homogeneous babbitting. If a ring oiled bearing were to be spin babbitted, the slot for the ring oiler in the cast iron shell would be plugged off with damming compound. This would be slicked off flush with the inside of the cast iron box. A piece of sheet metal and a hose clamp or some similar arrangement would be cinched around the bearing shell to hold the damming compound in the slot during the spinning of the bearing shell.
For your application, the mandrel and damming compound would be fine. The bearings would be poured from one end, with the other end dammed off with a steel 'washer' or collar to hold the mandrel centered. The bearing shell would be set vertically. At the top/open end, the mandrel would need to be held by some sort of fixturing to hold it centered and true in the bearing shell, yet with room to pour in the babbitt. You could pour the bearings using a mandrel made a few thousandths larger than the finished size of the journals and get away with no boring to finish up the bearings. Some cleanup with a bearing scraper and maybe scratching in an oil groove extending on either side of the ring oiler slot for a short distance would complete the job.
In answer to your question: Ring oiled one-piece bearings were quite common. Bronze electric motor bearings having ring oiling were made as a one-piece bronze bushing with a slot cut in the top (approximately between 10:00 and 2:00) for the ring to ride the shaft in. Babbitted one piece bearings were made for ring oiling as well. This was done in a few ways depending on size of the bearing and slot for the ring oiler:
-the ring oiler slot in the cast iron 'box' or shell was plugged with babbitt damming compound (a putty used to seal or dam off molds and bearing housings when pouring babbitt). A mandrel, which could be at the same diameter as the shaft journal, or a bit smaller (if the bearing were to be bored to finished diameter) was centered in the bearing shell. The mandrel was given a coating of carbon soot (aka "lampblack") to keep the babbitt from sticking to it. The mandrel was clamped to hold it centered in the bearing shell, the whole works was preheated, and the babbitt was poured in. After the babbitt and the bearing had cooled, the mandrel was pulled out of the babbitt. The damming compound was removed from the slot in the iron shell. The slot for the ring oiler was then cut in through the babbitt, hacksaw, coarse files, or by milling. The inside of the babbitted bearing at the ring oiler slot opening was cleaned up with scrapers to get rid of burrs
- a piece of steel was cut to the size/shape of the slot and fitted closely into it. After the mandrel was in place, this piece of steel, also smoked, was placed in the slot and sealed off with damming compound. The steel fitted snugly against the mandrel (curve machined on the end of the steel form to saddle onto the mandrel).
The whole works of bearing shell, mandrel and steel slot form (a core in foundry terminology) was preheated and the babbitt poured in. The mandrel and core for the slot were then pulled once the bearing had cooled.
-Some babbitted bearings are poured using centrifugal casting, also known as "spin babbitting". This gives a harder and totally homogeneous babbitting. If a ring oiled bearing were to be spin babbitted, the slot for the ring oiler in the cast iron shell would be plugged off with damming compound. This would be slicked off flush with the inside of the cast iron box. A piece of sheet metal and a hose clamp or some similar arrangement would be cinched around the bearing shell to hold the damming compound in the slot during the spinning of the bearing shell.
For your application, the mandrel and damming compound would be fine. The bearings would be poured from one end, with the other end dammed off with a steel 'washer' or collar to hold the mandrel centered. The bearing shell would be set vertically. At the top/open end, the mandrel would need to be held by some sort of fixturing to hold it centered and true in the bearing shell, yet with room to pour in the babbitt. You could pour the bearings using a mandrel made a few thousandths larger than the finished size of the journals and get away with no boring to finish up the bearings. Some cleanup with a bearing scraper and maybe scratching in an oil groove extending on either side of the ring oiler slot for a short distance would complete the job.
wrenchguy
Plastic
- Joined
- Dec 5, 2011
- Location
- NW Indiana
The bearing that was not wallowed out but was seized on the shaft has hairline cracked almost all the way round. I'm making new simple bearings using some heavy pipe or cored round with bronze bearings pressed in. The cracked had to be the result of pulling it off the galled/buggered shaft. It was a bear even using a large puller. I've installed 6" channel under the floor contact frames to provide a platform for jackshaft mounting.
john.k
Diamond
- Joined
- Dec 21, 2012
- Location
- Brisbane Qld Australia
I bought a couple of "roller benches" from the railways here .....same era,but maintained by a huge workshop ......everything perfect condition......sold one to a farmer who had a bench in the condition shown....worse actually.....he was of the breed where oil had to used four or five times ...car to truck ,to tractor and finally oil thick as tar could be used on machinery.........or painted onto his horses hooves ,which was apparently more important than the saw bench.
wrenchguy
Plastic
- Joined
- Dec 5, 2011
- Location
- NW Indiana
Jackshaft progress. 3minute viedo.
