I collect antique wheels such as flat belt pulleys, flywheels, handwheels, and the like. It’s just interesting. I recently got one that has me stumped. It’s 8" diameter with flat 1.5" face (not crowned). The hub is 2" through in the axle direction. It’s obviously supposed to just spin on the axle (that is, on a dead shaft) because there’s no means to lock it to the shaft, so it’s some sort of idler. What’s weird is that the bore is coned, with an ID tapering from 1.5" to 1". I also got what it mounted to, which was a cone shaft with a small hole for some kind of pin to keep the pulley (?) from coming off, on the end of a straight heavy iron bar a couple feet long with a long slot for mounting bolts, which looks reasonable for an idler. The whole deal could have been for tensioning a V belt from its back face, or possibly for a flat belt if it were mounted close to a crowned pulley for belt tracking.
A tapered fit likes that usually indicates the 2 pieces are supposed to be driven together to transmit power. Like a Morse taper drill. Car axles were like this to drive the rear hub. They are tough to get apart after a few years. Generator rotors fit on the engine like this also.
The axle is fixed to something? As @mixdenny suggests a conic joint is usually meant for transmitting power through a press fit joint. That might have been it’s original purpose and repurposed. What you describe does seem like a belt tensioner. Maybe as an idler it was used on a slow moving belt carrying a heavy load. While just an idler in this particular part it may have matched conic joints on other parts of the machine and the wheels would all be interchangeable.
You wouldn’t just let a pulley rotate on a shaft like that; you’d have a bearing. What the others said about tapered shafts is right; a press-fit shaft can transmit quite a lot of power. Heat the pulley to install; once in place it’ll definitely stay there. The taper means the diameter of the shaft and hole don’t have to be matched so precisely for a tight fit.
That said, it may well still be an idler due to the flat face. It just isn’t spinning over the shaft.
In the top photo I’ve wedged a couple pencils into the hub with a wad of paper towel between them to illustrate the angle of the cone. In the bottom photo we’re looking at the wider end of the bore.
By the way, the cone is much too wide to be pressed. I have for example a drill press with a Morse taper chuck; it’s way narrower, way more gradual. I’m sure the pulley rotates and the straight mounting arm doesn’t rotate. Sadly I took the arm to the ironmonger’s so can’t post a picture of it.
The pulley wheel wasn’t going to spin on a simple tapered shaft; there had to be some sort of bearing in there too. It may have been oiled bronze or something similarly low tech and thin; heck modern ICE engine crankshafts still use plain bearings.
The alternative is that the pulley did not rotate on the shaft that penetrated it. But that shaft was supported elsewhere and had bearings there. I’m imagining a couple of pillow blocks or some such.
When you bought this stuff it was already old raggeddy scrap / junk. I think there may be an unwarranted assumption here that you have all the parts of a complete installation. I’m thinking there might have been one or more other parts that would make what you’re seeing make a lot more sense. If only we / you had them.
I can’t believe the shaft turned. The arm had to stick out two feet or so, in only one radial direction. The two parts did look like they were made to function together. I do have in my collection other pulleys and wheels with bored hubs and no setscrew or keyway. And one assembly with wheels and a dead axle, no bearing assemblies or bushings, just steel wheel spinning on steel shaft
I don’t know. It’s certainly not marked one way or the other. Usually I would try to measure important dimensions accurately and see whether they’re closer to integer values of fractional inches or millimeters, but the whole thing is rusty and crude and worn. I don’t think I could pin it down accurately. As it is, the inch dimensions I cited are pretty close.
Found a picture showing an assembly roughly like mine, on an old potato digger. In the photo, there’s a bush-roller chain running diagonally, somewhat left of photo center. There’s an idler roller pushing on the back of the chain to tension it. Mine has a straight bar, not curved. The pulley has some sort of cotter pin to hold it on the shaft, the bar doesn’t wrap around. And mine’s much heavier. Otherwise, they look quite similar.
A slight taper could be to allow for a good fit even with some imprecision in manufacturing, but a taper of 3:2? Anyone who needs to allow that much imprecision in manufacturing has no business being near any sort of tool.
What matters is the slope, not the ratio. The aforementioned Morse taper is roughly 8:7, and while quite long-lived, it’s in widespread modern use. The tapered part of an R8 collet is roughly 4:3 (that collet has a keyway, but the actual driving force goes through the taper, and the keyway is just for alignment).
The slope here is just 0.25" over a 2" width, so roughly 1/8. Small enough that heating the pulley a bit and sliding it on would give a very tight non-slip fit.
I don’t know enough about antique pulley design to say if that’s what’s happening here for sure, but it’s definitely a possibility.
Nice photos, but want to mention that Discourse has stretched the top photo horizontally for some reason. Clicking on the top photo brings up the undistorted pic.
Unless there is a some kind of bearing and a lubricating system this almost has to be a press fit whether heated or tapped in place. If it was a greased assembly it would need some kind of end piece to keep it from falling off and a seal on the other end to keep the grease in.
The only other thing I can think of is a horizontal idler pulley where gravity keeps it in place but I’ve never seen anything like that and I like looking at old steam/farm equipment.
Something like that potato digger probably runs very slowly so it’s not out of the question that the wheel is an idler. Still seems odd to use a conic bore unless it matches other wheels that are powered on the same machine.
Do you know how old it is? Ball and roller bearings are unlikely past some point in time. Babbet bearings would be more likely. Maybe you don’t have some additional part.
